MicroRNAs (miRNAs) are small, non-coding regulatory RNAs that regulate gene expression by facilitating target mRNA cleavage in plants. They are crucial for responses to diverse stresses. The novel drought-responsive miRNA ZmmiR190 was previously identified during an analysis of the maize transcriptome. In this study, we revealed that transgenic Arabidopsis thaliana overexpressing ZmmiR190 is more sensitive to drought than the wild-type control. The transcript of a nuclear-localized gene, ZmCRP04, was identified as a likely target of ZmmiR190. Moreover, ZmmiR190 and ZmCRP04 had the opposite expression profiles following drought and salt treatments. Additionally, 5' RACE and coexpression analyses in A. thaliana provided evidence of the in vivo targeting of the ZmCRP04 transcript by ZmmiR190. Furthermore, the overexpression of ZmCRP04 in A. thaliana and rice significantly enhanced drought tolerance, with lower malonaldehyde contents and relative electrolyte leakage in the transgenic A. thaliana and rice plants than in the wild-type control. Transgenic plants overexpressing ZmmiR190 or ZmCRP04 were hypersensitive to abscisic acid. These results suggest that the ZmCRP04 transcript is targeted by ZmmiR190 and may encode a protein that positively regulates drought stress tolerance via an abscisic acid-dependent pathway. These findings may be relevant for future molecular breeding aimed at improving crop drought tolerance.
Keywords: Drought stress tolerance; Maize; ZmCRP04; ZmmiR190.
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