Genetic male sterility has been studied for its biological significance and
commercial use in hybrid seed production. Although many male-sterile mutants
have been identified in maize (Zea mays L.), most genes that cause male
sterility are unknown. The team of Ke Xie from the University of Science and
Technology Beijing in China reports a maize mgenesant, male sterility33
(ms33), which has small, pale yellow anthers, and complete male sterility.

Researchers identified that the mutation in the maize GRMZM2G070304 gene was
responsible for the mutant. Using CRISPR-Cas9, the team knocked out the
GRMZM2G070304 gene. The resulting gene-edited lines had similar traits as
the ms33 mutant, confirming GRMZM2G070304 to be the gene responsible for the
mutant.

The gene was found to encode a sn-2glycerol-3-phosphate acyltransferase
(GPAT) in maize. Expression of the gene was also revealed to rescue the
male-sterile phenotype of the male-sterile ms33 mutant. The gene, denoted as
ZmMs33, was found to be expressed in immature anthers and root tissues.

The study reveals that the monocot-specific GPAT3 protein plays an important
role in male fertility in maize. This gene may be of great value in maize
male-sterile line breeding and hybrid seed production.

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