Genomic Survey and Cold-Induced Expression Patterns of bHLH Transcription Factors in Liriodendron chinense (Hemsl) Sarg.

Abstract

bHLH transcription factors play an animated role in the plant kingdom during growth and development, and responses to various abiotic stress. In this current study, we conducted, the genome-wide survey of bHLH transcription factors in Liriodendron chinense (Hemsl) Sarg., 91 LcbHLH family members were identified. Identified LcbHLH gene family members were grouped into 19 different subfamilies based on the conserved motifs and phylogenetic analysis. Our results showed that LcbHLH genes clustered in the same subfamily exhibited a similar conservative exon-intron pattern. Hydrophilicity value analysis showed that all LcbHLH proteins were hydrophilic. The Molecular weight (Mw) of LcbHLH proteins ranged from 10.19 kD (LcbHLH15) to 88.40 kD (LcbHLH50). A greater proportion, ~63%, of LcbHLH proteins had a theoretical isoelectric point (pI) less than seven. Additional analysis on the collinear relationships within species and among dissimilar species illustrated that tandem and fragment duplication are the foremost factors of amplification of this family in the evolution process, and they are all purified and selected. RNA-seq and real-time quantitative PCR analysis of LcbHLH members showed that the expression of LcbHLH35, 55, and 86 are up-regulated, and the expression of LcbHLH9, 20, 39, 54, 56, and 69 is down-regulated during cold stress treatments while the expression of LcbHLH24 was up-regulated in the short term and then later down-regulated. From our results, we concluded that LcbHLH genes might participate in cold-responsive processes of L. chinense. These findings provide the basic information of bHLH gene in L. chinense and their regulatory roles in plant development and cold stress response.