摘要
Freezing tolerance is a significant trait in plants that grow in cold environments and survive through the winter.Apple(Malus domestica Borkh.)is a cold-tolerant fruit tree,and the cold tolerance of its bark is important for its survival at low temperatures.However,little is known about the gene activity related to its freezing tolerance.To better understand the gene expression and regulation properties of freezing tolerance in dormant apple trees,we analyzed the transcriptomic divergences in the bark from 1-year-old branches of two apple cultivars,“Golden Delicious”(G)and“Jinhong”(H),which have different levels of cold resistance,under chilling and freezing treatments.“H”can safely overwinter below−30℃in extremely low-temperature regions,whereas“G”experiences severe freezing damage and death in similar environments.Based on 28 bark transcriptomes(from the epidermis,phloem,and cambium)from 1-year-old branches under seven temperature treatments(from 4 to−29°C),we identified 4173 and 7734 differentially expressed genes(DEGs)in“G”and“H”,respectively,between the chilling and freezing treatments.A gene coexpression network was constructed according to this expression information using weighted gene correlation network analysis(WGCNA),and seven biologically meaningful coexpression modules were identified from the network.The expression profiles of the genes from these modules suggested the gene regulatory pathways that are responsible for the chilling and freezing stress responses of“G”and/or“H.”Module 7 was probably related to freezing acclimation and freezing damage in“H”at the lower temperatures.This module contained more interconnected hub transcription factors(TFs)and cold-responsive genes(CORs).Modules 6 and 7 contained C-repeat binding factor(CBF)TFs,and many CBF-dependent homologs were identified as hub genes.We also found that some hub TFs had higher intramodular connectivity(KME)and gene significance(GS)than CBFs.Specifically,most hub TFs in modules 6 and 7 were acti
基金
supported by the Agricultural Science and Technology Innovation Program of Jilin Province,“Precise identification and QTL location of cold resistance of new apple germplasm”(program number,CXGC2017JQ020)
“Phylogenetic reconstruction technique and gene family reconstruction technique of Malus plants”(program number,C8223001602).