Special Issue: Plant Vascular Biology and Agriculture   

January 2010, Volume 52 Issue 1, Pages 1C124.

Cover Caption: Plant Vascular Biology and Agriculture
The focus of this special issue is on vascular biology, an area which has emerged in recent years, exploring the integrative nature of plant transport systems and various approaches to investigate them. The cover picture shows a transverse section of a Populus stem, stained with toluidine blue. Full genome sequencing, advanced genetic tools and ability to assay gene function using transgenics makes Populus an excellent model for the study of the plant vascular system. The cover picture is provided by Andrew Groover (see pages 17C27 for details).


JIPB in 2010 C A More Reader-Friendly International Journal  
Author: Chun-Ming Liu
Journal of Integrative Plant Biology 2010 52(1): 2-3
Published Online: January 1, 2010
DOI: 10.1111/j.1744-7909.2010.00917.x

Online publication and online reading are gradually becoming routine for scientists and students. Most researchers now follow the scientific development in their expertise area through PubMed, Google Scholar, E-alert and Faculty 1000, etc. This in turn will bring changes to the way of scientific publishing. In JIPB’s case, we have seen a sharp increase of the number of downloads and online subscriptions during the last couple of years, compared to a rather stable hardcopy subscription rate for the same period. As a consequence, during the board meeting on Aug. 10, 2009 in Yantai, it was decided that JIPB will change its format from the beginning of 2010, and make the online version of the journal more user-friendly by using full color for all pictures and figures, and with extensive links to figures, tables and references. These new features make JIPB a pioneer among all plant biology journals. This particular issue, organized by Prof. Lucas, is the first one using the new format. During the trial period, we welcome comments and suggestions from our readers. I hope you will enjoy reading the new JIPB.

As we leave 2009 behind us and move into 2010, I am very happy to conclude that the past year was an exceedingly successful and productive one. The journal’s impact factor continued to increase (up 30%) and we are now certain that we will reach above 1.1 for 2009.

In addition, 2010 will undoubtedly be an exciting year as we have expanded our editorial board, making it more international than ever before. With the help from our dedicated Associate Editors and Co-Editors, 18 new Co-Editors have been recruited to join the JIPB board in its mission to facilitate the development of global plant science. The current distribution of the editorial board is 47% editors from China and 53% from abroad. A brief introduction to the new Co-Editors is attached at the end of the editorial. By expanding our editorial board, apart from adding to JIPB’s collective expertise, it is our hope that this will raise the journal’s international profile and attract more international submission. It is also my intention to continue to raise the quality of the journal and bring it to a broader international audience; however, this can only be achieved with a strong editorial board. Having said this, I would like to extend my warmest welcome to our new Co-Editors. I am sure their expertise and their critical judgment will make a big difference to the journal.

Using this special occasion, on behalf of the JIPB board, I would also like to express our sincere thanks to Drs. Peter Shaw and Mark Tester for their dedication to JIPB in the last two years. Their support has been invaluable to us and we wish you all the best for the future.

Newly recruited Co-Editors:

Dr. Peter Doerner, Senior Lecturer, University of Edinburgh, UK. Area of expertise: Cell division control, growth control nutrient signaling, root and meristem development.

Dr. John Doonan, Project Leader, John Innes Centre, UK. Area of expertise: Cell cycle, microtubules, Arabidopsis, and grain development.

Dr. Kurt Fagerstedt, Professor, University of Helsinki, Finland. Area of expertise: Cell wall structures; lignin biosynthesis; monolignols and plant physiology.

Dr. Richard Haslam, Senior Researcher, Rothamsted Research, UK. Area of expertise: Lipid metabolism & analysis, carbon assimilation & partitioning and xenobiotic metabolism.

Dr. Tetsuya Higashiyama, Professor, Nagoya University, Japan. Area of expertise: plant molecular cell biology and intercellular signaling in plant reproduction.

Dr. Ildoo Hwang, Associate Professor, POSTECH Biotech Center, Pohang University, Republic of Korea. Area of expertise: Intracellular signal transduction controlling plant growth and development, and agricultural improvement.

Dr. Ulrik John, Statewide Leader, Primary Industries Victorian Agri-Biosciences Centre, Australia. Area of expertise: Crop low temperature and freezing tolerance and extremophiles.

