Photosynthetic efficiency of transgenic tobacco plants (Nicotiana tabacum L.) over-expressing mtlD gene under drought and paraquat stress

Indian Journal of Plant Physiology15 (2),2010
AlamBadre 1, Jacob James1,Earl Hugh J.2,3

1Plant Physiology Division, Rubber Research Institute of India, Kottayam-686 009, India.
2Department of Crop and Soil Sciences, Plant Sciences Building, University of Georgia, Athens, GA 30602-7272, USA.
3Department of Plant Agriculture, University of Guelph, Guelph, Canada.
E Mail: badrealam@gmail.com

• Abstract:The objective of this study was to examine the performance of genetically transformed tobacco plants over-expressing mannitol 1-phosphate dehydrogenase (mtlD) in maintaining better photosynthetic activity than the untransformed wild plants during water deficit stress and in combination with paraquat stress. Inhibitions in the rates of net CO2 assimilation (PN) and the non-cyclic photosynthetic electron transport across photosystem II (ETR) due to water deficit stress were much smaller in the mtlD transformed plants (22% and 9%, respectively) than in the untransformed wild ones (55% and 52%, respectively). These differences were even more marked when the plants experiencing water deficit stress were treated with paraquat, which blocks the photosynthetic electron transfer chain and diverts the excitation energy into producing reactive oxygen species (ROS). The minimal inhibitions in the photochemical activity (9–10%) of mtlD transformed plants resulting from the environmental stresses agree with their expected efficient use of photosynthetic electrons. Results of the present study thus suggest that mtlD transformed tobacco plants tolerated the stress better than the untransformed wild plants which is noteworthy for further attention.