Genome-wide identification of STERILE APETALA (SAP) like genes in Gossypium and functional characterization of...

Cotton is one of the most important economic crops, with its fiber and seeds being natural textile raw materials and important sources of edible oil, respectively. STERILE APETALA (SAP) gene belongs to a class of transcription regulator. Previous studies indicated that SAP has critical role in the development of flower and organ size in plants. However, few reports about SAP-like genes in cotton, and the function of SAP in cotton is not clear. In the present study, we identified a total of 12 SAP-like genes in the two cultivated tetraploids species (G. hirsutum and G. barbadense) and diploid ancestral species (G. arboreum and G. raimondii). In addition, overexpression of GhSAP_A07 in Arabidopsis and cotton significantly altered seed size and leaf morphology, validating GhSAP_A07 have multiple function in cotton. Furthermore, comparative transcriptome analysis identified 1162 differentially expressed genes at different developmental stages of ovules between wild type and overexpression line. GO and KEGG enrichment analysis showed that DEGs were enriched in auxin signaling transduction and transport. qRT-PCR showed auxin related genes were highly expressed in overexpression line, indicating that GhSAP_A07 might regulate seed size by affecting the expression of auxin related genes. Our study provided information about the functions and molecular mechanisms of SAP-like genes in seed development, and laying a solid foundation for improving cotton in the future.