Abstract
BackgroundTranscription factors operate as important switches of transcription networks, and NAC (NAM, ATAF, and CUC) transcription factors are a plant-specific family involved in multiple biological processes. However, this gene family has not been systematically characterized in cotton.ResultsHere we identify a large number of genes with conservative NAC domains in four cotton species, with 147 found in Gossypium arboreum, 149 in G. raimondii, 267 in G. barbadense and 283 in G. hirsutum. Predicted membrane-bound NAC genes were also identified. Phylogenetic analysis showed that cotton NAC proteins clustered into seven subfamilies and homologous protein pairs showed similar characteristics. Evolutionary property analysis revealed that purifying selection of NAC genes occurred between diploid and polyploid cotton species, and variation analysis showed GhNAC genes may have been subjected to selection and domestication. NAC proteins showed extensive transactivation and this was dependent on the C-terminus. Some development and stress related cis-elements were enriched in the promoters of GhNAC genes. Comprehensive expression analysis indicated that 38 GhNAC genes were candidates for involvement in fiber development, and 120 in stress responses. Gene co-expression network analysis revealed relationships between fiber-associated NAC genes and secondary cell wall (SCW) biosynthesis genes.ConclusionsNAC genes were identified in diploid and tetraploid cotton, revealing new insights into their evolution, variation and homology relationships. Transcriptome analysis and co-expression network indicated roles for GhNAC genes in cotton fiber development and stress response, and NAC genes may prove useful in molecular breeding programmes.
Highlights
Transcription factors operate as important switches of transcription networks, and NAC (NAM, ATAF, and CUC) transcription factors are a plant-specific family involved in multiple biological processes
Genome-wide identification of NAC family genes in Gossypium spp Based on the PlantTFDB database and multiple sequence alignment analysis, we identified multiple non-redundant and complete NAC genes in four cotton species, with 147 found in Gossypium arboreum, 149 in G. raimondii, 267 in G. barbadense and 283 in G. hirsutum (Additional file 1: Table S1)
NAC proteins from four cotton species group into seven subfamilies (I-VII), and each subfamily contains the NAC proteins derived from four cotton species (Fig. 1b)
Summary
Transcription factors operate as important switches of transcription networks, and NAC (NAM, ATAF, and CUC) transcription factors are a plant-specific family involved in multiple biological processes. This gene family has not been systematically characterized in cotton. NAC (NAM, ATAF, and CUC) proteins are among the largest plant-specific transcription factor (TF) superfamily with 117 members in Arabidopsis, in rice, in soybean, and 251 in switchgrass [1,2,3]. The structures of NAC proteins can be divided into two regions, the conserved N-terminal DNA-binding domains (BD) and the high divergent C-terminal transcriptional regulatory regions (TR) [4, 5].
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