Abstract:

Sugars are always transported to the other organs via sugar transporters to play their important functions in plants. SWEET （sugars will eventually be exported transporters） is a kind of sugar transporters which plays important function in plant growth and development as well as in resistance or tolerance to diverse biotic and abiotic stresses. To analyze the expressions of SWEET genes during pod and seed developments and under different stress conditions in soybean， the SWEET genes were firstly analyzed based on the newly published cultivated and wild soybean genomes in the present study. Subsequently， the gene expressions were evaluated during pod and seed developments， as well as in resistance to soybean mosaic virus （SMV） and tolerance to low phosphorus. The results showed that 48 SWEET genes were identified in the cultivated soybean genome （Wm82a4v1）， which encoded protein with length 174~354 amino acids and located on 15 chromosomes. Meanwhile， 51 SWEET genes were identified in the wild soybean genome （W05）， which encoded length of 84~392 amino acids and located on 16 chromosomes. The phylogenetic tree of SWEET genes in cultivated and wild soybeans showed that they were clustered into 3 sub-groups. Moreover， 16 SWEET genes were expressed in soybean pods with the expressions of Glyma.06G122200， Glyma.14G159900 and Glyma.14G160100 etc. increased during the pod development process. 12 SWEET genes were expressed in soybean seeds， and the expressions of Glyma.08G025100， Glyma.13G041300 and Glyma.14G120300 were increased during the seed development， suggesting their important roles for soybean seed development. The SWEET genes showed different expressions after the inoculation of SMV， and the expressions of Glyma.08G009900 and Glyma.13G264400 were induced in leaves of resistant variety， while had no change in the sensitive variety， implying that they might involve in SMV resistance. The expressions of Glyma.04G198400， Glyma.14G160100 and Glyma.15G211800 were induced in soybean roots after low phosphorus treatment， indicating their important functions in the tolerance to low phosphorus stress. In addition， the single nucleotide polymorphism（SNP）analysis of SWEET genes showed that 43 genes contained 220 nonsynonymous SNPs with 103 located in the conserved domains of encoding proteins. Thus， above results provided candidate genes for molecular breeding of soybean pod and seed yield and diverse stress resistances.

Key words: soybean, SWEET gene, pod and seed development, stress, differential expressions

摘要：

植物叶片光合作用产生的糖类物质需要经过糖转运蛋白运输到其他器官进而发挥其重要功能。SWEET（sugars will eventually be exported transporters）是一类可实现糖类物质运输的蛋白，对植物生长发育及抵御外界生物和非生物胁迫具有重要意义。为分析大豆SWEET基因在荚粒发育过程中以及逆境胁迫下的表达，利用栽培大豆和野生大豆最新公布基因组数据鉴定SWEET基因，然后利用转录组数据分析基因在荚粒发育和抵抗花叶病毒与低磷逆境中的表达。结果表明，栽培大豆Williams82最新版本基因组（Wm82a4v1）有48个SWEET基因，分布于15条染色体，编码蛋白长度为174~354个氨基酸；野生大豆W05基因组有51个SWEET基因，分布于16条染色体，编码蛋白长度为84~392个氨基酸；系统进化树分析显示，99个栽培大豆和野生大豆SWEET基因分为3个亚组。对不同大豆品种转录组数据分析发现，16个SWEET基因在豆荚表达，其中Glyma.06G122200、Glyma.14G159900和Glyma.14G160100等随不同品种豆荚发育进程表达量增加；12个SWEET基因在籽粒表达，其中Glyma.08G025100、Glyma.13G041300和Glyma.14G120300随不同品种籽粒发育进程表达量增加，表明其在豆荚和籽粒发育中具有重要作用。接种大豆花叶病毒后，不同抗性品种间SWEET基因的表达存在较大差别，其中Glyma.08G009900和Glyma.13G264400在抗病品种叶片接种后诱导表达，而在感病品种接种前后表达量没有变化，说明其可能参与大豆抗病反应。对SWEET基因在低磷胁迫前后的表达分析发现，Glyma.04G198400、Glyma.14G160100和Glyma.15G211800等在大豆根系受低磷胁迫诱导表达，可能参与大豆耐低磷反应。栽培大豆SWEET基因单核苷酸多态性（single nucleotide polymorphism，SNP）等位变异分析发现，有43个SWEET基因含有220个非同义突变SNPs，其中103个位于编码蛋白的保守域，可能影响基因功能。研究结果为大豆豆荚和籽粒产量以及抗病耐逆分子育种提供了基因资源。

关键词: 大豆, SWEET基因, 荚粒发育, 逆境胁迫, 差异表达