Establishment Of Low-Temperature Memory System Of Pepper (Capsicum Annuum L.) And Study Of Carotenoids Responding To Low-Temperature Memory

Low temperature stress seriously affects the distribution,growth and development of pepper(Capsicum annuum L.).Carotenoids,which are important members of the photosystem,also play an important role in the process of stress resistance.In this research,the low-temperature resistant‘Shenghan740’and the low-temperature sensitive‘Guota 169’were used as materials to establish the low-temperature stress memory system of pepper by analyzing the effects of continuous and intermittent low temperature on the low-temperature memory elicitation of pepper,the effect of cold start on cold stress memory,and the memory ability of pepper plants on low-temperature stress.After that,the 5~°C low temperature–25~°C rewarming–5~°C low temperature was performed,the carotenoid component changes were analyzed,the key enzyme gene LCYb of carotenoid metabolism was silenced by virus-induced gene silencing(VIGS)technology,carotenoid-related genes were determined,and the relationship between carotenoids and low-temperature stress memory of pepper was explored.(1)The results of continuous low temperature and intermittent low temperature treatment showed that the semi-lethal temperature at continuous low temperature and intermittent 12 h low temperature decreased with the extension of treatment time,and the trend of increasing first and then decreasing at intermittent 36h low temperature in batches.The increase of low temperature stress time will increase the MDA content,and the MDA content is generally lower than that of low temperature.The activity of antioxidant enzymes(SOD,POD,CAT,APX),cold response genes CBF3,Le COR413PM2 and CHS all increased first and then decreased with the extension of low temperature duration.The expression of antioxidant enzyme activity and cold response gene under intermittent low temperature treatment generally showed a trend of rewarming lower than low temperature.The results showed that the low temperature memory effect induced by continuous low temperature and interval 12 h low temperature was better than that of interval36 h,and dedomestication may occur in interval 36 h.(2)The semi-lethal temperature results showed that the plants with cold start in advance were restored for 3 days and then treated with low temperature again,which enhanced the cold resistance of the plants.The results of 4 d recovery and 5 d recovery showed that the increase of low temperature time could enhance the cold resistance of plants.MDA content,POD,APX enzyme activity,CBF3 and Le COR413PM2 expression in plants directly exposed to low temperature were higher than those previously cold started.SOD,CAT enzyme activity,and CHS expression showed a tendency of pre-cold start higher than direct exposure to low temperature.It was shown that pre-cold start could enhance the low temperature memory of plants,which was more intuitive in the results of recovery for 3 d,and the increase of low temperature treatment time could also enhance the low temperature memory of plants.(3)The results of low-temperature stress memory ability analysis of pepper showed that SOD and POD enzymes participated in low-temperature memory of pepper for 3 d,CAT and APX enzymes for 4 d,cold response genes CBF3,Le COR413PM2 and CHS were 3 d～4 d,and‘Shenghan 740’maintains better effect,LT50 was 3 d,and the damage of low temperature to plant cell membranes lasted for 4 days.(4)Under the treatment of 5~°C low temperature–25~°C rewarming–5~°C low temperature(P3-R3-RP3),zeaxanthin,capsaicin,lutein,β-cryptoxanthin all participated in the“memory”process of pepper on low temperature stress,its content increased at the first low temperature stress(P3),decreased when rewarmed(R3),lower than the first low temperature stress(P3)but higher than the control(P0)and rewarming(R3)when the second low temperature stress(RP3)was lower,andβ-carotene also had such a trend.However,it only increases slightly at low temperature(RP3)again,so it plays a smaller role than other carotenoids.(5)Under the treatment of 5~°C low temperature–25~°C rewarming–5~°C low temperature(P3-R3-RP3),ZEP in wild-type plants played an important role in the memory process of pepper on low temperature stress,and its expression increased under both low temperature stresses,and the expression was higher than that of the control(P0)under low temperature stress(RP3)again.LCYe,ECH and ZEP in silencing LCYb plants play important roles in the memory process of pepper hypothermia,but the expression of ZEP is lower than that of the control(P0)during re-hypothermia stress(RP3).