November 2013 issue | Plant Omics Journal

Metabolite profiling reveals the effect of drought on sorghum (Sorghum bicolor L. Moench) metabolism

Ourania I. Pavli*¹, Christos E. Vlachos¹, Chrysanthi Kalloniati², Emmanouil Flemetakis², George N. Skaracis¹
¹Laboratory of Plant Breeding and Biometry, Department of Crop Science, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece
²Laboratory of Molecular Biology, Department of Agricultural Biotechnology, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece

Abstract
Plants exposed to limited water availability respond with a series of developmental, morphological, biochemical and molecular adaptations, aiming at safeguarding basal levels of metabolic activity. Given that sorghum (Sorghum bicolor L. Moench) is regarded as a drought-tolerant species, it provides an ideal model to study the molecular and physiological mechanisms underlying such tolerance. Young sorghum seedlings grown under controlled conditions were subjected to drought stress, induced by polyethylene glycol (PEG) 6000 at two levels of stress (2.5% and 5% PEG), for 7 days. Non-stressed plants were also included as controls. Metabolite profiling on leaves and roots of stressed and control plants was performed by Gas-chromatography combined with Mass-spectrometry (GC-MS). For each treatment and tissue type, four biological replications were conducted. In total, the analysis yielded 143 quantifiable compounds with highly reproducible patterns. Comparative metabolite profiling of stressed versus control plants revealed that drought stress substantially alters the metabolite content in both leaves and roots. In leaves, most profound alterations were observed in compounds belonging to the group of sugars, including D-mannose, D-glucose, isomaltose, fructose and sucrose, but also myo-inositol and L-asparagine whereas in roots, most influencing compounds were certain sugars, such as D-glucose, fructose, sucrose and D-(+)trehalose, as well as D-mannitol. Deduced metabolomics data are discussed and suggested as functional tools towards understanding the underlying regulatory networks involved in the physiology of drought tolerance in sorghum.

Pages 371-376 | Full Text PDF | Supplementary data

Pivotal metabolic pathways related to water deficit tolerance and growth recovery of whole maize plant

Chang-Bin Sun, Xian-Wei Fan, Hai-Yang Hu, Yu Liang, Zhang-Bao Huang, Jian-Long Pan, Liang Wang, and You-Zhi Li^*

Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering; State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources; College of Life Science and Technology, Guangxi University; Nanning, Guangxi 530005, P. R. China

Abstract
Tolerance to water deficit as well as growth recovery from water deficit by re-watering are two important and inseparable processes for maize survival. However, details of metabolic mechanisms are unknown and still need to be filled. Leaf water potential and photosynthetic parameters of three-leaf-stage seedlings of maize inbred line Huangzao 4 under progressive water deficit and re-watering were measured, and metabolites of the seedlings under the corresponding treatments were identified and subjected to analyses of hierarchical cluster, principal component and self-organizing mapping. A total of 142 polar metabolites, 127 in leaves and 125 in roots, were identified, including 13 amino acids, 17 organic acids, 8 sugars, 2 sugar alcohols, and 4 others, of which 85 in leaves and 53 in roots showed a significant change in metabolic level under water deficit. Fifty-nine metabolites had a significant change in metabolic level under re-watering, the majority of which were organic acids and anmino acids. In conclusion, there is a significant crosstalk of metabolisms between water deficit tolerance and growth recovery under re-watering, with glycolysis, starch and protein degradation as pivotal pathways; metabolic level changes in the roots are to maximize water uptake whereas the changes in the leaves are to prevent water loss and to increase water-use efficiency; water deficit tolerance depends on metabolic level-controlled balance between the networks; and maize uses an emergency repair mechanism for growth recovery. The results give informative clues to address the mechanisms of maize water deficit tolerance and growth recovery at the metabolic level.

