Classification and molecular mechanisms of gametophytic male sterility in Arabidopsis, rice and maize.

Plant male sterility (MS) is a fundamental model for studying reproductive development, yet a critical but often overlooked distinction exists between sporophytic male sterility (SMS) and gametophytic male sterility (GAMS). Unlike SMS, which is controlled by the sporophyte's genotype, GAMS is uniquely determined by the gametophyte's own genome, leading to subtle phenotypes that are challenging to identify. Here, we systematically classify 59 identified GAMS genes in Arabidopsis, rice, and maize into three functional categories based on their defective phenotypes during pollen development: Pollen Maturation Defects (PMD), Pollen Germination Defects (PGD), and Male-Female Communication Defects (MFCD). Leveraging the evolutionary conservation of these pathways, we employed a comparative genomics approach to identify 18 high-confidence candidate GAMS genes in maize. Functional validation of ZmCESA6 as a PGD-type GAMS gene confirms the effectiveness of our strategy. This study provides a comprehensive functional map of GAMS and offers valuable genetic resources for hybrid breeding in major crops.