Phosphoproteomics of Jatropha curcas seedling under chilling stress

As a promising energy plant for biodiesel, Jatropha curcas is a tropical and subtropical shrub. Chilling is a major abiotic stress affecting the growth and development of J. curcas. In this study, we adopt the phosphoproteomic analysis, physiological measurement, ultrastructure observation to illustrate molecular mechanisms of J. curcas seedling under chilling (4 °C) stress. After chilling for 6 h, 308 significantly changed phosphoproteins were detected in J. curcas seedling without obvious physiological injury. When obvious physiological injury can be observed after chilling for 24 h, a total of 332 phosphoproteins were examined to be significantly changed, after recovery (28 °C) for 24 h, 291 phosphoproteins were varied at the phosphorylation level. The results of Gene Ontology analysis showed that phosphoproteins were mainly responsible for cellular protein modification process, transport, cellular component organization and signal transduction at the chilling and recovery periods. On the basis of protein-protein interaction network analysis, several protein kinases, such as SnRK2 (serine threonine-protein kinase srk2), MEKK1 (mitogen-activated protein kinase kinase kinase 1), EDR1, CDPK (calcium-dependent protein kinase), EIN2 (Ethylene-insensitive protein 2), EIN4, PI4K (phosphatidylinositol 4-kinase alpha 1) and 14-3-3 were possible responsible for cross-talk between ABA, Ca2+, ethylene, phosphoinositide and 14-3-3 mediated signaling pathways. We also highlighted the phosphorylation of HOS1 (E3 ubiquitin-protein ligase HOS1), APX (Cytosolic ascorbate peroxidase-1) and PIP2 (Aquaporin pip2) played vital roles in J. curcas seedling under chilling stress, and they will be valuable in further study form the molecular breeding perspective.