Bioinformatic and Expression Analyses of the Wall-Associated Kinase Genes Under High-Temperature Stress in Sorghum

Sorghum (Sorghum bicolor L. Moench) is the world's fifth most-produced cereal. The wall-associated kinases (WAKs) gene family plays a crucial regulatory role in various aspects of plant biology, including the response to environmental stress and pathogens. Therefore, we aimed to characterize the members of the WAK gene family in sorghum using bioinformatics tools and to determine their functional roles in heat stress by detecting transcript levels using RT-qPCR. A total of 98 SbWAK/SbWAKL proteins were identified and classified into six phylogenetic groups. The SbWAKs/SbWAKL genes were unevenly distributed across ten chromosomes, and 33 duplications were observed on nine chromosomes. The number of amino acids and molecular weight of SbWAKs/SbWAKLs ranged from 496 to 1149 aa and 55.38 to 124.89 kDa, respectively. Forty-eight SbWAK/SbWAKL were unstable, with an instability index greater than 40. The synteny analyses revealed sixteen SbWAK/SbWAKL genes similar in foxtail millet, thirteen in maize, and seven in the rice genome. Additionally, 107 miRNAs, including cell wall-related miRNAs, targeted 85 SbWAK/SbWAKL genes. The cis-acting elements in SbWAK/SbWAKL genes pointed out that these genes may be associated with light, hormone, development, and environmental stress responses. RT-qPCR analysis of 13 SbWAK/SbWAKL genes revealed a relatively high transcript fold change in 6 SbWAK/SbWAKL under high-temperature conditions. In conclusion, cis-acting elements, protein-protein and miRNA interactions, and higher gene expression levels at high temperatures may indicate the existence of candidate SbWAKs/SbWAKLs genes with functions in abiotic and biotic stress response and their usage in future gene editing for breeding purposes.