Exogenous strigolactones enhance salinity tolerance in cotton (Gossypium hirsutum L.) seedlings

All around the world, salt stress has severely restricted plant development. Cotton is one of the most important cash crops, but the saline soil negatively influences the quality and output of plants. Strigolactones (SLs) is a new type of phytohormone that plays an important role in the development of plants. However, the underlying mechanism of how SLs alleviate the high salinity stress is unclear in cotton. In this research, we observed that exogenous 10 mu\M GR24 (a synthetic analog of SLs) significantly alleviated the salt stress (200 mM NaCl) in the hydroponically planted seedlings. Under salt stress, the contents of proline, O2  malondialdehyde, and hydrogen peroxide were greatly decreased by 48.40%, 45.57%, 31.03%, and 35.52%. Combined with transcriptome analysis and corresponding verification, it was figured out that with the application of exogenous GR24, the genes encoding antioxidant enzymes, chlorophyll biosynthesis, and photosynthesis system were significantly upregulated, while the activities of antioxidant enzymes, the content of chlorophyll, and the efficiency of photosynthesis were also significantly improved under salt stress in cotton seedlings. Thus, the exogenous application of SLs could enhance the salt tolerance of cotton seedlings, which displayed its great potential for cotton production in salinized land.