Effects Of Ascorbate Peroxidase And Pheophytinase’s Regulation OnPreservation Of Chinese Kale

Rich in vitamin C (Vc) and chlorophyll, the Chinese kale shows nutritional value andsensory quality. The activities of ascorbate peroxidase and pheophytinase (PPH) associatewith Vc and chlorophyll degradation, have direct impact on the Chinese kale’s nutritionalvalue and sensory quality. It is valuable to study the gene expression and activity change ofthese two enzymes in Chinese kale’s growth and storage process. The effects of physical andchemical processing on gene expression and activity change of ascorbate peroxidase and PPHin Chinese kale were determined and the results were as follows:The chloroplast stroma ascorbate peroxidase (SAP) gene and the conserved sequence ofthe PPH gene were cloned from Chinese kale. The total length of SAP was1065bp, whichencodes354amino acids and the similarity was98%with that of Brassica oleracea. Theconserved region of PPH was fished out also; the471bp segment has a similarity of89%with that of Arabidopsis thaliana.Effects of ethephon and6-benzylaminopurine (6-BA) on cytosolic ascorbate peroxidasegene (APX), SAP and PPH expressions of growth and detached seedlings were investigated.All of their expression levels increased under high concentrations of ethephon (1200mg/L)treatment of growth seedlings, but APX expression level increased whereas SAP expressionlevel decreased in detached seedlings. Chlorophyll degradation and PPH expression levelincreased with the ethephon treatment. APX and SAP expression levels increased with6-BAtreatment in growth and detached seedlings. PPH expression level was promoted by6-BAtreatment in the growth seedlings, but no significant effect on detached ones.Chlorophyll and Vc degradation, gene expression and enzyme activity in post-harvestChinese kale at different temperatures were determined. Compared with22°C storage,chlorophyll degradation was delayed, due to PPH expression and PPH activity reduced under4°C storage; PPH expression and activity were reduced44.75%,66.67%on the first dayrespectively. Meanwhile, Vc content, APX and SAP expression levels reduced; Vc lost11.75%after five days and the amount was twice compared with that under22°C storage. Theexpressions of APX and SAP were86.33%and56.12%of those under22°C storage.Influences of ultraviolet C (UV-C) irradiation on chlorophyll and Vc degradation, geneexpression and enzyme activity in post-harvest Chinese kale were then studied. Samples wereirradiated by UV-C for20min, and stored for5days at22°C. Results showed that APXexpression level was higher by37.45%, while SAP expression level was lower by27.40%compared with the control. Degradation of Vc was promoted by UV-C irradiation and theamount decreased by98.55%, however, UV-C irradiation delayed the degradation ofchlorophyll, whose amount was higher by32.46%than of that of the control. In addition,UV-C irradiation reduced the PPH expression and PPH activity by15.82%and50.12%compared with the control.