APETALA2 floral identity determination and CoCP1-related tapetal degradation contribute to petaloid male sterility in Camellia oleifera

Camellia oleifera is an important woody oilseed crop, and petaloid male-sterile germplasm provides valuable female parents for hybrid breeding by reducing the need for manual emasculation. However, the molecular events linking stamen petaloidy with pollen abortion remain poorly understood. Here, we compared normal anthers of the cultivar ‘Huashuo’ (HS) with petaloid anthers of its male-sterile mutant (HSP) using RNA-seq, WGCNA, endogenous hormone profiling, cytological observation, PCD detection, and transient/heterologous functional assays. A total of 55,166 unigenes and 6454 DEGs were identified across the anther petaloidy gradient. Petaloid anthers showed elevated IAA and CTK levels, reduced GA₃ content, and altered expression of hormone-signaling genes, indicating that hormonal reprogramming is associated with anther identity transition. WGCNA highlighted CoAPETALA2 ( CoAP2 ), an A-class floral identity gene, and CoCP1 , a cysteine protease gene related to tapetal PCD, as candidate regulators. HSP anthers exhibited premature tapetal PCD at the microsporocyte stage, accompanied by H₂O₂ accumulation and increased CoCP1 expression. In Nicotiana benthamiana , ectopic expression of CoAP2 affected stamen development, CoAP1 promoted petaloid anther-like malformations, and CoCP1 overexpression disrupted anther locule formation and reduced pollen fertility. Our findings support a regulatory model in which altered A-class floral identity activity contributes to anther petaloidy, whereas CoCP1 -associated premature tapetal PCD contributes to pollen abortion in C. oleifera .