MYB21 interacts with MYC2 to control the expression of terpene synthase genes in flowers of Freesia hybrida and Arabidopsis thaliana

Abstract

<jats:title>Abstract</jats:title> <jats:p>Previously, linalool was found to be the most abundant component among the cocktail of volatiles released from flowers of Freesia hybrida. Linalool formation is catalysed by monoterpene synthase TPS1. However, the regulatory network developmentally modulating the expression of the TPS1 gene in Freesia hybrida remains unexplored. In this study, three regulatory genes, FhMYB21L1, FhMYB21L2, and FhMYC2, were screened from 52 candidates. Two MYB transcription factor genes were synchronously expressed with FhTPS1 and could activate its expression significantly when overexpressed, and the binding of FhMYB21L2 to the MYBCORE sites in the FhTPS1 promoter was further confirmed, indicating a direct role in activation. FhMYC2 showed an inverse expression pattern compared with FhTPS1; its expression led to a decreased binding of FhMYB21 to the FhTPS1 promoter to reduce its activation capacity when co-expressed, suggesting a role for an MYB–bHLH complex in the regulation of the FhTPS1 gene. In Arabidopsis, both MYB21 and MYC2 regulators were shown to activate the expression of sesquiterpene synthase genes, and the regulatory roles of AtMYB21 and AtMYC2 in the expression of the linalool synthase gene were also confirmed, implying conserved functions of the MYB–bHLH complex in these two evolutionarily divergent plants. Moreover, the expression ratio between MYB21 and MYC2 orthologues might be a determinant factor in floral linalool emission.</jats:p>

Differential regulation of triterpene biosynthesis induced by an early failure in cuticle formation in apple

“…TFs from the R2-R3 MYB, WRKY, basic helix–loop–helix (bHLH) and ethylene-responsive factor (ERF) classes were differentially expressed in RU compared with GD. Of particular interest were MYB TFs as some MYBs have been linked to the regulation of both cuticle 41 and terpene biosynthesis 42 , 43 and, in apple, triterpenes are an integral part of cutin-associated and suberin-associated waxes 28 . A regularised canonical correlation analysis (rCCA) was performed to identify MYBs that were related to the production of specific types of triterpenes.…”

The spatio‐temporal biosynthesis of floral flavonols is controlled by differential phylogenetic MYB regulators in Freesia hybrida

“…S10). Based on the fact that regulatory genes and their targets are usually expressed synchronously with each other (Yang et al ., 2020), Pearson's correlation of the fragments per kilobase million (FPKM) values was calculated for FhFLS2 and the potential regulators; 36 candidates were obtained (Fig. S11), which were further co‐transfected with FLS2‐F pro : GUS into protoplasts.…”

“…Moreover, in the myb21myb24 double mutant flowers, the release of volatile sequiterpenes was decreased, and this was accompanied by the downregulation of terpene synthase genes AtTPS11 and AtTPS21 , indicating the involvement of these MYB regulators in the biosynthesis of volatile compounds. Recently, we verified that the MYB‐bHLH complex consisted of MYB21 and IIIe‐bHLH proteins, and that this complex could also cooperatively regulate the expression of TPS genes (Yang et al ., 2020). In accordance with the MYB triad in Arabidopsis (Battat et al ., 2019), a similar MYB triad containing PhEOBI, PhEOBII and PhODO1 was also shown to coregulate genes responsible for the flower volatile compounds in Petunia hybrida (Van Moerkercke et al ., 2011; Spitzer‐Rimon et al ., 2012).…”

“…The sequences obtained were subjected to a manual Blastx search of the National Center for Biotechnology Information (NCBI) database, and the best hits were defined as candidate FhFLS and FhMYBF transcripts. Moreover, the established Freesia regulator database was employed to screen for FhFLS2 candidate factors using Pearson’s correlation of reads per kilobase per million mapped reads (RPKM) values at the 1% significance level, as described in our recent study (Yang et al ., 2020, Dataset S2). For promoter isolation, the 5′ flanking sequences of Freesia flavonol biosynthetic genes were cloned using a Genome Walking Kit (Takara, Dalian, China) according to the manufacturer’s instructions.…”

Comparative transcriptomics reveals hidden issues in the plant response to arthropod herbivores

“…Members of the MYB and bHLH TF families act together regulating the biosynthesis of secondary metabolites. MYB21 interacts with MYC2 to control the expression of terpene synthase genes (Yang et al, 2020); MYB28, 29, 34, and 122 interact with MYC2, both being involved in the production of indole and aliphatic glucosinolates (Schweizer et al, 2013); and MYB24 together with a set of MYB‐bHLH interacting partners regulate the biosynthesis of flavonoids and anthocyanins (Xu et al, 2014; Battat et al, 2019).…”