Pages 377-387 | Full Text PDF | Supplementary data

The prediction of protein-protein interaction of A. thaliana and X. campestris pv. campestris based on protein domain and interolog approaches

Nilubon Kurubanjerdjit^1,2, Jeffrey J.P Tsai¹, Chen-Yu Sheu^{1, 3}, Ka-Lok Ng^{1, 4 *}
¹Department of Biomedical Informatics, Asia University, 41354 Taiwan
²School of Information Technology, Mea Fah Luang University, 57100. Thailand
³Department of Electrical Engineering and Computer Science, University of California, Irvine, USA
⁴School of Pharmacy, China Medical University, Taichung, Taiwan 40402
Abstract
Plant pathogenic bacteria cause many serious disease symptoms by injecting a variety of effector proteins to reprogram the host defense mechanism. Protein-protein interaction is an essential process playing a crucial role in host-pathogen interactions and pathogenicity. However few have been known for how pathogen bacteria interact with their hosts. In this study, the interactions of A. thaliana proteins and Xanthomonas campestris pv.campestris (Xcc) pathogen bacteria proteins are identified by two different approaches: the domain-based approach which infers interspecies protein-protein interactions by known domain-domain interactions recorded by various databases; and the interolog approach that identifies protein-protein interactions based on homologous pairs of protein interactions across different organisms. The results from these two methods are integrated and the densely protein interaction regions are specified by clique percolation analysis. In particular, the plant resistance genes (PRG) information and the bacterial effector proteins are studied to provide new insights into the molecular mechanism of plant immunity systems against bacteria. From our findings, we demonstrate that a pathogen employs five strategies to reprogram the host defense mechanism. First, ome Xcc proteins tend to interact with A. thaliana’s hub proteins or the PRGs. Second, Xcc proteins tend to interact with many A. thaliana proteins indicating that a pathogen mutates its genes to infect the host. Third, some Xcc proteins target a group of A. thaliana proteins that are involved in responding to cadmium ions, a significant plant biological process against pathogen. Fourth, many Xcc proteins target a few A. thaliana proteins which are involved in the plant-pathogen interaction pathways. Finally, the pathogen may make use of a type III effector protein to reprogram the host protein-protein interactions. Host-pathogen interactions remain a largely unexplored area in computational biology. The present work may provide some key information useful for revealing the biological mechanism of a plant’s immune system against bacteria. A web-based interface has been established (<http://ppi.bioinfo.asia.edu.tw/AtXccPPI>) where investigators can pose queries.

Pages 388-398 | Full Text PDF

The oil palm stearoyl-acyl-carrier-protein desaturase (Des) promoter drives transient gene expression in tomato fruits and is affected by gibberellic acid

Siow Li Leong¹, Ismanizan Ismail^1,3*, Rima Saed Taha¹, Zamri Zainal^1,3,Siti Nor Akmar Abdullah^2,4
¹School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
²Department of Agriculture, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
³Institute of Systems Biology (INBIOSIS), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
⁴Laboratory of Plantation Crops, Institute of Tropical Agriculture, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia

Abstract
Stearoyl-acyl-carrier-protein (ACP) desaturase gene plays an important role in oil palm mesocarp where main substrate stearic acid is converted to oleic acid. In this study, ß-glucuronidase (GUS) activity regulated by the oil palm stearoyl-ACP desaturase promoter (Des) and the effects of gibberellic acid (GA₃) treatment on promoter activation were evaluated in transgenic tomato. A high level of GUS activity in transformed tomato (Solanum lycopersicum) revealed that Des promoter is active in heterologous system. With histochemical assays, we detected GUS activity in all of the agroinfiltrated tomato tissues. Fluorometric GUS assays indicated that the GUS activity was markedly higher when regulated by the Des promoter constructs in comparison with the CaMV 35S promoter. The analysis of 5’-deletion of the Des promoter indicated that the GUS activity driven by a 590-bp region were approximately 1.2-fold stronger than that of the full-length Des promoter. Semi-quantitative reverse transcriptase PCR results also showed that the 590-bp region of Des promoter directed the highest level of uidA expression. The GUS activity of Des1-transformed tomato mesocarp was induced by 1.7-fold, whereas the expression driven by the shortest promoter fragment of Des4 was reduced by 1.9-fold following incubation with 10 µM GA₃. These results suggest that gibberellic acid-responsive elements reside within the region between nt -590 and nt -306 of the Des promoter, and based on our 5’-deletion analysis, the cis-element(s) necessary for strong promoter activity is also located within the region from -590 to -306 from the transcriptional start site. The oil palm Des promoter was activated by GA₃and is potentially useful for engineering fruit-specific gene expression to enhance quality of fruits.

