Nitric oxide, actin reorganization and vacuoles change are involved in PEG 6000-induced stomatal closure in Vicia faba.
Water deficit and the resulting osmotic stress affect stomatal movement. There are two types of signals, hydraulic and chemical signals, involving in the regulation of stomatal behavior responses to osmotic stress. Compared with the chemical signals, little has been known about the hydraulic signals and the corresponding signal transduction network and regulatory mechanisms. Here, using an epidermal-strip bioassay and laser-scanning confocal microscopy, we provide evidence that nitric oxide (NO) generation in Vicia faba guard cells can be induced by hydraulic signals. We used polyethylene glycol (PEG) 600 to simulate hypertonic conditions. This hydraulic signal led to stomatal closure and rapid promotion of NO production in guard cells. The effects were decreased by NO scavenger 2-(4-carboxyphenyl)-4,4,5, 5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO) and NO synthase (Enzyme Commission 1.14.13.39) inhibitor N(G)-nitro-L-Arg-methyl ester (L-NAME). These results indicate that PEG 6000 induces stomatal closure by promoting NO production. Cytochalasin B (CB) inhibited stomatal closure induced by PEG 6000 but did not prevent the increase of endogenous NO levels, indicating that microfilaments polymerization participate in stomatal closure induced by PEG 6000, and may act downstream of NO signaling. In addition, big vacuoles split into many small vacuoles were observed in response to PEG 6000 and sodium nitroprusside (SNP) treatment, and CB inhibited these changes of vacuoles, the stomatal closure was also been inhibited. Collectively, these results suggest that the stomatal closure induced by PEG 6000 may be intimately associated with NO levels, reorganization of actin filaments and the changes of vacuoles, showing a crude outline of guard-cells signaling process in response to hydraulic signals.
Huang
Ai-Xia
AX
Key Laboratory of Medicinal Plant Resource and Natural Pharmaceutical Chemistry of Ministry of Education, College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China.
She
Xiao-Ping
XP
Cao
Bin
B
Zhang
Bei
B
Mu
Juan
J
Zhang
Shao-Jie
SJ
D000199:Actins / Q000378:metabolism*; D001565:Benzoates / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D018613:Microscopy, Confocal; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology*; D018526:Plant Transpiration; D011092:Polyethylene Glycols / Q000494:pharmacology*; D014617:Vacuoles / Q000502:physiology*; D031307:Vicia faba / Q000187:drug effects / Q000502:physiology*; D014867:Water / Q000502:physiology
D000199:Actins; D001565:Benzoates; D007093:Imidazoles; D014867:Water; C079393:1,3-dihydroxy-4,4,5,5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole; D009569:Nitric Oxide; D003571:Cytochalasin B; D011092:Polyethylene Glycols; D019331:NG-Nitroarginine Methyl Ester