Integrated Analysis of Transcriptome and Metabolome Provides Insights into Phenylpropanoid Biosynthesis of Blueberry Leaves in Response to Low-Temperature Stress

The phenylpropanoid compounds are crucial secondary metabolites for blueberry plants. Low temperatures induce the expression of phenylpropanoid biosynthesis genes and regulate the accumulation of phenylpropanoid metabolites. However, the molecular mechanisms of blueberry leaves in response to low-temperature stress are unknown. To explore the molecular mechanisms of phenylpropanoid biosynthesis under low-temperature stress, the 6-month-old blueberry plants were cultured at 10 °C for 0, 6, 12, 24, and 48 h. The total of 16,388 differentially expressed genes (DEGs) and 303 differentially accumulated metabolites (DAMs) were identified by transcriptome deep sequencing (RNA-seq) and ultra-high performance liquid mass spectrometry, respectively. The most enriched low-temperature-responsive genes are mainly involved in the phenylpropanoid biosynthesis pathway and the main low-temperature-responsive metabolites come from the phenylpropanoid superclass based on transcriptome and metabolome data, respectively. CBF2 plays essential roles in the ICE-CBF-COR regulatory pathway, and transcription factors (TFs) ERF109, MYB14, WRKY40, HSP30, MPSR1, ZHD4, MADS3, and MADS27 might be responsible for blueberry leaf low-temperature tolerance. The MYB TFs from group 5, group 6, and group AtMYB5 may regulate the accumulation of phenylpropanoid metabolites by regulating expression of phenylpropanoid biosynthesis genes. These findings uncover possible molecular mechanisms of phenylpropanoid biosynthesis during low-temperature stress and provide a basis for future studies and crop improvement.