The cotton 70-kDa heat shock protein GhHSP70-26 plays a positive role in the drought stress response

•The cotton cytoplasmic subgroup gene GhHSP70-26 is transcribed in response to polyethylene glycol and abscisic acid treatment and salt, cold, and heat stress.•Overexpression of the GhHSP70-26 gene in tobacco and silencing of the GhHSP70-26 gene in cotton showed that the GhHSP70-26 gene can improve plant tolerance to drought stress.•GhbZIP43 and GhHSF8 bind to cis-acting ABREs and HSEs, respectively, to regulate the transcription of GhHSP70-26, and the GhHSP70-26 protein interacts with the GhAPX2 protein.