香蕉一个Ⅲ类酸性几丁质酶基因与果实成熟关系的研究

为了解Ⅲ类酸性几丁质酶基因(MaCHⅢ)与香蕉果实采后成熟过程的相互关系,对经乙烯和1-甲基环丙烯(1-MCP)处理的巴西香蕉果实采后乙烯释放量、Ⅲ类酸性几丁质酶基因(MaCHⅢ)表达以及几丁质酶活性进行了测定.结果显示:(1)乙烯催熟处理的香蕉果实,乙烯释放量比对照处理的果实提前15 d达到高峰;1-MCP处理的香蕉果实,乙烯生物合成和果实成熟明显受到了抑制.(2)外源乙烯加速了MaCHⅢ基因的下调表达和Ⅲ类酸性几丁质酶活性的下降,MaCHⅢ表达量和Ⅲ类酸性几丁质酶活性分别在采后第3天和第4天下降到最小值.(3)1-MCP处理使MaCHⅢ基因呈现上调表达,Ⅲ类酸性几丁质酶活性上升,MaCHⅢ基因表达量和Ⅲ类酸性几丁质酶活性分别在采后18 d和25 d达到高峰.研究表明,MaCHⅢ基因可能与香蕉果实采后成熟呈负相关.

A Class Ⅲ Acidic Chitinase Gene Was Closely Correlated with Postharvest Banana Fruit Ripening

In order to understand the relationship between MaCHⅢ and banana fruit ripening,ethylene release,MaCHⅢ expression and chitinase activity were measured after ethylene and 1-MCP(1-methylcyciopropene) treatment.The results showed that under ethylene treatment,gene expression and chitinase activity decreased faster than that of naturally ripened fruit and decreased to the lowest level at 3 and 4 days after harvest (DAH),respectively.With application of 1-MCP treatment,gene expression and chitinase activity gradually increased and reached peak at the 18 and 25 DAH,respectively.On the other hand,exogenous ethylene induced ethylene biosynthesis and ethylene production and then reached peak at 3 DAH,which was 15 days earlier than naturally ripened fruits.While 1-MCP greatly suppressed ethylene biosynthesis and fruit ripening.It was suggested that this gene might negatively correlate with postharvest fruit ripening.