Evolution of the chromatin remodeling complex FACT: Functional analysis of SSRP1 and SPT16 in early anther...

Facilitates chromatin transcription (FACT) is a histone chaperone composed of SSRP1 and SPT16, which regulates both vegetative and reproductive development in plants. However, its evolutionary history and specific role in anther development remain unexplored. We conducted a comprehensive molecular evolutionary analysis of the SSRP1 and SPT16 genes across eukaryotes, revealing their redundant functions in anther development. SSRP1 and SPT16 have similar evolutionary patterns that originated before plants, animals, and fungi split. Both SSRP1 and SPT16 genes maintained single-copy numbers in animals and fungi, while in plants they were expanded. One gene duplication has occurred in poaceae for SPT16, and one gene duplication has occurred in both monocot and eudicot for SSRP1, respectively. Segmental duplication was the main mechanism for amplifying of SSRP1 and SPT16 in plants. SSRP1 and SPT16 showed similar spatial-temporal expression patterns in anthers. Both the single mutants of ssrp1 and spt16 reduced the numbers of stamens and anther lobes, and the double mutant exhibited more severe anther phenotypes, indicating their redundant functions in male fertility. Our studies provide a deeper understanding of the phylogenetic relationships of SSRP1 and SPT16 genes in eukaryotes and indicate that SSRP1 and SPT16 function in the same pathway to regulate anther lobe formation and anther cell differentiation.