Phenylalanine-cultured Meyerozyma caribbica enhances cysteine metabolism to improve black spot disease resistance in jujube

The yeast strain Meyerozyma caribbica (M. caribbica) is a highly effective control measure for black spot rot in jujube. Our previous studies have shown that phenylalanine can improve the biocontrol efficacy of M. caribbica, but the related molecular mechanism is unknown. This study pointed out that phenylalanine could improve the ability of M. caribbica to induce black spot rot resistance in jujube fruit. Transcriptomic results showed the expression of several amino acid metabolism genes were up-regulated after M. caribbica treatment, and these genes was mainly enriched in the cysteine metabolism pathway. Phenylalanine-cultured M. caribbica enhanced the activities of O-acetylserine (thiol)lyase (OASTL), L-cysteine desulfhydrase (LCD), and D-cysteine desulfhy-drase (DCD) in the cysteine metabolism pathway of jujube fruit, promoted the accumulation of cysteine, hydrogen sulfide, and glutathione, and increased the expression of CysE, CysK, LCD, BCAT, and AGXT. In addition, it stimulated the creation of hydrogen peroxide and improved SOD, CAT, and POD activities in jujube. In summary, phenylalanine-cultured M. caribbica improved jujube fruit black spot resistance by activating cysteine metabolism.