Effects of exogenous sucrose on root physiology and transcriptome of Malus baccata Borkh. under sub-low root-zone temperature

The root, a key organ for sensing the soil environment, is easily damaged by environmental stresses such as low soil temperature. Although the exact mechanism is unknown, exogenous sucrose can mitigate the oxidative damage to the root caused by low temperatures in the root zone. In this study, we examined how exogenous sucrose affected the transcriptome and physiology of Malus baccata Borkh. seedling roots at sub-low root-zone temperature (LRT). The exogenous sucrose treatment was more effective than other treatments in mitigating LRT stress injury. This was achieved by decreasing reactive oxygen species (O 2 .- and H2O2) 2 O 2 ) and malondialdehyde content, increasing the activities of antioxidant enzymes (SOD, POD, CAT, APX, GR, and MDHAR), increasing AsA and GSH content, and increasing soluble sugar content. Transcriptome analysis revealed that alpha-linolenic acid metabolism, fatty acid biosynthesis, phenylpropane biosynthesis, and glycolysis/gluconeogenesis were the primary areas of enrichment for the differentially expressed genes identified under the LRT treatment. Exogenous sucrose may enhance the tolerance of Malus baccata Borkh. to LRT by regulating the expression of differentially expressed genes ( GST, LOX, SS, PFK, ADH, , and 4CL) ) related to the antioxidant system, carbohydrate metabolism, alpha-linolenic acid metabolism, and phenylpropane biosynthesis pathways. These results offer a foundation for additional investigation into the molecular mechanism underlying the modulation of the root response to low temperature by exogenous sucrose.