Coordinated regulation of two LacI family regulators, GvmR and GvmR2, on guvermectin production in .

Guvermectin, a purine nucleoside natural product produced by the genus S, has recently been registered as a new biopesticide to boost rice yield. Despite its economic and agricultural significance, the regulatory mechanisms of guvermectin biosynthesis remain essentially unknown, hindering industrial production and widespread agricultural application. Here, we examined the roles of two LacI family regulators, and , located within and adjacent to the guvermectin biosynthesis cluster, respectively, in guvermectin production in NEAU6. GvmR activated the expression of the guvermectin cluster by binding to the promoters of , , and , while GvmR2 repressed the guvermectin cluster via competitive binding to promoters containing GvmR-binding sites, specifically, a 14-bp palindromic sequences: 5'-RTCATWCGYATGAY-3' (R = G/A, W = A/T, Y = T/C). Moreover, GvmR indirectly activates the expression of while GvmR2 feedback inhibits transcription, suggesting a functional interaction between the two regulators for coordinating guvermectin production. Overexpression of via the T7 RNA polymerase-T7 promoter system in the mutant significantly elevated guvermectin production by 125 % (from 631 mg L to 1422 mg L), compared to the parental strain NEAU6. This suggested that combinatorial manipulation of and is useful for improving guvermectin production. These findings enrich our knowledge of the regulatory network for guvermectin biosynthesis, and offer key targets and effective strategies for high-titer guvermectin production.