Dr. Catherine Kidner, Lecturer at University of Edinburgh and Royal Botanic Garden Edinburgh, UK. Area of expertise: Leaf development, plant evolutionary development.<br>Dr. Keith Lindsey, Professor, Durham University, UK. Area of expertise: Plant embryogenesis, meristems, root development, and gene expression control.

Dr. Shan Lu, Professor at Nanjing University, China. Area of expertise Secondarymetabolism, isoprenoids, phytochemistry and phycology.

Dr. Autar K. Mattoo, Research Leader, USDA Beltsville, USA. Area of expertise: Plant hormone biosynthesis and action, photosystem II and protein turnover in chloroplasts, agricultural biotechnology, and phytonutrients.

Dr. Minami Matsui, Professor, Genomic Sciences Center, RIKEN, Japan. Area of expertise: Cell cycle regulation, protein degradation, light signal transduction.

Dr. Alessandra Moscatelli, Associate Professor, University of Milan, Italy. Area of expertise: Pollen tube, tip growth, cytoskeleton, membrane trafficking, endocytosis.

Dr. Lars Ostergaard, Project Leader, John Innes Centre, UK. Area of expertise: Fruit development, Arabidopsis, Brassica, plant hormones.

Dr. Giovanna Serino, Associate Professor, University of Rome, Italy. Area of expertise: ubiquitin, proteasome, Arabidopsis thaliana, light signaling, and protein degradation.

Dr. Imran Siddiqi, Professor, Center for Cellular and Molecular Biology, India. Area of expertise: Meiosis; gametogenesis; apomixis; chromosome organization; epigenetics.<br>Dr. Tomohiko Tsuge, Assistant Professor at Kyoto University, Japan. Area of expertise: Light signaling pathways, protein degradation; photomorphogenesis and leaf development.

Dr. David Twell, Director of Electron Microscope Laboratory, Leicester University, UK. Area of expertise: Male gametophyte development; cell polarity and asymmetric division, germline cell specification and cell cycle control.

Dr. Stephan Wenkel, University of T¨ubingen, Germany. Area of expertise: Polarity setup, leaf developmental, and meristem function.

Chun-Ming Liu, PhD
Editor-in-Chief, JIPB

Abstract (Browse 1789)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Plant Vascular Biology and Agriculture  
Author: William J. Lucas
Journal of Integrative Plant Biology 2010 52(1): 4-7
Published Online: January 1, 2010
DOI: 10.1111/j.1744-7909.2010.00918.x

The evolution of animal and plant vascular systems played a pivotal role in the advancement from simple to complex organisms, through the provision of a delivery system for the distribution of components essential for both metabolism and growth. Interestingly, although these two vascular systems conform to the same general rules of fluid dynamics (Murray 1926; McCulloh et al. 2003), the developmental mechanisms adopted by plants and animals, to generate these long-distance transport systems, have little in common. In animals, the arterial and venous system of tubules circulates blood, as an extracellular fluid, around the body of the organism by means of a pressure gradient generated by the heart. This system allows for the delivery of signal molecules, such as metabolites, peptides and proteins, from sites of production to target tissues. The circulatory nature of the animal vascular system allows for feedback to occur between distantly located tissues and organs.


The Unique Aspects of the Plant Vascular System

The plant vascular system is comprised of xylem and phloem conducting elements. The xylem transpiration system, which conducts water and mineral nutrients from the roots to above ground organs such as stems, leaves, flowers and fruits, is derived from stem cells (termed procambial cells) that differentiate into xylem conducting elements. Upon expansion, these cells undergo a process of programmed cell death (PCD), thereby giving rise to files of tracheary elements that form a low resistance pathway for the flow of water which is driven by a tensional gradient established within the cell walls of transpiring leaves; i.e., water is pulled up the body of the plant. The phloem translocation system, which delivers sugars, amino acids, mineral nutrients and hormones to heterotrophic tissues, is also derived from cambial cells that differentiate into sieve cells and their associated companion cells. In angiosperms, these sieve cells undergo partial PCD, thereby giving rise to files of evacuolate and enucleote cells connected, end-toend, by sieve plates (containing large open pores) to form conducting tubes. Retention of the plasma membrane allows the sieve tube system to function as an osmotic unit; loadingof sugars in the mature leaves (source of photosynthetically fixed sugars) generates a high turgor pressure, whereas unloading of sugars in developing tissues causes a drop in turgor pressure. These osmotically-driven turgor pressures establish a positive pressure gradient that drives the phloem translocation stream from autotrophic to heterotrophic tissues and organs.


