Arabidopsis ROOT HAIR DEFECTIVE3 is involved in nitrogen starvation‐induced anthocyanin accumulation

Abstract

Anthocyanin accumulation is a common phenomenon seen in plants under environmental stress. In this study, we identified a new allele of ROOT HAIR DEFECTIVE3 (RHD3) showing an anthocyanin overaccumulation phenotype under nitrogen starvation conditions. It is known that ethylene negatively regulates light-and sucrose-induced anthocyanin biosynthesis. We hypothesized that RHD3 achieves its negative effect on anthocyanin biosynthesis via an ethylene-regulating pathway. In support of this, similar to rhd3 mutants, the Arabidopsis ethylene signaling mutants etr1, ein2, and ein3/eil1 showed an anthocyanin overaccumulation phenotype under nitrogen starvation conditions. The ethylene precursor ACC strongly suppressed anthocyanin accumulation, dependent on ETR1, EIN2, EIN3/EIL1, and, partially, RHD3. In addition, inactivating RHD3 partially reversed the suppressive effect of ETO1 inactivation-evoked endogenous ethylene production on anthocyanin accumulation. The expression of nitrogen starvation-induced anthocyanin biosynthesis genes was negatively regulated by RHD3, but ethylene response genes were positively regulated by RHD3. Wild-type seedlings overexpressing RHD3 showed similar phenotypes to rhd3 mutants, indicating the existence of a fine-tuned relationship between gene expression and function. RHD3 was initially identified as a gene involved in root hair development. This study uncovered a new physiological function of RHD3 in nitrogen starvationinduced anthocyanin accumulation and ethylene homeostasis.[Correction added on 6 August 2015, after first online publication: "RND3" corrected to "RHD3".]

Do Extended Cultivation Periods and Reduced Nitrogen Supply Increase Root Yield and Anthocyanin Content of Purple Carrots?

“…As the N concentrations in roots and leaves of carrots from all treatments ( Figure 2) were within the range of those reported for orange carrot varieties [18,37], they were not a limiting factor for plant performance. Thus, a reduced N supply did not result in increased synthesis of anthocyanins in leaves and roots (Figure 4), contrary to our expectations based on reports for various other plant species [15,[22][23][24][25][26]. It was shown that the concentration of phenolic compounds increased in well-fertilized compared to non-fertilized orange carrot plants [29] suggesting a positive relationship of N supply and concentration of phenolics in carrots.…”

“…Indeed, for a wide range of plant species, including model plants such as Arabidopsis thaliana [15,23,24] and agricultural or horticultural crops [24][25][26], it was shown that N deficiency results in the accumulation of foliar anthocyanins. For orange carrots, Seljasen et al [8,27] proposed a relatively low level of N fertilization, having benefits for their composition and their sensory properties.…”

Anthocyanin Management in Fruits by Fertilization

“…For example, a detailed overview of the effects of N and P deficiency on the expression levels of all major enzymes of the anthocyanin biosynthesis pathway in leaves and roots of Arabidopsis was presented by Lillo, et al 41 . The results of this study together with other publications of the recent years 38,39,[42][43][44][45][46][47][48][49][50][51][52] indicate that anthocyanins are produced in a highly regulated, fine-tuned, and nutrient-specific manner as a result of a metabolic adaptation to nutrient stress. Especially anthocyanin-specific genes, namely dihydroflavonol 4-reductase (DFR) and anthocyanidin synthase (ANS), as well as genes involved in anthocyanidin glycosylation and sequestration into the vacuole are highly expressed in response to nutrient deficiency, indicating that the observed anthocyanin accumulation is not simply the result of an up-regulation of the general phenylpropanoids pathway, which also yields other secondary metabolites such as flavonols and lignin.…”

A SIMPLE Pipeline for Mapping Point Mutations

“…Browsing the SNP population in this region identifies a premature stop codon in RHD3 (AT3G13870). Indeed, this line has a short root and wavy root hair phenotype similar to the mapped M2-300/M3-300-4 line and to rhd3-1 (Wang et al, 1997(Wang et al, , 2015. Supplemental File S1 lists all putative causal SNPs from line M2-194, with four (marked in boldface) that have allele frequencies that resemble contaminating wild-type plants in the mutant bulk.…”

“…Line 300 (and 300-4, a segregating line of 300) was crossed with rhd3-1 (Wang et al, 1997(Wang et al, , 2015, and the F1 progeny have short root and wavy phenotype similar to the parental lines, suggesting that these lines are allelic. Line 300-7 was crossed with SALK line 063371 (Liu et al, 2010), and the F1 progeny phenocopied both parental lines.…”