Abstract

Acidity is an important factor influencing the organoleptic quality of apple fruits. In this study, an apple pyrophosphate-energized proton pump (PEPP) gene was isolated and designated MdMa12. On the basis of a phylogenetic analysis in Rosaceae species, PEPP genes were divided into three groups, with apple PEPP genes most closely related to pear PEPP genes. Gene expression analysis revealed that high malic acid content was generally accompanied by high MdMa12 expression levels. Moreover, MdMa12 was mainly expressed in the fruit. A subcellular localization analysis suggested that MdMa12 is a mitochondrial protein. The ectopic expression and overexpression of MdMa12 in “Micro-Tom” tomato and apple calli, respectively, increased the malic acid content. One (MDH12) of four malate dehydrogenase genes highly expressed in transgenic apple calli was confirmed to encode a protein localized in mitochondria. The overexpression of MDH12 increased the malate content in apple calli. Furthermore, MdMa12 overexpression increased MdDTC1, MdMa1, and MdMa10 expression levels, which were identified to transport malate. These findings imply that MdMa12 has important functions related to apple fruit acidity. Our study explored the regulatory effects of mitochondria on the complex mechanism underlying apple fruit acidity.

中文翻译：

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线粒体焦磷酸酶泵基因苹果 Ma12 的过表达导致番茄和苹果愈伤组织中苹果酸积累和苹果酸脱氢酶的上调

摘要

酸度是影响苹果果实感官品质的重要因素。在这项研究中，分离了苹果焦磷酸激发质子泵 (PEPP) 基因并命名为MdMa12。根据蔷薇科物种的系统发育分析，将PEPP基因分为三组，其中苹果PEPP基因与梨PEPP基因关系最密切。基因表达分析表明，高苹果酸含量通常伴随着高MdMa12表达水平。此外，MdMa12主要在果实中表达。亚细胞定位分析表明 MdMa12 是一种线粒体蛋白。MdMa12的异位表达和过表达在“Micro-Tom”番茄和苹果愈伤组织中，分别增加了苹果酸含量。在转基因苹果愈伤组织中高度表达的四种苹果酸脱氢酶基因中的一种（MDH12）被证实编码定位于线粒体中的蛋白质。MDH12的过表达增加了苹果愈伤组织中的苹果酸含量。此外，MdMa12过表达增加了 MdDTC1、MdMa1和MdMa10 的表达水平，这些表达水平被鉴定为运输苹果酸。这些发现暗示MdMa12具有与苹果果实酸度相关的重要功能。我们的研究探讨了线粒体对苹果果实酸度复杂机制的调节作用。