Secretome Analysis of the Banana Fusarium Wilt Fungi and Reveals a New Effector OASTL Required for Full Pathogenicity of in Banana.

Banana Fusarium wilt (BFW), which is one of the most important banana diseases worldwide, is mainly caused by f. sp. tropic race 4 (). In this study, we conducted secretome analysis of and and discovered a total of 120 and 109 secretory proteins (SPs) from cultured alone or with banana roots, respectively, and 129 and 105 SPs respectively from cultured under the same conditions. and shared numerous SPs associated with hydrolase activity, oxidoreductase activity, and transferase activity. Furthermore, in culture with banana roots, and secreted many novel SPs, of which approximately 90% (; 57/66; ; 50/55) were unconventional SPs without signal peptides. Comparative analysis of SPs in and revealed that not only generated more specific SPs but also had a higher proportion of SPs involved in various metabolic pathways, such as phenylalanine metabolism and cysteine and methionine metabolism. The cysteine biosynthesis enzyme O-acetylhomoserine (thiol)-lyase (OASTL) was the most abundant root inducible -specific SP. In addition, knockout of the gene did not affect growth of ; but resulted in the loss of pathogenicity in banana 'Brazil'. We speculated that OASTL functions in banana by interfering with the biosynthesis of cysteine, which is the precursor of an enormous number of sulfur-containing defense compounds. Overall, our studies provide a basic understanding of the SPs in and ; including a novel effector in .