两个与盐和赤霉病菌胁迫相关的小麦糖基转移酶基因的克隆与表达

Cloning and expression analysis of two salt and Fusarium graminearum stress associated UDP-glucosyltransferases genes in wheat

在植物体内,糖基转移酶通过参与多种物质的糖基化而在植物抗逆境方面起着重要作用。为了解小麦糖基转移酶基因响应病原菌和盐胁迫的分子机制,文章分离了两个小麦糖基转移酶基因(TaUGT1,TaUGT2)。这两个基因均编码496个氨基酸,cDNA序列相似性为90%。它们均含有一个内含子,分别为335bp(TaUGT1)和324bp(TaUGT2)。序列比对分析表明,TaUGT1和TaUGT2与尿苷二磷酸葡萄糖醛酸/尿苷二磷酸葡萄糖转移酶(UDP-glucoronosyl and UDP-glucosyl transferase)基因同源性最高,且都含有PSPG(Putative secondary plant glycosyltransferase)保守结构域。Real-time PCR表达分析显示,TaUGT1受赤霉病菌抑制表达,而TaUGT2受赤霉病菌诱导表达;在高浓度NaCl胁迫下,TaUGT1和TaUGT2的相对表达量分别为对照的2.87及4.56倍,差异达到极显著水平。以上结果表明,TaUGT2可能与小麦赤霉病抗性有关,而TaUGT1和TaUGT2可能共同参与了小麦对盐胁迫的响应。

Glycosyltransferases （GTs） play important roles in stress responses of plants by glycosylating hormones and secondary metabolites. UDP-glucosyltransferases （UGTs）, which use UDP-glucuronic acid in animals, UDP-glucose, UDP-galactose, and UDP- rhanmose in plant as sugar donors, belong to family 1 of GTs. As a secondary metabolite pro- duced by Fusarium graminearum during infection of grains, deoxynivalenol （DON） is not only harmful to human and ani- mal＇s health by inhibiting protein synthesis, but also acts as a virulence factor during fungal pathogenesis. In order to study expression profile of UGT genes in wheat, two UGTs, designated TaUGT1 and TaUGT2, were isolated from bread wheat （Triticum aestivum L.） by reverse transcriptase-polymerase chain reaction. The genomic sequences of both genes had one intron. Their coding sequences shared 91% and 90% similarities at nucleic acid level and the deduced protein sequence level. The analysis of conserved domain revealed that these two cDNAs encoded UDP-glucoronosyl and UDP-glucosyl transferase with PSPG （Putative secondary plant glycosyltransferase） domain. Real-time PCR was carried out to detect the expression profiles of the two UGTs in wheat under various stress conditions. In young spikes infected by Fusarium graminearum, TaUGT2 was induced but TaUGT1 was repressed. These two genes were upregulated under higher NaC1 concentration. In conclusion, TaUGT2 may participate in wheat resistance to Fusarium head blight in which mycotoxin DON plays a role, and these two genes might be involved in responses of wheat to salt stress.