A SlMYB75-centred transcriptional cascade regulates trichome formation and sesquiterpene accumulation in tomato

Abstract

Tomato trichomes act as a mechanical and chemical barrier against pests. An R2R3 MYB transcription factor gene, SlMYB75, is highly expressed in type II, V, and VI trichomes. SlMYB75 protein is located in the nucleus and possesses transcriptional activation activity. Down-regulation of SlMYB75 increased the formation of type II, V, and VI trichomes, accumulation of δ-elemene, β-caryophyllene, and α-humulene in glandular trichomes, and tolerance to spider mites in tomato. In contrast, overexpression of SlMYB75 inhibited trichome formation and sesquiterpene accumulation, and increased plant sensitivity to spider mites. RNA-Seq analyses of the SlMYB75 RNAi line indicated massive perturbation of the transcriptome, with a significant impact on several classes of transcription factors. Expression of the MYB genes SlMYB52 and SlTHM1 was strongly reduced in the RNAi line and increased in the SlMYB75-overexpressing line. SlMYB75 protein interacted with SlMYB52 and SlTHM1 and activated their expression. SlMYB75 directly targeted the promoter of the cyclin gene SlCycB2, increasing its activity. The auxin response factor SlARF4 directly targeted the promoter of SlMYB75 and inhibited its expression. SlMYB75 also bound to the promoters of the terpene synthase genes SlTPS12, SlTPS31, and SlTPS35, inhibiting their transcription. Our findings indicate that SlMYB75 perturbation affects several transcriptional circuits, resulting in altered trichome density and metabolic content.

Transcriptomic Characterization of Nitrate-Enhanced Stevioside Glycoside Synthesis in Stevia (Stevia rebaudiana) Bertoni

“…Although MYB TFs may regulate terpenoid biosynthesis as either activators or repressors (Supplemental Table S3), it seems that they have a positive regulatory effect in NO 3 − -mediated SGs synthesis, which was also confirmed in our more recent work [17]. Terpenoid-relevant MYB targeted promoters include those encoding GGPPS [64], dammarenediol synthase [65], CPS [66] and other TPS genes [67,68]. Other TFs such as AP2/ERF-ERF and bHLH have also been reported to play regulatory roles in terpenoid synthesis [69,70], but we could find no evidence of these being significant factors mediating N form-mediated metabolic reprogramming.…”

Genetic and physiological requirements for high-level sesquiterpene-production in tomato glandular trichomes

“…There was no differential expression in other transcription factors of potential interest. EOT1, MYC1 and MYB75 (Spyropoulou et al, 2014;Xu et al, 2018;Gong et al, 2021) did not significantly differ between the two genotypes studied here.…”

Transcriptome sequencing and gas chromatography–mass spectrometry analyses provide insights into β-caryophyllene biosynthesis in Brassica campestris

“…CpbHLH13 overexpression in A. thaliana ecotype Columbia-0 and tobacco genotype SR1 increased floral sesquiterpene BCP production in both transgenic plants ( Aslam, Lin, Li, Yang, & Chen, 2020 ). Downregulation of SlMYB75 increased the formation of type II, V, and VI trichomes and the accumulation of δ-elemene, BCP, and α-humulene in glandular trichomes ( Gong et al, 2021 ). The miR156-targeted SPL transcription factor plays an important role in the spatiotemporal regulation of sesquiterpene biosynthesis.…”