Conserved Aquaporins in Gossypium and Silencing of Ghpip2;7 and Ghtip2;1 Decreased Salt and Osmotic Stress Tolerances in Upland Cotton

Abstract Aquaporins (aquaporin), membrane channel proteins, facilitate the transport of water and small molecules across intrinsic membranes and play a critical role in abiotic stresses. Here, 111, 54, and 56 candidate AQP genes were identified in Gossypium hirsutum (AD1), G. arboreum (A2), and G. raimondii (D5), and classified into five subfamilies including PIP, TIP, NIP, SIP, and XIP, respectively. Some GhPIPs and GhTIPs exhibited high expression levels in drought and salt stress verified by transcriptome analysis and Quantitative Real-time PCR (qRT-PCR). The chlorophyll content, SOD activity, and POD activity were decreased in GhPIP2;7 gene-silenced plants versus the control (using blank vector) under 400 mM NaCl treatment, which indicated a negative role of GhPIP2;7 in cotton salt tolerance. Comparing with mock plants, GhTIP2;1 silenced cotton plant was more sensitive to osmotic stress. Overexpressed GhTIP2;1 plants exhibited less accumulation of H2O2 and MDA with higher proline contents detected under osmotic stress. Taken together these results, provide in-depth knowledge into plant response to abiotic stress and gene resource.