トマト果実のグルタミン酸蓄積とエチレンの関係

The effect of ethylene on the accumulation of glutamate in the fruit of normal tomato ('Rutgers' and 'Momotaro')and ripening inhibitor mutant (rin) tomato(Lycopersicon esculentum Mill.) during ripening was investigated.As fruit ripening progresse,glutamate content in the fruit pericarp tissue increased greatly in 'Rutgers' but remained low and constant level in rin tomato.Glutamine and γ-aminobutyric acid contents decreased gradually during ripening in both 'Rutgers'and rin fruit.Relatively high activities of glutamate dehydrogease,glutamate synthase and glutamine synthetase were detected throughout fruit ripening in both varieties,whereas no relationship was observed between glutamate content and the enzyme activieies.Treatment of 'Momotaro'fruit with diazocyclopentadience,an inhibitro of ethylene action,inhibited the increase in ethylene production and glutamate accumlation which are associated with fruit ripening,suggesting that glutamate accumlation may be mediated through ethylene.However,glumamate content in rin fruit treatde with exogenous ethylene remained low and unchanged uitil after four days.The results indicate that accumulation of glutamete in tomato fruit is likely to be related to the ripening process apart from the direct role of ethylene.

トマト果実の成熟に伴うグルタミン酸蓄積とエチレンとの関係を’Rutgers’、’桃太郎’およびrinを用いて調べた。1.’Rutgers’果実では、追熟に伴ってグルタミン酸含有が急激に増加したが、rin果実ではほとんど変化しなかった。グルタミンとγ-アミノ酪酸含量は両果実ともに追熟に伴って減少した。2.グルタミン酸代謝関連酵素として、グルタミン酸脱水素酵素、グルタミン酸合成酵素およびグルタミン合成酵素の追熟中の活性変化を調べたところ、’Rutgers’およびrin果実ともに高い活性を示した。3.’桃太郎’果実にDACP処理すると、追熟の進行に伴うエチレン生成の増加が抑制され、同時にグルタミン酸の蓄積を誘導しなかったが、6日後には増加した。5.以上のことより、トマト果実の成熟に伴うグルタミン酸の蓄積はエチレン生成によるものではなく、成熟に伴う現象であるように思われた。