OsC2DP, a Novel C2 Domain-Containing Protein Is Required for Salt Tolerance in Rice

Salt stress is one of the major factors limiting crop production globally, including rice (Oryza sativa). Although a number of genes involved in salt tolerance have been functionally identified, the mechanism underlying salt tolerance in rice is still poorly understood. Here, we reported a novel C2 domain-containing protein, OsC2DP required for salt tolerance in rice. OsC2DP was predominately expressed in the roots and its expression was repressed by salt stress. Transient expression of OsC2DP in rice protoplast cells showed that it was localized in the cytosol. Immunostaining further showed that OsC2DP was able to translocate from the cytosol to plasma membrane under salt conditions. Knockout of OsC2DP did not affect Na+ concentration in the roots, but increased shoot Na+ concentration, resulting in a significant sensitivity of rice to salt stress. Furthermore, the quantitative Real-time PCR and transcriptomic analysis showed that the expression level of some genes related to salt tolerance were indirectly regulated by OsC2DP, especially OsSOS1 and OsNHX4. These results indicate that OsC2DP has an important role in salt tolerance and these findings provide new insights into the regulation of OsC2DP gene for rice breeding with high salt tolerance.

OsSLI1, a Homeodomain Containing Transcription Activator, Involves Abscisic Acid Related Stress Response in Rice (Oryza sativaL.)

Homeodomain-leucine zipper type I (HD-Zip I) proteins are involved in the regulation of plant development and response to environmental stresses. In this study,OsSLI1(Oryza sativa stress largely induced 1), encoding a member of the HD-Zip I subfamily, was isolated from rice. The expression ofOsSLI1was dramatically induced by multiple abiotic stresses and exogenous abscisic acid (ABA).In silicosequence analysis discovered severalcis-acting elements including multiple ABREs (ABA-responsive element binding factors) in the upstream promoter region ofOsSLI1. The OsSLI1-GFP fusion protein was localized in the nucleus of rice protoplast cells and the transcriptional activity of OsSLI1 was confirmed by the yeast hybrid system. Further, it was found thatOsSLI1expression was enhanced in anABI5-Like1(ABL1) deficiency rice mutantabl1under stress conditions, suggesting that ABL1 probably negatively regulatesOsSLI1gene expression. Moreover, it was found thatOsSLI1was regulated in panicle development. Taken together,OsSLI1may be a transcriptional activator regulating stress-responsive gene expression and panicle development in rice.

Study on the Subcellular Localization of GAPDH in Rice (Oryza sativa)

The glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is considered to be a housekeeping glycolytic enzyme that catalyzes an important energy-yielding step in carbohydrate metabolism in the cytoplasm. However, GAPDH participates in several other biological activities via the changes of its subcellular localization, which depends largely on the modifications of its catalytic active site Cys residue. In this study, we demonstrated that the active site mutation C154S induced the cytoplasmic accumulation of GAPDH, whereas the wild type was present mainly in the cytoplasm. However, the C-terminal truncated mutant of GAPC, GAPC△C-GFP was present mainly in nuclei in rice protoplast. The further interaction analysis indicated that the GAPC△C disrupted the dimeric GAPC formation, may thus, facilitating its nuclear localization. The result suggested that the nuclear translocation of GAPDH also depends on its oligomeric forms in rice.