Wax Metabolism is involved in Response to Alternate Freeze-thaw Stress to Regulate Shoot Shriveling

Abstract

Abstract Shoot shriveling is one of the main challenges for apple (Malus×domestica) growth and productivity. Cuticular wax plays a critical role in plant resistance. In this study, branches of 'Asi' and 'Miyazaki' with different overwintering characters were selected, and a series of physiological indicators were measured. The results showed that shoot shriveling rate of 'Miyazaki' was 2.31 times than 'Asi', the critical water content of 'Asi' was higher than 'Miyazaki'; In freeze-thaw alternate phase of 'Asi', the activities of starch phosphorylase (SP) and amylase (Amy) was 1.54 and 1.2 times that of 'Miyazaki', the relative conductivity (REC) and Proline (Pro) were 0.89 and 0.65 times that of 'Miyazaki'. The wax content of the two varieties in the freezing-thawing phase decreased to 41.84% and 60.63%, respectively, 'Asi' wax was tightly distributed and wax components was much diversify than 'Miyazaki'. The correlation analysis showed that the wax content was positively correlated with the water content and negatively correlated with shoot shriveling rate. Subsequently, eleven wax-related genes were selected for expression to verify their reliability. Under freeze-thaw stress, the expression of CER1 dramatically increased, and the expression of KCS1, CER3 and WIN1 increased firstly and then decreased with the elongation of stress time. Compared with the sensitive shriveling 'Miyazaki', the anti-sensitive shriveling 'Asi' strengthens its overwintering by containing higher water content, triggering the expression of CER1, CER3, WIN1 and other genes, enriching its waxy components, increasing the content of osmotic adjustment substances, and improving the water retention performance during the overwintering process.