Abstract
Background
Soil salinity is one of the major abiotic stresses that threatens crop growth and the environment. G. hirsutum and G. barbadense, as two major cultivated cotton species, are widely cultivated worldwide. Also, they are preferred crops for saline cultivation due to their high salt tolerance. However, until recently, the differences and regulatory mechanisms of their responses to salt stress have rarely been reported.
Results
In this study, we comprehensively compared the effects of salt stress on G. hirsutum TM-1 and G. barbadense H7124. The results showed that salt stress severely inhibited the growth of both cotton species, with H7124 exhibiting a better growth phenotype, especially on the leaves. Further measurements found the leaves of H7124 maintained greater cellular homeostasis and better photosynthetic capacity under salt stress. Physiologically, we observed that H7124 exhibited superior osmotic regulation and antioxidant capability compared to TM-1, while TM-1 displayed greater K+ absorption capability than H7124 under salt stress. Transcriptome analysis revealed significant molecular differences between the two cotton species in response to salt stress. The key pathways of TM-1 induced by salt are mainly related to growth, development and regulation, such as porphyrin metabolism, DNA replication, ribosome and photosynthesis. Conversely, the key pathways of H7124 were mainly related to plant defense, such as plant hormone signal transduction, MAPK signaling pathway-plant, and phenylpropanoid biosynthesis. These differences underscore the varied molecular strategies adopted by the two cotton species to navigate through salt stress, and H7124 may exhibit stronger responses to salt stress. Furthermore, we identified 217 potential salt tolerance related DEGs based on gene function, 167 of which overlapped with the confidence intervals of significant SNPs identified in previous GWASs, indicating the high reliability of these genes. Finally, we selected key genes involved in different pathways and monitored their expression levels at different time points, revealing the time-specific differences between the two cotton species under salt stress.
Conclusions
These findings provide new insights into the differences in the regulatory mechanisms of salt tolerance between G. hirsutum and G. barbadense, and provide key candidate genes for salt tolerance molecular breeding in cotton.