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Article|01 Apr 2021|OPEN
Genomic analysis uncovers functional variation in the C-terminus of anthocyanin-activating MYB transcription factors
Jessica A. Rodrigues1, Richard V. Espley1 & Andrew C. Allan1,2,
1The New Zealand Institute for Plant and Food Research Limited, 120 Mount Albert Road, Sandringham, Auckland 1025, New Zealand
2School of Biological Sciences, University of Auckland, 3A Symonds St, Auckland 1010, New Zealand

Horticulture Research 8,
Article number: 77 (2021)
doi: 10.1038/hortres.2021.77
Views: 322

Received: 06 Dec 2020
Revised: 16 Feb 2021
Accepted: 01 Mar 2021
Published online: 01 Apr 2021

Abstract

MYB transcription factors regulate diverse aspects of plant development and secondary metabolism, often by partnering in transcriptional regulatory complexes. Here, we harness genomic resources to identify novel MYBs, thereby producing an updated eudicot MYB phylogeny with revised relationships among subgroups as well as new information on sequence variation in the disordered C-terminus of anthocyanin-activating MYBs. BLAST® and hidden Markov model scans of gene annotations identified a total of 714 MYB transcription factors across the genomes of four crops that span the eudicots: apple, grape, kiwifruit and tomato. Codon model-based phylogenetic inference identified novel members of previously defined subgroups, and the function of specific anthocyanin-activating subgroup 6 members was assayed transiently in tobacco leaves. Sequence conservation within subgroup 6 highlighted one previously described and two novel short linear motifs in the disordered C-terminal region. The novel motifs have a mix of hydrophobic and acidic residues and are predicted to be relatively ordered compared with flanking protein sequences. Comparison of motifs with the Eukaryotic Linear Motif database suggests roles in protein–protein interaction. Engineering of motifs and their flanking regions from strong anthocyanin activators into weak activators, and vice versa, affected function. We conclude that, although the MYB C-terminal sequence diverges greatly even within MYB clades, variation within the C-terminus at and near relatively ordered regions offers opportunities for exploring MYB function and developing superior alleles for plant breeding.