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Plants produce two phosphorylated enzymes: pyrophosphate-dependent fructose-6-phosphate phosphotransferase (PFP) and ATP-dependent phosphofructokinase (PFK). However, the characterization of phosphofructokinase (PFK) family members and their functions remains unexplored in Eastern Cottonwood (Populus deltoides). This study comprehensively analyzed 17 phosphofructokinase genes in the P. deltoides genome, including their gene structure, conserved domains, evolutionary relationships, and expression patterns. Genome-wide analysis of the poplar genome identified 11 genes belonging to PdPFK and 6 genes belonging to PdPFP. Phylogenetic, gene structure, and motif analyses revealed two main categories of PFK genes: PFK with eleven genes and PFP with six genes. Quantitative PCR (qPCR) analysis demonstrated that all 17 phosphofructokinase genes were induced in various tissues and developmental stages of P. deltoides. PFPs were strongly expressed throughout P. deltoides’ growth and development, notably in the roots, according to the transcript analysis. This genome-wide analysis provides insights into PFK and PFP genes and establishes a foundation for future investigations into the role of genes in P. deltoids.

Global climate change is heavily affected by an increase in CO2. As one of several efforts to cope with this, research on poplar, a representative, fast growing, and model organism in plants, is actively underway. The effects of elevated atmospheric CO2 on the metabolism, growth, and transcriptome of poplar were investigated to predict productivity in an environment where CO2 concentrations are increasing. Poplar trees were grown at ambient (400 ppm) or elevated CO2 concentrations (1.4× ambient, 560 ppm, and 1.8× ambient, 720 ppm) for 16 weeks in open-top chambers (OTCs). We analyzed the differences in the transcriptomes of Populusalba × Populus glandulosa clone “Clivus” and Populus euramericana clone “I-476” using high-throughput sequencing techniques and elucidated the functions of the differentially expressed genes (DEGs) using various functional annotation methods. About 272,355 contigs and 207,063 unigenes were obtained from transcriptome assembly with the Trinity assembly package. Common DEGs were identified which were consistently regulated in both the elevated CO2 concentrations. In Clivus 29, common DEGs were found, and most of these correspond to cell wall proteins, especially hydroxyproline-rich glycoproteins (HRGP), or related to fatty acid metabolism. Concomitantly, in I-476, 25 were identified, and they were related to heat shock protein (HSP) chaperone family, photosynthesis, nitrogen metabolism, and carbon metabolism. In addition, carbohydrate contents, including starch and total soluble sugar, were significantly increased in response to elevated CO2. These data should be useful for future gene discovery, molecular studies, and tree improvement strategies for the upcoming increased-CO2 environments.