Genome-wide analysis of the cotton COBRA-like gene family and functional characterization of GhCOBL22 in relation to drought tolerance.

Background: The COBRA-like (COBL) gene family is a crucial glycosylphosphatidylinositol (GPI)-anchored proteins that participate in various biological processes in plants by regulating the arrangement of cell wall microfibrils. While the functions of COBL genes have been analyzed in several plant species, their roles in cotton's response to abiotic stress remain unexplored.

Results: This study identified and characterized the COBL gene family in Gossypium hirsutum, revealing a total of 39 COBL family members classified into five subgroups. Transcriptome analysis indicated that the transcription levels of several GhCOBL genes were upregulated following PEG treatment, with GhCOBL22 being significantly induced. Further silencing of the GhCOBL22 gene through virus-induced gene silencing (VIGS) technology demonstrated that this gene's silencing reduced cotton's drought stress tolerance. Under drought stress conditions, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) enzymes, along with proline (PRO) content, were lower in GhCOBL22-silenced plants compared to control plants, while the accumulation of malondialdehyde (MDA) was significantly higher. Moreover, silencing the GhCOBL22 gene also led to reductions in the levels of cellulose, hemicellulose, and lignin content in cotton leaves.

Conclusion: A systematic survey of gene structure, motif composition, and evolutionary relationships of the COBL gene family was conducted in Gossypium hirsutum. Subsequent expression and functional studies indicated that GhCOBL22 plays a significant role in cotton's drought tolerance. These findings enhance our understanding of the biological functions of the COBL family and highlight the critical role of the GhCOBL22 gene in cotton's response to drought stress.