November 2009, Volume 51 Issue 11, Pages 981ĘC1060.


Cover Caption: Transposon Excision Triggered Site-specific Deletion
The maize Ac-Ds transposable element is an effective mutagen to create insertional mutants. However, Ac transposase (AcTPase) makes transposed Ds elements unstable. A strategy described by Qu et al. (pages 982ĘC992) solved the problem, in which AcTPase is flanked by two lox sites and Cre is separated from its promoter by Ds. The spotted GUS pattern presented in the cover showed that in transgenic rice Ds excision from T-DNA reactivated Cre recombinase, which then mediated lox-lox recombination and thereby deleted AcTPase.

 

          Cell and Developmental Biology
Construction and Application of Efficient Ac-Ds Transposon Tagging Vectors in Rice  
Author: Shaohong Qu, Jong-Seong Jeon, Pieter B.F. Ouwerkerk, Maria Bellizzi, Jan Leach, Pamela Ronald and Guo-Liang Wang
Journal of Integrative Plant Biology 2009 51(11): 982-992
Published Online: November 9, 2009
DOI: 10.1111/j.1744-7909.2009.00870.x
      
    

Transposons are effective mutagens alternative to T-DNA for the generation of insertional mutants in many plant species including those whose transformation is inefficient. The current strategies of transposon tagging are usually slow and labor-intensive and yield low frequency of tagged lines. We have constructed a series of transposon tagging vectors based on three approaches: (i) AcTPase controlled by glucocorticoid binding domain/VP16 acidic activation domain/Gal4 DNA-binding domain (GVG) chemical-inducible expression system; (ii) deletion of AcTPase via Cre-lox site-specific recombination that was initially triggered by Ds excision; and (iii) suppression of early transposition  rice callus through a dual-functional hygromycin resistance gene in a novel Ds element (HPT-Ds). We tested these vectors in transgenic rice and characterized the transposition events. Our results showed that these vectors are useful resources for functional genomics of rice and other crop plants. The vectors are freely available for the community.
 

Qu S, Jeon JS, Ouwerkerk PBF, Bellizzi M, Leach J, Ronald P, Wang GL (2009). Construction and application of efficient Ac-Ds transposon tagging vectors in rice. J. Integr. Plant Biol. 51(11), 982–992.

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          Metabolism and Biochemistry
Molecular Characterization of a Dehydroascorbate Reductase from Pinus bungeana
Author: Hai-Ling Yang, Ying-Ru Zhao, Cai Ling Wang, Zhi-Ling Yang, Qing-Yin Zeng and Hai Lu
Journal of Integrative Plant Biology 2009 51(11): 993-1001
Published Online: August 3, 2009
DOI: 10.1111/j.1744-7909.2009.00848.x
      
    

Dehydroascorbate reductase (DHAR) plays a critical role in the ascorbate-glutathione recycling reaction for most higher plants. To date, studies on DHAR in higher plants have focused largely on Arabidopsis and agricultural plants, and there is virtually no information on the molecular characteristics of DHAR in gymnosperms. The present study reports the cloning and characteristics of a DHAR (PbDHAR) from a pine, Pinus bungeana Zucc. ex Endl. The PbDHAR gene encodes a protein of 215 amino acid residues with a calculated molecular mass of 24.26 kDa. The predicted 3-D structure of PbDHAR showed a typical glutathione S-transferase fold. Reverse transcription-polymerase chain reaction revealed that the PbDHAR was a constitutive expression gene in P. bungeana. The expression level of PbDHAR mRNA in P. bungeana seedlings did not show significant change under high temperature stress. The recombinant PbDHAR was overexpressed in Escherichia coli following purification with affinity chromatography. The recombinant PbDHAR exhibited enzymatic activity (19.84 μmol/min per mg) and high affinity (a Km of 0.08 mM) towards the substrates dehydroascorbate (DHA). Moreover, the recombinant PbDHAR was a thermostable enzyme, and retained 77% of its initial activity at 55 ◦C. The present study is the first to provide a detailed molecular characterization of the DHAR in P. bungeana.
 

Yang HL, Zhao YR, Wang CL, Yang ZL, Zeng QY, Lu H (2009). Molecular characterization of a dehydroascorbate reductase from Pinus bungeana. J. Integr. Plant Biol. 51(11), 993-1001.

