Comparative Transcriptome Analysis Revealing the Potential Mechanism of Low-Temperature Stress in Machilus microcarpa

Abstract

<i>Machilus microcarpa</i> is a rare national tree species in China and possesses important ornamental and ecological value. <i>M. microcarpa</i> can be planted in low-temperature areas, depending on whether its seedlings can withstand the harm. To face this problem, the annual seedlings of <i>M. microcarpa</i> were subjected to five temperature treatments, and eight physiological indicators were measured. Furthermore, comparative transcriptome analysis was performed between <i>M. microcarpa</i> leaves treated at 25°C and -2.8°C. A total of 9,385 differentially expressed genes (DEGs) were involved in low-temperature stress in <i>M. microcarpa</i>. An upregulated (<i>cobA</i>) and five downregulated (<i>HEM, CHLM, CRD, CLH</i>, and <i>PORA</i>) genes associated with the porphyrin and chlorophyll metabolism pathway may reduce chlorophyll synthesis under low-temperature stress. Upregulation of six DEGs (two <i>GAPDHs, PFK, PGAM, PDC</i>, and <i>PK</i>) involved in the glycolysis/gluconeogenesis pathway provided energy for <i>M. microcarpa</i> under adverse cold conditions. Thirteen upregulated and seven downregulated genes related to antioxidant enzymes were also observed under low-temperature stress. Candidate transcription factors (TFs) played key roles in signal transduction under low-temperature stress in <i>M. microcarpa</i>, and quantitative real-time PCR (qRT-PCR) analysis validated the RNA-seq data. The results provide valuable information for further studies on the cold response mechanisms for low-temperature stress in <i>M. microcarpa</i>.