This paper reports ethylene production, expression levels of ethylene precursor’s genes, as well as carotenoid content and expression levels of carotenoid biosynthesis genes, during postharvest ripening of three different papaya genotypes of contrasting origin (2 creoles and 1 commercial) and pulp color (yellow, orange and red), under conditions that promote ethylene formation and under those inhibiting ethylene. Our study showed that naturally ripened papaya fruits presented relatively high ethylene production levels that was correlated with changes in expression levels of both ethylene precursor’s genes (CpACCs1, CpACCs2, CpACCo1 and CpACCo2), and carotenoid biosynthesis genes (CpPSY, CpZDS, CpLCY-β2, CpCHX-β). However, when papaya fruits were treated with an ethylene inducer (Ethephon; 2.5 g L^− 1 of 2-chloroethyl-phosphonic acid) fruits ripened faster (two days earlier than controls), and they also showed a higher ethylene peak and higher expression levels of both ethylene precursors genes and carotenoid biosynthesis genes, than control fruits. In contrast, papaya fruits treated with an ethylene inhibitor (1-MCP; 300 nL L^− 1 of 1-methylcyclopropene) never ripened (in fact they did not show changes in fruit firmness, °Brix, pH or acidity), and they showed very low ethylene production and low expression levels of ethylene precursors genes, as well as showing low expression of carotenogenic genes, throughout the postharvest ripening process. Correlation analysis showed that increased ethylene production was highly correlated with increased expression of both ethylene precursors genes and carotenoids biosynthesis genes, but the specific carotenogenic genes induced by ethylene differed among commercial and creole papaya genotypes.

本文报告了三种不同基因型不同来源（2种克里奥尔木和1种商业木瓜）和果肉颜色（黄色、橙色和红色），在促进乙烯形成的条件下和在抑制乙烯的条件下。我们的研究表明，自然成熟的木瓜果实表现出相对较高的乙烯产量水平，这与乙烯前体基因（CpACCs1、CpACCs2、CpACCo1 和 CpACCo2）和类胡萝卜素生物合成基因（CpPSY、CpZDS、CpLCY-β2、 CpCHX-β)。^{然而，当木瓜果实用乙烯诱导剂（乙烯利；2.5 g L - 1} 2-氯乙基膦酸）处理时，果实成熟得更快（比对照提前两天），并且还表现出更高的乙烯峰值和更高的表达水平乙烯前体基因和类胡萝卜素生物合成基因的含量均高于对照果实。相比之下，用乙烯抑制剂（1-MCP；300 nL L ^-1 1-甲基环丙烯）处理的木瓜果实从未成熟（事实上，它们没有表现出果实硬度、白利糖度、pH 或酸度的变化），并且它们表现出在整个采后成熟过程中，乙烯产量极低，乙烯前体基因的表达水平低，并且胡萝卜素基因的表达水平低。相关分析表明，乙烯产量的增加与乙烯前体基因和类胡萝卜素生物合成基因表达的增加高度相关，但乙烯诱导的特定胡萝卜素基因在商品木瓜和克里奥尔木瓜基因型之间存在差异。