Disease resistance induction by K. marxianus against green mold in citrus via transcriptome analysis and verification based on metabolites

Abstract

This study examined the transcriptional composition and changes in gene expression patterns in citrus fruit tissue treated with Kluyveromyces marxianus and its effects on key defense-related enzyme activities and metabolites. This analysis was carried out by the technique of RNA sequencing, the use of HPLC-MS, and GC–MS equipment. The sequencing data revealed that the induction of K. marxianus in the citrus fruit peel activated the expression of genes in 90 biological pathways. A total of 3785 genes were transcribed between the yeast-treated and control fruits. 1287 genes were expressed significantly, 682 genes were up-regulated representing 52.99 %, and 605 genes were down-regulated representing 47.00 %. Gene expressions in some of the pathways in the treated citrus stimulated an increase in the production of some defense-related enzymes, the synthesis of secondary metabolites such as phenolic compounds, flavonoids, phenolic acids, and an enhanced lignin production. The accumulation of these compounds contributed to the improvement of the antifungal activity and defense responses in the citrus. 8 phenolic acids, 12 sugars, 6 organic acids, and 17 amino acids were detected at varying concentrations. The investigations revealed that the production of the metabolites was significantly enhanced in the K. marxianus-treated fruits as compared to the control fruits. The study provides some fundamental understanding of the induced resistance mechanism in citrus by K. marxianus.