Hydrogen Sulfide And Ethylene In Regulating Ripening And Senescence Of Fruit And Vegetable

The fruit and vegetable are various and planted area is wide. They are necessities in our life. Production and consumption of fruit and vegetable are a large number in our country. Postharvest loss rate is high as 20%, because of senescene and rot. Many researchers study the mechanism of ripening and senescene. Ethylene (C2H4), one of the biological hormones, plays a key role in promoting fruit and vegetable maturity. Hydrogen sulfide (H2S) is a new gaseous signal molecule of preservation method in fruits and vegetables by inhibiting the production of reactive oxygen species (ROS) and enhancing antioxidant capacity in recent years. Whether H2S functions in involving in ethylene-mediated ripening and senescence of fruit and vegetabl are largely unknown. In this paper, we study ripening and scenescence mechanism H2S and exogenous ethylene in fruit and vegetable. Broccoli and kiwifruit are used as the material to study in this work.Broccoli (Brassica oleracea) is an important vegetable crop. Existed evidence showed that conditions of darkness and ethylene induced the rapid senescence of plants. Results showed that H2S delayed the symptoms of senescence and maintained higher levels of chlorophyll and Rubisco and lower protease activity compared with water control. H2S treatment significantly reduced the accumulation of superoxide anion (·O2-) and maintained significantly higher activitie of catalase (CAT). RT-PCR results showed that H2S down-regulated the expression of chlorophyll degradation-related genes BoSGR, BoNYC, BoCLHl, BoPPH, BoRCCR and ethylene transduction pathway related genes BoACS2, BoACS3, BoERS and BoETRl. Expression of lipoxygenase gene BoLOXl and cysteine protease gene BoCP3 and aspartic protease gene BoLSC807 also down-regulated by H2S. H2S up-regulated the expression of sulfur metabolism genes BoSR and BoOASTL and the antioxidant gene BoCAT. These results show that H2S plays a vital role in alleviating broccoli senescence through a broad regulation on gene expression of ROS metabolism genes, ethylene synthesis genes, and protease genes.Kiwifuit (Actinidia deliciosa) is a typical climacteric fruit with a peak of respiration and ethylene production in the process of mature. It is particularly sensitive to ethylene and low concentrations of ethylene induce maturation and senescence immediately. In this paper, the results showed that H2S can delay piening process of kiwifruit by inhibiting C2H4. Compare with C2H4 treatment, H2S and C2H4 can delay degradation of titratable acid, reducing sugar, protein, starch, ascorbic acid and flavonoid. And, H2S and C2H4 treatemnt reduced the accumulations of the reactive oxygen species·O2- and H2O2. The activities of ascorbate peroxidase (APX), catalase (CAT) and phenylainine ammonialyase (PAL) maintained higher level than C2H4 treated fruit. Peroxidase (POD), polyphenol oxidase (PPO), lipoxygenase (LOX), poly-galacturonic acid enzyme, amylase and proteast activities retained lower level compare to C2H4 treatment. Further, PT-PCR results of genes expression showed that H2S inhibited the expression of ethylene synthesis gene AdACS, AdACO and fruit softing gene AdEXPl, AdGAL. And, H2S up-regulated salicylic acid synthesis gene AdICS, AdEDS, AdPAD4 and key enzymes gene in H2S synthesis pathway AdSR, AdLCD compare to C2H4 treatment. These results demonstrate that H2S can adverse the effect of exogenous ethylene in kiwifruit ripening and senescence process.