CDPK protein in cotton: genomic-wide identification, expression analysis, and conferring resistance to heat stress

Background: Calcium-dependent protein kinase (CDPK) plays a key role in cotton tolerance to abiotic stress. However, its role in cotton heat stress tolerance is not well understood. Here, we characterize the GhCDPK gene family and their expression profiles with the aim of identifying CDPK genes associated with heat stress tolerance.

Results: This study revealed 48 GhCDPK members in the cotton genome, distributed on 18 chromosomes. Tree phylogenetic analysis showed three main clustering groups of the GhCDPKs. Cis-elements revealed many abiotic stress and phytohormone pathways conserved promoter regions. Similarly, analysis of the transcription factor binding sites (TFBDS) in the GhCDPK genes showed many stress and hormone related sites. The expression analysis based on qRT-PCR showed that GhCDPK16 was highly responsive to high-temperature stress. Subsequent protein-protein interactions of GhCDPK16 revealed predictable interaction with ROS generating, calcium binding, and ABA signaling proteins. Overexpression of GhCDPK16 in cotton and Arabidopsis improved thermotolerance by lowering ROS compound buildup. Under heat stress, GhCDPK16 transgenic lines upregulated heat-inducible genes GhHSP70, GHSP17.3, and GhGR1, as demonstrated by qRT-PCR analysis. Contrarily, GhCDPK16 knockout lines in cotton exhibited an increase in ROS accumulation. Furthermore, antioxidant enzyme activity was dramatically boosted in the GhCDPK16-ox transgenic lines.

Conclusions: The collective findings demonstrated that GhCDPK16 could be a viable gene to enhance thermotolerance in cotton and, therefore, a potential candidate gene for improving heat tolerance in cotton.