Molecular regulation of <i>ZmMs7</i> required for maize male fertility and development of a dominant male-sterility system in multiple species

Abstract

Understanding the molecular basis of male sterility and developing practical male-sterility systems are essential for heterosis utilization and commercial hybrid seed production in crops. Here, we report molecular regulation by genic male-sterility gene <i>maize male sterility 7</i> (<i>ZmMs7</i>) and its application for developing a dominant male-sterility system in multiple species. <i>ZmMs7</i> is specifically expressed in maize anthers, encodes a plant homeodomain (PHD) finger protein that functions as a transcriptional activator, and plays a key role in tapetal development and pollen exine formation. ZmMs7 can interact with maize nuclear factor Y (NF-Y) subunits to form ZmMs7-NF-YA6-YB2-YC9/12/15 protein complexes that activate target genes by directly binding to CCAAT box in their promoter regions. Premature expression of <i>ZmMs7</i> in maize by an anther-specific promoter <i>p5126</i> results in dominant and complete male sterility but normal vegetative growth and female fertility. Early expression of <i>ZmMs7</i> downstream genes induced by prematurely expressed ZmMs7 leads to abnormal tapetal development and pollen exine formation in <i>p5126-ZmMs7</i> maize lines. The <i>p5126-ZmMs7</i> transgenic rice and <i>Arabidopsis</i> plants display similar dominant male sterility. Meanwhile, the <i>mCherry</i> gene coupled with <i>p5126-ZmMs7</i> facilitates the sorting of dominant sterility seeds based on fluorescent selection. In addition, both the <i>ms7-6007</i> recessive male-sterility line and <i>p5126-ZmMs7M</i> dominant male-sterility line are highly stable under different genetic germplasms and thus applicable for hybrid maize breeding. Together, our work provides insight into the mechanisms of anther and pollen development and a promising technology for hybrid seed production in crops.