LAUSR

Carbamoyl phosphate synthetase (CPS) catalyzes the synthesis of ammonia carbamoyl phosphate (CP), which plays a key role in the biosynthesis of arginine and pyrimidine nucleotides. There are two subunits of CPS enzyme in Populus trichocarpa, CarA (small subunit) and CarB (large subunit), respectively. Only when they coexist, CPS could catalyze to synthesize CP. However, it is not clear how CPS responds to nitrogen to affect arginine and pyrimidine nucleotides biosynthesis. In this study, bioinformatics methods were used to analyze the expression patterns of genes encoding CarA and CarB, and qRT-PCR and RNA-seq were used to investigate their molecular responses under different nitrogen concentrations. Phylogenetic analysis revealed that the phylogenetic trees of CarA and CarB had similar topologies. The results of qRT-PCR showed that the PtCarA and PtCarB genes were regulated by nitrogen, while their nitrogen-regulated patterns were different in different tissues. The expression patterns of PtCarA and PtCarB genes show a significant positive correlation according to qRT-PCR and RNA-seq. The analysis of promoter cis-acting elements showed that the promoter regions of PtCarA1, PtCarA2 and PtCarB contained some identical cis-acting elements. According to the analysis of phylogenetic tree, expression patterns and promoter elements, we speculated that there might be coevolution among PtCarA1, PtCarA2 and PtCarB. This study provided valuable information for further understanding the function of CPS of poplar, especially for nitrogen response, and provided new ideas for studying the evolution of gene families related to heteromultimers.