DETECTION OF ALUMINIUM IN ORGANELLA AND MOLECULAR COMPLEXES WITH PROTEIN OF THE ALUMINIUM-PREFERABLE RUZIGRASS, Brachiaria ruziziensis UNDER ALUMINIUM/ACID STRESS

¹ 2421 Suya, Nishigoshi Kikuchi-gun, Kumamoto 861-1192, Japan Kyushu National Agricultural Experiment Station

² 2-111-16 Yayoi Bunkyo-ku, Tokyo 13-0032, Japan Research Center for Nuclear Science and Technology, The University of Tokyo

³ 3-25-40 Sakura-josui Setagaya-ku, Tokyo 156-8550, Japan, Dept of Chmistry Collegeof Numanities and Science, Nihon University

Under acid condition (< pH 5.5), aluminium (Al) in the soil is ionized to inhibit the growth of roots and leaves in most plants, being one of the most serious growth liming factors in acid soils. The mechanism for the Al tolerance in barley is mainly concerned with exclusion of Al in the roots. On the other hand, a pasture cultivated in the acid soil around sub-tropical areas, ruzigrass (Brachiaria ruziziensis), can grow as well as, often better than in neutral soil, while the Al function for the plant growth is unknown. In this study, we analyzed ²⁷Al in the shoots in Al-tolerant barley variety Dayton, Al-sensitive barley var. Kearney, and Al-preferable ruzigrass. Moreover, we applied ²⁶Al as a tracer and measured it by an accelerator of mass spectrometer (AMS) without unavoidably abundant contamination of environmental ²⁷Al. The ²⁶Al amounts in leaf-cell organella (nuclei, chloroplast and mitochondria) were detected quantitatively at an ultra-micro level (10⁷ atoms/sample). Although amounts of ²⁶Al/mg protein of the chloroplast were not different between three plants tested, those of nuclei and mitochondria of Dayton, especially ruzigrass were abundant much more than Kearney. This result was inconsistent with the Al-exclusion mechanism found in Al-tolerant barley roots, suggesting that accumulated Al in the Dayton and ruzigrass shoots might be detoxified and might promote on the growth by some mechanisms different from barley. Also, we established a suspension cell culture of the ruzigrass to reveal Al function at a molecular level. The cell proliferation was enhanced by acid condition (pH 3.5-4.5) rather than general condition at pH 5.8. Furthermore, we performed electrophoresis in native polyacrylamide gel for the water soluble protein fraction from the ²⁶Al incorporated cell and AMS-analysis of ²⁶Al in the thin slice of the gel. It showed that some proteins were associated with ultra trace of ²⁶Al (at level of 10^-15g/gel slice).