‘Dangshansuli’ pear is a yellow–green fruit when mature, whereas that of the mutant ‘Xiusu’ is russeted. In this study, the contents of glucose, fructose and sucrose in the exocarp of ‘Xiusu’ were found to be lower than those in ‘Dangshansuli’ at 75–100 days after full bloom (DAFB) but were higher at 150 DAFB. Additionally, the contents of six polysaccharides in the exocarp of ‘Xiusu’ were higher than those in ‘Dangshansuli’ at 75 DAFB, the stage at which ‘Xiusu’ becomes russet in color, as well as at 150 DAFB; however, this was not observed for xylose. The contents of type I and II amino acids in the exocarp of ‘Xiusu’ were higher than those in ‘Dangshansuli’ at different stages, except for at 150 DAFB. The entire sequences of eight genes involved in the shikimate pathway and cell wall structure were cloned, and expression of these genes in the exocarp of ‘Dangshansuli’ and ‘Xiusu’ were significantly different during fruit development, indicating that these genes might be involved in the russeting process. It is speculated that the shikimate pathway connects primary and secondary metabolism and that high contents of sugars as carbon sources provide precursors for suberin, lignin and lignan to generate russet skin in pear.

中文翻译：

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'砀山苏里'梨及其赤褐色突变体外果皮中莽草酸通路的组成和基因表达表征

'砀山苏里'梨成熟时为黄绿色果实，而突变体'秀苏'则为赤褐色。本研究发现'秀苏'外果皮中葡萄糖、果糖和蔗糖的含量在盛花后75-100天（DAFB）低于'砀山苏里'，但在150 DAFB时较高。此外，在75 DAFB、'秀苏'变黄的阶段，'秀苏'外果皮6种多糖的含量高于'砀山苏里'，在150 DAFB时均高于'砀山苏里'；然而，木糖没有观察到这一点。除150 DAFB外，'修苏'外果皮I型和II型氨基酸含量在不同时期均高于'砀山苏里'。克隆了涉及莽草酸途径和细胞壁结构的八个基因的完整序列，'砀山素里'和'修素'果实发育过程中这些基因在外果皮中的表达量和表达量有显着差异，表明这些基因可能参与了赤褐色过程。据推测，莽草酸途径连接初级和次级代谢，高含量的糖作为碳源提供了木栓质、木质素和木脂素在梨中生成赤褐色皮的前体。