Stomata regulate the uptake of CO2, the loss of water vapour [1] and contribute to the control of water-use efficiency [2] in plants. Although the guard cell signalling 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 [3,4,5,6]. 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 hypothesised that TAG-derived fatty acids are metabolised 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, 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 evolutionary conserved mechanism in light-induced stomatal opening.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)