Latest Accepted Articles

The plant vascular system: From resource allocation, inter-organ communication and defense, to evolution of the monocot cambium
Author: William J. Lucas and Chun-Ming Liu
Online Date: March 22, 2017
DOI: 10.1111/jipb.12541

In recent years, considerable attention has been paid to exploring the complex gene regulatory networks involved in the development of the plant vascular system. Such information is crucial to our understanding of the molecular and cellular events which give rise to the integrated tissues of the xylem and phloem, leading to the formation of structurally continuous conduits that interconnect various organs of the plant. Vascular development begins in the embryo to form progenitor cells, and upon germination, these progenitor cells and their decedents in the shoot and root meristems will form phloem and xylem, and the cambium.

Abstract (Browse 30)   |   Full Text
  Special Issue: Plant Vascular Biology
Molecular regulation of sucrose catabolism and sugar transport for development, defence and phloem function
Author: Jun Li, Limin Wu, Ryan Foster and Yong-Ling Ruan
Received: March 10, 2017         Accepted: March 15, 2017
Online Date: March 17, 2017
DOI: 10.1111/jipb.12539

Sucrose (Suc) is the major end product of photosynthesis in mesophyll cells of most vascular plants. It is loaded into phloem of mature leaves for long-distance translocation to non-photosynthetic organs where it is unloaded for diverse uses. Clearly, Suc transport and metabolism is central to plant growth and development and the functionality of the entire vascular system. Despite of vast information in the literature about the physiological roles of individual sugar metabolic enzymes and transporters, there is a lack of systematic evaluation about their molecular regulation from transcriptional to post-translational levels. Knowledge on this topic is essential for understanding and improving plant development, optimising resource distribution and increasing crop productivity. We therefore focused our analyses on molecular control of key players in Suc metabolism and transport, including (i) the identification of promoter elements responsive to sugars and hormones or targeted by transcription factors and microRNAs degrading transcripts of target genes and (ii) modulation of enzyme and transporter activities through protein-protein interactions and other post-translational modifications. We highlighted major remaining questions and discussed opportunities to exploit current understanding to gain new insights into molecular control of carbon partitioning for improving plant performance.

Abstract (Browse 26)   |   Full Text
Transcript profiling of a novel plant meristem, the monocot cambium
Author: Matthew Zinkgraf, Suzanne Gerttula and Andrew Groover
Received: February 18, 2017         Accepted: March 15, 2017
Online Date: March 17, 2017
DOI: 10.1111/jipb.12538

While monocots lack the ability to produce a vascular cambium or woody growth, some monocot lineages evolved a novel lateral meristem, the monocot cambium, which supports secondary radial growth of stems. In contrast to the vascular cambium found in woody angiosperm and gymnosperm species, the monocot cambium produces secondary vascular bundles, which have an amphivasal organization of tracheids encircling a central strand of phloem. Currently there is no information concerning the molecular genetic basis of the development or evolution of the monocot cambium. Here we report high quality transcriptomes for monocot cambium and early derivative tissues in two monocot genera, Yucca and Cordyline. Monocot cambium transcript profiles were compared to those of vascular cambia and secondary xylem tissues of two forest tree species, Populus trichocarpa and Eucalyptus grandis. Monocot cambium transcript levels showed that there are extensive overlaps between the regulation of monocot cambia and vascular cambia. Candidate regulatory genes that vary between the monocot and vascular cambia were also identified, and included members of the KANADI and CLE families involved in polarity and cell-cell signaling, respectively. We suggest that the monocot cambium may have evolved in part through reactivation of genetic mechanisms involved in vascular cambium regulation.

Abstract (Browse 31)   |   Full Text
Transport of chemical signals in systemic acquired resistance
Author: Archana Singh, Gah-Hyun Lim and Pradeep Kachroo
Received: January 24, 2017         Accepted: March 14, 2017
Online Date: March 17, 2017
DOI: 10.1111/jipb.12537

Systemic acquired resistance (SAR) is a form of broad-spectrum resistance induced in response to local infections that protects uninfected parts against subsequent secondary infections by related or unrelated pathogens. SAR signaling requires two parallel branches, one regulated by salicylic acid (SA), and the other by azelaic acid (AzA) and glycerol-3-phosphate (G3P). AzA and G3P function downstream of the free radicals nitric oxide (NO) and reactive oxygen species (ROS). During SAR, SA, AzA, and G3P accumulate in the infected leaves, but only a small portion of these is transported to distal uninfected leaves. SA is preferentially transported via the apoplast, whereas phloem loading of AzA and G3P occurs via the symplast. The symplastic transport of AzA and G3P is regulated by gating of the plasmodesmata (PD). The PD localizing proteins, PDLP1 and PDLP5, regulate SAR by regulating PD gating as well as the subcellular partitioning of a SAR-associated protein.

