Genetic dissection of hormonal responses in the roots of arabidopsis grown under continuous mechanical impedance

継続的な機械刺激下におかれたシロイヌナズナ根の生長におけるホルモン応答の遺伝学的解析

岡本 崇*; 鶴見 誠二*; 柴崎 杏平*; 尾花 佳美*; 高地 博寛*; 大野 豊; Rahman, A.*

Okamoto, Takashi*; Tsurumi, Seiji*; Shibasaki, Kyohei*; Obana, Yoshimi*; Takaji, Hironori*; Ono, Yutaka; Rahman, A.*

機械的な刺激を与えるために透析膜でカバーした培地上で育成したシロイヌナズナの根は、エチレン反応に特徴的な形態を示した。この形態について詳しく調べたところ、エチレンの生産性ではなくエチレンの情報伝達がエチレン応答の増強に重要な役割を担っていることがわかった。さらに、エチレン反応の増加は、根におけるオーキシン応答にも影響を与えていることを明らかにした。以上の結果は、機械的刺激による根の生長変化におけるエチレンの役割について新たな知見を与えるものである。

The Arabidopsis seedlings grown horizontally on a dialysis membrane-covered agar plate encountered adequate mechanical impedance as the roots showed characteristic ethylene phenotypes: 2-fold reduction in root growth, increase in root diameter, decrease in cell elongation, and ectopic root hair formation. The root phenotype characterization of various mutants having altered response to ethylene biosynthesis or signaling, the effect of ethylene inhibitors on mechanically impeded roots, and transcription profiling of the ethylene-responsive genes led us to conclude that enhanced ethylene response plays a primary role in changing root morphology and development during mechanical impedance. Further, the differential sensitivity of horizontally and vertically grown roots toward exogenous ethylene suggested that ethylene signaling plays a critical role in enhancing the ethylene response. We subsequently demonstrated that the enhanced ethylene response also affects the auxin response in roots. Taken together, our results provide a new insight into the role of ethylene in changing root morphology during mechanical impedance.