micro RNA /micro RNA * complementarity is important for the regulation pattern of NFYA 5 by miR169 under dehydration shock in Arabidopsis

Summary Micro RNA s regulate gene expression at the mRNA and translational levels. Although our previous research showed that expression of miR169 and one of its targets, NFYA 5 , is down‐ and up‐regulated by drought stress, respectively, the current study shows that expression of both miR169 and NFYA 5 are induced by dehydration shock. Unlike overexpression of MIR 169a/b , overexpression of MIR 169i/l did not decrease NFYA 5 transcripts but increased NFYA 5 protein levels. NFYA 5 protein abundance also increased in mir169a knock‐out mutants and 35S:: MIR 169l   mir169a double mutants. When bulge #11 and bulge #16 in the miR169/miR169* duplex were mutated, both NFYA 5 transcripts and the corresponding protein levels were lower in 35S:: MIR 169l*‐mut transgenic plants than in wild‐type ( WT ) plants, and the 35S:: MIR 169l*‐mut transgenic plants were as sensitive to drought stress as the 35S:: MIR 169a plants. The mRNA and protein levels of NFYA 5 did not differ substantially between WT and 35S:: MIR 169a*‐mut transgenic plants when the two bulges were introduced in the miR169a/miR169a* duplex. Both bulge #11 and bulge #16 in the miR169/miR169* duplex were essential for different regulation patterns of NFYA 5 by miR169a and miR169l. These results increase the understanding of regulatory specialization in one MIR family, and also increase our understanding of the importance of micro RNA /micro RNA * secondary structure.