Abstract (Browse 41)   |   Full Text
The fungal UmSrt1 and maize ZmSUT1 sucrose transporters battle for plant sugar resources
Author: Anke Wittek, Ingo Dreyer, Khaled A.S. Al-Rasheid, Norbert Sauer, Rainer Hedrich and Dietmar Geiger
Received: March 1, 2017         Accepted: March 10, 2017
Online Date: March 15, 2017
DOI: 10.1111/jipb.12535

The biotrophic fungus Ustilago maydis causes the corn smut disease inducing tumor formation in its host Zea mays. Upon infection, the fungal hyphae invaginate the plasma membrane of infected maize cells establishing an interface where pathogen and host are separated only by their plasma membranes. At this interface the fungal and maize sucrose transporters, UmSrt1 and ZmSUT1, compete for extracellular sucrose in the corn smut/maize pathosystem. Here we biophysically characterized ZmSUT1 and UmSrt1 in Xenopus oocytes with respect to their voltage-, pH- and substrate-dependence and determined affinities towards protons and sucrose. In contrast to ZmSUT1, UmSrt1 has a high-affinity for sucrose and is relatively pH- and voltage-independent. Using these quantitative parameters, we developed a mathematical model to simulate the competition for extracellular sucrose at the contact zone between the fungus and the host plant. This approach revealed that UmSrt1 exploits the apoplastic sucrose resource, which forces the plant transporter into a sucrose export mode providing the fungus with sugar from the phloem. Importantly, the high sucrose concentration in the phloem appeared disadvantageous for the ZmSUT1, preventing sucrose recovery from the apoplastic space in the fungus/plant interface.

Abstract (Browse 45)   |   Full Text
Plant xylem hydraulics: what we understand, current research, and future challenges
Author: Martin D. Venturas, John S. Sperry and Uwe G. Hacke
Received: January 10, 2017         Accepted: March 9, 2017
Online Date: March 14, 2017
DOI: 10.1111/jipb.12534

Herein we review the current state-of-the-art of plant hydraulics in the context of plant physiology, ecology, and evolution, focusing on current and future research opportunities. We explain the physics of water transport in plants and the limits of this transport system, highlighting the relationships between xylem structure and function. We describe the great variety of techniques existing for evaluating xylem resistance to cavitation. We address several methodological issues and their connection with current debates on conduit refilling and exponential shape vulnerability curves. We analyze the trade-offs existing between water transport safety and efficiency. We also stress how limited is the information available on molecular biology of cavitation and the potential role of aquaporins in conduit refilling. Finally, we draw attention to how plant hydraulic traits can be used for modeling stomatal responses to environmental variables and climate change, including drought mortality.

Abstract (Browse 35)   |   Full Text
Implications of nitrogen phloem loading for carbon metabolism and transport during Arabidopsis development
Author: James P. Santiago and Mechthild Tegeder
Received: February 25, 2017         Accepted: March 9, 2017
Online Date: March 14, 2017
DOI: 10.1111/jipb.12533

Metabolite transport processes and primary metabolism are highly interconnected. This study examined the importance of source-to-sink nitrogen partitioning, and associated nitrogen metabolism, for carbon capture, transport and usage. Specifically, Arabidopsis aap8 (AMINO ACID PERMEASE 8) mutant lines were analyzed to resolve the consequences of reduced amino acid phloem loading for source leaf carbon metabolism, sucrose phloem transport and sink development during vegetative and reproductive growth phase. Results showed that decreased amino acid transport had a negative effect on sink development of aap8 lines throughout the life cycle leading to an overall decrease in plant biomass. During vegetative stage, photosynthesis and carbohydrate levels were decreased in aap8 leaves, while expression of carbon metabolism and transport genes, as well as sucrose phloem transport were not affected despite reduced sink strength. However, when aap8 plants transitioned to reproductive phase, carbon fixation and assimilation as well as sucrose partitioning to siliques were strongly decreased. Overall, this work demonstrates that phloem loading of nitrogen has varying implication for carbon fixation, assimilation and source-to-sink allocation depending on plant growth stage. It further suggests alterations in source-sink relationships, and regulation of carbon metabolism and transport by sink strength in a development-dependent manner.

