Background

Photosystem II (PSII) constitutes an intricate assembly of protein pigments, featuring extrinsic and intrinsic polypeptides within the photosynthetic membrane. The low-molecular-weight transmembrane protein PsbX has been identified in PSII, which is associated with the oxygen-evolving complex. The expression of PsbX gene protein is regulated by light. PsbX's central role involves the regulation of PSII, facilitating the binding of quinone molecules to the Qb (PsbA) site, and it additionally plays a crucial role in optimizing the efficiency of photosynthesis. Despite these insights, a comprehensive understanding of the PsbX gene's functions has remained elusive.

Results

In this study, we identified ten PsbX genes in Gossypium hirsutum L. The phylogenetic analysis results showed that 40 genes from nine species were classified into one clade. The resulting sequence logos exhibited substantial conservation across the N and C terminals at multiple sites among all Gossypium species. Furthermore, the orthologous/paralogous, Ka/Ks ratio revealed that cotton PsbX genes subjected to positive as well as purifying selection pressure might lead to limited divergence, which resulted in the whole genome and segmental duplication. The expression patterns of GhPsbX genes exhibited variations across specific tissues, as indicated by the analysis. Moreover, the expression of GhPsbX genes could potentially be regulated in response to salt, intense light, and drought stresses. Therefore, GhPsbX genes may play a significant role in the modulation of photosynthesis under adverse abiotic conditions.

Conclusion

We examined the structure and function of PsbX gene family very first by using comparative genomics and systems biology approaches in cotton. It seems that PsbX gene family plays a vital role during the growth and development of cotton under stress conditions. Collectively, the results of this study provide basic information to unveil the molecular and physiological function of PsbX genes of cotton plants.