BvMYB108‑BvERFs transcriptional switch enhances CLS (Cercospora leaf spot) resistance in Sugar beet (Beta vulgaris L.)

CLS (Cercospora leaf spot) of Sugar beet ( Beta vulgaris L. ssp. vulgaris ) seriously restricts sugar crop production, and its molecular mechanism underlying disease resistance remains to be elucidated. In this study, a transcription factor BvMYB108 was identified from sugar beet, which interacts with three ethylene-responsive factors, namely BvERF3/4/5, in the cell nucleus. After pathogen infection, the expression of BvERF4/5 is up-regulated while that of BvERF3 is down-regulated, but all three factors exhibit consistent regulatory effects on downstream target genes when co-expressed with BvMYB108. Dual-luciferase reporter assays demonstrated that BvMYB108 alone activates the lignin biosynthesis gene BvPAL and inhibits the chitinase genes BvCHIB1/8; when co-expressed with BvERF, BvMYB108 inhibits BvPAL and activates BvCHIB1/8. BvMYB108 does not contain an EAR repression motif, and its inhibitory function may be achieved through competitive binding or recruitment of co-repressors, with protein interaction mediating the functional switch. Physiological assays showed that jasmonic acid (JA) content increases, 1-aminocyclopropane-1-carboxylic acid (ACC) content decreases slightly, and lignin accumulation increases in resistant sugar beet varieties. This study reveals that the BvMYB108‑BvERF complex fine-tunes the regulation of CLS resistance in sugar beet by switching the transcriptional output of physical and chemical defense pathways, providing novel gene resources for disease-resistant breeding of sugar beet.