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          Plant-environmental Interactions
Dehydration Kinetics of Embryonic Axes from Desiccation-sensitive Seeds: An Assessment of Descriptive Models
Author: Tobias M. Ntuli and Norman W. Pammenter
Journal of Integrative Plant Biology 2009 51(11): 1002-1007
Published Online: November 9, 2009
DOI: 10.1111/j.1744-7909.2009.00875.x
      
    

The response of desiccation-sensitive plant tissues to dehydration is significantly affected by dehydration conditions, particularly the rate of drying. Consequently it is important to be able to quantify drying rate. The aim of the study was to assess two models that have been proposed to describe drying kinetics, and thus to provide a quantification of non-linear drying rates, of embryonic axes excised from recalcitrant seeds. These models are an exponential drying time course, and a modified inverse relationship, respectively. For the six species investigated here the inverse function was generally found to fit drying data better than the exponential function under both rapid and slow drying conditions, and so is recommended. The rate of drying, under the conditions used here, was determined by axis size and possibly the nature of the axis outer coverings, rather than the water activity difference between the tissue and surrounding air.
 

Ntuli TM, Pammenter NW (2009). Dehydration kinetics of embryonic axes from desiccation-sensitive seeds: An assessment of descriptive models. J. Integr. Plant Biol. 51(11), 1002–1007.

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Mobilization and Acquisition of Sparingly Soluble P-Sources by Brassica Cultivars under P-Starved Environment I. Differential Growth Response, P-Efficiency Characteristics and P-Remobilization
Author: Muhammad Shahbaz Akhtar, Yoko Oki and Tadashi Adachi
Journal of Integrative Plant Biology 2009 51(11): 1008-1023
Published Online: November 9, 2009
DOI: 10.1111/j.1744-7909.2009.00874.x
      
    

Phosphorus (P) starvation is highly notorious for limiting plant growth around the globe. To combat P-starvation, plants constantly sense the changes in their environment, and elicit an elegant myriad of plastic responses and rescue strategies to enhance P-solublization and acquisition from bound soil P forms. Relative growth responses, P-solublization and Pacquisition ability of 14 diverse Brassica cultivars grown with sparingly soluble P-sources (Rock-P (RP) and Ca3(PO4)2 (TCP)) were evaluated in a solution culture experiment. Cultivars showed considerable genetic diversity in terms of biomass accumulation, concentration and contents of P and Ca in shoots and roots, P-stress factor (PSF) and P use efficiency. Cultivars showed variable P-stress tolerance, and cultivars depicting low PSF and high P efficiency values were better adaptable to P-starvation. In experiment 2, after initial feeding on optimum nutrition for 12 d after transplanting (DAT), class-I (low P-tolerant (Oscar and Con-II)) and class-II (low P sensitive (Gold Rush and RL-18)) cultivars were exposed to P-free environment for 25 d. All of the cultivars remobilized P from above ground parts to their roots during growth in P-free environment, the magnitude of which was variable in tested cultivars. P-concentrations ([P]s) at 37 DAT were higher in developing compared with developed leaves. Translocation of absorbed P from metabolically inactive to active sites in Pstressed plants may have helped class-I cultivars to establish a better rooting system, which provided a basis for enhanced P-utilization efficiency (PUE) and tolerance against P-stress. By supplying TCP and RP spatially separated from other nutrients in split root study, class-I cultivars were still able to mobilize RP and TCP more efficiently compared with class-II cultivars. To compare the growth behavior under P-stress, cultivars were grown in pots for 41 d after sowing, using a soil low in P (NaHCO3-extractable P = 3.97 mg/kg, Mehlich-III-extractable P = 6.13 mg/kg) with (+P = 60 mg P/kg soil) or without P addition (0P) in study 4. Tested cultivars showed genetic diversity in PUE, P-efficiency (PE), P-efficiency ratio (PER) and PSF. P-stress markedly reduced biomass and plant P contents. Cultivars that produced higher root biomass accumulated higher total P-contents (r = 0.98** ), which in turn was related negatively to PSF (r = −0.95** ) and positively to shoot and total biomass. PER and PE showed significant correlations with shoot P-contents and biomass. Cultivars depicting high PUE and PE, and low PSF values showed better growth behavior under low soil P-environment. Systematic analysis and deployment of the plant rescue traits underlying the nutrient acquisition, assimilation, utilization and remobilization under P-starvation will bring more sparingly soluble P into cropping systems and will help to scavenge more P from plant unavailable bound P reserves.