Pages 399-407 | Full Text PDF

Transient overexpression of the Miscanthus sinensis glucose-6-phosphate isomerase gene (MsGPI) in Nicotiana benthamiana enhances expression of genes related to antioxidant metabolism

Eun Soo Seong¹, Ji Hye Yoo², Jae Geun Lee¹, Hee Young Kim², In Seong Hwang², Kweon Heo², Jung Dae Lim³, D. K. Lee⁴ , E. J. Sacks⁴, Chang Yeon Yu²
¹Bioherb Research Institute, Kangwon National University, Chuncheon 200-701, South Korea
²Department of Applied Plant Sciences, College of Agriculture and Life Science, Kangwon National University, Chuncheon 200-701, South Korea
³Department of Herbal Medicine Resource, Kangwon National University, Samcheok 245-907, South Korea
⁴Department of Crop Sciences, College of ACES, University of Illinois at Urbana-Champaign, IL 61801, USA

Abstract
We investigated the expression of genes related to antioxidant mechanisms through transient overexpression of the glucose-6-phosphate isomerase (GPI) gene of Miscanthus sinensis in Nicotiana benthamiana leaves. Full-length cDNA was isolated from M. sinensis GPI (MsGPI). An analysis of the MsGPI amino acid sequence revealed significant similarities to the GPIs of Festuca ovima (94%), Hordium vulgare (94%), Triticum aestivum (94%), and Zea mays (97%). RT-PCR showed that MsGPI expression was induced significantly by NaCl. Transient M. sinensis GPI sense construct overexpression resulted in increased N. benthamiana ascorbate peroxidase (NbAPX) and phenylalanine ammonia lyase (NbPAL) transcript levels in N. benthamiana leaves. These observations suggest that MsGPI is involved in antioxidant metabolism and that it is a transcriptional regulator of NbAPX and NbPAL.

Pages 408-414 | Full Text PDF

Identification and expression analysis of the heat shock transcription factor (HSF) gene family in Populus trichocarpa

Haizhen Zhang, Jingli Yang, Yunlin Chen, Xuliang Mao, Zhanchao Wang, Chenghao Li^*

State Key Laboratory of Forest Genetics and Tree Breeding, Northeast Forestry University, 26 Hexing Road, Harbin 150040, China

Abstract
In plants, heat shock transcription factors (HSFs) play key roles in regulating the heat shock (HS) response. Therefore, the genes encoding HSFs are important for adaptation to high temperatures and for tolerance to other abiotic stresses. There have been many studies on these genes in herbaceous plants, but few on the HSF family in woody plants. In this study, we identified 31 HSF genes in Populus trichocarpa and investigated their phylogenetic relationships with HSF genes in Arabidopsis and rice. Analyses of chromosomal duplications revealed that tandem/segmental duplications contributed to the expansion of the HSF gene family in P. trichocarpa. Gene structure was analyzed by investigating exon/intron organization and by using the MEME motif finder. Changes in gene expression were investigated using exPlot and digital northern analyses. Interestingly, nine of the HSF genes showed significant variations in expression patterns, suggesting that they have roles in stress responses. We evaluated changes in the transcript levels of the HSFs in response to abiotic stresses (heat, cadmium, salt, abscisic acid, and drought stresses) by analyzing log₂ fold change data. The transcript levels of the PoptrHSFA4a, PoptrHSFA4b and PoptrHSFA5a genes markedly increased in response to a wide range of stresses. The results of this study provide further information for cloning and expression of HSF genes, and for functional studies on the roles of these genes during development and in the responses to various environmental stimuli. Our results may help researchers design more efficient strategies to study the P. trichocarpa HSF family.

