Study On The Formation Mechanism Of Garlic Green In The Low Temperature

Garlic green is a common appearance during processing,which seriously affects the quality of garlic products.Garlic stored at the low temperature for a period of time would turn green while stored at room temperature could not turn green.Studies have shown that low temperature could induce the formation of garlic green precursor 1-PeCSO.Meanwhile,the mechanism underlying the low temperature regulation of garlic green remains unclear.Based on the existing research,this study analyzed the differences garlic transcription and protein at different storage temperatures,analyzed and validated the key pathways to regulate garlic green.The specific progress is as follows:Firstly,garlic was stored at different temperatures for analysis of the apparent,transcriptome sequencing and proteome analysis.The results showed that garlic stored at room temperature could not turn green,and garlic stored at low temperature was easily turned green.Garlic puree made by the garlic treated with different temperatures has a different appearance.There was significantly different expression in gene and protein of garlic under different temperature storage.There were 7308 down-regulated genes,7073 up-regulated genes,468 down-regulated proteins and 393 up-regulated proteins in the garlic treated with low temperature compared with room temperature.Secondly,KEGG function enrichment was performed based on the differentially expressed genes and proteins,and key metabolic pathways were screened.The energy metabolic pathways that provide the energy of garlic green was glycolysis pathway,citrate cycle pathway,and pentose phosphate pathway;the pathway involved in the formation of garlic green precursor 1-PeCSO was glutathione metabolic pathway;alanine,aspartic acid,glutamic acid metabolic pathway,glycine,serine and threonine metabolic pathway,cysteine metabolic pathway,cystine and methionine metabolism pathway and phenylalanine metabolism,tryptophan metabolism involved in the formation of intermediate pyrrole and amino acid;and plant hormone signaling pathways involved in plant hormone regulation metabolic pathways.Results showed that low temperature storage could maintain the energy level and provide sufficient energy basis for garlic greening.Low-temperature storage of garlic in the glutathione metabolism pathway promotes the production of providing sufficient garlic green precursor 1-PeCSO.In the metabolic pathway of amino acids,garlic stored at low temperature provided sufficient amino acids,promotes the formation of intermediate pyrrolidine amino acids.Only garlic breaks dormancy could turn green,while changes in gibberellin and abscisic acid can cause plants to break dormancy.The signal transduction pathways of Phytohormones in garlic stored at different temperatures were analyzed.The content of abscisic acid in garlic stored at low temperatures decreased,which prompted garlic to break its dormancy period.Finally,the above metabolic pathways were verified.Garlic stored at low temperature contains more ATP,which provides sufficient energy for garlic green.The correlation between q-PCR and RNA-seq sequencing results of key factors in the glutathione metabolism was 0.7182,which showed positive correlation.The key enzymes except glutathione sulfotransferase activity were enhanced,which promoted the formation of more precursors of garlic green.The content of amino acids in garlics can be much more during storage at the low temperature(4.29 g/100 g),which provides a good material basis for garlic green.