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5月26日，苏黎士理工大学综合生物学研究所的Diana Santelia团队在Plant Cell在线发表了题为Guard Cell Starch Degradation Yields Glucose for Rapid Stomatal Opening in Arabidopsis的研究论文。文章揭示了光照通过膜离子运输和淀粉代谢调控保卫细胞开闭的分子机制。
拟南芥保卫细胞中的淀粉在一天开始时被葡聚糖水解酶α-淀粉酶3(AMY3)和β-淀粉酶1(BAM1)迅速降解，以促进气孔开放。这一过程是通过质膜H+-ATPase下游的光敏素介导的蓝光信号来激活的。在气孔开放动力学的精细控制中，保卫细胞淀粉降解如何与光调控的膜运输过程相结合尚不清楚。
本文发现在amy3 bam1突变体保卫细胞质膜上的H+、K+和Cl-转运没有改变，表明淀粉降解产物不直接影响保卫细胞的离子转运能力。酶定量分析表明，在蓝光照射30min后，amy3 bam1保卫细胞的苹果酸水平与野生型相似，但糖的稳态发生了显着变化，几乎检测不到葡萄糖的含量。因此，在拟南芥保卫细胞中，葡萄糖而不是苹果酸是淀粉衍生的主要代谢物。进一步的研究表明，amy3 bam1突变体的淀粉降解受损会导致40min的开放时间常数增加。
因此，得出的结论是，黎明时快速的淀粉降解是维持细胞质糖库所必需的，而细胞质糖库显然是气孔快速打开所必需的。因此，亚细胞间代谢产物的转换和交换，能够通过膜离子运输来协调细胞的能量和代谢状态。
红光对保卫细胞糖代谢及气孔动力学的影响
附：
Abstract
Starch in Arabidopsis guard cells is rapidly degraded at the start of the day by the glucan hydrolases α-amylase3 (AMY3) and β-amylase1 (BAM1) to promote stomatal opening. This process is activated via phototropin-mediated blue light signaling downstream of the plasma membrane H+-ATPase. It remains unknown how guard cell starch degradation integrates with light-regulated membrane transport processes in the fine control of stomatal opening kinetics. We report that H+, K+ and Cl- transport across the guard cell plasma membrane is unaltered in the amy3 bam1 mutant, suggesting that starch degradation products do not directly affect the capacitiy to transport ions. Enzymatic quantification revealed that after 30 min of blue light illumination, amy3bam1 guard cells had similar malate levels as the wild type, but had dramatically altered sugar homeostasis, with almost undetectable amounts of glucose. Thus, glucose, not malate, is the major starch-derived metabolite in Arabidopsis guard cells. We further show that impaired starch degradation in the amy3bam1 mutant resulted in an increase in the time constant for opening of 40 min. We conclude that rapid starch degradation at dawn is required to maintain the cytoplasmic sugar pool, clearly needed for fast stomatal opening. The conversion and exchange of metabolites between subcellular compartments therefore coordinates the energetic and metabolic status of the cell with membrane ion transport.
文章链接：/content/early//05/26/tpc.18.00802
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