Abstract (Browse 36)   |   Full Text
What actually is the Münch hypothesis? A short history of assimilate transport by mass flow
Author: Michael Knoblauch and Winfried S. Peters
Received: February 13, 2017         Accepted: March 7, 2017
Online Date: March 9, 2017
DOI: 10.1111/jipb.12532

In the 1920ies, the German forestry scientists Ernst Münch postulated that photo-assimilate transport is a mass flow driven by osmotically-induced pressure gradients between source organs (high turgor) and sink organs (lower turgor). Two crucial components of Münch's hypothesis, the translocation by mass flow from sources to sinks and the osmotic mechanism of pressure flow, were established notions at the time, but had been developed by two institutionally separated groups of scholars. A conceptual separation of whole-plant biology from cellular physiology had followed the institutional separation of forestry science from botany in German-speaking central Europe during the so-called Humboldtian reforms, and was reinforced by the delayed institutionalization of plant physiology as an academic discipline. Münch did not invent a novel concept, but accomplished an integration of the organism-focused and the cell-focused research traditions, reducing the polarization that had evolved when research universities emerged in central Europe. Post-Münch debates about the validity of his hypothesis focused increasingly on the suitability of available research methodologies, especially the electron microscope and the proper interpretation of the results it produced. The present work reconstructs the influence of the dynamic scientific and non-scientific context on the history of the Münch hypothesis.

Abstract (Browse 31)   |   Full Text
Sucrose transporter2 contributes to maize growth, development, and crop yield
Author: Kristen A Leach, Thu M Tran, Thomas L Slewinski, Robert B Meeley and David M Braun
Received: December 30, 2016         Accepted: February 10, 2017
Online Date: February 16, 2017
DOI: 10.1111/jipb.12527

During daylight, plants produce excess photosynthates, including sucrose, which is temporarily stored in the vacuole. At night, plants remobilize sucrose to sustain metabolism and growth. Based on homology to other sucrose transporter (SUT) proteins, we hypothesized the maize (Zea mays) SUCROSE TRANSPORTER2 (ZmSUT2) protein functions as a sucrose/H+ symporter on the vacuolar membrane to export transiently stored sucrose. To understand the biological role of ZmSut2, we examined its spatial and temporal gene expression, determined the protein subcellular localization, and characterized loss-of-function mutations. ZmSut2 mRNA was ubiquitously expressed and exhibited diurnal cycling in transcript abundance. Expressing a translational fusion of ZmSUT2 fused to a red fluorescent protein in maize mesophyll cell protoplasts revealed that the protein localized to the tonoplast. Under field conditions, zmsut2 mutant plants grew slower, possessed smaller tassels and ears, and produced fewer kernels when compared to wild-type siblings. zmsut2 mutants also accumulated two-fold more sucrose, glucose, and fructose as well as starch in source leaves compared to wild type. These findings suggest 1) ZmSUT2 functions to remobilize sucrose out of the vacuole for subsequent use in growing tissues and 2) its function provides an important contribution to maize development and agronomic yield.

Abstract (Browse 54)   |   Full Text
  Letters to the Editor
Arabidopsis Forkhead-Associated Domain Protein 3 negatively regulates peroxisome division
Author: Mintu Desai, Ronghui Pan and Jianping Hu
Received: February 7, 2017         Accepted: March 21, 2017
Online Date: March 23, 2017
DOI: 10.1111/jipb.12542

Peroxisomes are ubiquitous and dynamic eukaryotic organelles capable of altering their abundance in response to environmental and developmental cues, yet the regulatory mechanism of plant peroxisome division/proliferation is unclear. To identify transcriptional regulators of the peroxisome division factor gene PEX11b, we performed a nuclear pull-down experiment and identified Arabidopsis Forehead-Associated Domain Protein 3 (FHA3) as a novel protein that binds to the promoter of PEX11b. Our data supported the conclusion that, in contrast to the previously identified HY5 HOMOLOG (HYH) protein that promotes the transcription of PEX11b, FHA3 is a negative regulator of PEX11b expression and peroxisome division.

