Department of Plant Breeding, Centro de Edafología y Biología Aplicada del Segura-Consejo Superior de Investigaciones Científicas, E-30100 Espinardo, Murcia, Spain.
Plant Physiol. 2012 Apr;158(4):1916-32. doi: 10.1104/pp.111.192021. Epub 2012 Feb 21.
Amygdalin is a cyanogenic diglucoside and constitutes the bitter component in bitter almond (Prunus dulcis). Amygdalin concentration increases in the course of fruit formation. The monoglucoside prunasin is the precursor of amygdalin. Prunasin may be degraded to hydrogen cyanide, glucose, and benzaldehyde by the action of the β-glucosidase prunasin hydrolase (PH) and mandelonitirile lyase or be glucosylated to form amygdalin. The tissue and cellular localization of PHs was determined during fruit development in two sweet and two bitter almond cultivars using a specific antibody toward PHs. Confocal studies on sections of tegument, nucellus, endosperm, and embryo showed that the localization of the PH proteins is dependent on the stage of fruit development, shifting between apoplast and symplast in opposite patterns in sweet and bitter cultivars. Two different PH genes, Ph691 and Ph692, have been identified in a sweet and a bitter almond cultivar. Both cDNAs are 86% identical on the nucleotide level, and their encoded proteins are 79% identical to each other. In addition, Ph691 and Ph692 display 92% and 86% nucleotide identity to Ph1 from black cherry (Prunus serotina). Both proteins were predicted to contain an amino-terminal signal peptide, with the size of 26 amino acid residues for PH691 and 22 residues for PH692. The PH activity and the localization of the respective proteins in vivo differ between cultivars. This implies that there might be different concentrations of prunasin available in the seed for amygdalin synthesis and that these differences may determine whether the mature almond develops into bitter or sweet.
苦杏仁苷是一种氰基二糖苷，构成苦杏仁（Prunus dulcis）的苦味成分。苦杏仁苷的浓度在果实形成过程中增加。单糖苷野樱苷是苦杏仁苷的前体。野樱苷可被β-葡萄糖苷酶野樱苷水解酶（PH）和苯甲醛肟裂解酶降解为氢氰酸、葡萄糖和苯甲醛，或与葡萄糖结合形成苦杏仁苷。在两个甜杏仁和两个苦杏仁品种的果实发育过程中，使用针对 PH 的特异性抗体确定了 PH 的组织和细胞定位。对种皮、珠心、胚乳和胚的切片进行共焦研究表明，PH 蛋白的定位取决于果实发育阶段，在甜和苦品种中，APoplast 和 Symplast 之间的定位模式相反。在甜杏仁和苦杏仁品种中已经鉴定出两个不同的 PH 基因 Ph691 和 Ph692。两个 cDNA 在核苷酸水平上有 86%的同源性，其编码的蛋白质彼此有 79%的同源性。此外，Ph691 和 Ph692 与黑樱桃（Prunus serotina）的 Ph1 显示出 92%和 86%的核苷酸同一性。两个蛋白都被预测含有一个氨基末端信号肽，Ph691 的大小为 26 个氨基酸残基，Ph692 的大小为 22 个氨基酸残基。不同品种之间的 PH 活性和体内相应蛋白的定位不同。这意味着种子中用于苦杏仁苷合成的野樱苷可能有不同的浓度，这些差异可能决定成熟杏仁是苦的还是甜的。
