Faculty of Biology, University of Latvia, 1 Jelgavas Street, Riga, LV-1004, Latvia.
Faculty of Chemistry, University of Latvia, 1 Jelgavas Street, Riga, LV-1004, Latvia.
Plant Physiol Biochem. 2019 Jul;140:18-26. doi: 10.1016/j.plaphy.2019.05.004. Epub 2019 May 3.
Arabidopsis thaliana cyclic nucleotide-gated ion channel gene 4 (AtCNGC4) loss-of-function mutant dnd2 exhibits elevated accumulation of salicylic acid (SA), dwarfed morphology, reduced hypersensitive response (HR), altered disease resistance and spontaneous lesions on plant leaves. An orthologous barley mutant, nec1, has been reported to over-accumulate indole-3-acetic acid (IAA) and to exhibit changes in stomatal regulation in response to exogenous auxin. Here we show that the Arabidopsis dnd2 over-accumulates both IAA and abscisic acid (ABA) and displays related phenotypic and physiological changes, such as, reduced stomatal size, higher stomatal density and stomatal index. dnd2 showed increased salt tolerance in root growth assay and significantly reduced stomatal conductance, while maintaining near wt reaction in stomatal conductance upon external application of ABA, and probably consequently increased drought stress tolerance. Introduction of both sid2-1 and fmo1 into dnd2 background resulting in removal of SA did not alter stomatal conductance. Hence, the closed stomata of dnd2 is probably a result of increased ABA levels and not increased SA levels. The triple dnd2sid2abi1-1 mutant exhibited intermediate stomatal conductance compared to dnd2 and abi1-1 (ABA insensitive, open stomata), while the response to external ABA was as in abi1-1 suggesting that reduced stomatal conductance in dnd2 is not due to impaired ABA signaling. In conclusion, Arabidopsis dnd2 mutant exhibited ABA overaccumulation and stomatal phenotypes, which may contribute to the observed improvement in drought stress resistance. Thus, Arabidopsis dnd2 mutant may serve as a model for studying crosstalk between biotic and abiotic stress and hormonal response in plants.
拟南芥环核苷酸门控离子通道基因 4（AtCNGC4）功能丧失突变体 dnd2 表现出水杨酸（SA）积累增加、植株矮小、过敏反应（HR）减弱、抗病性改变和叶片自发损伤。已报道同源大麦突变体 nec1 吲哚-3-乙酸（IAA）过度积累，并对外源生长素表现出气孔调节变化。本文显示，拟南芥 dnd2 过度积累 IAA 和脱落酸（ABA），并表现出相关的表型和生理变化，如气孔变小、气孔密度和指数增加。dnd2 在根生长测定中表现出耐盐性增强，气孔导度显著降低，而在外源施加 ABA 时维持接近 wt 的气孔导度反应，可能因此增强耐旱性。将 sid2-1 和 fmo1 引入 dnd2 背景中以去除 SA 并没有改变气孔导度。因此，dnd2 关闭的气孔可能是由于 ABA 水平增加而不是 SA 水平增加所致。三重 dnd2sid2abi1-1 突变体与 dnd2 和 abi1-1（ABA 不敏感，气孔开放）相比表现出中间的气孔导度，而对外源 ABA 的反应与 abi1-1 相同，表明 dnd2 中气孔导度的降低不是由于 ABA 信号受损所致。总之，拟南芥 dnd2 突变体表现出 ABA 过度积累和气孔表型，这可能有助于观察到的耐旱性提高。因此，拟南芥 dnd2 突变体可作为研究植物生物和非生物胁迫及激素反应交叉对话的模型。
