Loss of nitrate reductases NIA1 and NIA2 impairs stomatal closure by altering genes of core ABA signaling components in Arabidopsis

Abstract

Nitrate reductases NIA1 and NIA2 determine NO production in plants and are critical to abscisic acid (ABA)-induced stomatal closure. However, the role for NIA1 and NIA2 in ABA signaling has not been paid much attention in nitrate reductase loss-of-function mutant nia1nia2. Recently, we have demonstrated that ABA-inhibited K(+)in current and ABA-enhanced slow anion current were absent in nia1nia2. Exogenous NO restored regulation of these channels for stomatal closure in nia1nia2. In this study, we found that mutating NIA1 and NIA2 impaired nearly all the key components of guard cell ABA signaling pathway in Arabidopsis. We also propose a simplified model for ABA signaling in the nia1nia2 mutant.

Keywords: Abscisic acid; gene expression; guard cell; nitric oxide; signaling transduction.

Figure 1.

Heat map of abscisic acid and nitric oxide induced expression of key genes in the ABA signaling pathway. Abundance of gene expression in the Control of Col-0 was set to zero. Expression of the same genes under treatment or in nia1nia2 was calculated relative to the Control in Col-0. Quantitative real-time PCR was replicated six times. Abbreviations: ABA, abscisic acid: SNP, sodium nitroprusside (nitric oxide donor); TFs, transcription factors; RCAR, regulatory components of ABA receptor; ABI, abscisic acid-insensitive; CIPK, CBL-interacting protein kinase; OST1/SnRK2.6, open stomata 1; SOS2, salt overly sensitive 2; AKS, ABA-responsive kinase substrate; MYB, MYB domain protein; ABF1, ABA responsive element-binding factor; NIA, nitrate reductase; NOA1, nitric oxide associated 1; GLU1, glutamate Synthase 1; GLN1, glutamine Synthetase 1; KAT1, inwardly-rectifying K⁺ channel in Arabssinwardly-rectifying K⁺ channel; KC1, inwardly-rectifying K⁺ channel 1; GORK, guard cell outwardly-rectifying K⁺ channel; SLAC1, Slow anion channel 1; SLAH3, slow anion channel homolog 3; NRT, nitrate transporter.

Figure 2.

Schematic diagram of abscisic acid signaling transduction in guard cell of nia1nia2 of Arabidopsis. See text for more details. Abbreviations: ABA, abscisic acid; NO, nitric oxide; NR, nitrogen reductase: ROS, reactive oxygen species; TFs, transcription factors; ABI, abscisic acid insensitive; NR, nitrate reductase; NIA, nitrate reductase; KAT1, inwardly-rectifying K⁺ channel in Arabidopsis; GORK, guard cell outwardly-rectifying K⁺ channel; SLAC1, slow anion channel 1. solid red arrows, signal induction; solid blue arrows, signal inhibition; dashed red arrows, hypothetical induction; dashed blue arrows, hypothetical inhibition.