Fine mapping and discovery of MIR172e, a candidate gene 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, so they directly influence maize grain production and yield. Here, we isolated a recessive maize mutant, tasselseed2016 (ts2016), which exhibits pleiotropic inflorescence defects and reduced grain yield. These defects include the loss of determinacy and identity in meristems and floral organs, as well as a lack of the lower floret abortion in maize ear, and a smaller grain size. Using map-based cloning and allelic testing, we identified and confirmed the 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 lower floret abortion 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. We also found that a mutation in the DNA sequence of MIR172e affects 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.