title: The Breakdown of Stored Triacylglycerols Is Required during Light-Induced Stomatal Opening.
abstract: Stomata regulate the uptake of CO2 and the loss of water vapor [1] and contribute to the control of water-use efficiency [2] in plants. Although the guard-cell-signaling pathway coupling blue light perception to ion channel activity is relatively well understood [3], we know less about the sources of ATP required to drive K(+) uptake [3-6]. Here, we show that triacylglycerols (TAGs), present in Arabidopsis guard cells as lipid droplets (LDs), are involved in light-induced stomatal opening. Illumination induces reductions in LD abundance, and this involves the PHOT1 and PHOT2 blue light receptors [3]. Light also induces decreases in specific TAG molecular species. We hypothesized that TAG-derived fatty acids are metabolized by peroxisomal β-oxidation to produce ATP required for stomatal opening. In silico analysis revealed that guard cells express all the genes required for β-oxidation, and we showed that light-induced stomatal opening is delayed in three TAG catabolism mutants (sdp1, pxa1, and cgi-58) and in stomata treated with a TAG breakdown inhibitor. We reasoned that, if ATP supply was delaying light-induced stomatal opening, then the activity of the plasma membrane H(+)-ATPase should be reduced at this time. Monitoring changes in apoplastic pH in the mutants showed that this was the case. Together, our results reveal a new role for TAGs in vegetative tissue and show that PHOT1 and PHOT2 are involved in reductions in LD abundance. Reductions in LD abundance in guard cells of the lycophyte Selaginella suggest that TAG breakdown may represent an evolutionarily conserved mechanism in light-induced stomatal opening.
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
authors.forename: Deirdre H
authors.initials: DH
authors.lastname: McLachlan
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
authors.forename: Jue
authors.initials: J
authors.lastname: Lan
authors.affiliation: Institut fur Pflanzenernährung und Bodenkunde, Christian-Albrechts-Universität zu Kiel, Hermann-Rodewald- Straße 2, 24118 Kiel, Germany.
authors.forename: Christoph-Martin
authors.initials: CM
authors.lastname: Geilfus
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
authors.forename: Antony N
authors.initials: AN
authors.lastname: Dodd
authors.affiliation: Centre for Novel Agricultural Products, Department of Biology, University of York, York YO10 5DD, UK.
authors.forename: Tony
authors.initials: T
authors.lastname: Larson
authors.affiliation: Centre for Plant Sciences, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Alison
authors.initials: A
authors.lastname: Baker
authors.affiliation: Institute of Technology, University of Tartu, Nooruse 1, Tartu 50411, Estonia.
authors.forename: Hanna
authors.initials: H
authors.lastname: Hõrak
authors.affiliation: Institute of Technology, University of Tartu, Nooruse 1, Tartu 50411, Estonia.
authors.forename: Hannes
authors.initials: H
authors.lastname: Kollist
authors.affiliation: Centre for Novel Agricultural Products, Department of Biology, University of York, York YO10 5DD, UK.
authors.forename: Zhesi
authors.initials: Z
authors.lastname: He
authors.affiliation: Centre for Novel Agricultural Products, Department of Biology, University of York, York YO10 5DD, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Graham
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK; Department of Botany and Plant Pathology, Purdue University, 915 W. State Street, West Lafayette, IN 47907, USA.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Mickelbart
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK. Electronic address: alistair.hetherington@bristol.ac.uk.
authors.forename: Alistair M
authors.initials: AM
authors.lastname: Hetherington
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D008027:Light; D054046:Plant Stomata / Q000502:physiology; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D014280:Triglycerides