Poster: Nutrient Biology

Abs # 397: Overexpression of a plant mitochondrial citrate synthase in Eucalyptus trees.

Presenter:	Kawazu, Tetsu , tetsu-kawazu@ojipaper.co.jp
Authors	Kawazu, Tetsu  (A)   Suzuki, Yuji  (B) (A)  Wada, Tatsumi  (B)   Kondo, Keiko  (A)   Koyama, Hiroyuki  (B)
Affiliations:	(A): Forestry Research Institute, Oji Paper Co. (B): Faculty of Agriculture, Gifu University

Eucalyptus is one of major forest trees for the production of biomass and industrial materials, since it has good properties such as fast-growing and adaptability to various environments and aptitudes as lumber, pulp and etc. Afforestation of Eucalyptus species is conducted in various regions around the world. There is a necessity for improving the properties of eucalypts from tending of suitable land for afforestation shortage. Improvement of their growth under stress environment would be most important targets of molecular breeding to increase productivity. As we reported, overexpression of a mitochondrial citrate synthase gene improves growth of carrot cells and Arabidopsis thaliana under aluminum-induced Pi limited conditions by enhancement of citrate excretion. This result would be related to reduce P consumption by agriculture and forestry, especially in acid soil area. To examine whether the same strategy is useful to eucalypts or not, we introduced a mitochondrial citrate synthase gene from carrot into a hybrid eucalypts (Eucalyptus grandis �~ urophylla) using Agrobacterium-mediated transformation. Citrate synthase activity of both leaves and roots in the transgenic plants was increased up to five-fold of control plants. Citrate concentration in the roots was increased in transgenic plants as the citrate synthase activity was increased. When the transgenic plants were grown hydroponically with colloidal aluminum-phosphate as a sole phosphorous source, the growth of the roots was similar to that with Na-phosphate. On the other hand, reduction of root growth was found with several control plants. Further characterizations are clearly needed, but our strategy is useful to improve Pi-acquisition of eucalypts at least partially, when grow on acid soils.