Overexpression of a constitutively active truncated form of OsCDPK1 confers disease resistance by affecting OsPR10a expression in rice.

The rice pathogenesis-related protein OsPR10a was scarcely expressed in OsCDPK1-silenced (Ri-1) rice, which was highly sensitive to pathogen infection. After inoculating the leaves with bacterial blight (Xanthomonas oryzae pv. oryzae; Xoo), we found that the expression of OsPR10a was up- and down-regulated in OEtr-1 (overexpression of the constitutively active truncated form of OsCDPK1) and Ri-1 rice plants, respectively. OsPR10a and OsCDPK1 showed corresponding expression patterns and were up-regulated in response to the jasmonic acid, salicylic acid and Xoo treatments, and OsPR1 and OsPR4 were significantly up-regulated in OEtr-1. These results suggest that OsCDPK1 may be an upstream regulator involved in rice innate immunity and conferred broad-spectrum of disease resistance. Following the Xoo inoculation, the OEtr-1 and Ri-1 seedlings showed enhanced and reduced disease resistance, respectively. The dihybrid rice Ri-1/OsPR10a-Ox not only bypassed the effect of OsCDPK1 silencing on the susceptibility to Xoo but also showed enhanced disease resistance and, consistent with Ri-1 phenotypes, increased plant height and grain size. Our results reveal that OsCDPK1 plays novel key roles in the cross-talk and mediation of the balance between stress response and development and provides a clue for improving grain yield and disease resistance simultaneously in rice.