Chlorella Induces Stomatal Closure via NADPH Oxidase-Dependent ROS Production and Its Effects on Instantaneous Water Use Efficiency in Vicia faba

Abstract

Reactive oxygen species (ROS) have been established to participate in stomatal closure induced by live microbes and microbe-associated molecular patterns (MAMPs). Chlorella as a beneficial microorganism can be expected to trigger stomatal closure via ROS production. Here, we reported that Chlorella induced stomatal closure in a dose-and time-dependent manner in epidermal peels of Vicia faba. Using pharmacological methods in this work, we found that the Chlorella-induced stomatal closure was almost completely abolished by a hydrogen peroxide (H2O2) scavenger, catalase (CAT), significantly suppressed by an NADPH oxidase inhibitor, diphenylene iodonium chloride (DPI), and slightly affected by a peroxidase inhibitor, salicylhydroxamic acid (SHAM), suggesting that ROS production involved in Chlorella-induced stomatal closure is mainly mediated by DPI-sensitive NADPH oxidase. Additionally, Exogenous application of optimal concentrations of Chlorella suspension improved instantaneous water use efficiency (WUEi) in Vicia faba via a reduction in leaf transpiration rate (E) without a parallel reduction in net photosynthetic rate (Pn) assessed by gas-exchange measurements. The chlorophyll fluorescence and content analysis further demonstrated that short-term use of Chlorella did not influence plant photosynthetic reactions center. These results preliminarily reveal that Chlorella can trigger stomatal closure via NADPH oxidase-dependent ROS production in epidermal strips and improve WUEi in leave levels.

Bacillus subtilis-regulation of stomatal movement and instantaneous water use efficiency in Vicia faba

“…Recently, stomatal aperture is also observed to change in response to numerous biotic cues (Sawinski et al 2013). For instance, stomata can actively close on detection of the presence of live bacteria, barley mildew, yeast, yeast elicitor (YEL), Chlorella and purified microbe-associated molecular patterns (MAMPs) by activating a series of complex signaling transduction pathways (Melotto et al 2006;Khokon et al 2010a;Koers et al 2011;Gao et al 2013;Li et al 2014b). Interestingly, Kumar et al (2012) found that the root inoculation of the Bacillus subtilis FB17 could also induce stomatal closure to prevent foliar pathogen entry into leaf inner tissues.…”

Chlorella triggers stomatal closure mediated by NADPH oxidase and improves instantaneous water use efficiency inVicia faba

“…Our present work showed that optimal concentrations of Chlorella suspension caused significant reductions in leaf stomatal aperture, stomatal conductance (g s ) and transpiration rate (E) without a parallel reduction in net photosynthetic rate (P n ) and intercellular CO 2 concentration (C i ), favoring a higher WUE i in Vicia faba. 12 The chlorophyll fluorescence and content analysis further demonstrated that Chlorella did not affect plant photosynthetic reactions center after short-term foliar application. 12 Nevertheless, whether the leaf chlorophyll fluorescence and content are influenced after treatment with appropriate concentrations of Chlorella suspension for a longer time needs to be further assessed.…”

“…12 The chlorophyll fluorescence and content analysis further demonstrated that Chlorella did not affect plant photosynthetic reactions center after short-term foliar application. 12 Nevertheless, whether the leaf chlorophyll fluorescence and content are influenced after treatment with appropriate concentrations of Chlorella suspension for a longer time needs to be further assessed. Taken together, these results preliminarily suggest that optimal concentrations of Chlorella suspension can improve the WUE i in plants after short-term foliar spray, mainly attributing to a reduction in stomatal conductance above the threshold, under which transpiration rates are diminished significantly while photosynthetic rates hardly affected.…”

“…[8][9][10][11] Notably, Our recent work showed that Chlorella induced stomatal closure in a dose-and timedependent manner in Vicia faba, just as other microbes and MAMPs did. 2,5,6,12 The perception of MAMPs by pattern recognition receptors (PRRs) is the vital first step for the microbe-triggered stomatal closure. [13][14][15] MAMPs are some conserved molecules on the surface of microorganisms.…”

“…20 22,23 Our studies demonstrated that ROS production mainly via plasma membrane NADPH oxidase was involved in Chlorellainduced stomatal closure. 12 It is the same case as ABA-, methyl jasmonate (MeJA)-, ozone-, darkness, ethylene-, allyl isothiocyanate (AITC)-, low dose of UV B (UV-B)-, bacterial flagellum (flg22)-, bacterial elongation factor Tu (elf18)-, and bacterial lipopolysaccharides (LPS)-induced stomatal closure mediated by NADPH oxidase, 2,24-29 while distinct from SA-, high dose of UV-B-, chitosan-, yeast elicitor (YEL)-, methylglyoxal-, and yeast-triggered stomatal closure via cell wall peroxidase. [30][31][32][33][34][35] Besides ROS, whether Chlorella-induced stomatal closure depends on other components of ABA and SA signaling pathways need to be further explored.…”