Sporopollenin, a core structural component of spore and pollen walls in land plants, is critical for pollen formation, yet its metabolic mechanism in tomato ( Solanum lycopersicum ) remains unclear. In this study, an anther-specific gene SlFAR3 encoding a fatty acyl-CoA reductase was identified, which participates in sporopollenin biosynthesis by regulating fatty alcohol metabolism. Phenotypic analysis revealed that slfar3 mutants exhibited abnormal anther and pollen development, ultimately leading to pollen-free male sterility. Cytological evidence demonstrated defective Ubisch body formation and significantly reduced accumulation of sporopollenin precursors in slfar3 anthers. In vitro enzymatic assays confirmed that SlFAR3 specifically catalyzes the reduction of palmitoyl-ACP (C16:0-ACP) to hexadecanol (C16:0-OH). Mass spectrometry analysis of mutant anthers showed a marked decrease in cutin monomers, altered composition of epicuticular waxes, and distinct changes in soluble fatty acid and alcohol profiles. Integrated transcriptomic and metabolomic analyses revealed significant enrichment of differentially expressed genes and metabolites associated with the phenylpropanoid biosynthesis pathway in slfar3 , suggesting that SlFAR3-derived hexadecanol contributes to sporopollenin precursor formation via phenylpropanoid metabolism. This study systematically elucidates the molecular mechanisms by which SlFAR3 regulates sporopollenin synthesis to ensure pollen development in tomato, integrating insights from molecular, cellular, and metabolic perspectives. These findings advance the understanding of plant male gametophyte development and provide a foundation for engineering tomato male sterile lines.
Liu et al. (Fri,) studied this question.