Molecular and biochemical characterization of lipoxygenase candidate genes involved in the biosynthesis of flavour-related volatiles in cultivated apple (Malus x domestica)

脂肪氧合酶(LOX)在高等植物中催化分子氧加成多不饱和脂肪酸生成相应的过氧化氢，具有多种不同的生理功能。LOX反应提供底物，例如形成具有香气活性的C6-醛以及决定成熟和储存苹果果实香气模式的己基酯和己烯酯。因此，该项目的重点将放在苹果LOX基因家族的特征上，首次利用分子遗传学和生物化学的跨学科方法来研究栽培苹果果实香气形成的关键步骤。从QTL分析和候选基因定位方法获得的初步数据已经证实，脂肪氧合酶(LOX)是决定苹果不同基因型香气特征的重要基因。将对现有的苹果数据库进行LOX核苷酸序列筛选。属于该基因家族不同亚类的LOX基因将通过基于聚合酶链式反应的策略进行克隆，并在苹果基因组中进行遗传定位。将确定时间和空间表达模式，并通过异源表达系统(大肠杆菌、烟草、Fragaria)确定候选基因的功能特征。这些数据最终将被用于开发功能标记，以支持分子育种，并能够更有效地记录苹果基因库材料、苹果品种和育种材料中香气模式的生物多样性，将选择合适的杂交伙伴提高到一个新的效率水平。

Lipoxygenases (LOX) catalyze the addition of molecular oxygen to polyunsaturated fatty acids to produce their respective hydroperoxides and have many different putative physiological functions in higher plants. The LOX reaction provides the substrates, e.g. for the formation of aroma-active C6-aldehydes as well as hexyl and hexenyl esters that decisively shape the aroma pattern of ripe and stored apple fruits. Therefore, the focus of the project will be on the characterization of the LOX gene family in apple to investigate for the first time crucial steps of the aroma formation in fruits of the cultivated apple with an interdisciplinary approach using molecular genetic and biochemical methods. Preliminary data obtained from QTL analyses and candidate gene mapping approaches have confirmed that lipoxygenase (LOX) is an important gene which determines aroma profiles of apple genotypes. Available Malus databases will be screened for LOX nucleotide sequences. LOX genes belonging to different subclasses of the gene family will be cloned by PCR-based strategies and genetically mapped in the Malus genome. Temporal and spatial expression patterns will be determined and candidate genes functionally characterized by heterologous expression systems (E. coli, Nicotiana, Fragaria). The data will finally be used to develop functional markers to support molecular breeding and to enable a more efficient documentation of biodiversity of aroma patterns in Malus gene bank accessions, apple varieties and breeding material lifting the selection of suitable crossing partners to a new efficiency level.