Tomato Flavor Substances And Related Gene Expression In Different Ripening Stages Response To Low Temperature

Tomato(Solanum lycopersicum L.)is one of the main vegetable varieties cultivated in facility.With the improvement of living standards,people began to pay more attention to fruit flavor.The flavor of tomato is mainly affected by sugar,acid and a variety of volatile substances.And the current research mainly focuses on the effect of low temperature on tomato fruit quality during post-harvest storage,including sugar,acid metabolism and volatile matter changes.However,the effect of low temperature on fruit ripening quality in facility cultivation is rarely reported.In this study,‘AC’ was used as the test material,and tomato plants with fruits at different ripening stages were treated with low temperature.Through transcriptomics and metabolomics analysis methods,the key factors of low temperature affecting the changes of flavor in tomato fruits were explored,in order to clarify that low temperature affects tomato fruits The molecular mechanism of flavor change lays the theoretical foundation.The results of this test are as follows:1.Low temperature reduces sugar and acid content in tomato fruits on the vine and regulates the expression of related genes.Low temperature treatment of tomato plants with fruits at different ripening stages,the content of glucose,fructose and malic acid were significantly reduced,and the MGLT treatment decreased the most.High-throughput sequencing combined with q RT-PCR results showed that low temperature significantly induces HXK1 and HXK4,and significantly inhibits the expression of HXK5 and SS1 genes to affect the synthesis of sugar metabolism in fruits;low temperature significantly induces the expression of SUT4,SWEET12 c and SWEET14 genes,and significantly inhibits the expression of SWEET10 b and SWEET11 a genes to affect sugar transport in fruits.At the same time,PECPK gene expression is inhibited at low temperature,and MDH,NAD-ME,NADP-ME and Sl TDT gene expression are induced to affect the degradation and transport of malate.2.Low temperature causes a decrease in amino acids in tomato fruits on the vine and regulates the expression of genes related to amino acid metabolism.Glutamic acid,valine,leucine,proline,arginine,citrulline and tryptophan in tomato fruits were significantly reduced under low temperature.The expression of ADC,ODC and Sl PDH genes was significantly up-regulated,which induced degradation of proline and arginine,which led to the decrease of proline and arginine content under low temperature;the expression of GDH and GS genes was significantly up-regulated,GOGAT significantly down-regulated under low temperature.Glutamate synthesis decreases and decomposition increases,resulting in a significant decrease in glutamate content under low temperature treatment;the expression of KARI,DHAD and BCAT4 genes is significantly up-regulated,but leucine and valine content significantly decrease under low temperature treatment.It may be caused by increased protein degradation,indicating that low temperature treatment may decrease the leucine and valine content by increasing protein degradation.3.Low temperature causes the fatty acid in tomato fruit on the vine to show an upward trend and regulates the expression of fatty acid metabolism-related genes.The fatty acid metabolite linoleic acid in tomato fruits under low temperature was significantly reduced,palmitic acid,stearic acid,oleic acid and linolenic acid increased but not significantly,the FAD3 gene expression level was down-regulated,while the Le FAD7 and S1FAD2-1 gene expression levels were up-regulated to affect the content of lipids in the fruit under low temperature treatment,thereby affecting the low temperature fruit flavor.4.Low temperature causes an upward trend in flavonoids in tomato fruits on the vine.The flavonoid metabolites quercetin,rutin,and delphinium derivatives in tomato fruits increased significantly under low temperature treatment.Low temperature significantly induced the expression of PAL,C3 H,CHI and ANS genes in fruits,and inhibited the expression of C4 H genes.In MGLT,the expressions of HCT and FLS were significantly up-regulated,indicating that low-temperature treatment may induce the accumulation of flavonoids by up-regulating some structural genes of the flavonoid metabolism pathway.5.Low temperature regulates the content of volatiles in tomato fruits on the vine.The overall content of volatile substances in tomato fruits under low temperature is reduced.Low temperature treatment promotes the accumulation of trans-β-ionone,6-methyl-5-hepten-2-one and eugenol.It also inhibits the formation of 1-penten-3-one,phenylacetaldehyde,methyl salicylate,guaiacol and 3-methylbutyric acid.At the same time,low temperature changed the expression of many key genes related to the biosynthetic pathway of volatile substances,induced the expression of Tomlox C,Le AADC1 B,FLORAL 4 and CTOMT1 and inhibited the expression of ADH2 and Sl BCAT2 genes.