Genome-Wide Identification and Characterization of the Trehalose-6-Phosphate Synthetase Gene Family in Chinese Cabbage (Brassica rapa) and Plasmodiophora brassicae during Their Interaction

Trehalose is a nonreducing disaccharide that is widely distributed in various organisms. Trehalose-6-phosphate synthase (TPS) is a critical enzyme responsible for the biosynthesis of trehalose, which serves important functions in growth and development, defense, and stress resistance. Although previous studies have found that the clubroot pathogen Plasmodiophora brassicae can lead to the accumulation of trehalose in infected Arabidopsis organs, it has been proposed that much of the accumulated trehalose is derived from the pathogen. At present, there is very little evidence to verify this view. In this study, a comprehensive analysis of the TPS gene family was conducted in Brassica rapa and Plasmodiophora brassicae. A total of 14 Brassica rapa TPS genes (BrTPSs) and 3 P. brassicae TPS genes (PbTPSs) were identified, and the evolutionary characteristics, functional classification, and expression patterns were analyzed. Fourteen BrTPS genes were classified into two distinct classes according to phylogeny and gene structure. Three PbTPSs showed no significant differences in gene structure and protein conserved motifs. However, evolutionary analysis showed that the PbTPS2 gene failed to cluster with PbTPS1 and PbTPS3. Furthermore, cis-acting elements related to growth and development, defense and stress responsiveness, and hormone responsiveness were predicted in the promoter region of the BrTPS genes. Expression analysis of most BrTPS genes at five stages after P. brassicae interaction found no significant induction. Instead, the expression of the PbTPS genes of P. brassicae was upregulated, which was consistent with the period of trehalose accumulation. This study deepens our understanding of the function and evolution of BrTPSs and PbTPSs. Simultaneously, clarifying the biosynthesis of trehalose in the interaction between Brassica rapa and P. brassicae is also of great significance.