Pichia galeiformis-secreted protein PgSLP increases citrus fruit disease resistance by activating amino acid metabolism

Previous research has demonstrated that the Pichia galeiformis (P. galeiformis) secreted protein PgSLP reduced citrus fruit postharvest green mold. It is unclear how the secreted protein PgSLP enhances citrus fruit resistance. This study was conducted to determine the effect of PgSLP on the control of blue mold and investigate the biocontrol mechanisms. With the transient overexpression of PgSLP, the incidence of blue mold in citrus was reduced. The majority of differentially expressed genes (DEGs) were enriched in amino acid synthesis and metabolism pathways. Physiological and biochemical analyses showed that the activities of O-acetylserine (thiol)-lyase (OASTL), serine acetyltransferase (SAT), and glutathione reductase (GR) were increased when treated with PgSLP. The contents of phenylalanine, tyrosine, leucine, isoleucine, serine, phenylalanine, cysteine, and glutathione were increased. This study demonstrated that PgSLP could enhance the citrus fruit blue mold resistance by affecting amino acid synthesis and metabolism.