Function Analysis Of Flavonols In Drought Resistance And Water Saving Of Wheat

Under salt and drought stress,plants can promote the synthesis of flavonoids and other secondary metabolites to enhance tolerance.Flavonoids are classified into six categories including flavonols and anthocyanins,among which flavonols have the highest activities.Unlike other flavonoids,flavonols accumulate well in guard cells,suggesting flavonols may participate in the response to drought via modulating stomatal movement.Flavonols are synthesized by the catalysis of flavonol synthase（FLS）.Our lab previously found that the overexpression of FLS gene promoted flavonol accumulation,and enhanced drought tolerance via promoting stomatal closure;the FLS gene TaFLS1 was induced by drought in wheat,and the wheat introgression line SR3 produced more TaFLS1 transcripts and synthesized more flavonols than its parent JN177,showing the close relationship between flavonols and drought tolerance in wheat.Upon this issue,we conducted some experiments and obtained the following results.1.The water withholding assay indicated that the seedlings of SR3 had superior drought tolerance than JN177.The land assay showed that SR3 had higher yield and water use efficiency than JN177 under different water saving conditions.2.The water withholding assay found that TaFLSl overexpression obviously enhanced drought tolerance,water use efficiency and the ratio of ABA-induced stomatal closure,and decreased water loss rate,while TaFLS1 RNAi had an opposite effect,showing the in vivo flavonol accumulation enhances drought tolerance and water use efficiency via promoting stomatal closure.3.Flavonols include quercetin and kaempferol.The water withholding assay indicated that quercetin spray enhanced drought tolerance,water use efficiency and the ratio of ABA-induced stomatal closure,and decreased water loss rate,while kaempferol spray had no obvious effect.This result demonstrates that the role in drought tolerance is different between quercetin and kaempferol,and quercetin spray can mimic the effect of flavonol accumulation by TaFLSl overexpression.4.Both TaFLS1 overexpression and quercetin spray enhanced wheat yield under different water saving conditions,indicating that TaFLS1 is a candidate gene for molecular breeding for wheat drought tolerance,and quercetin has potential in chemical agriculture.5.The enhancement of drought tolerance by quercetin spray had dosage effect,and the obvious role was found when the concentration was more than 200 μM。The effect of quercetin spray was dependent on water status of leaves:quercetin spray elevated water loss rate of leaves under well-watered conditions,but reduced water loss rate of leaves under water withholding conditions.The effect on water loss rate was found after 36h of quercetin spray,but was not detectable after 60h,showing the effect of quercetin spray sustained a certain course.