Brassinosteroids in maize: Biosynthesis, signaling pathways, and impacts on agronomic traits

Maize is one of the most widely cultivated crops for producing human food, animal feed, and ethanol biofuel. Recent studies have indicated that brassinosteroids (BRs), essential phytohormones for plant growth, development and stress adaptation across plant species, significantly regulate several maize agronomic traits, such as plant height, leaf angle, reproductive development and kernel size. So far, most previous reviews have mainly focused on discussing molecular functions of BRs in model plants like Arabidopsis and rice. A detailed summary of BRs in maize, however, has not yet been presented. In this review, we provide a comprehensive overview of the biosynthesis and signaling transduction pathways of BRs, and summarize the roles of BRs in regulating some agronomic traits such as plant architecture and kernel yield in maize. We also discuss potential opportunities and challenges associated with leveraging BR-centered molecular design strategies for maize improvement.