Effects Of Postharvest UV-C Irradiation On The Synthesis Of GABA And Phenolic Compounds In Tomato Fruit

In recent years,UV-C irradiation has been widely used in postharvest treatment of fruit and vegetables to improve the storage quality.Tomato fruit contain many bioactive compounds which are beneficial to human health and play an important role in the study of fruit development and ripening.In this paper,4 k J/m2 UV-C irradiation was used to treat tomato fruit and storage at 13 ℃ and 95 % relative humidity(RH)in the dark.Then the effects of postharvest UV-C irradiation on the synthesis ofγ-aminobutyric acid(GABA)and phenolic compounds in tomato fruit were studied.In order to further explore the mechanism of the synthesis of phenolic compounds induced by UV-C irradiation,the transcription factors related to the synthesis of phenolic compounds were screened by yeast one-hybrid technology.The following results were obtained:1.Effects of postharvest UV-C irradiation on the synthesis of GABA in tomato fruit.UV-C irradiation significantly increased total soluble protein content,whereas decreased the content of total free amino acids.The results also showed that the content of glutamate,the precursor of GABA,was significantly reduced after UV-C irradiation in the late storage period.As compared to the control,the GABA content in tomato fruit was significantly increased after treated by UV-C irradiation,and UV-C irradiation could maintain a higher level of GABA after maturity.What’s more,the genes involved in the synthesis of GABA were significantly up-regulated after UV-C irradiation,including GAD1,GAD2 and GAD3.These results indicated that UV-C irradiation could promote the accumulation of GABA by inducing the expression of related genes in tomato fruit.2.Effects of postharvest UV-C irradiation on the synthesis of phenolic compounds in tomato fruit.UV-C irradiation significantly increased the total phenolic compounds,phenolic acids and flavonoids,including cafferic acid,p-coumaric acid,trans-ferulic acid,chlorogenic acid,gallic acid,protocatechuic acid,rutin and quercetin.In addition,UV-C irradiation also induced the expression of genes related to the synthesis of phenolic compounds,including PAL5,C4 H,4CL,CHS2,CHI,F3 H and FLS.The results showed that UV-C irradiation could promote the synthesis of phenolic compounds by regulating the expression of related genes in tomato fruit.3.Screening of transcription factors regulated by UV-C irradiation in the synthesis of phenolic compounds.The yeast one-hybrid technology was used to screen the transcription factors that regulated the expression of PAL5,the key gene related to the synthesis of phenolic compounds in tomato fruit.The transcription factor ERF7 was obtained by sequencing and blast homology analysis.And further experiments confirmed that ERF7 could interact with the promoter of PAL5.The results indicated that ERF7 may be involved in regulating the transcription of PAL5,and provided foundations for studying the regulation mechanism of the synthesis of phenolic compounds in tomato fruit induced by UV-C irradiation.