Pages 415-424 | Full Text PDF | Supplementary data

Genome-wide analysis of IQ67 domain (IQD) gene families in Brachypodium distachyon

Ertugrul Filiz¹*, Huseyin Tombuloglu², Ibrahim Ilker Ozyigit³
1Department of Crop and Animal Production, Cilimli Vocational School, Duzce University, 81750, Cilimli, Duzce, Turkey
²Fatih University, Faculty of Science and Arts, Department of Biology, 34500, Buyukcekmece, Istanbul, Turkey
³Marmara University, Faculty of Science and Arts, Department of Biology, 34722, Goztepe, Istanbul, Turkey

Abstract
In plants, Ca²⁺concentrationis important for the regulation of developmental processes and responses against biotic and abiotic stress factors. The eukaryotic Ca²⁺ binding protein calmodulin (CaM: CALcium MODULating proteIN) was found in Arabidopsis which contains a characteristic plant-specific IQ67 (Ile, Glu) domain (IQD). In this study, a genome wide analysis was performed in Bracyhpodium distachyon to identify IQD genes. Using several bioinformatics tools, we determined 23 BdIQD genes which were distributed on all chromosomes and the highest gene number was detected on chromosome 2 including 12 IQD genes. 22 of the predicted proteins were considered to be basic proteins. Gene duplication analysis revealed that 8 of 23 BdIQD genes were involved in duplication event, either segmental or tandem. Phylogenetic analysis showed that two main groups were observed in joined tree with rice and Arabidopsis. Especially, monocot species (Brachypodium and rice) were grouped together with the highest bootstrap value (100%), whereas monocot and dicot species (Arabidopsis) were clustered with lower bootstrap values. Digital expression profile analysis indicated that the most of the BdIQD genes were expressed in leaves (8 genes) and flowers (6 genes), respectively. In conclusion, this comparative genomics analysis contributes to understanding IQD genes in grass species.

Pages 425-432 | Full Text PDF | Supplementary data

In silico comparative analysis of LEA (Late Embryogenesis Abundant) proteins in Brachypodium distachyon L.

Ertugrul Filiz*¹, Ibrahim Ilker Ozyigit², Huseyin Tombuloglu³, Ibrahim Koc⁴1Duzce University, Cilimli Vocational School, Department of Crop and Animal Production, 81750, Duzce, Turkey
²Marmara University, Faculty of Science and Arts, Department of Biology, 34722, Goztepe, Istanbul, Turkey
³Fatih University, Faculty of Science and Arts, Department of Biology, 34500, Buyukcekmece, Istanbul, Turkey
⁴Gebze Institute of Technology, Faculty of Science, Department of Molecular Biology and Genetics, 41400, Gebze, Kocaeli, Turkey

Abstract
The Late Embryogenesis Abundant (LEA) proteins in plants are basically related with water deficiency. Recent studies showed that LEA proteins might be molecular chaperones regulating many physiological functions. In this study, LEA proteins were analyzed in model grass Brachypodium distachyon L. The data represented here may help to further analyze the LEA genes in model grass Brachypodium in order to understand their functions especially under conditions of water deficiency and/or other physiological mechanisms. By using the Pfam database, proteins containing at least one LEA conserved repeat (LEA2, LEA3, LEA4, LEA5, and LEA6) were classified as LEA family members. According to these results, 36 LEA proteins were identified in B. distachyon. LEA2 repeat was found as the dominant protein among 28 members followed by LEA3 (5 members). Physicochemical analysis showed that pI values and GRAVY index ranged from 4.40 to 11.1 and 0.48 to -1.423, respectively. Many LEA proteins were considered as basic character (26 members, 72.2%), while 10 proteins (27.8%) were in acidic form. Moreover, GRAVY index revealed that 19 of the 36 sequences were considered hydrophobic (52.8%) while others were hydrophilic (47.2%). Comparative phylogenetic analysis revealed that BdLEA proteins fall into eight subgroups. They were basically divided into two main groups. Chromosomal distribution of LEA genes was determined and segmental and tandem duplications were found in eight genes which may cause expansions of LEA genes through the Brachypodium genome. These results can be helpful for the further functional analysis of LEA proteins in Brachypodium.