Abstract (Browse 40)   |   Full Text
  Molecular Physiology
A zinc finger protein, interacted with cyclophilin, affects root development via IAA pathway in rice
Author: Peng Cui, Hongbo Liu, Songlin Ruan, Basharat Ali, Rafaqat Ali Gill, Huasheng Ma, Zhifu Zheng and Weijun Zhou
Received: November 4, 2016         Accepted: February 28, 2017
Online Date: March 7, 2017
DOI: 10.1111/jipb.12531

The plant hormone auxin plays a crucial role in lateral root development. To better understand the molecular mechanisms underlying lateral root formation, an auxin-responsive gene OsCYP2 (Os02g0121300) was characterized from rice. Compared to the wild type, OsCYP2-RNAi lines exhibited distinctive defects in lateral root development. Yeast two-hybrid and GST pull-down results confirmed that OsCYP2 interacted with a C2HC-type zinc finger protein (OsZFP, Os01g0252900) which is located in the rice nucleus. T2 OsZFP-RNAi lines had significantly fewer lateral roots than did wild type plants, which suggests a role for OsCYP2 and OsZFP in regulating lateral root development. Quantitative RT-PCR showed that the expression of certain Aux/IAA genes was altered in OsCYP2- and OsZFP-RNAi lines in response to IAA. These findings imply that OsCYP2 and OsZFP participate in IAA signal pathways controlling lateral root development. More importantly, OsIAA11 showed functional redundancy not only in OsCYP2-RNAi lines but also in OsZFP-RNAi lines, which provides important clues for the elucidation of mechanisms controlling lateral root development in response to auxin.

Abstract (Browse 35)   |   Full Text
  Cell and Developmental Biology
Poly (ADP-ribose) polymerases regulate cell division and development in Arabidopsis roots
Author: Caifeng Liu, Qiao Wu, Weiwei Liu, Zongyin Gu, Wenjing Wang, Ping Xu, Hong Ma and Xiaochun Ge
Received: February 3, 2017         Accepted: February 28, 2017
Online Date: March 6, 2017
DOI: 10.1111/jipb.12530

Root organogenesis involves cell division, differentiation and expansion. The molecular mechanisms regulating root development are not fully understood. In this study, we identified poly (ADP-ribose) polymerases (PARPs) as new players in root development. PARP catalyzes poly (ADP-ribosyl)ation of proteins by repeatedly adding ADP-ribose units onto proteins using nicotinamide adenine dinucleotide (NAD+) as the donor. We found that inhibition of PARP activities by 3-aminobenzomide (3-AB) increased the growth rates of both primary and lateral roots, leading to a more developed root system. The double mutant of Arabidopsis PARPs, parp1parp2, showed more rapid primary and lateral root growth. Cyclin genes regulating G1-to-S and G2-to-M transition were up-regulated upon treatment by 3-AB. The proportion of 2C cells increased while cells with higher DNA ploidy cells declined in the roots of treated plants, resulting in an enlarged rootmeristematic zone. The expression level of PARP2 was very low in the meristematic zone but high in the maturation zones, consistent with a role of PARP in inhibiting mitosis and promoting cell differentiation. Our results suggest that PARPs play an important rolein root development by negatively regulating root cell division.

Abstract (Browse 34)   |   Full Text
  Sexual Plant Reproduction
Acetylglutamate kinase is required for both gametophyte function and embryo development in Arabidopsis thaliana
Author: Jie Huang, Dan Chen, Hailong Yan, Fei Xie, Ying Yu, Liyao Zhang, Mengxiang Sun and Xiongbo Peng
Received: February 10, 2017         Accepted: March 14, 2017
Online Date: March 15, 2017
DOI: 10.1111/jipb.12536

The specific functions of the genes encoding arginine biosynthesis enzymes in plants are not well characterized. We report the isolation and characterization of Arabidopsis thaliana N-acetylglutamate kinase (NAGK), which catalyzes the second step of arginine biosynthesis. NAGK is a plastid-localized protein and is expressed in most developmental processes in Arabidopsis. Heterologous expression of the Arabidopsis NAGK gene in a NAGK-deficient Escherichia coli strain fully bacterial growth on arginine-deficient medium. nagk mutant pollen tubes grow more slowly than wild type pollen tubes and the phenotype is restored by either specifically complementation NAGK in pollen or exogenous supplementation of arginine. nagk female gametophytes are defective in micropylar pollen tube guidance due to the fact that female gametophyte cell fate specification was specifically affected. Specific expression of NAGK in synergid cells rescues the defect of nagk female gametophytes. Loss-of-function of NAGK results in Arabidopsis embryos not developing beyond the four-celled embryo stage. The embryo-defective phenotype in nagk/NAGK plants cannot be rescued by watering nagk/NAGK plants with arginine or ornithine supplementation. In conclusion, the results reveal a novel role of NAGK and arginine in regulating gametophyte function and embryo development, and provide valuable insights into arginine transport during embryo development.

Abstract (Browse 35)   |   Full Text


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