Abstract
BackgroundPhysic 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.ResultsIn 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.ConclusionsThis 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0397-x) contains supplementary material, which is available to authorized users.
Highlights
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
All the differentially expressed gene (DEG) were annotated using the results of blastp queries against the NCBI non-redundant protein sequences database and the Arabidopsis Information Resource Proteins database and the results were analyzed in AgBase
The results showed that two NCED genes (JC_C100001845 and JC_C100015061) were significantly up-regulated in roots under drought stress treatments, and two genes in an abscisic acid (ABA) dependent pathway, ABF (JC_C100011364) and RD26 (JC_C100019357), were significantly up-regulated in leaves (Figure 3C)
Summary
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. Following its biosynthesis, ABA acts via a signaling pathway with participants that include receptors of the PYR/PYL family, protein phosphatase 2C (PP2C), Serine/threonine-protein Kinase SRK (SnRK), and ABA Responsive Element Binding Factors (AREBs/ABFs) [10,11]. Downstream of this signaling pathway, the expression of partially responsive to desiccation (RD) genes, RD22, RD26, RD20A, and RD29B, is induced in response to drought in an ABA-dependent manner [6,12]. A number of drought stress induced genes, such as RD29A and ERD1, are ABA-independent [13], and are regulated by the ABAindependent transcription factors DREB2A [14] and members of the NAC and HD-ZIP families of proteins [6,15]
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