PARENT SESSION
Posters P7D Chloroplast factories and transformation. Abstracts (754-758)

Creation of transgenic tobacco plants with enhanced photosynthetic capacity by chloroplast transformation technology. Yukinori Yabuta^*,1, Kumiko Yamamoto², Yasuko Aoyama², Masahiro Tamoi¹, Akiho Yokota³, Ken-Ichi Tomizawa⁴, Shigeru Shigeoka^{1, 2}, ¹ Department of Food and Nutrition, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara, Japan² Advanced Life Science, Graduate School, Kinki University, 3327-204 Nakamachi, Nara, Japan³ Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Japan⁴ Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizu-cho, Soraku-gun, Japan

ABSTRACT- To analyze the potential of the Calvin cycle, we generated transgenic tobacco plants which were introduced a fbp/sbp encoding fructose-1,6-/sedoheptulose-1,7-bisphosphatase (FBP/SBPase) of Synechococcus PCC7942 with a tomato promoter and a transit peptide of rbcS3C into nuclear genome by Agrobacterium-mediated gene transfer. On the other hand, transformation of the plastid genome has several advantages over nuclear transformation. Since plastids in most agronomically important plant species are maternally inherited, introduction of foreign genes into the plastid genome prevents pollen-mediated outcrossing. To create further excellent transgenic plants, we generated transplastomic tobacco plants which had the S.7942 fbp/sbp gene in the plastid genome. Nine spectinomycin resistant transplastomic tobacco plants carrying the fbp/sbp transgene were generated (pTpsbAFS-1 ∼ -9). High levels of FBP/SBPase protein derived from the transgene were detected in the extracts prepared from the leaves of all transplastomic tobacco plants. In pTpsbAFS-3 and pTpsbAFS-9, total FBPase activities were approx. 30- to 40-fold higher than those in wild-type plant. To evaluate the effect of the FBP/SBPase overexpression on growth and photosynthetic activity, the pTpsbAFS-3, pTpsbAFS-9, and wild-type plants were grown hydroponically under a 12-h photoperiod with, 300 mol m^-2 s^-1, 60% relative humidity, and day/night temperatures of 25/20°C. Transplastomic plants grew significantly larger than wild-type plants at 12 weeks after planting. After 18 weeks, pTpsbAFS-3 and pTpsbAFS-9 plants increased about 1.3-fold in height compared with that of wild-type plants. Under normal conditions (25°C, mol m^-2 s^-1, 360 p.p.m. CO₂), the photosynthetic activities in the fourth leaf of the pTpsbAFS-3 and pTpsbAFS-9 were approx. 1.5- to 1.8-fold higher than that of wild-type plants. Analysis of sugar and other photosynthetic metabolites in the transplastomic tobacco plants is now underway in our laboratory.

KEY WORDS: fructose-1,6-/sedoheptulose-1,7-bisphosphatase, chloroplast transformation, Calvin cycle, transplastomic plants