Fine mapping and discovery of a candidate gene MIR172e required for inflorescence development and lower floret abortion in maize ear

Maize (Zea mays L.) is a monoecious grass species with separate male and female inflorescences which form the tassel and ear, respectively. The mature ear inflorescences usually bear hundreds of grains, thus directly influence maize grain production and yield. Here, we isolated a recessive maize mutant, tasselseed2016 (ts2016), which exhibits pleiotropic inflorescence defects and a reduction in grain yield. These defects include loss of determinacy and identity in meristems and floral organs, as well as a lack of the lower floret abortion in maize ear, and the smaller grain size. Using map-based cloning and allelic test, we identified and confirmed a microRNA gene MIR172e as the target gene controlling these related traits. Furthermore, our evidence uncovered a new potential miR172e/ETHYLENE RESPONSIVE ELEMENT BINDING197 (EREB197) regulatory module which controls the abortion of lower floret in maize ear. Transcriptome analysis revealed that the mutation of MIR172e represses multiple biological processes, particularly the flower development and hormone-related pathways in maize ear. Additionally, we found the mutation in the DNA sequence of MIR172e affects in RNA transcription, resulting in elongation blockage at the mutant site. Our results reveal the function and molecular mechanism of MIR172e in maize inflorescences and grain yield, and this study deepens our knowledge of maize inflorescence development.