title: Global analysis of gene expression profiles in physic nut (Jatropha curcas L.) seedlings exposed to drought stress.
abstract: BACKGROUND
  Physic nut (Jatropha curcas L.) is a small perennial tree or large shrub, which is well-adapted to semi-arid regions and is considered to have potential as a crop for biofuel production. It is now regarded as an excellent model for studying biofuel plants. However, our knowledge about the molecular responses of this species to drought stress is currently limited.
  
  
  RESULTS
  In this study, genome-wide transcriptional profiles of roots and leaves of 8-week old physic nut seedlings were analyzed 1, 4 and 7 days after withholding irrigation. We observed a total of 1533 and 2900 differentially expressed genes (DEGs) in roots and leaves, respectively. Gene Ontology analysis showed that the biological processes enriched in droughted plants relative to unstressed plants were related to biosynthesis, transport, nucleobase-containing compounds, and cellular protein modification. The genes found to be up-regulated in roots were related to abscisic acid (ABA) synthesis and ABA signal transduction, and to the synthesis of raffinose. Genes related to ABA signal transduction, and to trehalose and raffinose synthesis, were up-regulated in leaves. Endoplasmic reticulum (ER) stress response genes were significantly up-regulated in leaves under drought stress, while a number of genes related to wax biosynthesis were also up-regulated in leaves. Genes related to unsaturated fatty acid biosynthesis were down-regulated and polyunsaturated fatty acids were significantly reduced in leaves 7 days after withholding irrigation. As drought stress increased, genes related to ethylene synthesis, ethylene signal transduction and chlorophyll degradation were up-regulated, and the chlorophyll content of leaves was significantly reduced by 7 days after withholding irrigation.
  
  
  CONCLUSIONS
  This study provides us with new insights to increase our understanding of the response mechanisms deployed by physic nut seedlings under drought stress. The genes and pathways identified in this study also provide much information of potential value for germplasm improvement and breeding for drought resistance.
authors.affiliation: Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China. ahzc2009@163.com.|University of Chinese Academy of Sciences, Beijing, 100049, China. ahzc2009@163.com.
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China. zlhelen@163.com.|Department of Environmental Engineering and Chemistry, Luoyang Institute of Science and Technology, Luoyang, 471023, China. zlhelen@163.com.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Biology, South University of Science and Technology of China, Shenzhen, 518055, China. zhangshenglao@126.com.
authors.forename: Sheng
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China. zhushuang611@163.com.|University of Chinese Academy of Sciences, Beijing, 100049, China. zhushuang611@163.com.
authors.forename: Shuang
authors.initials: S
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China. pzwu@scbg.ac.cn.
authors.forename: Pingzhi
authors.initials: P
authors.lastname: Wu
authors.affiliation: Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China. chenyp@scbg.ac.cn.
authors.forename: Yaping
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China. limr@scbg.ac.cn.
authors.forename: Meiru
authors.initials: M
authors.lastname: Li
authors.affiliation: Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China. hwjiang@scib.ac.cn.
authors.forename: Huawu
authors.initials: H
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China. wugj@scbg.ac.cn.
authors.forename: Guojiang
authors.initials: G
authors.lastname: Wu
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D057914:Agricultural Irrigation; D002734:Chlorophyll / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D055864:Droughts; D005227:Fatty Acids / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D063990:Gene Ontology; D017343:Genes, Plant; D031286:Jatropha / Q000235:genetics*; D018515:Plant Leaves / Q000235:genetics; D011392:Proline / Q000378:metabolism; D011887:Raffinose / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D036226:Seedlings / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics; D013312:Stress, Physiological / Q000235:genetics*; D014199:Trehalose / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics
chemical_list: D005227:Fatty Acids; D002734:Chlorophyll; D000040:Abscisic Acid; D011392:Proline; D014199:Trehalose; D011887:Raffinose