Exogenous sugars alleviate low-temperature injury in Camellia weiningensis through transcriptional regulation and modulating the phyllosphere microbial communities

Abstract

Low temperatures restrict the development and spread of Camellia weiningensis in Guizhou Province, China. Exogenous sugars have demonstrated effectiveness in alleviating low-temperature damage in plants. However, the function of exogenous sugars and their mechanisms remain to be explored in depth. The current study assessed the effects of various exogenous sugars on the physiology, transcriptional regulation, and phyllospheric microorganisms of C. weiningensis under low-temperature stress. The results revealed that low temperature led to significant changes in endogenous sucrose, trehalose, and galactose levels. Spraying exogenous sugars effectively lowered reactive oxygen species, malondialdehyde and relative electrical conductivity levels. Field experiments showed that exogenous galactose (Gal) treatment had the best effect and significantly enhanced the fruit setting rate by 71 % compared to the control. Physiological analyses revealed that Gal treatment notably elevated the proline content by 1.6 times, as well as peroxidase and glutathione activities by 65 % and 46 %; exogenous sucrose treatment significantly enhanced the activities of superoxide dismutase and catalase by 79 % and 2.2 times, respectively, and also increased the contents of jasmonic acid and flavonoids by 48 % and 3.3 times, respectively. Transcriptome data indicated that brassinosteroid biosynthesis, carotenoid and chlorophyll metabolic pathways were activated in C. weiningensis under low-temperature stress. In addition, exogenous sugar spraying changed the community structure of C. weiningensis phyllosphere microbes in response to low-temperature stress. The bacterial ACE and Shannon indices were elevated by 1.2-fold and 1.1-fold, respectively, following Gal treatment. Specific sugar spraying selectively decreased some common pathogenic genera (Ramularia, Alternaria, Cladosporium, etc.), and recruited potentially beneficial dominant genera (Sphingomonas, Arthrobacter, Pseudomonas, etc.). This study provides important theoretical support for reducing low-temperature injury in C. weiningensis cultivation through exogenous sugar application.