Abstract
BackgroundMale fertility is crucial for rice yield, and the improvement of rice yield requires hybrid production that depends on male sterile lines. Although recent studies have revealed several important genes in male reproductive development, our understanding of the mechanisms of rice pollen development remains unclear.ResultsWe identified a rice mutant oslap6 with complete male sterile phenotype caused by defects in pollen exine formation. By using the MutMap method, we found that a single nucleotide polymorphism (SNP) variation located in the second exon of OsLAP6/OsPKS1 was responsible for the mutant phenotype. OsLAP6/OsPKS1 is an orthologous gene of Arabidopsis PKSA/LAP6, which functions in sporopollenin metabolism. Several other loss-of-function mutants of OsLAP6/OsPKS1 generated by the CRISPR/Cas9 genomic editing tool also exhibited the same phenotype of male sterility. Our cellular analysis suggested that OsLAP6/OsPKS1 might regulate pollen exine formation by affecting bacula elongation. Expression examination indicated that OsLAP6/OsPKS1 is specifically expressed in tapetum, and its product is localized to the endoplasmic reticulum (ER). Protein sequence analysis indicated that OsLAP6/OsPKS1 is conserved in land plants.ConclusionsOsLAP6/OsPKS1 is a critical molecular switch for rice male fertility by participating in a conserved sporopollenin precursor biosynthetic pathway in land plants. Manipulation of OsLAP6/OsPKS1 has potential for application in hybrid rice breeding.
Highlights
Male fertility is crucial for rice yield, and the improvement of rice yield requires hybrid production that depends on male sterile lines
The results showed that all the pollen grains of oslap6 were aborted (Fig. 1d, e), indicating that this mutant exhibited a complete male sterile phenotype
Via merging the micrographs from each channel, we found that the green fluorescent protein (GFP) signals detected in OsLAP6/OsPKS1-GFP overlapped with the red fluorescent protein (RFP) signals of endoplasmic reticulum (ER)-marker (Fig. 6c)
Summary
Male fertility is crucial for rice yield, and the improvement of rice yield requires hybrid production that depends on male sterile lines. Recent studies have revealed several important genes in male reproductive development, our understanding of the mechanisms of rice pollen development remains unclear. Pollen, as the male reproductive cell of rice, is closely associated with yield; and in-depth understanding of the mechanism of pollen development is extremely important for the improvement of rice yield. As the protective structure of male gametes, pollen exine plays important roles in the development of pollen grains, resisting environmental stress, and the interaction of male and female gametes (Dumas et al 1998; Hafidh et al 2016; Mccormick 2004; Blackmore et al 2007).
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