Atsushi Miyasaka

Contribution of Ethylene Biosynthesis for Resistance to Blast Fungus Infection in Young Rice Plants

The role of ethylene (ET) in resistance to infection with blast fungus (Magnaporthe grisea) in rice (Oryza sativa) is poorly understood. To study it, we quantified ET levels after inoculation, using young rice plants at the four-leaf stage of rice cv Nipponbare (wild type) and its isogenic plant (IL7), which contains the Pi-i resistance gene to blast fungus race 003. Small necrotic lesions by hypersensitive reaction (HR) were formed at 42 to 72 h postinoculation (hpi) in resistant IL7 leaves, and whitish expanding lesions at 96 hpi in susceptible wild-type leaves. Notable was the enhanced ET emission at 48 hpi accompanied by increased 1-aminocyclopropane-1-carboxylic acid (ACC) levels and highly elevated ACC oxidase (ACO) activity in IL7 leaves, whereas only an enhanced ACC increase at 96 hpi in wild-type leaves. Among six ACC synthase (ACS) and seven ACO genes found in the rice genome, OsACS2 was transiently expressed at 48 hpi in IL7 and at 96 hpi in wild type, and OsACO7 was expressed at 48 hpi in IL7. Treatment with an inhibitor for ACS, aminooxyacetic acid, suppressed enhanced ET emission at 48 hpi in IL7, resulting in expanding lesions instead of HR lesions. Exogenously supplied ACC compromised the aminooxyacetic acid-induced breakdown of resistance in IL7, and treatment with 1-methylcyclopropene and silver thiosulfate, inhibitors of ET action, did not suppress resistance. These findings suggest the importance of ET biosynthesis and, consequently, the coproduct, cyanide, for HR-accompanied resistance to blast fungus in young rice plants and the contribution of induced OsACS2 and OsACO7 gene expression to it.

Synthesis of Sulfur Atom-Substituted Poly(phenylacetylene) Using Rh Complex Catalyst-Columnar Formation and cis-to-trans Isomerization

硫黄原子を側鎖に含む置換アセチレンは, トリエチルアミン溶媒の存在下, ロジウム (Rh) 錯体触媒によって, 立体規則的に重合が進行し, シス体の置換ポリアセチレンが選択的かつ高収率で生成する. このシス体ポリアセチレン主鎖はらせん構造を有し, 分子集合体であるカラムナー結晶を形成していることを見いだした. このシス体ポリマーに約200kg/cm2の圧力をかけると, シス体の二重結合が回転解裂し, シス体とトランス体の2種類のラジカルが生成し, 前者の不対電子はベンゼン環のパラ位についているアルキルスルホキシド部位まで移動し, その結果非常に大きなg値, すなわちg=2.0081, 線幅ΔHmsl=11GのtripletのESRのスペクトルを示すことを見いだした. スルホキシド硫黄の隣のメチレンにスピン密度が現われることは半経験的量子化学的計算法, AM1法を用いて確認した. 一方, トランス体ラジカルは共役平面構造を有し, スピン密度はその主鎖に非局在化し速い運動性を示すソリトン様の磁気的な振舞いを示すことを見いだした.