Abstract
Background : As a superfamily of transcription factors (TFs), the basic helix-loop-helix (bHLH) proteins have been identified and functionally characterized in many plants. However, no comprehensive analysis of the bHLH family in papaya ( Carica papaya L. ) has been reported previously.
Results: In this study, a total of 73 CpbHLH genes were found in papaya, and these genes were classified into 18 subfamilies based on phylogenetic analysis, with one orphans. Almost all of the CpbHLH in the same subfamily shared similar gene structures and protein motifs according to an analysis of exon/intron organizations and motif compositions. The number of exons in CpbHLH genes varied from 1 to 11 with an average of 5. The amino acid sequences of the bHLH domains were quite conservative, especially Leu-27 and Leu-63. Promoter cis -element analysis revealed that most of the CpbHLH genes contained cis -elements that can respond to various biotic/abiotic stress-related events. Gene ontology (GO) analysis revealed that Cp bHLH mainly functions in protein dimerization activity and DNA-binding, and most Cp bHLH proteins were predicted to localize in the nucleus. Abiotic stress treatment and quantitative real-time PCR (qRT-PCR) revealed some predicted CpbHLH genes that might be responsible for abiotic stress responses in papaya.
Conclusions : A total of 73 bHLH transcription factors were identified from papaya, and their gene structures, conserved domains, sequence features, phylogenetic relationship, promoter cis -element, GO annotation and gene expression profiles responsible for abiotic stress were investigated. Our findings lay a foundation for further evolutionary and functional elucidation of Cp bHLHs.
Keywords : papaya, genome-wide analysis, bHLH transcription factors, abiotic stress
Genome-wide analysis of basic helix-loop-helix (bHLH) transcription factors in Brachypodium distachyon
