Abstract
Effects of methyl jasmonate (MeJA) on ethylene production in mungbean (Phaseolus radiatus L.) hypocotyl and leaf segments were studied. Ethylene production in mungbean hypocotyl segments was decreased in proportion to MeJA concentrations and $450\;\mu\textrm{M}$ of MeJA showed 50% inhibitory effect. This inhibitory effect appeared after 3 h of incubation period and continued for 24 h. Inhibition of ethylene production by MeJA was due to the decrease in 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase activity. However, MeJA treatment had no effect on ACC content and ACC synthase activity. MeJA also inhibited auxin-induced ethylene production in hypocotyls. To investigate the mechanisms of the inhibitory effect of MeJA on the auxin-induced ethylene production, ACC synthase and ACC oxidase activity were examined after MeJA treatment. MeJA decreased the ACC content and ACC synthase activity as weD as ACC oxidase activity in the auxin-treated tissue. These results suggest that the inhibition of MeJA on auxin-induced ethylene production is not due to the direct inhibitory effect of MeJA on the ACC synthase, but to the inhibition of the ability of IAA to promote the synthesis of ACC synthase. In contrast, ethylene production from the detached mungbean leaves was stimulated by MeJA. The rate of ethylene production increased approximately 65% over the control after 12 h of incubation period by $4.5\;\mu\textrm{M}$ MeJA. When MeJA was applied to detached leaves along with IAA, the effect of MeJA appeared to be additive. In an effort to elucidate mechanisms of MeJA action on auxin-induced ethylene production in the leaf tissue, enzyme activities of ACC synthase and ACC oxidase were examined. MeJA stimulated ACC oxidase activity but did not affect ACC synthase activity in leaf tissue. Together, these results suggest that MeJA plays different roles in the ethylene production in the different mungbean tissues.issues.
Methyl jasmonate(MeJA)가 녹두(Phaseolus radiatus L.) 하배축과 잎에서 에틸렌 생성에 미치는 영향을 조사하였다. 녹두 하배축 조직에서의 에틸렌 생성은 MeJA의 농도에 비례해서 감소했으며 그 억제 효과는 3시간 이후부터 현저하게 나타났다. 1-Aminocyclopropane-1-carboxylic acid (ACC) oxidase의 활성에 대한 MeJA의 억제 효과 역시 3시간 이후부터 나타났으며 ACC synthase의 활성에는 별 효과가 없었다. $450\;\mu\textrm{M}$ MeJA가 포함된 배지에서 배양시킨 녹두 하배축 조직에서 옥신 유발 에틸렌 생성은 대조구에 비하여 현저히 억제되었는데 이러한 옥신 유발 에틸렌 생성에 대한 MeJA의 억제 기작을 알아보기 위하여 ACC synthase의 활성과 ACC oxidase의 활성을 조사하였다. MeJA는 옥신이 처리된 조직내 ACC양과 ACC synthase 활성 및 ACC oxidase의 활성을 감소시켰다. 따라서 옥신 유발 에틸렌 생성에 대한 MeJA의 억제 효과는 MeJA가 ACC synthase의 활성 뿐만 아니라 ACC oxidase의 활성을 감소시킴으로써 나타난다고 볼 수 있다. 하배축과는 반대로 $4.5\;\mu\textrm{M}$로 처리한 잎 조직에서의 에틸렌 생성은 대조구에 비해 약 50% 촉진되었으며 옥신에 의해 유발된 에틸렌 생성량은 MeJA에 의해 증가되었다. 잎에서의 MeJA에 의한 에틸렌의 합성 증가는 ACC oxidase의 활성 증가에 기인하였으며 ACC synthase의 효소활성은 변화가 없어TEk. 따라서 MeJA는 녹두의 서로 다른 조직에서 에틸렌 합성에 대해 서로 상반된 효과를 나타내었다.