Pages 433-440 | Full Text PDF | Supplementary data

Assemblages of endophytic bacteria in chili pepper (Capsicum annuum L.) and their antifungal activity against phytopathogens in vitro

Narayan Chandra Paul¹, Seung Hyun Ji¹, Jian Xin Deng^1,2and Seung Hun Yu^1*¹Department of Agricultural Biology, College of Agriculture and Life Sciences, Chungnam National University, Daejeon 305-764, Republic of Korea
²Department of Plant Protection, College of Agriculture, Yangtze University, Jingzhou 434025, China

Abstract
Endophytic bacteria which show antagonism against phytopathogens were isolated from healthy tissues of leaves, stems and roots of chili pepper plants (Capsicum annum L.) in 2010-2011. Antifungal activities of all collected isolates were tested against plant pathogens by dual culture method. Pathogenic fungi used in this study were Alternaria panax, Botrytis cinerea, Colletrotichum acutatum, Fusarium oxysporum and Phytophthora capsici. A total of 283 bacteria were recovered and grouped into 44 morpho-groups by observing the morphology on nutrient agar media. The isolation rate of endophytic bacteria in leaf, stem and root samples were 4.9%, 44.9% & 50.2%, respectively. 16S rDNA gene sequence analysis detected fourteen distinctive bacterial genotypes at >97% sequence similarity threshold. The most abundant genus was Pseudomonas followed by Bacillus and Burkholderia. A diverse range of other bacterial taxa were isolated and identified- Actinobacter, Arthrobacter, Enterobacter, Escherichia, Kitasatospora, Pandoraea, Pantoea, Rhizobium, Ralstonia, Paenibacillus, and Serratia. Dual culture antifungal activity indicated that 22 bacterial isolates (12%) inhibited at least one pathogenic fungus tested. Bacillus tequilensis (CNU082075), Burkholderia cepacia (CNU082111), Pseudomonas aeruginosa (CNU082137 and CNU082142) showed antifungal activity against all tested fungi. Crude extracts of selected isolates showed antifungal activity against Botrytis cinerea and among others the isolate CNU082111 performed strongest antifungal activity (inhibition zone >55 mm) by paper disk method.

Pages 441-448 | Full Text PDF

Genome-wide identification and analysis of heat shock transcription factor family in cucumber (Cucumis sativus L.)

Shengjun Zhou^1*, Peng Zhang¹, Zange Jing², Jianlei Shi²
¹Institute of Vegetables, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, People’s Republic of China
²Southern Zhejiang Key Laboratory of Crop Breeding, Department of Agriculture and Biotechnology, Wenzhou Vocational College of Science and Technology, Wenzhou 325006, People’s Republic of China

