Effects of simultaneously elevated temperature and CO2 levels on Nicotiana benthamiana and its infection by different positive-sense RNA viruses are cumulative and virus type-specific

We have studied how simultaneously elevated temperature and CO2 levels [climate change-related conditions (CCC) of 30 degrees C, 970 parts-per-million (ppm) of CO2 vs. standard conditions (SC) of 25 degrees C, similar to 405 ppm CO2] affect physiochemical properties of Nicotiana benthamiana leaves, and also its infection by several positive sense RNA viruses. In previous works we had studied effects of elevated temperature, CO2 levels separately. Under CCC, leaves of healthy plants almost doubled their area relative to SC but contained less protein/unit-of-area, similarly to what we had found under conditions of elevated CO2 alone. CCC also affected the sizes/numbers of different foliar cell types differently. Under CCC, infection outcomes in titers and symptoms were virus type-specific, broadly similar to those observed under elevated temperature alone. Under either condition, infections did not significantly alter the protein content of leaf discs. Therefore, effects of elevated temperature and CO2 combined on properties of the pathosystems studied were overall cumulative.