Genome wide identification, classification and functional characterization of heat shock transcription factor in cultivated and ancestral cotton (Gossypium).

Heat shock transcription factors (HSF) have been demonstrated to play a significant transcriptional regulatory role in plants and considered as an integral part of signal transduction pathways against environmental stresses. 42, 39, 67, and 79 nonredundant HSF genes were identified from G. arboreum (A2), G. raimondii (D5), G. barbadense (AD2) and G. hirsutum (AD1) and clustered in the reference genomes from cotton functional genomics database. There are 131 HSF genes belong to class A, 80 to class B, and 16 to class C subfamily. Moreover, a detailed analysis of HSF gene family in four species of cotton elucidated the role of allopolyploid and hybridization during evolutionary cascade of allotetraploid cotton. Comparatively, existence of more orthologous genes in cotton species than Arabidopsis, advocated that polyploidization produced new cotton specific orthologous gene clusters. Phylogenetic, collinearity and multiple synteny analysis exhibited dispersed, segmental, proximal, and tandem gene duplication events in HSF gene family. Duplication of gene events suggests that HSF gene family of cotton evolution was under strong purifying selection. G. hirsutum exhibited high level synteny. Expression analysis revealed that GarHSF04 were found to be actively involved in PEG and salinity tolerance in G. arboreum. GhiHSF14 upregulated in heat and downregulated in salinity whilst almost illustrated similar behavior under cold and PEG treatments and GhiHSF21 exhibited down regulation almost across all the stresses in G. hirsutum. Overwhelmingly, present study paves the way to better understand the evolution of cotton HSF genes and lays a foundation for future investigation of HSF genes in improving abiotic stress tolerance in cotton.