Evolution of A bHLH Interaction Motif

Abstract

Intrinsically disordered proteins and regions with their associated short linear motifs play key roles in transcriptional regulation. The disordered MYC-interaction motif (MIM) mediates interactions between MYC and MYB transcription factors in Arabidopsis thaliana that are critical for constitutive and induced glucosinolate (GLS) biosynthesis. GLSs comprise a class of plant defense compounds that evolved in the ancestor of the Brassicales order. We used a diverse set of search strategies to discover additional occurrences of the MIM in other proteins and in other organisms and evaluate the findings by means of structural predictions, interaction assays, and biophysical experiments. Our search revealed numerous MIM instances spread throughout the angiosperm lineage. Experiments verify that several of the newly discovered MIM-containing proteins interact with MYC TFs. Only hits found within the same transcription factor family and having similar characteristics could be validated, indicating that structural predictions and sequence similarity are good indicators of whether the presence of a MIM mediates interaction. The experimentally validated MIMs are found in organisms outside the Brassicales order, showing that MIM function is broader than regulating GLS biosynthesis.

Quantitative trait loci analysis of glucosinolate, sugar, and organic acid concentrations in Eruca vesicaria subsp. sativa

“…No SNP changes are in proximity to the two DNA-binding domains (DBDs; positions 72 to 123, and 126 to 174) but the changes at positions 229 and 231 are near the highly conserved MYC-interaction motif (MIM; [F]LN[R][V]A). The core xLNxxA motif is required for binding with bHLH (basic helix-loop-helix) MYC transcription factors, such as MYC2, MYC3 and MYC4, which are responsible for the interaction of GSL transcription factors with the JA signaling pathway (Millard et al 2021 ). It is therefore likely that the identified ortholog of MYB51 is associated with the regulation, biosynthesis, and metabolism of 4MGB in Eruca .…”

“…Its proximity to two IGMT gene isoforms also indicates that this is a locus for both transcriptional regulation and synthesis of the compound. MYB51 is known to interact directly with MYC2 via a MIM, which is conserved between all known GSL-regulating MYB transcription factors (Millard et al 2021 ). The presence of a JAZ5 ( TIFY 11A ) gene underlying a separate locus for 4MGB on LG12 indicates that JA signaling may influence concentrations via interaction with MYC2.…”

Genome-Wide Identification and Characterization of the bHLH Gene Family and Its Response to Abiotic Stresses in Carthamus tinctorius

“…Members within this subfamily may act similarly to those found in Panax ginseng, where these factors are involved in regulating phenylpropane biosynthesis [60]. The interaction between MYB and bHLH TFs has been shown to influence various processes, including defense metabolism, anthocyanin biosynthesis, and organ development, such as trichome initiation [67][68][69][70].…”

Effects of BrMYC2/3/4 on Plant Development, Glucosinolate Metabolism, and Sclerotinia sclerotiorum Resistance in Transgenic Arabidopsis thaliana

“…It was reported that bHLH-type MYC TFs, participating in crosstalk among JA and other hormones as well as environmental signals, allow the coordinated and rapid regulation of GS genes (Mitreiter and Gigolashvili, 2021). MYC-interaction motif mediates interactions between MYC and MYB TFs in A. thaliana that are critical for constitutive and induced GS biosynthesis (Millard et al, 2021). MYC3/4 act additively with MYC2 to stimulate GS biosynthesis (Guo et al, 2013).…”