Abstract
Heat shock transcription factor (HSF) plays an important role in the expression regulation of thermal response genes in plants. However, little is known about this family in cucumber. Recently, the availability of cucumber genome sequences has provided an opportunity for identifying these Hsfs. In the present study, all members of the HSF gene family of cucumber (Cucumis sativus L.) were identified from the sequenced genome and analyzed in silico. We identified at least 21 HSF genes in the cucumber, which encode proteins with length between 184 and 560 amino acids. Multiple sequence alignments showed that cucumber HSF proteins possess highly conserved DNA binding domains and other extensively conserved motifs. These HSF genes are unevenly distributed in all seven chromosomes, with chromosomes 2 and 3 both having the greatest number of HSF genes. In addition, phylogenetic analysis of the HSFs from cucumber and Arabidopsis thaliana showed that these proteins could be divided into three families (A, B and C). The A family was then further divided into nine subfamilies, and there were eight pairs of orthologous genes and five pairs of paralogous genes. HSF members in some subfamilies were from cucumber and Arabidopsis, indicating that the HSF gene family existed before the separation of cucumber and Arabidopsis thaliana.

Pages 449-455 | Full Text PDF

Comparative proteomics analysis of seed coat from two black colored soybean cultivars during seed development

Yu Ji Kim¹, Su-ji Lee¹, Hye Min Lee¹, Byong Won Lee², Tae Joung Ha², Dong Won Bae³, Beom-Young Son⁴, Yul Ho Kim⁴, Seong-Bum Baek⁴, Yong Chul Kim¹, Sang Gon Kim^4,*, Sun Tae Kim^1,*
1Department of Plant Bioscience, Pusan National University, Miryang, 627-707, South Korea
²Department of Functional Crops, NICS, RDA, Miryang 627-803, South Korea
³Center for Research Facility, Gyeongsang National University, Jinju 660-701, South Korea
⁴National Institute of Crop Science, Rural Development Administration, Suwon 441-857, South Korea

Abstract
The seed coat plays an important role in the life cycle of soybean by controlling embryo development and determining seed dormancy and germination. In the present study, comparative proteomics analysis of the seed-coat from two black-colored soybean cultivars, Seonheuk and Geomjeong 2 which have different anthocyanin and isoflavone contents, was conducted. Two-dimensional gel electrophoresis (2-DE) coupled with matrix-assisted laser desorption/ionization-time of flight time of flight (MALDI-TOF/TOF) mass spectrometry analysis of total proteins from seed coats identified 36 proteins spots showing qualitative variation according to color changing stages of seed coat. Among them, 24 proteins were down regulated, while 11 were up regulated at stage 2 and 3 compared to stage 1. In addition, ten of the 36 protein spots may be differentially regulated by different contents of anthocyanin and isoflavone between Seonheuk and Geomjeong 2 at color changing stage of seed coat. Interestingly, the expression of trypsin inhibitors (TIs) and manganese superoxide dismutase (MnSOD) showed a greater reduction in Geomjeong 2 than Seonheuk, while isoflavone reductase homolog 1 (IFR1) showed a greater increase in Geomjeong 2 than Seouheuk, indicating that antioxidant activity of Geomjeong 2 may be higher than Seouheuk. Furthermore, their expression patterns were confirmed by Western blot analysis using rice isoflavone reductase-like protein (OsIRL), confirming the results of 2-DE. Overall, our results indicate that various proteins differentially expressed in accordance with seed-coat color may contribute to seed quality and; therefore, have a beneficial effect on human health.

Pages 456-463 | Full Text PDF

Global characterization of Arabidopsis protein interactome

Jian Yang, Jiabin Wang, Yuling Hu, Yiheng Tang, Xugang Hou, Xiao Li*

College of Life Science, Sichuan University, Key Laboratory of Resource Biology and Eco-environment, Ministry of Education, Sichuan Key Laboratory of Molecular Biology and Biotechnology, Chengdu, 610064, China

