The Breakdown of Stored Triacylglycerols is Required during Light-Induced Stomatal Opening

Deirdre H McLachlan, Jue Lan, Christoph-Martin Geilfus, Antony N Dodd, Tony Larson, Alison Baker, Hanna Hõrak, Hannes Kollist, Zhesi He, Ian Graham, Michael V Mickelbart, Alistair M Hetherington*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

51 Citations (Scopus)
386 Downloads (Pure)

Abstract

Stomata regulate the uptake of CO2 and the loss of water vapor and contribute to the control of water-use efficiency in plants. Although the guard-cell-signaling pathway coupling blue light perception to ion channel activity is relatively well understood, we know less about the sources of ATP required to drive K+ uptake. 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. 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.

Original languageEnglish
Pages (from-to)707-712
Number of pages6
JournalCurrent Biology
Volume26
Issue number5
Early online date18 Feb 2016
DOIs
Publication statusPublished - 7 Mar 2016

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    McLachlan, D. H., Lan, J., Geilfus, C-M., Dodd, A. N., Larson, T., Baker, A., Hõrak, H., Kollist, H., He, Z., Graham, I., Mickelbart, M. V., & Hetherington, A. M. (2016). The Breakdown of Stored Triacylglycerols is Required during Light-Induced Stomatal Opening. Current Biology, 26(5), 707-712. https://doi.org/10.1016/j.cub.2016.01.019