Plant Vascular Development

Clearly, an important functional difference between the animal and plant vascular systems is that the latter is non-circulatory in nature; thus, direct feedback signaling cannot occur between mature leaves and, for example, developing shoot meritstems (Lough and Lucas 2006). This raises the interesting question as to the mechanisms developed by plants to coordinate physiological and developmental processes at the whole-plant level. An important facet of plant vascular development relates to the production of functional xylem and phloem conducting tissues. This process must be both spatially and temporally controlled to permit the formation of transport systems that can deliver optimal quantities of water and nutrients to distantlylocated tissues and organs. Recent studies have provided important insights into this process. In this Special Issue, Hirakawa et al. (2010), review our progress in understanding the complex signaling events that underlie regulation of xylem and phloem cell differentiation from procambial cells. The action of non-cell-autonomous signals, involving CLE peptides, is discussed, as is the role of intercellular signaling from both the xylem and phloem as necessary inputs to coordinate vascular organization.


Secondary Growth & Wood Formation

Secondary growth of the plant vascular system is a very important process, as it leads to an expanded  of the cambium, derived from the procambium, gives rise to woody tissues which can afford additional mechanical support – this feature has allowed for the growth of perennial plantsthat can live for several thousand years and reach to heights of 100 meters or more. Obviously, an understanding of the evolutionary processes that have allowed for such longevity, as well as the formation of economically important tissues as wood, are of basic and applied importance. To lead us along this pathway, Du and Groover (2010) provide a review of recent studies in this area that indicate a role for transcriptional networks in regulating plant secondary growth. Future progress in this area will most surely have important applications in terms of engineering forest trees with improved traits.


Phloem as a Vascular Information Superhighway

Although it was long held that the phloem translocation stream carried only nutrients to support the growth of developing tissues, recent studies have revealed the presence of a complex sets of proteins and nucleic acids (Balachandran et al. 1997; Ruiz-Medrano et al. 1999; Lough and Lucas 2006; Lin et al. 2009). These findings support the hypothesis that the phloem functions as an information superhighway (Jorgensen et al. 1998). The presence of mRNA, as well as small interfering (si-) and micro (mi-)RNA, in the angiosperm sieve tube system raised important questions as to their possible roles in coordinating physiological and developmental processes, at the whole-plant level (Lough and Lucas 2006). Wang and Ding (2010) review these new findings and describe the use of plant viroids as a powerful tool to dissect the molecular determinants controlling the entry and exit of RNA species into and out of the sieve tube system.

Important agricultural traits, such as photoperiodic induction of flowering, have long been known to be controlled by florigenic agent(s) delivered to the shoot apex by the phloem (Zeevaar 1962). Recently, an important component of florigen was shown to be FLOWERING LOCUS T, a 20 kDa protein  the sieve tube system for translocation to the shoot apex (Corbesier et al. 2007; Lin et al. 2007; Mathieu et al. 2007; Tamaki et al. 2007). A role for long-distance transport of RNA in leaf development has been established (Ruiz-Medrano et al. 1999; Haywood et al. 2005) and now, in this Special Issue, Hannapel (2010) reviews recent findings that illustrate the role of phloem-delivery of mRNA in the orchestration of tuber formation in the agriculturally important crop, potato. Collectively, these recent discoveries indicate that pioneering studies on the phloem will likely underpin the bioengineering of novel long-distance signaling systems that will afford unique control over such important agronomically important traits as partitioning of photosynthetically fixed carbon.


Cytokinins and Vascular Signaling

It has long been known that plant hormones can be transported through the vascular system. The involvement of a class of phytohormones, known as the cytokinins, in local and longdistance signaling is well established. The role of cytokinins in nitrogen homeostasis has been the subject of intensive investigation by a number of plant scientists. Here, Kudo et al. (2010) review progress in this area of vascular signaling and show that root-to-shoot delivery of trans-zeatin, via the xylem, plays an important role in nitrogen metabolism. Phloem delivery of N6-(2-isopentenyl) adenine-type cytokinins to the roots and developing shoot apices appears to be important for developmental regulation. As cytokinins appear to be involved in the regulation of a multitude of physiological and developmental activities, one could consider this class of phytohormones as true systemic regulators! Knowledge concerning the longdistance transport of cytokinins may well pave the way for engineering of plants with both enhanced nutrient use efficiency and overall yield.


