<i>Pichia galeiformis</i> Induces Resistance in Postharvest Citrus by Activating the Phenylpropanoid Biosynthesis Pathway

Abstract

This study aimed to investigate the effect of <i>Pichia galeiformis</i> on disease resistance and elucidate the changes in phenylpropane biosynthesis treated by <i>P. galeiformis</i> in postharvest citrus. The results showed that <i>P. galeiformis</i> reduced the disease incidence and lesion diameters without direct contact with the pathogen <i>Penicillium digitatum</i>. Transcriptome analysis revealed that phenylpropanoid biosynthesis was triggered by <i>P. galeiformis</i>. Genes encoding phenylpropanoid biosynthesis were upregulated, including phenylalanine ammonia-lyase (PAL), 4-coumaroyl-CoA ligase (4CL), cinnamate-4-hydroxylase (C4H), peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD), O-methyltransferase, and hydroxyl cinnamoyl transferase. Moreover, <i>P. galeiformis</i> increased the activity of PAL, 4CL, C4H, POD, polyphenol oxidase, and CAD in citrus pericarp. In addition, <i>P. galeiformis</i> treated citrus displayed higher levels of total phenolic compounds, flavonoid, and lignin and higher amounts of ferulic and sinapic acid. In conclusion, these results suggested that <i>P. galeiformis</i> could induce resistance through modulating the pathway of phenylpropanoid biosynthesis in postharvest citrus.