Multiple pathways involved in the Ca ascorbate-induced enhancement of Meyerozyma guilliermondii biocontrol efficacy

Abstract

The external environment and yeast’s inherent physiological characteristics play important roles in the biocontrol efficacy of antagonistic yeast. Attention has been focused on increasing biocontrol efficacy by improving yeast environmental adaptability in recent years. In this study, the effect and mechanism of calcium ascorbate (Ca ascorbate) on enhancement of Meyerozyma guilliermondii biocontrol effectiveness were investigated based on transcriptome sequencing, and physiological and biochemical activity analysis of yeast cells. The results demonstrated that the yeast induced by 0.2 g/L Ca ascorbate inhibit gray decay substantially compared with the control, non-induced, ascorbic acid (VC) and calcium chloride (CaCl2) induced groups.The results of transcriptome sequencing showed that the differentially expressed genes (DEGs) of M. guilliermondii induced by Ca ascorbate were mainly enriched in those GO functions such as “cell process, metabolic process, antioxidant” and KEGG pathways such as “ribosome, metabolism, cell cycle”. Ca ascorbate induction could significantly upregulate the expression of genes related to ribosome synthesis (RIM101, PAN3, NHP2, and RPS19A), growth and metabolism (HXT2 and SDH4), and antioxidation (FMN1 and SNZ1). The accelerated growth dynamics and cell metabolic activity as well as the elevated antioxidant enzyme activity were all in line with the transcriptomic data. As expected, the increased antioxidant enzyme activity reduced the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA). These results demonstrated that the mechanism of Ca ascorbate-induced enhancement of biocontrol efficacy is related to accelerating yeast proliferation and colonization, improving nutrient utilization, enhancing cell homeostasis and cell wall structure, and improving the environmental adaptability of yeast cells. Additionally, Ca2+ also has a synergistic effect on yeast physiological activity and antioxidant activity to promote the improvement of yeast biocontrol efficacy.