Involvement of intracellular Ca²⁺ in blue light‐dependent proton pumping in guard cell protoplasts from Vicia faba

Abstract

intracellular stores, and by 10 mM 2,5-di-(tert-butyl)-1,4-ben-Recent studies have suggested that Ca 2 + /calmodulin (CaM) or CaM-like proteins may be involved in blue light (BL)-de-zohydroquinone (BHQ) and 10 mM cyclopiazonic acid (CPA), inhibitors of Ca 2 + -ATPase in the sarcoplasmic and endoplas-pendent proton pumping in guard cells. As the increase in cytosolic concentration of Ca 2 + is required for the activation mic reticulum (ER). By contrast, the inhibitions were not observed by 10 mM thapsigargin, an inhibitor of animal of CaM and CaM-like proteins, the origin of the Ca 2 + was ER-type Ca 2 + -ATPase. The inhibitions by caffeine and BHQ investigated by measuring BL-dependent proton pumping with were reversible. Light-dependent stomatal opening in the epi-various treatments using guard cell protoplasts (GCPs) from Vicia faba. BL-dependent proton pumping was affected nei-dermis of Vicia was inhibited by caffeine, BHQ, and CPA. ther by Ca 2 + channel blockers nor by changes of Ca 2 + From these results, we conclude that the Ca 2 + thought to be concentration in the medium used for the GCPs. Addition of required for BL-dependent proton pumping may originate Ca 2 + ionophores and an agonist to GCPs did not induce from intracellular Ca 2 + stores, most likely from ER in guard cells, and that this origin of Ca 2 + may generate a stimulus-proton pumping. However, BL-dependent proton pumping was inhibited by 10 mM caffeine, which releases Ca 2 + from the specific Ca 2 + signal for stomatal opening.

Protein phosphatase 1 positively regulates stomatal opening in response to blue light in Vicia faba

“…However, the mechanisms of signal transduction from phototropins to the plasma membrane H ϩ -ATPase are largely unknown. Several components, including cytosolic Ca 2ϩ , RPT2 (ROOT PHOTOTROPISM2), and protein kinase in the plasma membrane, have been suggested to play a role, but the evidence to support these claims is not conclusive (12)(13)(14).…”

A Plant-Specific Protein Essential for Blue-Light-Induced Chloroplast Movements

“…Although these transient increases in cytosolic Ca 21 have been shown to be required for phototropism, inhibition of hypocotyl growth and stomatal regulation (Allen et al, 1999;Shimazaki et al, 1999;Folta et al, 2003;Babourina et al, 2004), it is unclear how or if they are required for blue-light-induced chloroplast movements.…”

Blue light activates calcium-permeable channels inArabidopsismesophyll cells via the phototropin signaling pathway

“…To date, little is known about the signal transduction elements following the blue-light perception by phot1 and phot2 (2,16,(20)(21)(22)(23)(24). In guard cells, blue-light activation of the plasma membrane H ϩ -ATPase depends on phototropins, driving turgor formation and stomatal opening (16).…”