Title : Tapetum PCD retardation is critical for amino acid biosynthesis and aliphatic metabolism during sesame anther development
Anther development and male fertility was critical for crop seed formation and yield production. Male sterile plants provide an efficient pollination control system for hybrid breeding. Sesame 95ms-5AB was a novel recessive genic male sterile two-type line controlled by a single RGMS gene. The male abortion of 95ms-5A was appeared after tetrad stage. iTRAQ analysis and Metabolomics analysis between sterile anthers (95ms-5A) and fertile anthers (95ms-B) were performed to unravel the mechanisms of 95ms-5 male sterility. iTRAQ analysis indicated that differential expressed proteins (DEPs) were mainly involved in programed cell death (PCD), amino acid biosynthesis and lipid metabolism. Tunnel analysis further confirmed that tapetal cell degeneration was delayed in male sterile plant. Callose staining analysis indicated that callose degradation was abnormal in sterile plants during anther development. Lipid staining analysis revealed that lipid accumulation was higher in sterile anthers as compared with fertile anthers. TEM observation further confirmed the delayed tapetum PCD and the pollen wall polymerization and patterning were disturbed in sterile anthers. Metabolomic analysis as well revealed that differential metabolites between sterile anthers and fertile anthers were mainly accumulated in amino acid biosynthesis and fatty acid metabolism. Comparing to fertile anthers, the content of amino acid was reduced in tetrad stage, while was increased in microspore stage in sterile anthers and the branched amino acids were mainly altered in sterile anthers. Metabolomic analysis also confirmed the lipid content, mainly the fatty acid content, was altered in sterile anthers as compared with fertile anthers. This study demonstrated that delayed tapetum PCD disturbed amino acid biosynthesis and fatty acid metabolism, leading to male gametogenesis inhibited in sesame. Our study provides a first insight into the mechanism that result in genetic male sterility in sesame and contributes to a better understanding of the regulatory network involved in anther development in sesame.