Genome-wide identification analysis of aldo–keto reductase gene family in cotton and GhAKR40 role in salt stress tolerance

In this study, a comprehensive genome-wide identification and analysis of the aldo–keto reductase (AKR) gene family was performed to explore the role of Gossypium hirsutumAKR40 under salt stress in cotton. A total of 249 AKR genes were identified with uneven distribution on the chromosomes in four cotton species. The diversity and evolutionary relationship of the cotton AKR gene family was identified using physio-chemical analysis, phylogenetic tree construction, conserved motif analysis, chromosomal localization, prediction of cis-acting elements, and calculation of evolutionary selection pressure under 300 mM NaCl stress. The real-time qPCR showed that genes encoding members of the aldo–keto reductase (AKR) family in Gossypium hirsutum displayed distinct expression patterns various stress treatments. Specifically, the expression levels of certain genes were significantly upregulated under drought and salt stress. Notably, the role of GhAKR40 gene in salt stress tolerance was validated using virus-induced gene silencing (VIGS) technology in cotton. The GhAKR40-silenced plants experienced leaf wilting under salt stress compared with wild-type and null-control plants. In addition, a series of physio-biochemical such as DAB staining and measurement of RWCL (relative water content in leaves) indexes also indicated that silencing of the AKR40 gene reduced the salt tolerance in cotton. Transcriptome sequencing and analysis of the VIGS-silenced lines suggest that GhAKR40 may enhance salt tolerance in cotton plants by potentially participating in plant-pathogen interactions and the MAPK signaling pathway, thereby modulating both pathways. These data demonstrate that GhAKRs play a significant role in salt stress tolerance. GhAKR40 functions as a positive regulator with a significant impact on stress tolerance. This study not only establishes a theoretical foundation for the comprehensive utilization of resistant germplasm resources in cotton but also paves the way for further exploration of resistance genes in the species.