The ethylene response factor AtERF98 enhances tolerance to salt through the transcriptional activation of ascorbic acid synthesis in Arabidopsis

Abstract

SUMMARYAscorbic acid (AsA) is an important antioxidant in plants, and its biosynthesis is finely regulated through developmental and environmental cues; however, the regulatory mechanism remains unclear. In this report, the knockout and knockdown mutants of Arabidopsis AtERF98 decreased the AsA level, whereas the overexpression of AtERF98 increased it, which suggests that AtERF98 plays an important role in regulating AsA biosynthesis. AtERF98-overexpressing plants showed enhanced expression of AsA synthesis genes in the D-mannose/L-galactose (D-Man/L-Gal) pathway and the myo-inositol pathway gene MIOX4, as well as of AsA turnover genes. In contrast, AtERF98 mutants showed decreased expression of AsA synthesis genes in the D-Man/L-Gal pathway but not of the myo-inositol pathway gene or AsA turnover genes. In addition, the role of AtERF98 in regulating AsA production was significantly impaired in the D-Man/L-Gal pathway mutant vtc1-1, but the expression of the myo-inositol pathway gene or AsA turnover genes was not affected, which indicates that the regulation of AtERF98 in AsA synthesis is primarily mediated by the D-Man/L-Gal pathway. Transient expression and chromatin immunoprecipitation assays further showed that AtERF98 binds to the promoter of VTC1, which indicates that AtERF98 modulates AsA biosynthesis by directly regulating the expression of the AsA synthesis genes. Moreover, the knockout mutant aterf98-1 displayed decreased salt-induced AsA synthesis and reduced tolerance to salt. The supplementation of exogenous AsA increased the salt tolerance of aterf98-1; coincidently, the enhanced salt tolerance of AtERF98-overexpressing plants was impaired in vtc1-1. Thus, our data provide evidence that the regulation of AtERF98 in AsA biosynthesis contributes to enhanced salt tolerance in Arabidopsis.

From network to phenotype: the dynamic wiring of an Arabidopsis transcriptional network induced by osmotic stress

“…A mutant in STZ has previously been shown to be more tolerant to sorbitol‐induced stress and salt stress (Mittler et al , 2006), which also corresponds to its mannitol‐tolerant phenotype observed in this study. In contrast, erf98 has been described to be more sensitive to salt stress, which we could not observe under mannitol stress (Zhang et al , 2012). Overexpression of WRKY33 has been reported to infer an increased tolerance to high concentrations of salt (Jiang & Deyholos, 2009), whereas inducible activation of WRKY33 leads to a higher sensitivity to mild mannitol‐induced stress.…”

KONJAC1 and 2 Are Key Factors for GDP-Mannose Generation and Affect l-Ascorbic Acid and Glucomannan Biosynthesis in Arabidopsis

“…Due to the pivotal role of this enzyme, efforts to enhance AsA levels in planta have targeted VTC1 gene expression (Cronje et al, 2012). Recently, a transcription factor, ETHYLENE RESPONSE FACTOR98 (ERF98) has been identified as a positive regulator of VTC1 (Zhang et al, 2012). However, a protein factor that directly stimulates the GMPP activity of VTC1 remains to be identified.…”

Arabidopsis CSN5B Interacts with VTC1 and Modulates Ascorbic Acid Synthesis

“…Ascorbic acid (AsA; vitamin C) is an important plant-derived antioxidant and constitutes a major source of dietary vitamin C in humans; in plants, AsA plays important roles in growth, development, and stress responses (Smirnoff and Wheeler, 2000;Hemavathi et al, 2010;Zhang et al, 2012). AsA has been proposed to function as an enzyme cofactor in photosynthesis and the syntheses of ethylene, gibberellins, and anthocyanins.…”