WRKY46 promotes ammonium tolerance in Arabidopsis by repressing NUDX9 and indole‐3‐acetic acid‐conjugating genes and by inhibiting ammonium efflux in the root elongation zone

Abstract

Summary Ammonium (NH4+) is toxic to root growth in most plants, even at moderate concentrations. Transcriptional regulation is one of the most important mechanisms in the response of plants to NH4+ toxicity, but the nature of the involvement of transcription factors (TFs) in this regulation remains unclear. Here, RNA‐seq analysis was performed on Arabidopsis roots to screen for ammonium‐responsive TFs. WRKY46, the member of the WRKY transcription factor family most responsive to NH4+, was selected. We defined the role of WRKY46 using mutation and overexpression assays, and characterized the regulation of NUDX9 and indole‐3‐acetic acid (IAA)‐conjugating genes by WRKY46 via yeast one‐hybrid and electrophoretic mobility shift assays and chromatin immunoprecipitation‐quantitative real‐time polymerase chain reaction (ChIP‐qPCR). Knockout of WRKY46 increased, while overexpression of WRKY46 decreased, NH4+‐suppression of the primary root. WRKY46 is shown to directly bind to the promoters of the NUDX9 and IAA‐conjugating genes (GH3.1, GH3.6, UGT75D1, UGT84B2) and to inhibit their transcription, thus positively regulating free IAA content and stabilizing protein N‐glycosylation, leading to an inhibition of NH4+ efflux in the root elongation zone (EZ). We identify TF involvement in the regulation of NH4+ efflux in the EZ, and show that WRKY46 inhibits NH4+ efflux by negative regulation of NUDX9 and IAA‐conjugating genes.

OsEIL1 protects rice growth under NH4+ nutrition by regulating OsVTC1‐3‐dependent N‐glycosylation and root NH4+ efflux

“…This result indicates that NH 4 + flux is not affected by AtEIN3. Similar to rice OsVTC1‐3, the Arabidopsis AtVTC1 mutant also shows higher NH 4 + efflux (Di et al, 2021; Q. Li et al, 2010; Figure 4d). However, NH 4 + did not affect Arabidopsis AtVTC1 expression (Figure 6e), consistent with previous reports (C. Qin et al, 2008; L. Zhang et al, 2021), and there was also no difference between the wild type ( Col‐0 ) and the ein3‐1 mutant.…”

“…OsEIL1 is located in the nucleus (C. Yang, Ma, et al, 2015), and we, therefore, needed to examine how the gene might be engaged in the regulation of root NH 4 + fluxes. Previous studies have produced evidence indicating a critical role for AtVTC1 in controlling root NH 4 + fluxes in Arabidopsis (Di et al, 2021; Q. Li et al, 2010). There are three VTC1 homologs, designated as OsVTC1‐1, OsVTC1‐3 and OsVTC1‐8, in rice.…”

“…An alternative explanation lies with direct downstream targets. AtVTC1 acts as a key modulator in the regulation of NH 4 + efflux in Arabidopsis (Di et al, 2021; Q. Li et al, 2010; C. Qin et al, 2008), and both NH 4 + efflux and inhibition of N‐glycosylation were more pronounced in the atvtc1 mutant than in the wild type. In contrast to the observation that OsEIL1 is upregulated by NH 4 + and binds directly to the promoter EBS sites of OsVTC1‐3, AtEIN3 does not directly interact with the AtVTC1 promoter and also has no effect on the AtVTC1 expression (Figure 6e,f).…”

“…Although the transcription of OsVTC1-3 is much lower in oseil1 than that of wild type under NH 4 + (Figure 2f interaction of proteins (Zeng et al, 2018). AtVTC1 has been reported to be involved in regulating Arabidopsis NH 4 + efflux by regulating protein N-glycosylation (Di et al, 2021;Q. Li et al, 2010;C.…”

MicroRNAs Are Involved in Regulating Plant Development and Stress Response through Fine-Tuning of TIR1/AFB-Dependent Auxin Signaling

“…In plants, auxin plays a central role in growth and development as well as responses to abiotic and biotic stresses [ 2 , 3 , 135 , 136 , 137 ]. Precise regulation of auxin homeostasis and its signaling is extremely critical.…”