中文摘要：

【目的】为了解枇杷（Eriobotrya japonica Lindl.）1-脱氧木酮糖-5-磷酸（DXP）还原异构酶基因（DXR）的序列特点及其在果实成熟过程的表达特性,【方法】以不同类型枇杷品种‘早钟6号’（红肉）和‘白玉’（白肉）不同成熟阶段的果肉和果皮为试材,采用RT-PCR结合RACE法和qRT-PCR方法对DXR基因进行了克隆,并对其在枇杷果实成熟过程中的表达进行了分析,【结果】枇杷DXR基因的cDNA序列全长1 743 bp,编码473个氨基酸,蛋白质相对分子质量（Mw）为51 299.8 Da,等电点（pI）为6.52（GenBank登录号：JX089590）。qRT-PCR分析表明,在枇杷果实成熟过程中,DXR在不同类型枇杷的不同时期表达不尽相同：在果皮中,‘早钟6号’品种的DXR基因在果实成熟的各个阶段的表现为表达量较为稳定,而在‘白玉’品种中,DXR基因的表达存在较为明显的先增加后降低的过程,其表达量在褪绿期达到最高。而在果肉中,无论是‘早钟6号’还是‘白玉’品种,DXR基因的表达从果实成熟过程中的未转色期到黄熟期表现为持续下降;到成熟期时,‘早钟6号’品种的DXR基因存在明显的上调现象,而在‘白玉’品种中则无此明显变化,【结论】DXR基因对于枇杷类胡萝卜素的合成没有限制作用,至少作用不明显。

英文摘要：

[Objective]The objective of this study was to illuminate sequence features and expression char- acteristics of 1-deoxy-D-xyluoose 5-phosphate gene （DXR）during the different ripening stages of fruit in loquat （Eriobotryajaponica Lindl.）. [Method]With the peel and flesh from different ripening stages and different cultivars as experimental materials, the complete cDNA sequence of DXR of loquat was obtained by reverse transcription polymerase chain reaction （RT-PCR）with rapid amplification of cDNA ends（RACE）. And the expression of this gene was surveyed by real-time quantitative PCR （qRT-PCR） during different fruit ripening stages in loquat. [Result]The complete nucleotide sequences of DXR were 1 743 bp and encoded a protein of 473 amino acid residues. Its molecular weight was 51 299.8 Da with isoelectric point 6.52（GenBank accession number JX089590）. The qRT-PCR results showed that in differ- ent cultivars, the DXR expression were different at different ripening stages. During the different ripening stages, the DXR expression were almost the same in the peel of ＇Zaozhong 6＇ which means its stable ex- pression, however, the DXR expression were first increase then decrease, and reached a peak at de- greening stage in ＇Baiyu＇. In the flesh of both cultivars, DXR expression decreased during immature green stage to yellow mature stage, but increased obviously in ＇Zaozhong 6＇ at whole mature stage, while keep nearly no change in ＇Baiyu＇. [Conclusion]DXR gene doesn＇t restrict the carotenoid synthesis in lo- quat, or the restriction is not obvious at least.