| Wheat is one of the main food crops in China and its yield is closely related to food security of China.In arid and semi-arid areas of northwest China,drought is the main factor limiting wheat yield,so breeding has become an important approach to improve wheat yield under drought conditions.With the rapid development of genetic engineering in the improvement of plant abiotic stress resistance,transcription factor genes may become a kind of practical and effective targets for wheat drought resistance.Many GRAS family transcription factors regulate the growth and development of plants,and regulate the molecular and physiological metabolism of plant resistance.However,until now,the researches on wheat GRAS family transcription factors have mainly focused on the the composition,distribution,gene structure,expression profile analysis and whole-genome identification of the family,but the effect of SCR gene of GRAS family transcription factor on wheat plant growth and drought resistance has not been revealed.Therefore,it can provide fundamental theoretical basis for high-yield cultivation and selection of stress-resistant varieties of wheat,and has important guiding significance for the application of biotechnology in wheat breeding by studying the effects of TaSCR gene on growth and physiology of wheat under drought stress.In this study,we selected the non-transgenic wheat "Ningchun 16"(CK)and the transgenic TaSCR gene wheat as materials to systematically analyze the transgenic TaSCR gene root and aboveground growth parameters,drought-resistant physiological parameters,the variation of yield and yield components under different water conditions employed indoor hydroponic experiment and pot experiment from 2020 to2021.The aim of this study was to clarify the effects of TaSCR gene on wheat growth and drought resistance improvement under drought stress.The main conclusions were odtained as follows:(1)Transgenic TaSCR overexpressed wheat strains had higher relative water content and lower malondialdehyde content in leaves,and shoot and root growth were better compared with non-transgenic control wheats under drought stress at seedling stage.Total root length,root surface area,root volume,maximum root length,shoot and root dry weight,root shoot ratio were all higher in overexpressed strains than nontransgenic control wheats.The indexes of silent strains showed an opposite trend to those of overexpressed strains.The results of root anatomy showed that the cortical and endodermis cells of all lines were significantly changed under drought stress,and the cortical cells of silent lines were the most disorderly and irregular.The endodermis disappeared and the cortical cells were seriously deformed under 20% PEG treatment.These results suggest that TaSCR gene regulate drought resistance of wheat by affecting osmotic stress resistance at seedling stage,thus affecting the growth and development of wheat.(2)Leaf relative water content,net photosynthetic rate,stomatal conductance and chlorophyll content of transgenic TaSCR overexpressed wheat strains were significantly increased,malonaldehyde accumulation was reduced,soluble protein content,POD,SOD and CAT activity increased compared with non-transgenic control wheats,but the changes of these indexes in silent strains were opposite to those in overexpressed strains.These results indicated that the overexpression of TaSCR gene increased the drought resistance of wheat during the middle and late development,while the silencing of TaSCR gene decreased the drought resistance of wheat.(3)The plant height,leaf area,number of main stem leaves and tillers,aboveground and underground biomass,number of spikes and spikelets,grain yield,1000-grain weight and water use efficiency of the transgenic TaSCR overexpressed wheat strains were higher than non-transgenic control wheat,while all these indexes decreased in silent strains.These results indicated that the overexpression of TaSCR gene positively regulated the growth in the middle and late stage of wheat development,and ultimately improved the wheat yield,while the silencing of TaSCR gene adversely affected the growth and yield formation in the middle and late stage of wheat development.These results show that TaSCR gene can regulate the development of root system and aboveground growth and drought resistance physiology metabolism process in the period of wheat seedling and middle and later stage under the drought stress.Therefore,the growth of wheat root system and aboveground and the photosynthetic ability of wheat flag leaf and spike were improved under drought stress,and the yield and drought resistance were promoted.These results provide a theoretical basis for further study on the effects of TaSCR gene on wheat plant growth and drought resistance. |
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