Abstract
The network of all protein-protein interactions (PPIs) in an organism, named as the interactome, is a powerful tool for understanding biological processes as an integrated system. Studies in several model species indicate that interactomes exhibit some unique features, such as the scale-free topology and the correlations with genomic information. Here we constructed an Arabidopsis interactome comprised of high-quality protein interactions from several publicly available databases. The interactome contained a total of 3,432 distinct PPIs, among 1,679 proteins identified uniquely by genome locus IDs. The analysis showed that the Arabidopsis interactome shares similar features with those of model organisms at the global level, but also exhibits a local divergence. We found that two interacting proteins show a much higher level of co-localization than randomly-selected protein pairs. Our investigation also indicates that there is a significant correlation between interacting proteins and biological functions. Interactome comparison between Arabidopsis and non-plant species showed that protein complexes involved in the core biological processes may undergo more evolutionary pressure to remain conserved. To facilitate the plant focused research, we also constructed a database server called PlaPID (Plant Protein Interaction Database). It is an integrative information platform for system-level understanding of gene function and biological processes in plant and is free to access at http:www.plapid.net.

Pages 464-473 | Full Text PDF | Supplementary data PDF | xls

Review article

Zinc finger protein (ZFP) in plants-A review

Wei-Tao Li*, Min He, Jing Wang, Yu-Ping Wang

Rice Research Institute, Sichuan Agricultural University, Wenjiang, Sichuan, 611130, China

Abstract
Zinc finger protein (ZFP) possesses one or more ‘zinc finger’ that bond one or more zinc ions by its residues Histidine (His) and Cysteine (Cys). ZFP also belongs to a large family of transcription factor. It plays many important regulatory roles in plants. Here, we explained that the percentage of ZFP transcription factor in total transcription factors is similar among plant species. The ZFP functions were implicated in development, growth, stress response and phytohormone responses based on the conclusion of four ZFP families, C2H2, CCCH, C3HC4 and C4. Meanwhile, there was one main function in each ZFP family. On the basis of analyses of the ZFP gene expression in the CCCH family of rice, the regulation controlled by rice ZFP in various tissues was significantly related with each other, as well as in responses to different abiotic stresses. Expression of some rice tissues-specific ZFP genes was significantly related to abiotic or biotic stresses.

Pages 474-480 | Full Text PDF | Supplementary data

Improved drought tolerance through drought preconditioning associated with changes in antioxidant enzyme activities, gene expression and osmoregulatory solutes accumulation in White clover (Trifolium repens L.)

Zhou Li, Peng Shi and Yan Peng*

College of Animal Science and Technology, Sichuan Agricultural University, Ya’an 625014, China

Abstract
Improving drought tolerance through drought preconditioning is an important way to understand drought tolerance mechanism in plants. Some limited researches have focused on the gene expression patterns in conjunction with the underlying enzymes promoting drought tolerance and post-drought recovery in white clover. The objective of this study was to identify whether preconditioning-induced drought tolerance is in relation to changes of antioxidant enzyme activities, gene expression and osmoregulatory solutes in white clover. Plants of white clover cultivar, ‘Chuanyin Ladino’ (drought sensitive), were exposed to two cycles of drought preconditioning (non-preconditioned, well-watered plants, as a control) then exposed to drought stress for 11 days and rewatered for 6 days in a growth chamber with 14 h photoperiod at day/night temperature of 21/16 °C, 70 % relative humidity, and 300 µmol m^-2 s^-1photosynthetic photon flux density. Results showed that drought preconditioning improved drought tolerance and post-drought recovery in white clover, as demonstrated by significantly lower (p=0.05) lipid peroxidation, better cell membrane stability and higher relative water content in drought-preconditioned plants as compared to non-preconditioned plants under drought stress and rewatering. Drought-preconditioned plants exhibited higher superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and guaiacol peroxidase activities (POD), as well as higher transcript level of Cu/Zn SOD gene. Meanwhile, more accumulation of soluble sugars and betain and less accumulated proline were also observed in preconditioned plants. Enhanced antioxidant enzyme activities and significantly higher transcript level of Cu/Zn SOD gene may be the critical reasons in acquiring drought tolerance through drought preconditioning. This study also suggests that drought preconditioning improved white clover drought tolerance, which could be related to more accumulation of soluble sugars and betain, while the accumulated proline is associated with the degree of drought stress injury in white clover.

Pages 481-489 | Full Text PDF