Molecular regulation of ZmMs7 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 maize male sterility 7 (ZmMs7) and its application for developing a dominant male-sterility system in multiple species. ZmMs7 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 ZmMs7 in maize by an anther-specific promoter p5126 results in dominant and complete male sterility but normal vegetative growth and female fertility. Early expression of ZmMs7 downstream genes induced by prematurely expressed ZmMs7 leads to abnormal tapetal development and pollen exine formation in p5126-ZmMs7 maize lines. The p5126-ZmMs7 transgenic rice and Arabidopsis plants display similar dominant male sterility. Meanwhile, the mCherry gene coupled with p5126-ZmMs7 facilitates the sorting of dominant sterility seeds based on fluorescent selection. In addition, both the ms7-6007 recessive male-sterility line and p5126-ZmMs7M 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.

ZmFAR1 and ZmABCG26 Regulated by microRNA Are Essential for Lipid Metabolism in Maize Anther

“…In addition to miRNAs, the expressions of lipid metabolic GMS genes are usually regulated by TF GMS genes, and also by feedback regulation of other lipid metabolic GMS genes. The expression pattern changes of ZmFAR1 and ZmABCG26 in anther development were analyzed by using seven sets of maize anther transcriptomes, including three TF GMS mutant lines ( ms23 , ms7-6007 , and lob30 ) [ 12 , 42 , 44 , 45 ], two TF overexpression GMS lines ( p5126-ZmMs7 and p5126-ZmLOB30 ) [ 44 ], and two lipid metabolic GMS mutant lines ( ms30 and ms33 ) [ 7 , 46 , 47 , 48 ] ( Figure S5 A,B, Table S3 ). In ms23 mutant, ZmFAR1 expression was not significantly changed, while ZmABCG26 expression was significantly downregulated at stages 6 and 7 ( Figure S5 (A1), indicating TF ZmMs23 may positively regulate ZmABCG26 expression.…”

“…Images of the tassels and anthers were captured with a Canon EOS 700D digital camera (Canon, Tokyo, Japan) and a SZX2-ILLB stereomicroscope (Olympus, Tokyo, Japan) respectively. Routine analysis of I 2 -KI staining and SEM (scanning electron microscopy) were performed as described previously [ 44 ]. SEM images of anther and pollen grain were detected with a HITACHI S-3400N scanning electron microscope (HITACHI, Tokyo, Japan).…”

CRISPR/Cas9‐based discovery of maize transcription factors regulating male sterility and their functional conservation in plants

“…RNA sequencing (RNA‐seq) provides a more precise and quantitative measurement of gene expression than microarrays (Wan and Li, 2019; Wang et al ., 2009). Several RNA‐seq transcriptomes have been reported for whole anther (An et al ., 2020; Nan et al ., 2017; Zhu et al ., 2020) or anther single cells (Nelms and Walbot, 2019) in maize. Based on maize anther RNA‐seq data of Oh43 line at six developmental stages (S5 to S9) and maize orthologs of the reported GMS genes identified in Arabidopsis and rice but without functional characterizations in maize, we predicted 62 putative maize GMS genes (Wan et al ., 2019).…”

Exploiting Genic Male Sterility in Rice: From Molecular Dissection to Breeding Applications

“…Very recently, a maize male fertility gene ( ZmMS26 ) was targeted by the CRISPR/Cas system to produce a one-step hybrid ( Qi et al, 2020 ). Similarly, another lipid-metabolism-related maize gene ZmMs17 has recently been used to create male sterility in rice, and interestingly, it did not affect the vegetative growth and female fertility ( An et al, 2020 ). Importantly, rice also contains ZmMs17 and ZmMS26 -like genes, specifically PTC1/OsMS1 and CYP704B , respectively, whereby this technology can be readily applied to these genes in rice plants, along with other fertility-determining genes in order to establish and develop stable hybrid rice seeds in future.…”