Shahbaz Akhtar M, Oki Y, Adachi T (2009). Mobilization and acquisition of sparingly soluble P-sources by Brassica cultivars under P-starved environment. I. Differential growth response, P-efficiency characteristics and P-remobilization. J. Integr. Plant Biol. 51(11), 1008–1023.

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Mobilization and Acquisition of Sparingly Soluble P-Sources by Brassica Cultivars under P-Starved Environment II. Rhizospheric pH changes, Redesigned Root Architecture and Pi-Uptake Kinetics
Author: Muhammad Shahbaz Akhtar, Yoko Oki and Tadashi Adachi
Journal of Integrative Plant Biology 2009 51(11): 1024-1039
Published Online: November 9, 2009
DOI: 10.1111/j.1744-7909.2009.00873.x
      
    

Non-mycorrhizal Brassica does not produce specialized root structures such as cluster or dauciform roots but is an effective user of P compared with other crops. In addition to P-uptake, utilization and remobilization activity, acquisition of orthophosphate (Pi) from extracellular sparingly P-sources or unavailable bound P-forms can be enhanced by biochemical rescue mechanisms such copious H+ efflux and/or carboxylates exudation into rhizosphere by roots via plasmalemma H+ ATPase and anion channels triggered by P-starvation. To visualize the dissolution of sparingly soluble Ca-phosphate (Ca-P), newly formed Ca-P was suspended in agar containing other essential nutrients. With NH4+ applied as the N source, the precipitate dissolved in the root vicinity can be ascribed to rhizosphere acidification, whereas no dissolution occurred with nitrate nutrition. To observe in situ rhizospheric pH changes, images were recorded after embedding the roots in agar containing bromocresol purple as a pH indicator. P-tolerant cultivar showed a greater decrease in pH than the sensitive cultivar in the culture media (the appearance of typical patterns of various colors of pH indicator in the root vicinity), and at stress P-level this acidification was more prominent. In experiment 2, low P-tolerant class-I cultivars (Oscar and Con-II) showed a greater decrease in solution media pH than low P-sensitive class-II (Gold Rush and RL-18) cultivars, and P-contents of the cultivars was inversely related to decrease in culture media pH. To elucidate P-stressinduced remodeling and redesigning in a root architectural system, cultivars were grown in rhizoboxes in experiment 3. The elongation rates of primary roots increased as P-supply increased, but the elongation rates of the branched zones of primary roots decreased. The length of the lateral roots and topological index values increased when cultivars were exposed to a P-stress environment. To elucidate Pi-uptake kinetics, parameters related to P influx: maximal transport rate (Vmax), the Michaelis-Menten constant (Km), and the external concentration when net uptake is zero (Cmin) were tested in experiment 4. Lower Km and Cmin values were better indicative of the P-uptake ability of the class-I cultivars, evidencing their adaptability to P-starved environmental cues. In experiment 5, class-I cultivars exuded two- to threefold more carboxylates than class-II cultivars under the P-stress environment. The amount and types of carboxylates exuded from the roots of P-starved plants differed from those of plants grown under P-sufficient conditions. Nevertheless, the exudation rate of both class-I and class-II cultivars decreased with time, and the highest exudation rate was found after the first 4 h of carboxylates collection. Higher P uptake by class-I cultivars was significantly related to the drop in root medium pH, which can be ascribed to H+-efflux from the roots supplied with sparingly soluble rock-P and Ca3(PO4)2. These classical rescue strategies provided the basis of P-solubilization and acquisition from sparingly soluble P-sources by Brassica cultivars to thrive in a typically stressful environment.


Shahbaz Akhtar M, Yoko O, Tadashi A (2009). Mobilization and acquisition of sparingly soluble P-sources by Brassica cultivars under P-starved environment. II. Rhizospheric pH changes, redesigned root architecture and Pi-uptake kinetics. J. Integr. Plant Biol. 51(11), 1024–1039.

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          Molecular Physiology
Substrate Selectivity of Glycerol-3-phosphate Acyl Transferase (GPAT) in Rice  
Author: Su-Qin Zhu, Hua Zhao, Rong Zhou, Ben-Hua Ji and Xiao-Yan Dan
Journal of Integrative Plant Biology 2009 51(11): 1040-1049
Published Online: November 9, 2009
DOI: 10.1111/j.1744-7909.2009.00876.x
      
    

