DcC4H and DcPER Are Important in Dynamic Changes of Lignin Content in Carrot Roots under Elevated Carbon Dioxide Stress

In our study, isobaric tags for relative and absolute quantification (iTRAQ) was conducted to determine the significantly changed proteins in the fleshy roots of carrots under different carbon dioxide (CO₂) treatments. A total of 1523 proteins were identified, of which 257 were differentially expressed proteins (DEPs). On the basis of annotation analysis, the DEPs were identified to be involved in energy metabolism, carbohydrate metabolism, and some other metabolic processes. DcC4H and DcPER, two lignin-related proteins, were identified from the DEPs. Under elevated CO₂ stress, both carrot lignin content and the expression profiles of lignin biosynthesis genes changed significantly. The protein-protein interactions among lignin-related enzymes proved the importance of DcC4H and DcPER. The results of our study provided potential new insights into the molecular mechanism of lignin content changes in carrot roots under elevated CO₂ stress.