Nitrogen Fixation and Vascular Signaling

Fixation of atmospheric nitrogen in legumes, through a symbiotic relationship with rhizobia, makes an important contribution to global nitrogen nutrition. This plant-rhizobium interaction involves a complex signaling network which is reviewed in this Special Issue by Ferguson et al. (2010). Interestingly, to optimize nitrogen acquisition and utilization, legumes have evolved an intricate mechanism to regulate the level to which their root systems will respond to soil-borne bacteria to allow nodule development. In the presence of adequate exogenously supplied nitrogen, nodulation is down-regulated; this process ensures optimal utilization of carbon allocation – putting it another way, nodulation and rhizobial nitrogen fixation are processes that cost the plant carbon resources that could otherwise be used for growth and cellular maintenance. Ferguson et al. (2010) describe recent insights afforded into the role played by the plant vascular system as an integrator in this process of autoregulation of nodulation. Obviously, a comprehensive understanding of the processed underlying symbiotic nitrogen fixation will have an immeasurable impact not agriculture and its capacity to feed the peoples of the world.


Root-to-shoot Signaling Systems Control Physiological and Developmental Programs

The pioneering studies of Fritz Went (1943) revealed the involvement of root-derived signals that appeared to regulategrowth of the vegetative regions of the plant. The roles of these signals in water use efficiency, control over shoot branching and overall shoot growth are reviewed in this Special Issue by Sieburth and Lee (2010). The identification of a novel protein, BYPASS1, is discussed with respect to its function in interdicting the synthesis of a novel root-to-shoot signal; this molecule may well be a branch product of the carotenoid biosynthetic pathway. Xylem delivery of this BYPASS1-regulated molecule appears to modify shoot growth through its affect on local auxin signaling. Insights from these and other studies on root-to-shoot signaling, via the xylem transpiration stream, suggests the potential for engineering of plants with enhanced agronomic traits, including higher water use efficiency, novel branching patterns and enhanced growth characteristics under non-optimal environmental conditions.

Vascular Defense – a Role for Secondary Metabolites

As mentioned above, secondary growth gave rise to woody perennial plants whose life cycles can span many centuries to even thousands of years. Given that plants are sessile, such longevity can come with a price – they become prime targets for attack by insects and other pathogens, such as various fungi and bacteria. Through the course of their evolution, woody plants have developed a number of strategies to protect themselves from such attacks. Zulak and Bohlmann (2010) delve into pathogen-induced terpenoid biosynthesis as an effective means to produce secondary metabolites that can block the attacks mounted on confers by a range of pests and pathogens. In their review, the authors illustrate how plants use a combination of specialized anatomical features, such as xylem resin ducts, and oleoresin terpenoids to mount a defense against insect attack.


Flavonoids as Local and Long-distance Signaling Agents

A role for flavonoids as low molecular weight signaling molecules is examined in the review by Buer et al. (2010). Here, again, we learn how plants have utilized their capacity for secondary metabolite production to synthesize a wide range of structural variants through the flavonoid branch of the phenylpropanoid pathway. Flavonoids are involved in a broad spectrum of physiological and developmental process, including modulating hormone signaling, functioning as components in such signaling cascades as those involved in legumebacteria symbiosis, and plant defense. Recent studies have shown that flavonoids are transported throughout the plant and, as discussed by Buer et al. (2010), studies on the mode of transport will provide important new insights into the manner inwhich these secondary metabolites influence plant growth and development.


Biofuels Production

Woody perennial plants produce significant biomass on a seasonal basis. The ligno-cellulosic content of the secondary xylem can be utilized as a renewable energy source. As worldwide energy demand increases, many  strategies to expand their use of biomass energy production in ways that will avoid negative effects on food production and security. In this Special Issue, Tang et al. (2010) analyze the capacity for energy production within China using biomass grown on marginal lands. This review nicely highlights the potential associated with bringing approximately 45 million hectares of marginal land into biomass energy production. The biomass cropping systems and approaches being developed in China could well have utility in other regions of Asia.