Substrate selectivity of glycerol-3-phosphate acyltransferase (EC 2. 3. 1. 15) of rice (Oryza sativa L.) was explored in a comparative study of acyltransferases from seven plant species. In vitro labeling of acyl  arrier protein (ACP) with 14C or 3H showed that acyltransferase from chill-sensitive plants, such as rice that uses either oleic (18:1) or palmitic acid (16:0) as acyl donor at comparable rates, displays lower selectivity than the enzyme from chill-resistant plants, such as spinach, which preferentially uses oleic acid (18:1) rather than palmitic acid (16:0) as an acyl donor. This may be a result of the size and character of the substrate-binding pocket of acyltransferase. Homology modeling and protein structure-based sequence alignment of acyltransferases revealed that proteins from either chill-sensitive or chill tolerant plants shared a highly conserved domain containing the proposed substrate-binding pocket. However, the aligned residues surrounding the substrate-binding pocket are highly heterogeneous and may have an influence mainly on the size of the substrate binding pockets of acyltransferases. The substrate selectivity of acyltransferase of rice can be improved by enlarging the substrate-binding pocket using molecular biological methods.
 

Zhu SQ, Zhao H, Zhou R, Ji BH, Dan XY (2009). Substrate selectivity of glycerol-3-phosphate acyl transferase in rice. J. Integr. Plant Biol. 51(11), 1040–1049.

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          Molecular Ecology and Evolution
Water Supply Changes N and P Conservation in a Perennial Grass Leymus chinensis
Author: Ju-Ying Huang, Hai-Long Yu, Ling-Hao Li, Zhi-You Yuan and Samuel Bartels
Journal of Integrative Plant Biology 2009 51(11): 1050-1056
Published Online: November 9, 2009
DOI: 10.1111/j.1744-7909.2009.00872.x
      
    

Changes in precipitation can influence soil water and nutrient availability, and thus affect plant nutrient conservation strategies. Better understanding of how nutrient conservation changes with variations in water availability is crucial for predicting the potential influence of global climate change on plant nutrient-use strategy. Here, green-leaf nitrogen (N) and phosphorus (P) concentrations, N- and P resorption proficiency (the terminal N and P concentration in senescent leaves, NRP and PRP, respectively), and N- and P-resorption efficiency (the proportional N and P withdrawn from senescent leaves prior to abscission, NRE and PRE, respectively) of Leymus chinensis (Trin.) Tzvel., a typical perennial grass species in northern China, were examined along a water supply gradient to explore how plant nutrient conservation responds to water change. Increasing water supply at low levels (< 9000 mL/year) increased NRP, PRP and PRE, but decreased green-leaf N concentration. It did not significantly affect green-leaf P concentration or NRE. By contrast, all N and P conservation indicators were not significantly influenced at high water supply levels (> 9000 mL/year). These results indicated that changes in water availability at low levels could affect leaf-level nutrient characteristics, especially for the species in semiarid ecosystems. Therefore, global changes in precipitation may pose effects on plant nutrient economy, and thus on nutrient cycling in the plant-soil systems.
 

Huang JY, Yu HL, Li LH, Yuan ZY, Bartels S (2009). Water supply changes N and P conservation in a perennial grass Leymus chinensis. J. Integr. Plant Biol. 51(11), 1050–1056.

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          Erratum
Erratum
Author:
Journal of Integrative Plant Biology 2009 51(11): 1057-1057
Published Online: November 9, 2009
DOI: 10.1111/j.1744-7909.2009.00889.x
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          Recruitment Notice
Recruitment Notice
Author:
Journal of Integrative Plant Biology 2009 51(11): 1058-1058
Published Online: November 9, 2009
DOI: 10.1111/j.1744-7909.2009.00907.x
      
    

Senior Managing Editor, Journal of Integrative Plant Biology

Journal of Integrative Plant Biology (JIPB) is a monthly plant biological journal that reports scientific iscoveries by using integrative genetic, chemical, cell and molecular biological approaches. As one of iley-Blackwell's leadingjournals, JIPB is available in over 7,800 libraries worldwide and indexed by 45 abases such as PubMed, Google Scholar, SCI, CA, BA and BIOSIS (www.jipb.net). We are looking for a nior Managing Editor to be fully in-charge of the Editorial Office, to work under the supervision of the hief ditor and the board members to promote the journal in the plant science community, to bridge the munication between the editorial board, the reviewers, the authors and the publisher. he ideal candidate hould be creative in increasing the journal’s visibility through organizing special issues, setting up a ser riendly public access system, and ensuring an efficient publication cycle. The annual salary range will be 100,000 RMB to 180,000 RMB, depending on the qualification. This position opens opens for pplication from 1 September, 2009, till the position is filled.

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