Comparative cytology and transcriptome analysis revealed that PpMED15A drives the fertility of peach pollen

• Peach variety "Jiushuo" (JS) is unable to produce fertile pollen during the mononuclea microspore stage due to the abnormal degeneration of the tapetum cells. • Reactive oxygen species may be the signal for the abnormal degradation of "Jiushuo"(JS) tapetal cells. • PpMED15A is the gene that could be related to the sterility of the JS peach. Abnormal pollen development has a significantly deleterious impact on commercial peach yields, warranting studies on peach pollen fertility.In this study,cytological observations indicated that the tapetum cells of pollen-sterile "Jiushuo" (JS) failed to condense or degenerate compared with pollen-fertile "Jiucui" (JC) at the S4 mononuclear microspore stage, resulting in the inability to form fertile pollen microspores. Differentially expressed genes (DEGs) during the S2(tetrad stage), S3(from tetrad to mononuclear microspore stage), and S4 (mononuclear microspore stage) stages were significantly enriched in Ubiquinone and other terpenoid-quinone biosynthesis,oxidoreductase activity and ascorbate and aldarate metabolism pathways. The H 2 O 2 content in JS flower buds was higher than those in JC in S2 and S3 periods,the glutathione(GSH) level of JS was significantly lower than that of JC during the S2 period, while it was significantly higher than that of JC during the S3 period. However, during the S2 and S3 stages, the enzymatic activities of Ascorbate Peroxidase(APX) and the other three antioxidant enzymes showed no significant differences. Therefore, the balance of reactive oxygen species in the JS flower buds has been affected. Based on the premise that the pollen fertility gene is located on chromosome 6, combined with the analysis of DEGs, the PpMED15A gene was finally selected.Complementation in the Arabidopsis med15a mutant indicated that the gene drove fertility, making it crucial for normal pollen development. The salicylic acid content in JS flower buds is significantly lower than that in JC, and SA may affect pollen development through ROS.Our findings provide a foundation for future studies on the mechanism by which PpMED15A regulates pollen fertility.