Abstract (Browse 3935)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Invited Expert Reviews
Regulation of Vascular Development by CLE Peptide-receptor Systems  
Author: Yuki Hirakawa, Yuki Kondo and Hiroo Fukuda
Journal of Integrative Plant Biology 2010 52(1): 8-16
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00904.x

Cell division and differentiation of stem cells are controlled by noncell-autonomous signals in higher organisms. The plant vascular meristem is a stem-cell tissue comprising procambial cells that produce xylem cells on one side and phloem cells on the other side. Recent studies have revealed that TDIF(tracheary element differentiation inhibitory factor)/CLE41/CLE44 peptide signal controls the procambial cell fate in a non-cell-autonomous manner. TDIF produced in and secreted from phloem cells is perceived by TDR/PXY, a leucine-rich repeat receptor kinase located in the plasma membrane of procambial cells. This signal suppresses xylem cell differentiation of procambial cells and promotes their proliferation. In addition to TDIF, some other CLE peptides play roles in vascular development. Here, we summarize recent advances in CLE signaling governing vascular development.

Hirakawa Y, Kondo Y, Fukuda H (2010) Regulation of vascular development by CLE peptide-receptor systems. J. Integr. Plant Biol. 52(1), 8–16.

Abstract (Browse 1400)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Transcriptional Regulation of Secondary Growth and Wood Formation  
Author: Juan Du and Andrew Groover
Journal of Integrative Plant Biology 2010 52(1): 17-27
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00901.x

Secondary growth and wood formation are products of the vascular cambium, a lateral meristem. Although the mechanisms have only recently begun to be uncovered, transcriptional regulation appears
increasingly central to the regulation of secondary growth. The importance of transcriptional regulation is illustrated by the correlation of expression of specific classes of genes with related biological processes occurring at specific stages of secondary growth, including cell division, cell expansion, and cell differentiation. At the same time, transcription factors have been characterized that affect specific aspects of secondary growth, including regulation of the cambium and differentiation of cambial daughter cells. In the present review, we summarize evidence pointing to transcription as a major mechanism for regulation of secondary growth, and outline future approaches for comprehensively describing transcriptional networks underlying secondary growth.

Du J, Groover A (2010) Transcriptional regulation of secondary growth and wood formation. J. Integr. Plant Biol. 52(1), 17–27.

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Viroids: Small Probes for Exploring the Vast Universe of RNA Trafficking in Plants  
Author: Ying Wang and Biao Ding
Journal of Integrative Plant Biology 2010 52(1): 28-39
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00900.x

Cell-to-cell and long-distance trafficking of RNA is a rapidly evolving frontier of integrative plant biology that broadly impacts studies on plant growth and development, spread of infectious agents and plant defense responses. The fundamental questions being pursued at the forefronts revolve around function, mechanism and evolution. In the present review, we will first use specific examples to illustrate the biological importance of cell-to-cell and long-distance trafficking of RNA. We then focus our discussion on research findings obtained using viroids that have advanced our understanding of the underlying mechanisms involved in RNA trafficking. We further use viroid examples to illustrate the great diversity of trafficking machinery evolved by plants, as well as the promise for new insights in the years ahead. Finally, we discuss the prospect of integrating findings from different experimental systems to achieve a systems-based understanding of RNA trafficking function, mechanism and evolution.

Wang Y, Ding B (2010) Viroids: Small probes for exploring the vast universe of RNA trafficking in plants. J. Integr. Plant Biol. 52(1), 28–39.

Abstract (Browse 1683)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
A Model System of Development Regulated by the Long-distance Transport of mRNA  
Author: David J. Hannapel
Journal of Integrative Plant Biology 2010 52(1): 40-52
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00911.x

BEL1-like transcription factors are ubiquitous in plants and interact with KNOTTED1-types to regulate numerous developmental processes. In potato, the RNA of several BEL1-like transcription factors has been identified in phloem cells. One of these, StBEL5, and its Knox protein partner regulate tuber formation by targeting genes that control growth. RNA detection methods and grafting experiments demonstrated that StBEL5 transcripts move across a graft union to localize in stolon tips, the site of tuber induction. This movement of RNA originates in source leaf veins and petioles and is induced by a short-day photoperiod, regulated by the untranslated regions, and correlated with enhanced tuber production. Addition of the StBEL5 untranslated regions to another BEL1-like mRNA resulted in its preferential transport to stolon tips leading to increased tuber production. Upon fusion of the untranslated regions of StBEL5 to a β-glucuronidase marker, translation in tobacco protoplasts was repressed by those constructs containing the 3' untranslated sequence. The untranslated regions of the StBEL5 mRNA are involved in mediating its long-distance transport and in controlling translation. The 3' untranslated sequence contains an abundance of conserved motifs that may serve as binding motifs for RNA-binding proteins. Because of their presence in the phloem sieve tube system, their unique untranslated region sequences and their diverse RNA accumulation patterns, the family of BEL1-like RNAs from potato represents a valuable model for studying the long-distance transport of full-length mRNAs and their role in development.

