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

Glycoalkaloids (GAs), including α-solanine and α-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 α-solanine or α-chaconine was evaluated. In total, 3170 and 2783 differential expressed genes (DEGs) were found in α-solanine- and α-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 components 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 α-solanine was degraded to β1-solanine, β2-solanine, γ-solanine, and solanidine by β-glucosidase, α-rhamnosidase, and β-galactosidase. Meanwhile, α-chaconine was degraded to β1-chaconine, β2-chaconine, γ-chaconine, and solanidine by β-glucosidase and α-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.