Volatile esters are key compounds contributing to flavor intensity in commonly consumed fruits including apple (Malus domestica), strawberry (Fragaria spp.), and banana (Musa sapientum). In kiwifruit (Actinidia spp.), ethyl butanoate and other esters have been proposed to contribute fruity, sweet notes to commercial cultivars. Here, we investigated the genetic basis for ester production in Actinidia in an A. chinensis mapping population (AcMPO). A major quantitative trait loci for the production of multiple esters was identified at the high-flavor intensity (HiFI) locus on chromosome 20. This locus co-located with eight tandemly arrayed alcohol acyl transferase genes in the Red5 genome that were expressed in a ripening-specific fashion that corresponded with ester production. Biochemical characterization suggested two genes at the HiFI locus, alcohol acyl transferase 16-b/c (AT16-MPb/c), probably contributed most to the production of ethyl butanoate. A third gene, AT16-MPa, probably contributed more to hexyl butanoate and butyl hexanoate production, two esters that segregated in AcMPO. Sensory analysis of AcMPO indicated that fruit from segregating lines with high ester concentrations were more commonly described as being “fruity” as opposed to “beany”. The downregulation of AT16-MPa–c by RNAi reduced ester production in ripe “Hort16A” fruit by >90%. Gas chromatography-olfactometry indicated the loss of the major “fruity” notes contributed by ethyl butanoate. A comparison of unimproved Actinidia germplasm with those of commercial cultivars indicated that the selection of fruit with high concentrations of alkyl esters (but not green note aldehydes) was probably an important selection trait in kiwifruit cultivation. Understanding ester production at the HiFI locus is a critical step toward maintaining and improving flavor intensity in kiwifruit.

中文翻译：

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高风味强度位点的醇酰基转移酶基因有助于猕猴桃中的酯生物合成

挥发性酯是影响苹果 (Malus Domestica)、草莓 (Fragaria spp.) 和香蕉 (Musa sapientum) 等常用水果风味强度的关键化合物。在猕猴桃（猕猴桃属）中，丁酸乙酯和其他酯已被提议为商业品种提供果香和甜味。在这里，我们研究了中华猕猴桃作图群体（AcMPO）中猕猴桃酯产生的遗传基础。在 20 号染色体上的高风味强度 (HiFI) 基因座上鉴定了用于产生多种酯的主要数量性状基因座。该基因座与 Red5 基因组中的八个串联排列的醇酰基转移酶基因位于同一位置，这些基因在成熟过程中表达-与酯生产相对应的特定时尚。生化表征表明 HiFI 位点上的两个基因，醇酰基转移酶 16-b/c (AT16-MPb/c)，可能对丁酸乙酯的产生贡献最大。第三个基因 AT16-MPa 可能对丁酸己酯和己酸丁酯的生产贡献更大，这两种酯在 AcMPO 中分离。AcMPO 的感官分析表明，来自具有高酯浓度的分离品系的果实更常被描述为“果味”而不是“豆味”。RNAi 对 AT16-MPa-c 的下调使成熟“Hort16A”果实中的酯产量降低了 90% 以上。气相色谱-嗅觉测定表明丁酸乙酯带来的主要“果味”香气消失了。未改良的猕猴桃种质与商业品种的比较表明，选择具有高浓度烷基酯（而不是绿味醛）的果实可能是猕猴桃栽培中的一个重要选择性状。了解 HiFI 基因座的酯生成是维持和改善猕猴桃风味强度的关键一步。