HSP70 and APX1 play important roles in cotton male fertility by mediating ROS homeostasis.

Male sterility is used in the production of hybrid seeds and can improve the breeding efficiency of cotton hybrids. Reactive oxygen species is closely associated with the tapetum and pollen development, but their relationship in cotton male fertility remains unclear. In this study, we comprehensively compared the cytology and proteome of the anthers from an Upland cotton (Gossypium hirsutum) material, Shida 98 (WT), and its nearly-isogenic male sterile line Shida 98A (MS). Cytology indicated delayed PCD in the tapetum and defects in microspores in MS anthers. And further studies revealed disruption of ROS homeostasis. Proteomic analysis identified proteins with differential abundance mainly being related to redox homeostasis, protein folding, and apoptotic signaling pathways. GhAPX1 interacted with GhHSP70 and played a crucial role in the development of cotton anthers. Exogenous application of HSP70 inhibitor increased HO content and decreased the activity of APX1 and pollen viability. The GhAPX1 mutants generated by CRISPR/Cas9-mediated gene editing exhibited premature degradation of the tapetum, significant decrease in pollen viability, and significant increase in HO content. Altogether, our results imply HSP70 and APX1 being the key players jointly regulating male fertility by mediating ROS homeostasis. These results provide insights into the proteins associated with male fertility.