Abstract: Glycosyltransferases play an important role in the flavonoid metabolism, which is important for plant development and plant-environment interplay. In order to study the biological function of glycosyltransferase in Medicago truncatula, a series of small and emerald1 (se1) mutants with short plant and dark green leaves by directional screening Tnt1 retrotransposon-tagged lines of M. truncatula was isolated and characterized. The SE1 gene was cloned by PCR-based genotyping of flanking sequence tags (FST) in segregating populations. SE1 encoded a glycosyltransferase that had 52.8% homology with AtUGT84A1, which regulated flavonoid biosynthesis in Arabidopsis. Flavonoid analysis showed that the content of total flavonoids was significantly reduced in the se1 mutants. qRT-PCR analysis revealed that the expression of CHS, F3H and F3’H, key genes of flavonoids synthesis pathway, were down-regulated in the se1 mutants. Subcellular localization showed that SE1 might fulfill its functions in both cytoplasm and nucleus. These data together demonstrated that the glycoltransferase gene SE1 might be involved in the regulation of flavonoid metabolism in M. truncatula, thus influencing M. truncatula growth and development. In addition, the study also revealed that the SE1 gene could negatively regulate M. truncatula chlorophyll biosynthesis.

Key words: Medicago truncatula, SE1, glycosyltransferase, flavonoid biosynthesis, chlorophyll biosynthesis

摘要： 类黄酮代谢对于植物生长发育和植物-环境互作至关重要，其中糖基转移酶介导的糖基化修饰在类黄酮代谢中发挥着重要作用。为了研究蒺藜苜蓿中糖基转移酶的生物学功能，通过定向筛选蒺藜苜蓿Tnt1逆转座子插入突变体库，获得了一类植株矮小、叶片深绿的突变体small and emerald1 (se1)。通过基因表型连锁性分析成功克隆了SE1基因，该基因编码1个糖基转移酶，与拟南芥中调控类黄酮生物合成的AtUGT84A1氨基酸同源性为52.8%。对野生型和se1突变体叶片的类黄酮含量进行测定发现类黄酮总量在se1突变体中显著降低(P<0.01)。进一步研究发现在se1突变体中类黄酮合成途径关键基因CHS、F3H和F3’H表达水平下降。亚细胞定位显示SE1可能在细胞质和细胞核中发挥生物学功能。研究表明糖基转移酶基因SE1可能参与蒺藜苜蓿类黄酮合成代谢调控，进而影响其生长发育。此外，研究还发现SE1基因对于叶绿素合成可能具有负向调控作用。

关键词: 蒺藜苜蓿, SE1, 糖基转移酶, 类黄酮合成, 叶绿素合成