The nonclimacteric guava cultivar 鈥楯en-Ju Bar鈥?is defective in system 2 1-aminocyclopropane-1-carboxylate synthase activity

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• 作者：Te-Chun Liu¹ ; Yu-Chang Liu¹ ; Kuo-En Chen² ; Chen-Wei Chao ; Chun-Ta Wu ; ^{wuct@ntu.edu.tw}
• 关键词：Guava (Psidium guajava L.) ; Ripening ; Ethylene ; ACC synthase ; ACC oxidase
• 刊名：Postharvest Biology and Technology
• 出版年：2012
• 期刊代码：89_09255214
• 类别：abs
• 出版时间：May, 2012
• 卷：67
• 期：Complete
• 页码：10-18
• 文件大小：884 K

摘要

The ripening characteristics and physiology of two guava cultivars, 鈥楯en-Ju Bar鈥?(鈥楯JB鈥? and 鈥楲i-Tzy Bar鈥?(鈥楲TB鈥?, were investigated and compared because of their divergent storability. During storage at 20 掳C, mature-green 鈥楲TB鈥?fruit exhibited ripening behavior typical for a climacteric fruit, including increases in respiration and ethylene production (3.75 mmol CO₂ kg^鈭? h^鈭? and 1.37 脳 10³ nmol C₂H₄ kg^鈭? h^鈭? at peak levels, respectively), yellow color development, flesh softening, and volatile production. By contrast, 鈥楯JB鈥?is considered a nonclimacteric fruit because it features low and stable rates of respiration (0.61-0.73 mmol CO₂ kg^鈭? h^鈭?) and ethylene production (less than 4 nmol C₂H₄ kg^鈭? h^鈭?) while retaining its pale-green color and firmness throughout a 20 d observation period. Furthermore, the nonclimacteric nature of 鈥楯JB鈥?fruit was revealed through its responses to various levels of applied ethylene, as its respiration rate increased in a concentration-dependent manner. This respiration enhancement occurred only when exogenous ethylene was present and could be evoked repeatedly in the same 鈥楯JB鈥?fruit. The ripening characteristics of 鈥楯JB鈥?do not result from a defect in ethylene signaling, but instead result from a lack of autocatalytic ethylene synthesis, as propylene ventilation stimulated normal fruit ripening and an upsurge of respiration without a massive endogenous ethylene release. However, a cutting treatment of 鈥楯JB鈥?was able to induce stress-responsive ethylene production expected from system 1 ethylene biosynthesis. The finding that 1-aminocyclopropane-1-carboxylic acid (ACC) content and ACC synthase (ACS) activity were significantly lower in 鈥楯JB鈥?than in 鈥楲TB鈥?fruit after harvest, together with the finding that treatment with ACC (rather than S-adenosyl-l-methionine) led to both fully ripened 鈥楯JB鈥?fruit and endogenous ethylene production, strongly suggest that insufficient ACC synthesis, i.e., the reaction catalyzed by ACS, prevents system 2 ethylene biosynthesis in 鈥楯JB鈥?guava fruit.