title: Abscisic acid-responsive guard cell metabolomes of Arabidopsis wild-type and gpa1 G-protein mutants.
abstract: Individual metabolites have been implicated in abscisic acid (ABA) signaling in guard cells, but a metabolite profile of this specialized cell type is lacking. We used liquid chromatography-multiple reaction monitoring mass spectrometry for targeted analysis of 85 signaling-related metabolites in Arabidopsis thaliana guard cell protoplasts over a time course of ABA treatment. The analysis utilized ∼ 350 million guard cell protoplasts from ∼ 30,000 plants of the Arabidopsis Columbia accession (Col) wild type and the heterotrimeric G-protein α subunit mutant, gpa1, which has ABA-hyposensitive stomata. These metabolomes revealed coordinated regulation of signaling metabolites in unrelated biochemical pathways. Metabolites clustered into different temporal modules in Col versus gpa1, with fewer metabolites showing ABA-altered profiles in gpa1. Ca(2+)-mobilizing agents sphingosine-1-phosphate and cyclic adenosine diphosphate ribose exhibited weaker ABA-stimulated increases in gpa1. Hormone metabolites were responsive to ABA, with generally greater responsiveness in Col than in gpa1. Most hormones also showed different ABA responses in guard cell versus mesophyll cell metabolomes. These findings suggest that ABA functions upstream to regulate other hormones, and are also consistent with G proteins modulating multiple hormonal signaling pathways. In particular, indole-3-acetic acid levels declined after ABA treatment in Col but not gpa1 guard cells. Consistent with this observation, the auxin antagonist α-(phenyl ethyl-2-one)-indole-3-acetic acid enhanced ABA-regulated stomatal movement and restored partial ABA sensitivity to gpa1.
authors.affiliation: Biology Department, Pensylvania State University, University Park, Pensylvania 16802.
authors.forename: Xiaofen
authors.initials: X
authors.lastname: Jin
authors.forename: Rui-Sheng
authors.initials: RS
authors.lastname: Wang
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Zhu
authors.forename: Byeong Wook
authors.initials: BW
authors.lastname: Jeon
authors.forename: Reka
authors.initials: R
authors.lastname: Albert
authors.forename: Sixue
authors.initials: S
authors.lastname: Chen
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Assmann
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics*; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D055442:Metabolome / Q000187:drug effects*; D009154:Mutation; D010937:Plant Growth Regulators / Q000494:pharmacology*; D025341:Principal Component Analysis; D013312:Stress, Physiological
chemical_list: D029681:Arabidopsis Proteins; C429765:GPA1 protein, Arabidopsis; D044385:GTP-Binding Protein alpha Subunits; D010937:Plant Growth Regulators; D000040:Abscisic Acid