Hannapel DJ (2010) A model system of development regulated by the long-distance transport of mRNA. J. Integr. Plant Biol. 52(1), 40–52.

Abstract (Browse 1754)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Metabolism and Long-distance Translocation of Cytokinins  
Author: Toru Kudo, Takatoshi Kiba and Hitoshi Sakakibara
Journal of Integrative Plant Biology 2010 52(1): 53-60
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00898.x

During plant development, distantly-located organs must communicate in order to adapt morphological and physiological features in response to environmental inputs. Among the recognized signaling molecules, a class of phytohormones known as the cytokinins functions as both local and long-distance regulatory signals for the coordination of plant development. This cytokinin-dependent communication system consists of orchestrated regulation of the metabolism, translocation, and signal transduction of this phytohormone class. Here, to gain insight into this elaborate signaling system, we summarize current models of biosynthesis, transmembrane transport, and long-distance translocation of cytokinins in higher plants.

Kudo T, Kiba T, Sakakibara H (2010) Metabolism and long-distance translocation of cytokinins. J. Integr. Plant Biol. 52(1), 53–60.

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Molecular Analysis of Legume Nodule Development and Autoregulation  
Author: Brett J. Ferguson, Arief Indrasumunar, Satomi Hayashi, Meng-Han Lin, Yu-Hsiang Lin, Dugald E. Reid and Peter M. Gresshoff
Journal of Integrative Plant Biology 2010 52(1): 61-76
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00899.x

Legumes are highly important food, feed and biofuel crops.With few exceptions, they can enter into an intricate symbiotic relationship with specific soil bacteria called rhizobia. This interaction results in the formation of a new root organ called the nodule in which the rhizobia convert atmospheric nitrogen gas into forms of nitrogen that are useable by the plant. The plant tightly controls the number of nodules it forms, via a complex root-to-shoot-to-root signaling loop called autoregulation of nodulation (AON). This regulatory process involves peptide hormones, receptor kinases and small metabolites. Using modern genetic and genomic techniques, many of the components required for nodule formation and AON have now been isolated. This review addresses these recent findings, presents detailed models of the nodulation and AON processes, and identifies gaps in our understanding of these process that have yet to be fully explained.

Ferguson BJ, Indrasumunar A, Hayashi S, Lin MH, Lin YH, Reid DE, Gresshoff PM (2010) Molecular analysis of legume nodule development and autoregulation. J. Integr. Plant Biol. 52(1), 61–76.

Abstract (Browse 2444)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
BYPASS1: How a Tiny Mutant Tells a Big Story about Root-to-shoot Signaling  
Author: Leslie E. Sieburth and Dong-Keun Lee
Journal of Integrative Plant Biology 2010 52(1): 77-85
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00902.x

Plants coordinate their development using long-distance signaling. The vascular system provides a route for long-distance movement, and specifically the xylem for root-to-shoot signaling. Root-toshoot
signals play roles communicating soil conditions, and these signals are important for agricultural water conservation. Using genetic approaches, the Arabidopsis bypass1 (bps1) mutant,which over-produces a root-derived signal, was identified. Although bps1 mutants have both root and shoot defects, the shoot can develop normally if the roots are removed, and the mutant root is sufficient to induce arrest of the wild-type shoot. BYPASS1 encodes a protein with no functionally characterized domains, and BPS1-like genes are found in plant genomes, but not the genomes of animals. Analyses of hormone pathways indicate that the mobile compound that arises in bps1 roots requires carotenoid biosynthesis, but it is neither abscisic acid nor strigolactone. The current model suggests that BPS1 is required to prevent the synthesis of a novel substance that moves from the root to the shoot, where it modifies shoot growth by interfering with auxin signaling.

