Abscisic acid (ABA) increases reactive oxygen species (ROS; 活性氧物质) in guard cells (保卫细胞) to close Arabidopsis stomata (气孔). In Solanum lycopersicum (番茄) we find that ABA increased ROS is followed by stomatal closure (气孔关闭) and both responses are blocked by inhibitors of ROS-producing respiratory burst oxidase enzymes (呼吸爆发氧化酶). ABA-induced ROS sensor fluorescence accumulates in the nucleus, chloroplasts, and in endomembranes (内膜). Accumulation of flavonol antioxidants (黄酮类抗氧化剂) in guard cells, but not surrounding pavement cells (扁平细胞), were visualized by confocal microscopy (共聚焦显微镜) using a flavonol-specific fluorescent dye (荧光染料). Decreased flavonols in guard cells in the are mutant and elevated levels in the aw mutant were quantified by confocal microscopy and in leaf extracts by mass spectrometry (质谱分析). Consistent with flavonols acting as antioxidants, higher levels of ROS were detected in guard cells of the tomato are mutant and lower in aw both at homeostasis and after treatment with ABA. These results demonstrate the inverse relationship (相反关系) between flavonols and ROS. Guard cells of are show greater ABA-induced closure than WT, reduced light-dependent guard cell opening, and reduced water loss, with aw having opposite responses. Ethylene treatment of wild-type tomato plants increased flavonol accumulation in guard cells; however, no flavonol increases were observed in Neverripe (Nr), an ethylene receptor mutant. Consistent with lower levels of ROS due to elevated flavonols, ethylene treatments decreased ABA-induced stomatal closure in wildtype, but not Nr, with ethylene responses attenuated (衰减) in the are mutant. Together these results are consistent with flavonols dampening (抑制) the ABA-dependent ROS burst that drives stomatal closure and facilitating stomatal opening to modulate leaf gas exchange.

First Published data: October 19, 2017.