The Effect Of Yeast On Regulating Water Use Efficiency And The Mechanism Of Yeast-induced Stomatal Immunity In Crops

It has been proved that phyllosphere microorganisms can induce stomatal immunity against pathogen invasion. Previous studies mainly focused on the roles of stomatal closure in disease resistance. Stomata can also control gas exchange, but the effects of stomatal immunity on CO2uptake or water loss from the leaf is scant. Can yeast-induced stomatal closure increase water use efficiency (WUE)? Based on the principles of stomatal biology and photosynthetic physiology, we hypothesized that yeast-induced stomatal immunity can increase water use efficiency, but the plants differ in their manners in which concentration of yeast are applied. More specifically, microbes can induce stomatal closure as well as decrease transpiration and photosynthesis, resulting in increasing WUE. The appropriate concentration of microorganisms is changed with plant species and the growing stages due to variations in stomatal structures and metabolic differences. The main objectives of this work were to find out the mechanism of yeast-induced stomatal closure and to find out whether yeast can improve plant water use efficiency by using direct microscopic observation, gas exchange measurement and chlorophyll fluorescence imaging. We can summarize the results as follows:(1) Phyllosphere yeast increased intrinsic water use efficiency (WUEi) and the appropriate concentration of yeast is different for different plants. Yeast iecreased WUEi of broad beans, tomato and rice. WUEi of broad beans was increased to similar extents under treatment with105,107and109cfu/ml of yeast. The appropriate concentration of yeast is different for tomato and rice is10and10cfu/ml, respectively.(2) The effects of yeast for rice were different at different growing stages. Under well-watered conditions, application of yeast increased WUEi and irrigation water use efficiency (IWUE). Under drought conditions, applying yeast increased WUEi during middle stages compared with the drought without yeast. Under drought conditions, yeast application increased seed set rate,1000-grain weight, grain yield, harvest index(HI), grain:straw and IWUE compared with drought without yeast.(3) H2O2, NO and Ca2+are involved in yeast-induced stomatal closure. S. cerevisiae induced stomatal closure in a dose-dependent manner on Vicia faba L.(cv. Daqingpi). Using pharmacological inhibitors in this study, we found that H2O2was mostly produced by cell wall peroxidases and NO in guard cells of V.faba is derived from both NOS-like enzyme and nitrate reductase.(4) Trehalose can reduce stomatal aperture by a hydrogen-peroxide-dependent pathway on Vicia faba L., resulting in significantly lower values of net PN, gS and E. At8h and24h, the drastic reduction in photosynthesis was caused by stomatal inhibition. At48h and72h, the drastic reduction in photosynthesis was caused by non-stomatal inhibition.In summary, we revealed that in a certain developmental stage, the phyllosphere microbes-induced stomatal immunity can improve plant WUE at appropriate concentration of applied yeast. The appropriate concentration of microorganisms is changed with plant species and the growing stages. Stomatal immunity response is triggered by trehalose of yeast cell through adjusted cell signaling pathways such as H2O2, NO as well as Ca2+and water channels. Our results may have an important role for understanding the interactions between microbe and plants and finding out the mechanism and quantitative relationship between yeast-induced stomatal immunity response and crop water physiological processes as well as WUE. Furthermore, our findings can be used to develop a new environmental harmless anti-transpiration agent, which has a important application in reduction of agricultural pollution.