The Molecular Mechanism of in Response to Iron Deficiency in Cotton Seedlings.

Iron deficiency caused by high pH of saline-alkali soil is a major source of abiotic stress affecting plant growth. However, the molecular mechanism underlying the iron deficiency response in cotton () is poorly understood. In this study, we investigated the impacts of iron deficiency at the cotton seedling stage and elucidated the corresponding molecular regulation network, which centered on a hub gene . Iron deficiency induced the expression of genes with roles in the response to iron deficiency, especially . The suppression of with virus-induced gene silence technology reduced seedlings' tolerance to iron deficiency, with low photosynthetic efficiency and severe damage to the structure of the chloroplast. Contrarily, ectopic expression of in enhanced tolerance to iron deficiency. Further analysis of protein/protein interactions revealed that GhbHLH121 can interact with GhbHLH IVc and GhPYE. In addition, GhbHLH121 can directly activate the expression of , and independent of GhbHLH IVc. All told, GhbHLH121 is a positive regulator of the response to iron deficiency in cotton, directly regulating iron uptake as the upstream gene of . Our results provide insight into the complex network of the iron deficiency response in cotton.