The MYB family is one of the most abundant transcription factor families in plants. MYB proteins are involved in plant development, abiotic stress tolerance, hormone signal transduction and disease resistance. Here we perform genome-wide identification of MYB family transcription factors in an energy plant J. curcas, including determining family composition, phylogenetic evolution and functional prediction analysis. In addition, we further elucidate the function of the JcMYB2 gene. The phylogenetic trees were constructed by using the neighbor-joining method in MEGA 5.2. The biological functions of some JcMYBs were predicted according to orthology. The full length cDNA of JcMYB2 was cloned by using the RACE method. GUS histochemical staining was used to test the activity of the JcMYB2 promoter. Expression patterns of JcMYB2 were detected by using qPCR Transcriptional activity JcMYB2 were confirmed through yeast one hybrid. Subcellular Localization of JcMYB2 Protein were demonstrated by transient expression in the tobacco leaf. The function of JcMYB2 in salt and freezing tolerance were detected in transgenic plants. A genome-wide analysis identified 128 MYB genes, including 123 R2R3-MYBs, 4 R1R2R3-MYBs and 1 4R-MYB. All of the R2R3-MYBs are further classified into 19 groups which indicated functional conservation among previously identified groups of R2R3-MYB proteins. Among of these newly identified MYBs, the JcMYB2 belongs to group G11 and its expression is induced obviously by cold, salt and MeJA (Methyl Jasmonate) and slightly by ABA (abscisic acid). JcMYB2 is localized to the nucleus and has transcriptional activity. JcMYB2 overexpressing plants are more tolerant to salt and cold stress than wild type plants. Tissue specific expression profiles showed that the JcMYB2 gene was expressed ubiquitously throughout the plant, with higher expression levels observed in the root. A comprehensive genome-wide analysis and phylogenetic relationship of R2R3-MYB subfamily in J. curcas present the global identification and functional prediction of JcR2R3-MYBs. Additionally, JcMYB2 regulates the stress response signaling networks by interacting with MeJA and ABA signaling pathway and functions in the root development of J. curcas.

As a promising energy plant for biodiesel, Jatropha curcas is a tropical and subtropical shrub and its growth is affected by one of major abiotic stress, chilling. Therefore, we adopt the phosphoproteomic analysis, physiological measurement and ultrastructure observation to illustrate the responsive mechanism of J. curcas seedling under chilling (4 °C) stress. After chilling for 6 h, 308 significantly changed phosphoproteins were detected. Prolonged the chilling treatment for 24 h, obvious physiological injury can be observed and 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. GO analysis showed that significantly changed 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, phosphorylation of several protein kinases, such as SnRK2, MEKK1, EDR1, CDPK, EIN2, EIN4, PI4K and 14-3-3 were possibly responsible for cross-talk between ABA, Ca²⁺, ethylene and phosphoinositide mediated signaling pathways. We also highlighted the phosphorylation of HOS1, APX and PIP2 might be associated with response to chilling stress in J. curcas seedling. These results will be valuable for further study from the molecular breeding perspective.