Molecular cloning and functional analysis of NAC family genes associated with leaf senescence and stresses in Gossypium hirsutum L.

The NAC domain genes encode a large family of plant-specific transcription factors that play diverse roles in plant development and stress regulation. In this study, a total of 60 full-length putative NAC genes were isolated from Gossypium hirsutum L. Based on their phylogeny, all GhNAC genes were clustered into seven distinct subfamilies, which exhibit functional similarity. Similarly, a phylogenetic tree for GhNAC genes and their motif showed close resemblance among the subfamilies. The isolated 60 full-length GhNAC genes were located on 13 different chromosomes of D sub-genome. Majority of the NACs showed specific temporal and spatial expression patterns in tissue-specific (fibers, cotyledon leaf, mature leaf, stem, root and flower) studies based on qRT-PCR analyses. Furthermore, the roles of GhNAC genes were monitored using qRT-PCR during leaf senescence and following treatment with ethylene, abscisic acid, gibberellic acid and drought or salinity. This first comprehensive study of GhNAC family elucidates the essential role of these genes in cotton development and in response to various stresses. This study lays fundamental foundations for future research and development in cotton genome.