Sieburth LE, Lee DK (2010) BYPASS1: How a tiny mutant tells a big story about root-to-shoot signaling. J. Integr. Plant Biol. 52(1), 77–85.

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Terpenoid Biosynthesis and Specialized Vascular Cells of Conifer Defense  
Author: Katherine G. Zulak and Jörg Bohlmann
Journal of Integrative Plant Biology 2010 52(1): 86-97
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00910.x

Defense-related terpenoid biosynthesis in conifers is a dynamic process closely associated with specialized anatomical structures that allows conifers to cope with attack from many potential pests and pathogens. The constitutive and inducible terpenoid defense of conifers involves several hundred different monoterpenes, sesquiterpenes and diterpenes. Changing arrays of these many compounds are formed from the general isoprenoid pathway by activities of large gene families for two classes of enzymes, the terpene synthases and the cytochrome P450-dependent monooxygenases of the CYP720B group. Extensive studies have been conducted on the genomics, proteomics and molecular biochemical characterization of these enzymes. Many of the conifer terpene synthases are multi-product enzymes, and the P450 enzymes of the CYP720B group are promiscuous in catalyzing multiple oxidations, along homologous series of diterpenoids, from a broad spectrum of substrates. The terpene synthases and CYP720B genes respond to authentic or simulated insect attack with increased transcript levels, protein abundance and enzyme activity. The constitutive and induced oleoresin terpenoids for conifer defense accumulate in preformed cortical resin ducts and in xylem trauma-associated resin ducts. Formation of these resin ducts de novo in the cambium zone and developing xylem, following insect attack or treatment of trees with methyl jasmonate, is a unique feature of the induced defense of long-lived conifer trees.

Zulak KG, Bohlmann J (2010) Terpenoid biosynthesis and specialized vascular cells of conifer defense. J. Integr. Plant Biol. 52(1), 86–97.

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Flavonoids: New Roles for Old Molecules  
Author: Charles S. Buer, Nijat Imin and Michael A. Djordjevic
Journal of Integrative Plant Biology 2010 52(1): 98-111
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00905.x

Flavonoids are ubiquitous in the plant kingdom and have many diverse functions including defense, UV protection, auxin transport inhibition, allelopathy, and flower coloring. Interestingly, these compounds also have considerable biological activity in plant, animal and bacterial systems – such broad activity is accomplished by few compounds. Yet, for all the research over the last three decades, many of the cellular targets of these secondary metabolites are unknown. The many mutants available in model plant species such as Arabidopsis thaliana and Medicago truncatula are enabling the intricacies of the physiology of these compounds to be deduced. In the present review, we cover recent advances in flavonoid research, discuss deficiencies in our understanding of the physiological processes, and suggest approaches to identify the cellular targets of flavonoids.

Buer CS, Imin N, Djordjevic MA (2010) Flavonoids: new roles for old molecules. J. Integr. Plant Biol. 52(1), 98–111.

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Marginal Land-based Biomass Energy Production in China  
Author: Ya Tang, Jia-sui Xie and Shu Geng
Journal of Integrative Plant Biology 2010 52(1): 112-121
Published Online: January 4, 2010
DOI: 10.1111/j.1744-7909.2010.00903.x

Fast economic development in China has resulted in a significant increase in energy demand. Coal accounts for 70% of China’s primary energy consumption and its combustion has caused many environmental and health problems. Energy security and environmental protection requirements are the main drivers for renewable energy development in China. Small farmland and food security
make bioenergy derived from corn or sugarcane unacceptable to China: the focus should be on generating bioenergy from lignocellulosic feedstock sources. As China cannot afford biomass
energy production from its croplands, marginal lands may play an important role in biomass energy production. Although on a small scale, marginal land has already been used for various purposes. It is estimated that some 45 million hm2 of marginal land could be brought into high potential biomass energy production. For the success of such an initiative, it will likely be necessary to develop multipurpose plants. A case study, carried out on marginal land in Ningnan County, Sichuan Province with per capita cropland of 0.07 ha, indicated that some 380 000 tons of dry biomass could be produced each year from annual pruning of mulberry trees. This study supports the feasibility of producing large quantities of biomass from marginal land sources.

Tang Y, Xie JS, Geng S (2010) Marginal land-based biomass energy production in China. J. Integr. Plant Biol. 52(1), 112–121.

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