A total of 3970 and 4433 genes were differentially expressed in WY and WP, respectively, with 2030 differentially expressed genes (DEGs) were specific to WY. Specifically, the categories “defense response”, “secondary metabolites”, and “ABC transporters” were enriched among WY-specific DEGs. Several transcription factor genes might be involved in cold stress response, including RAP2-3, NAC2, NAC43, WRKY47, and WRKY51, which were induced only in WY, and CBF3, ZAT10, MYB308, and WER exhibited greater cold stress-induced expression changes in WY compared with WP, which may partially explain the distinct transcriptomic changes induced by cold stress between the two ecotypes. Greater fold changes in the expression of starch metabolism-related genes such as BAM1/3 and lower fold changes in the expression of DPE2 were detected in WY, which was consistent with its greater abundance of total soluble sugars.
The stronger transcriptional differentiation of related genes under cold stress in WY may explain its greater cold resistance compared with the WP ecotype, providing important genetic resources for improving cold-resistant characteristics in P. bournei. In addition, two interaction networks were constructed, resulting in identification of a series of hub genes, which facilitates functional dissection of the molecular mechanisms involved in the response to cold stress of P. bournei and extends the ability to improve cold resistance in this valued species.
A heat map for AP2 genes in the two ecotypes of P. bournei under cold stress