The Effect Of Exogenous γ-aminobutyric Acid On Improving Low Temperature Tolerance In Tea Plant(Camellia Sinensis L.)

Tea plant(Camellia sinensis(L.)O.Kuntze)is one of the important economic crops in China,while the extension of tea cultivation is restricted by low temperature stress.It is an arduous task to deeply study the regulation mechanism of tea tree under low temperature,which could improve the cold resistance of tea plants through cultivation,exogenous amino acid supplying and genetic engineering,as well as cold resistant varieties breeding.In order to do further study how GABA affects the resistance in tea plants under low temperature,this research was based on the determination of physiological indexes under low temperature stress and exogenous GABA applied under low temperature;Additionally,the iTRAQ technology was employed to analyze the unused and differentially abundant proteins of tea plant under low temperature stress and treated with exogenous GABA under low temperature.The main results are as follows:1.Physiological indexes of tea plant treated with normal temperature(T1),low temperature(T3)and low temperature+5 mM GABA(T4)were measured,and each treatment was repeated three times.It was found that the exogenous GABA could increase the content of chlorophyll(SPAD)in tea leaves under low temperature,while the malondialdehyde(MDA)content reduced by a certain extent,as well as the growth rate of part J of OJIP green fluorescence curve was significantly increased.The results showed that GABA could effectively alleviate the cell membrane damage and photosynthetic system of tea plant under low temperature stress.2.iTRAQ technology was employed for identifying the credible and differential abundance proteins of tea plants treated with normal temperature(T1),normal temperature+5 mM GABA(T2),low temperature(T3)and low temperature+5 mM GABA(T4),and each treatment was repeated three times.The results were as follows:A total of 1736 proteins were screened out from protein group 1.1756 credible proteins were screened from the credible protein group 2.A total of 1,736 trusted proteins were screened out from the trusted protein group 3.1303 proteins were identified in all three groups.In the comparison group,202,183,213,141 and 253 differential abundance proteins were screened from T2/T1,T3/T1,T4/T1,T4/T2 and T4/T3,respectively.3.Do functional annotation of differential abundance proteins against Uniport Arabidopsis thaliana database.The functional categories of differential abundance proteins include protein metabolism and nucleotide metabolism,energy metabolism,amino acid transport and metabolism,carbohydrate transport and metabolism,antioxidant and stress defense.These results provide a large number of candidate proteins for the study of how GABA participates in the response mechanism under low temperature of tea plants,and also provide a theoretical basis for the application of exogenous GABA under low temperature stress of tea plants.4.The comparison group of T4/T3 has 253 differential abundance proteins.The further classification and GO function analysis of the differences in protein reveal the influence of GABA in some metabolic pathways of tea plant,such as flavonoid metabolism,amino acid metabolism,AsA/glutathione cycle,TCA cycle,glyoxylate cycle,carbon fixation in photosynthetic organisms,oxidative pentose phosphate pathway and purine metabolism cause an interaction among plant cell components like chloroplasts,plastids and thylakoids.It was found that the expression patterns of some key genes in these metabolic pathways which conducted by qRT-PCR,were consistent with the corresponding differentially abundant protein expression patterns.The mechanism of how GABA participates in response to low temperature stress was preliminarily explored.The results not only enriched the data resources of tea plant proteome,but also laid a solid foundation for the development of tea plant cultivation and promotion.