Conserved Zma-miR164 family is responsible for maize heterosis by negatively regulating NAC transcription factor during internode elongation

Abstract

The miR164 and NAC (NAM, ATAF1/2 and CUC2) transcription factors regulatory network is evolutionarily conserved among plant species. Although NAC transcription factors play important roles in multiple biological processes such as plant development, and negatively regulated by miR164. However, the involvement of miR164 and NAC genes in maize internode expansion were poorly deciphered. In this study, the conserved genic features and expression profiles of Zma-miR164s and their target Zma-NAC genes at the eighth leaf stage of maize were analyzed using bioinformatics and quantitative reverse transcription polymerase chain reaction (qRT-PCR) methods. Eight Zma-miR164 members with 5’-UGGAGAAGCAGGGCACGUGCA-3’ as the standard mature sequence were identified in maize, while the mature sequences of Zma-miR164f, Zma-miR164h and Zma-miR164e displayed six different nucleotide substitutions. Seven Zma-NACs were computational predicted as the Zma-miR164 targets, which displayed a conserved miR164-binding region (miR164BR) in the C-terminus of NAC domain. Five Zma-NACs showed a tissue-specific expression at the internode elongation stage, with GRMZM2G063522 displayed the highest while GRMZM2G009892 exhibited the lowest expression level. When compared with their expression in their parents, all Zma-miR164s were differentially repressed expression while five Zma-NACs were expressed additively in Zhengdan958 and Yuyu22. These results indicated that Zma-miR164s might participate in maize heterosis during internode elongation, and exert an influence on ear and plant height via the decay of their target NAC genes. This study mainly provided a valuable foundation for future comprehensive analysis of miR164-NAC network, and further research work is needed to confirm its regulatory roles during internode expansion.