Map-based cloning and characterization of <italic>Zea mays male sterility33</italic> (<italic>ZmMs33</italic>) gene, encoding a glycerol-3-phosphate acyltransferase.

Key message: Map-based cloning of maize <italic>ms33</italic> gene showed that <italic>ZmMs33</italic> encodes a <italic>sn</italic>-<italic>2</italic> glycerol-3-phosphate acyltransferase, the ortholog of rice OsGPAT3, and it is essential for male fertility in maize.Abstract: Genetic male sterility has been widely studied for its biological significance and commercial value in hybrid seed production. Although many male-sterile mutants have been identified in maize (<italic>Zea mays</italic> L.), it is likely that most genes that cause male sterility are unknown. Here, we report a recessive genetic male-sterile mutant, <italic>male sterility33</italic> (<italic>ms33</italic>), which displays small, pale yellow anthers, and complete male sterility. Using a map-based cloning approach, maize <italic>GRMZM2G070304</italic> was identified as the <italic>ms33</italic> gene (<italic>ZmMs33</italic>). <italic>ZmMs33</italic> encodes a novel <italic>sn</italic>-<italic>2</italic> glycerol-3-phosphate acyltransferase (GPAT) in maize. A functional complementation experiment showed that <italic>GRMZM2G070304</italic> can rescue the male-sterile phenotype of the <italic>ms33</italic>-<italic>6029</italic> mutant. <italic>GRMZM2G070304</italic> was further confirmed to be the <italic>ms33</italic> gene via targeted knockouts induced by the clustered regularly interspersed short palindromic repeats (CRISPR)/Cas9 system. <italic>ZmMs33</italic> is preferentially expressed in the immature anther from the quartet to early-vacuolate microspore stages and in root tissues at the fifth leaf growth stage. Phylogenetic analysis indicated that ZmMs33 and OsGPAT3 are evolutionarily conserved for anther and pollen development in monocot species. This study reveals that the monocot-specific GPAT3 protein plays an important role in male fertility in maize, and <italic>ZmMs33</italic> and mutants in this gene may have value in maize male-sterile line breeding and hybrid seed production. [ABSTRACT FROM AUTHOR]