中文摘要：

SWEET（sugars will be eventually exported transporters）是真核生物中普遍存在的一类多基因家族糖转运蛋白,在植物生理代谢、生长发育及植物-微生物互作过程中起重要调控作用。本研究利用RT-PCR、RACE技术,从珍稀药用铁皮石斛（Dendrobium officinale Kimura et Migo）中分离到一个全新的SWEET基因,命名为DoSWEET1（Gen Bank注册号KT957550）。DoSWEET1基因cDNA全长1 150 bp,编码1条262个氨基酸组成的多肽,分子质量29.18 kD,等电点9.49。推定的DoSWEET1蛋白无信号肽,具有7个跨膜域,包含植物SWEET家族2个保守MtN3_slv结构域（11-94、130-212）。多序列比对表明,DoSWEET1与多种植物SWEET蛋白一致性较高（45%~54.6%）。进化树结果显示,DoSWEET1与水稻OsSWEET13、OsSWEET14和OsSWEET15亲缘关系最近,隶属于SWEET蛋白家族分子进化树的ClassⅡ分支。qPCR分析揭示,DoSWEET1在石斛3个器官中差异表达,该转录本在根中相对表达量最高,叶中次之,分别为茎中的9.88倍和2.85倍;在胶膜菌Tulasnella sp.侵染石斛共生萌发的3级种子中,该基因转录本剧烈上调为对照的1 359.06倍,说明其参与种子接菌共生萌发过程。DoSWEET1克隆和分子特征为进一步研究该基因在铁皮石斛糖转运及种子共生萌发过程中的调控作用奠定基础。

英文摘要：

SWEET（sugars will be eventually exported transporters） constitute a large and conserved gene family of sugar transporters in eukaryotes, which are important in the cellular metabolisms, growth and development, and plant-microbe interaction in plants. In the present study, a full length cDNA of SWEET encoding gene, designed as DoSWEET1（Gen Bank accession No. KT957550）, was identified in Dendrobium officinale using RT-PCR and RACE approaches. DoSWEET1 was 1 150 bp in length and encoded a 262-aa protein with a molecular weight of 29.18 k D and an isoelectric point of 9.49. The deduced DoSWEET1 protein contained seven transmembrane regions and two conserved MtN3-slv domains（11-94, 130-212）. Multiple sequence alignment revealed that DoSWEET1 had high identities（45%-54.6%） with SWEET proteins from various plants. A neighbor joining phylogenetic analysis suggests that DoSWEET1 belonged to the class Ⅱ subgroup of the SWEET evolutionary tree, and was closely related to rice OsSWEET13, OsSWEET14, and OsSWEET15. qPCR analysis demonstrated that DoSWEET1 gene was differentially expressed in the three included organs of D. officinale, and the expression was most abundant in the roots at 9.88 fold over that of the stems, followed by that of the leaves with 2.85 fold higher. In the 3~（rd） symbiotic germinating seeds infected by Tulasnella sp., the transcipts were dramatically induced by 1 359.06 fold over that in the ungerniamted control seeds, suggesting a vital role of the gene in the D. officinale symbiotic germination process. Molecular cloning and characterization of the novel DoSWEET1 gene provides a foundation for the functional study of the gene in sugar translocation during the D. officinale symbiotic germination process.