DIFFERENCES IN PHOTOSYNTHESIS AND TERPENE CONTENT IN LEAVES AND ROOTS IN WILD-TYPE AND TRANSGENIC Arabidopsis PLANTS

--We investigated the hypotheses that two different varieties of Arabidopsis thaliana show differences in physiology and terpene production. The two varieties of A. thaliana used in this study were wild-type (WT) and transgenic line (CoxIV-FaNES I) genetically modified to emit nerolidol with linalool/nerolidol synthase (COX). Photosynthetic rate, electron transport rate, fluorescence, leaf volatile terpene contents and root volatile terpene contents were analyzed. For both types, we found co-eluting α-pinene+β-ocimene, limonene, and humulene in leaves; and in the roots we found co-eluting α-pinene+β-ocimene, sabinene+β-pinene, β-myrcene, limonene, and humulene. At the end of the growing cycle, COX plants tended to have lower pools of terpene compounds in their leaves, with 78.6% lower photosynthesis rates and 30.8% lower electron transport rates, compared with WT plants at that time. The maximal photochemical efficiency Fv/Fm was also significantly lower (25.5%) in COX plants, indicating that these varieties were more stressed than WT plants. However, COX plants had higher (239%) root terpene contents compared to WT plants. COX plants appear to favor root production of volatile terpenes rather than leaf production. Thus we conclude that there were significant differences between COX and WT plants in terms of terpenoid pools, stress status and physiology. ----------------------------------------------------------------Abbreviations: A---CO2 uptake; COX--transgenic line (CoxIV-FaNES I); ETR---electron transport rate; Fv/Fm---maximum photochemical efficiency of PSII; F/F’m---actual photochemical efficiency of PSII; gs---stomatal conductance; TPSs---terpene synthases; VOCs---volatile organic compounds; WT---wild-type.