Comparison Of The Reactive Oxygen Species Metabolism During The Berry Development Between 'Kyoho' And Its Early Ripening Bud Mutant 'Fengzao'

The reactive oxygen species?ROS?play key roles in regulating plant growth.Recent years,more and more evidence has been reported that ROS involved in the regulation of fruit development and ripening.‘Fengzao' is the early ripening bud mutant of ‘Kyoho',in this study,indexes of catalase?CAT?,superoxide dismutase?SOD?,ascorbic acid?AsA?,glutathione?GSH?,NADPH oxidase?NOX?,hydrogen peroxide?H₂O₂?,superoxide anion?O₂·-?,lipoxygenase?LOX?,malondialdehyde?MDA?in the two cultivars were measured to compare the differences of ROS.Based on the process above,an exogenous ROS agents-Riboflavin was sprayed on the berries of ‘Kyoho' for the study of the regulation of ROS in fruit development.The main conclusions are as follow:?1?Before EL-34,there were no significant differences of NOX?main enzyme of O₂·-generation?activity as well as the rate of O₂·-production,indicated that the generation of O₂·-was equivalent in the two cultivars.However,the SOD activity was lower in ‘Fengzao' than that in ‘Kyoho',suggested that the eliminated O₂·-in ‘Fengzai' was less than that in ‘Kyoho',indicated that the accumulation of O₂·-in ‘Fengzao' was higher than that in ‘Kyoho',so the oxidation status in ‘Fengzao' was higher than that in ‘Kyoho'.So,the higher oxidation status in ‘Fengzao' may related to the early ripening.?2?There was an increasing trend of H₂O₂ content from EL-33 to EL-35,and it reached a peak in ‘Fengzao' at EL-35 period then decreased until EL-36 which showed an obvious characteristic of oxidative burst.But H₂O₂ content in ‘Kyoho' showed a decreased trend from EL-31 to EL-36,presented an obvious difference with ‘Fengzao'.H₂O₂ content in ‘Fengzao' was significant higher than that in ‘Kyoho',but the difference of SOD activity in the two cultivars was not significant.Accordingly,the LOX activity raised to a higher level after EL-34,so the higher H₂O₂ content in ‘Fengzao' might be generated from other pathway such as LOX.However,the higher H₂O₂ content did not cause a rise of MDA content,suggested that the higher H₂O₂ content did not cause a cell damage,indicated that H₂O₂ probably play a role of signal molecule in promoting the development process of berry.?3?The rate of O₂·-production in ‘Fengzao' was increased abruptly at EL-36 with no significant difference of SOD activity in the two cultivars.simultaneously,the decrease of H₂O₂ content in ‘Fengzao' suggested that the dismutation of O₂·-was decreased,indicated that there was a higher O₂·-accumulation in ‘Fengzao',and the higher O₂·-accumulation might cause oxidative stress to accelerate the ripening process,and the lower MDA content in ‘Fengzao' suggested that the higher O₂·-accumulation caused the oxidative stress but did not cause cell damage.?4?The most efficient concentration of riboflavin is 0.5 mmol/L,which accelerated the maturity about 15 days earlier than the control.The activity of CAT and content of As A,GSH was enhanced by the treatment of riboflavin,but the rate of O₂·-and activity of SOD was reduced.No significant differences of NOX activity between the treatment with riboflavin and control,but the LOX activity was increased in the treatment group,which also proved the inference that the high level H₂O₂ in treatment group was not generated by the respiratory electron transport chain but other pathway such as LOX.Simultaneously,a significantly enhance of PG and cellulose in treatment group indicated that the H₂O₂ generated by other pathway regulated the progress of grape development and ripening by regulating the activity of PG,cellulose and other cell wall metabolism relevant enzymes.Evidence in this study indicated that H₂O₂ play a key role in the formation of early ripening trait of ‘Fengzao'.