Role of cin-miR2118 in drought stress responses in Caragana intermedia and Tobacco.

The miR2118 is highly conserved in leguminous plants. Its function is to regulate the expression of genes encoding the TIR-NBS-LRR resistance protein. In this study, cin-miR2118 from Caragana intermedia was functionally characterized, especially with regard to its role in drought stress resistance. Two target genes of cin-miR2118 were predicted and cloned, the occurrence of miR2118 target sequence in both genes indicated that they might be targets of cin-miR2118. We investigated the expression patterns of cin-miR2118 and its target genes in C. intermedia stems and found diverse changes in expression in response to drought stress. CiDR1 was negatively correlated with corresponding miR2118 expression while CiDR2 was positively correlated with cin-miR2118. For further study, induced tolerance was observed in the transgenic Tobacco with overexpression cin-miR2118 upon 140-min water deficiency. And the expression level of cin-miR2118 was dramatically increased under drought stress. These results reveal that cin-miR2118 exert positive effects on drought stress tolerance. In addition, our study unexpectedly found that overexpression of cin-miR2118 in Tobacco can cause phenotype changes, which suggested that cin-miR2118 may have a novel function as a growth regulator in Tobacco.