Body of Abstract: Plant Carbon (C) and Nitrogen (N) metabolism are intricately connected. Rising atmospheric CO2 levels directly affect the C and N metabolism and their interactions. Elevated CO2 grown C3 plants has altered allocation of N causing reduced investment in Rubisco and has reduced carboxylation rate (Vc,max). These changes contribute to the negative acclimation of photosynthetic capacity. A decline in plant N concentration is also observed under elevated CO2 leading to decreased nutritional quality of C3 plants. Altering genetic factors controlling CxN metabolic crosstalks could provide genotypes better suited for high CO2 conditions, i.e., has little to no acclimation of photosynthetic capacity and maintain N concentration similar to ambient CO2-grown C3 plants.
We constructed a gene regulatory network of Arabidopsis plants grown under CO2 and N treatments. We found bZIP1 as one of the regulators of CxN responsive genes. Next, we analyzed the overexpression of bZIP1 TF experimentally. bZIP1-overexpression (bZIP1-OX) line accumulated more plant biomass under elevated CO2 conditions than wildtype plants, while N and protein concentration remained similar between the two genotypes. RNA seq analysis of bZIP1-OX plants revealed CxN responsive genes differentially regulated by bZIP1-OX are enriched in Jasmonic Acid (JA) signaling and synthesis pathways. Further, co-expression network analysis was utilized to identify the gene modules correlated with above-ground biomass. Modules having a significant positive correlation with biomass constitute genes related to JA-related processes.
In conclusion, our study shows bZIP1 as a potential target for biomass increase under elevated CO2. RNA seq analysis shows in bZIP1-OX plants, biomass increase, and JA-related genes’ expression are correlated. This indicates that JA plays a role in C & N crosstalks in Arabidopsis and may play a role in biomass regulation under elevated CO2 conditions.