Disruption of the endoplasmic reticulum-localized fatty acyl-ACP thioesterase IPF1 caused partial male sterility in rice.

The fatty acyl ACP thioesterases, catalyzing the final step of fatty acid synthesis in the plastid, regulate various critical processes in plants, including seed oil accumulation, seed development, plant growth, and drought tolerance. However, their roles in male fertility have seldom been demonstrated. In this study, the function of a newly FAT, Impaired Pollen Fertility 1 (IPF1) in male fertility was investigated. IPF1 expressed prominently in microspores and tapetum. IPF1 specifically located in the endoplasmic reticulum. IPF1 knock-out mutants produced by the CRISPR/Cas9 system displayed significant reduction in seed-setting rate compared to WT. The decreased seed-setting rate in the ipf1 mutants was found to be attributed to the defects of pollen viability, not the female gamete fertility. The aborted pollen in the ipf1 mutants showed impaired pollen wall formation and diminished lipid deposition. Consistently, the expression levels of six genes critical to pollen wall formation and lipid metabolism (GPAT3, OsC6, DPW2, OsPKS1, OsPKS2, and OsSTRL2) were significantly decreased in the ipf1 mutant. Taken together, these results demonstrate that IPF1 regulates rice pollen fertility through the modulation of lipid synthesis.