Schematic diagram of ABA and nitric oxide (NO) interaction in the guard cells of nia1nia2of Arabidopsis thaliana. Based on the well established ABA signalling pathway, we hypothesize that, in the absence of NO production of nia1nia2, ABA is still transported to guard cells and sensed by the PYR/PYL/RCAR receptor complex (Rc). However, ABA-induced up-regulation of protein phosphatase 2C (PP2C; ABI1 and ABI2) genes in nia1nia2 blocks the downstream SnRK2.6/OST1 that inactivates anion channels (A−). Further, low endogenous NO is unable to inhibit IK,in in a Ca2+-dependent manner. Basic helix–loop–helix (bHLH) transcription factor AKS1 enhances both the K+in channel gene KAT1 at the transcriptional level and 14-3-3 protein for phosphorylation of H+-ATPase at the post-translational level. K+out channel GORK is still responsive to ABA via protein phosphorylation. Also, other transcription factors (TFs; e.g. MYBs, ABF1) are involved in this impaired stomatal closure as positive or negative regulators (see Fig. 10 and Table 1). Red arrows, signal induction; red arrows with cross, no signal activation; red stop arrows, signal inhibition.
Nitrate reductase mutation alters potassium nutrition as well as nitric oxide-mediated control of guard cell ion channels in Arabidopsis
by Chen Z.-H., Wang Y. W.-W., Babla M., Zhao C., Garcia-Mata C., Sani E., Differ C., Mak M., Hills A., Amtmann A., Blatt M. R. (2015)
Zhong-Hua Chen, Yizhou WaJian-Wen Wang, Mohammad Babla, Chenchen Zhao, Carlos García-Mata, Emanuela Sani, Christopher Differ, Michelle Mak, Adrian Hills, Anna Amtmann, Michael R. Blatt
in New Phytologist 209(4): 1456–1469 –
- Maintaining potassium (K+) nutrition and a robust guard cell K+ inward channel activity is considered critical for plants’ adaptation to fluctuating and challenging growth environment. ABA induces stomatal closure through hydrogen peroxide and nitric oxide (NO) along with subsequent ion channel-mediated loss of K+ and anions. However, the interactions of NO synthesis and signalling with K+ nutrition and guard cell K+ channel activities have not been fully explored in Arabidopsis.
- Physiological and molecular techniques were employed to dissect the interaction of nitrogen and potassium nutrition in regulating stomatal opening, CO2 assimilation and ion channel activity. These data, gene expression and ABA signalling transduction were compared in wild-type Columbia-0 (Col-0) and the nitrate reductase mutant nia1nia2.
- Growth and K+ nutrition were impaired along with stomatal behaviour, membrane transport, and expression of genes associated with ABA signalling in the nia1nia2mutant. ABA-inhibited K+in current and ABA-enhanced slow anion current were absent in nia1nia2. Exogenous NO restored regulation of these channels for complete stomatal closure in nia1nia2.
- While NO is an important signalling component in ABA-induced stomatal closure in Arabidopsis, our findings demonstrate a more complex interaction associating potassium nutrition and nitrogen metabolism in the nia1nia2 mutant that affects stomatal function.