Combined whole transcriptome analysis and physical-chemical reveals the leaf color change mechanism of Ulmus pulima under heat stress

Abstract

Ulmus pulima ‘ZhonghuaJinye’ (JY-elm) is a new variety of Ulmus genus with high landscape ecological benefits and golden leaves. However, the leaf color of JY-elm is significantly influenced by temperature, which changed from golden to white (albino) gradually under heat stress. Therefore, the present study explores the mechanism of JY-elm leaf color changes under high-temperature stress conditions. The photosynthetic pigment contents and related enzyme activities decreased significantly, leaf color changed from green to white, and the arrangement of palisade tissue was loose enough to disappear with abnormal thylakoid structures and fewer grana lamellae in JY-elm leaves under high-temperature stress. The photosynthetic parameters of JY-elm, Pn, Tr, and Cs decreased significantly with the increasing temperature, which caused plants to almost lose photosynthetic capacity. Further, the whole RNA-Seq profile was used to establish the ceRNA network, and the photosynthesis and chlorophyll metabolism pathways and related key regulated genes responses to heat stress were identified in this network. The results indicated that JY-elm leaf bleaching is irreversible damage at 37 °C, while plants are in a phase of resistance to high temperatures at 29 °C. This may be related to the damage to the chloroplast structure of elm under high temperature stress. This study revealed the mechanism of leaf color variation and response to heat stress in elm, and the established ceRNA network provided a basis for further research in the future.