Functional characterization of ZmbHLH121, a bHLH transcription factor, focusing on Zea mays kernel development

Abstract

Seed size is a result of the complex interactions among embryo, endosperm, seed coat and the mother plant. The final yield of maize depends on the kernel size and weight. Here we demonstrate that, ZmbHLH121, a maize bHLH transcription factor positively regulates kernel size and weight in maize. Over expression of ZmbHLH121 (ZmbHLH121-OE) produced larger and heavier kernels while ZmbHLH12-RNA interference (ZmbHLH121-RNAi) produced smaller and lighter kernels compared with non-transgenic plants. The biochemical studies suggested that, ZmbHLH121 is a transcriptional activator and binds to G-box cis-element ABA responsive element (ABRE). The expression analysis of ZmbHLH121indicated that, ZmbHLH121 expressed throughout the reproductive developmental stages of maize and higher expression was observed in the early kernel developmental stages. Transcriptome analysis revealed that, ZmbHLH121 regulated the transcription of downstream genes involved in plant cell death, cell differentiation and cell wall modifications. Therefore, our data established a molecular network of regulating kernel size and weight in maize and suggested ZmbHLH121 as a promising target of grain yield in maize.