Double-stranded RNA-binding protein DRB3 negatively regulates anthocyanin biosynthesis by modulating PAP1 expression in Arabidopsis thaliana

Abstract

The model plant Arabidopsis thaliana has five double-stranded RNA-binding proteins (DRB1-DRB5), two of which, DRB1 and DRB4, are well characterized. In contrast, the functions of DRB2, DRB3 and DRB5 have yet to be elucidated. In this study, we tried to uncover their functions using drb mutants and DRB-over-expressed lines. In over-expressed lines of all five DRB genes, the over-expression of DRB2 or DRB3 (DRB2ox or DRB3ox) conferred a downward-curled leaf phenotype, but the expression profiles of ten small RNAs were similar to that of the wild-type (WT) plant. Phenotypes were examined in response to abiotic stresses. Both DRB2ox and DRB3ox plants exhibited salt-tolerance. When these plants were exposed to cold stress, drb2 and drb3 over-accumulated anthocyanin but DRB2ox and DRB3ox did not. Therefore, the over-expression of DRB2 or DRB3 had pleiotropic effects on host plants. Microarray and deep-sequencing analyses indicated that several genes encoding key enzymes for anthocyanin biosynthesis, including chalcone synthase (CHS), dihydroflavonol reductase (DFR) and anthocyanidin synthase (ANS), were down-regulated in DRB3ox plants. When DRB3ox was crossed with the pap1-D line, which is an activation-tagged transgenic line that over-expresses the key transcription factor PAP1 (Production of anthocyanin pigmentation1) for anthocyanin biosynthesis, over-expression of DRB3 suppressed the expression of PAP1, CHS, DFR and ANS genes. DRB3 negatively regulates anthocyanin biosynthesis by modulating the level of PAP1 transcript. Since two different small RNAs regulate PAP1 gene expression, a possible function of DRB3 for small RNA biogenesis is discussed.

A noninvasive, machine learning–based method for monitoring anthocyanin accumulation in plants using digital color imaging

“…pap1‐D is an activation tagging mutant with an enhanced expression of MYB75 , which is a master regulator of the anthocyanin biosynthesis pathway (Borevitz et al., ). Due to the activation of MYB75 in pap1‐D , several genes encoding key enzymes in anthocyanin biosynthesis (e.g., chalcone synthase, dihydroflavonol reductase, and anthocyanidin synthase) are upregulated in this mutant, resulting in its overproduction of anthocyanin (Sawano et al., ). ref2 and b2b3 are mutants with defects in the enzymes involved in the biosynthesis of defense compounds called glucosinolates (Zhao et al., ; Hemm et al., ).…”

Map‐based cloning of the pear gene MYB114 identifies an interaction with other transcription factors to coordinately regulate fruit anthocyanin biosynthesis

“…() reported that miR858 negatively regulates anthocyanin biosynthesis by modulating the expression of two R2R3 MYB TFs. A dsRNA binding protein DRB3 negatively regulates anthocyanin biosynthesis by modulating PAP1 expression in Arabidopsis (Sawano et al ., ). Xie et al .…”

Plant RNA Binding Proteins as Critical Modulators in Drought, High Salinity, Heat, and Cold Stress Responses: An Updated Overview

“…This class of RBPs harbors an evolutionarily conserved, double-stranded RNA (dsRNA)binding domain (dsRBD)/dsRNA-binding motif (dsRBM) [76]. Plant proteins can have one or more DSRM, and each is comprised of 65 conserved amino acids with a characteristic (α1-β1-β2-β3-α2) fold that interact with double-stranded RNAs [12,76]. Studies with Arabidopsis DRBPs revealed their association with small plant RNA biogenesis pathways [120].…”

“…Five DRBPs (DRBP1-5) were reported in Arabidopsis. Of these, overexpression of DRB2 and DRB3 exhibited salt tolerance [76]. Upon exposure to cold stress conditions, drb2 and drb3 mutants enhanced the accumulation of anthocyanins by regulating anthocyanin biosynthesis genes.…”