Table_1_Stomatal responses to VPD utilize guard cell intracellular signaling components.pdf

Stomatal pores, vital for CO2 uptake and water loss regulation in plants, are formed by two specialized guard cells. Despite their importance, there is limited understanding of how guard cells sense and respond to changes in vapor pressure difference (VPD). This study leverages a selection of CO2 hyposensitive and abscisic acid (ABA) signaling mutants in Arabidopsis, including heterotrimeric G protein mutants and RLK (receptor-like kinase) mutants, along with a variety of canola cultivars to delve into the intracellular signaling mechanisms prompting stomatal closure in response to high VPD. Stomatal conductance response to step changes in VPD was measured using the LI-6800F gas exchange system. Our findings highlight that stomatal responses to VPD utilize intracellular signaling components. VPD hyposensitivity was particularly evident in mutants of the ht1 (HIGH LEAF TEMPERATURE1) gene, which encodes a protein kinase expressed mainly in guard cells, and in gpa1-3, a null mutant of the sole canonical heterotrimeric Gα subunit, previously implicated in stomatal signaling. Consequently, this research identifies a nexus in the intricate relationships between guard cell signal perception, stomatal conductance, environmental humidity, and CO2 levels.

气孔（stomatal pores）是植物摄取二氧化碳、调控水分散失的核心结构，由一对特化的保卫细胞构成。尽管其生理功能至关重要，但学界对保卫细胞如何感知并响应水汽压亏缺（vapor pressure difference, VPD）的分子机制仍缺乏深入认知。本研究选取了拟南芥（Arabidopsis）中对二氧化碳不敏感的突变体及脱落酸（abscisic acid, ABA）信号通路突变体——包括异三聚体G蛋白（heterotrimeric G protein）突变体与类受体激酶（receptor-like kinase, RLK）突变体——并结合多种甘蓝型油菜栽培品种（canola cultivars），深入探究了驱动保卫细胞响应高VPD引发气孔关闭的胞内信号转导机制。研究人员使用LI-6800F气体交换系统（LI-6800F gas exchange system），测定了气孔导度对水汽压亏缺阶跃变化的响应。本研究结果显示，植物响应VPD的气孔调控过程依赖于胞内信号组分。其中，ht1（HIGH LEAF TEMPERATURE1, HT1）基因（其编码主要在保卫细胞中表达的蛋白激酶）突变体，以及gpa1-3——该突变体是唯一经典异三聚体Gα亚基（heterotrimeric Gα subunit）的功能缺失突变体，此前已被证实参与气孔信号转导——均表现出显著的VPD不敏感表型。综上，本研究明确了保卫细胞信号感知、气孔导度、环境湿度与二氧化碳水平之间复杂调控网络中的关键节点。