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.

Maize (Zea mays L.) is one of the most important food crops in the world, and starch is the main component of its endosperm. Transcriptional regulation plays a vital role in starch biosynthesis. However, it is not well understood in maize. We report the identification of the transcription factor ZmNAC126 and its role in regulation of starch synthesis in maize. Transcriptional expression of ZmNAC126 was higher in maize endosperm and kernels than in roots or stems. ZmNAC126 shared a similar expression pattern with starch synthesis genes during seed development, and its expression pattern was also consistent with the accumulation of starch. ZmNAC126 is a typical transcription factor with a transactivation domain between positions 201 and 227 of the amino acid sequence, is located in the nucleus, and binds to CACG repeats in vitro. Yeast one-hybrid assay revealed that ZmNAC126 bound the promoters of ZmGBSSI, ZmSSIIa, ZmSSIV, ZmISA1, and ZmISA2. Transient overexpression of ZmNAC126 in maize endosperm increased the activities of promoters pZmSh2, pZmBt2, pZmGBSSI, pZmSSIIIa, and pZmBT1 but inhibited the activities of pZmISA1 and pZmISA2. ZmNAC126 thus acts in starch synthesis by transcriptionally regulating targeted starch synthesis-related genes in maize kernels.