Alkalihalobacillus clausii PA21 transcriptome profiling and functional analysis revealed the metabolic pathway involved in glycoalkaloids degradation

Glycoalkaloids (GAs), including alpha-solanine and alpha-chaconine, are secondary metabolites found in potato, which are toxic to higher animals. In a previous study, Alkalihalobacillus clausii PA21 showed the capacity to degrade GAs. Herein, the transcriptome response of PA21 to alpha-solanine or alpha-chaconine was evaluated. In total, 3170 and 2783 differential expressed genes (DEGs) were found in alpha-solanine-and alpha-chaconine-treated groups, respectively, with most DEGs upregulated. Moreover, GAs activated transmembrane transport, carbohydrate metabolism, transcription, quorum sensing, and bacterial chemotaxis in PA21 to withstand GA-induced stress and promote GAs degradation. Furthermore, qRT-PCR analysis confirmed the upregulation of degrading enzymes and com-ponents involved in GA degradation in PA21. In addition, the GAs-degrading enzymes were heterologous expressed, purified, and incubated with GAs to analyze the degradation products. The results showed that alpha-solanine was degraded to beta 1-solanine, beta 2-solanine, gamma-solanine, and solanidine by beta-glucosidase, alpha-rhamnosi-dase, and beta-galactosidase. Meanwhile, alpha-chaconine was degraded to beta 1-chaconine, beta 2-chaconine, gamma-chaconine, and solanidine by beta-glucosidase and alpha-rhamnosidase. Overall, the molecular mechanism underlying GAs degradation by PA21 was revealed by RNAseq combined with protein expression and function studies, thus providing the basis for the development of engineered bacteria that can efficiently degrade GAs to promote their application in the control of GAs in potatoes.