乙烯与脂氧合酶在番茄果实香气合成中的作用

通过对番茄成熟突变体和野生型果实香气物质、乙烯释放量、氢过氧化物裂解酶(HPL)、脂氧合酶(LOX)活性及基因表达的测定,明确LOX与乙烯在番茄果实香气物质合成中的作用。以番茄成熟突变体rin、nor、cnr、nr(均为乙烯合成缺陷突变体)、hp-1(高色素突变体,乙烯生成正常)和野生型Ailsa Craig(AC)为试材,分别在果实破色期(0 d)、破色3 d(3 d)和破色7 d(7 d)取果实,测定香气物质、乙烯释放量、LeHPL基因表达、LOX活性和TomloxC基因表达。结果表明,随着果实的成熟,4种乙烯合成突变体果实中的香气物质种类和含量与野生型AC相比均减少,但突变体hp-1果实中香气物质与AC无显著差异;rin、nor、cnr突变体中不产生乙烯,nr中产生少量乙烯,hp-1和AC果实中能正常生成乙烯;除AC果实外,突变体rin、nor、cnr果实中LOX酶活性和TomloxC基因表达水平均较低,而在hp-1和nr破色7 d果实中酶活性和基因表达量均最高;Le HPL表达量在AC和hp-1果实中随果实成熟显著增加,在nor破色7 d显著高于破色期(0 d)和破色3 d的,而在cnr、rin和nr破色7 d均显著下降。在乙烯合成缺陷突变体果实中香气物质种类和含量较野生型减少,且不能合成乙烯或合成少量乙烯,同时LOX酶活性降低,TomloxC及LeHPL表达下降,表明番茄果实香气物质合成的LOX途径是依赖乙烯的过程。

Role of Lipoxygenase and Ethylene in Tomato Fruit Aroma Synthesis

In order to acquire a better insight into the ethylene and lipoxygenase control of flavour compound generation and links between these metabolites and the central regulators of ripening，five pleiotropic mutant tomato lines were subjected to volatile metabolite profiling in comparison with wild-type Ailsa Craig（AC）. Five tomato mature mutants rin，nr，nor，cnr，hp-1 and wild type AC were sampled at breaker color（0 d），three days after breaker（3 d）and seven days after breaker（7 d）， respectively. Aroma，ethylene and gene expression of hydroperoxide lyase（HPL），lipoxygenase（LOX） activity and gene expression of TomloxC were investigated. With fruits growth and development，compared with the control，the aroma compounds in the mutant fruits were decreased. LOX enzyme activity and gene expression of TomloxC were lower in rin，nor，cnr fruits than that in wild-type AC fruits. However， expression of TomloxC were significantly increased in the hp-1 fruits and nr fruits at seven days after breaker. The aroma compounds in ripening mutants of tomato were less than those in wild type，and they can’t synthesize ethylene or synthesize small amounts of ethylene. Along with fruits growth and development，the expression of LeHPL in AC and hp-1 were increased，seven days after breaker were significantly higher than breaker and three days after breaker in the nor fruits，in rin and nr fruits were significantly decreased at seven days after breaker. Above all，in the mutants lack of ethylene，the aroma contents and types were lower than those in wild type，the ethylene synthesis were inhibited，LOX activity and gene expression of LeHPL，TomloxC were decreased. Those results indicated that LOX was regulated by ethylene in aroma volatiles synthesis of fruits.