Abstract
Glucosinolates (GSLs) are widely known secondary metabolites that have anticarcinogenic and antioxidative activities in humans and defense roles in plants of the Brassicaceae family. Some R2R3-type MYB (myeloblastosis) transcription factors (TFs) control GSL biosynthesis in Arabidopsis. However, studies on the MYB TFs involved in GSL biosynthesis in Brassica species are limited because of the complexity of the genome, which includes an increased number of paralog genes as a result of genome duplication. The recent completion of the genome sequencing of the Brassica species permits the identification of MYB TFs involved in GSL biosynthesis by comparative genome analysis with A. thaliana. In this review, we describe various findings on the regulation of GSL biosynthesis in Brassicaceae. Furthermore, we identify 63 orthologous copies corresponding to five MYB TFs from Arabidopsis, except MYB76 in Brassica species. Fifty-five MYB TFs from the Brassica species possess a conserved amino acid sequence in their R2R3 MYB DNA-binding domain, and share close evolutionary relationships. Our analysis will provide useful information on the 55 MYB TFs involved in the regulation of GSL biosynthesis in Brassica species, which have a polyploid genome.
Highlights
Plants produce various secondary metabolites that are involved in traits such as taste, color, and scent, and have roles in plant defense against environmental changes or stress unrelated to the primary functions of plants, such as development, reproduction, and photosynthesis [1]
MYB34, MYB51, and MYB122 have been shown to regulate indolic GSL. We describe these various findings to provide an integrative understanding of divergence and a functional diversification of the MYB transcription factors (TFs) involved in GSL biosynthesis following genome duplication in A. thaliana and Brassica species
MYB34 group formed a subgroup with MYB51. These results indicated that the six MYB TFs related to GSL biosynthesis were evolutionarily conserved in Brassica species and exhibit functional conservation
Summary
Plants produce various secondary metabolites that are involved in traits such as taste, color, and scent, and have roles in plant defense against environmental changes or stress unrelated to the primary functions of plants, such as development, reproduction, and photosynthesis [1]. The completion of the polyploid genome sequence of the Brassica species permits the identification of various gene families of secondary metabolites by comparative genome analysis with A. thaliana. BrFLCs showed different expression levels in tissue (leaf and root) and in unvernalized and vernalized B. rapa [13] Such variation in the copy number of genes could play a major role in regulatory processes in the Brassica genus. Functional analysis of these genes has demonstrated that GSL biosynthesis in Brassica species is controlled by more regulators than in Arabidopsis, because of their polyploid genomes [16,17]. We describe these various findings to provide an integrative understanding of divergence and a functional diversification of the MYB TFs involved in GSL biosynthesis following genome duplication in A. thaliana and Brassica species
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