木薯UDP依赖型糖基转移酶基因MeUGT25在抗细菌性枯萎病中的功能研究

Functions of MeUGT25 in Resistance of Cassava to Bacterial Wilt Disease

【目的】克隆木薯中UDP依赖型糖基转移酶(UDP-glycosyltransferases,UGTs)基因MeUGT25,并进行抗枯萎病功能研究,为木薯抗病分子育种提供新的基因资源。【方法】通过RT-PCR技术从木薯叶片(SC124)中克隆MeUGT25基因。随后,利用病毒诱导的基因沉默(virus induced gene silencing,VIGS)和地毯草黄单胞菌(Xamthomonas axonopodis pv.Manihotis,Xam)侵染试验研究MeUGT25基因在木薯中的抗病功能。【结果】病菌Xam能显著诱导MeUGT25基因的表达。在3株阳性干扰植株中,qRT-PCR检测显示它们的MeUGT25基因表达量分别降低71%、70%和69%。Xam侵染试验结果表明,叶片接种Xam 6 d后,MeUGT25V-2和MeUGT25V-3植株叶片上的细菌数量相比对照明显增多,但MeUGT25V-1阳性植株的细菌统计数量和对照叶片相比没有显著差异。然而,从叶片的发病情况来看,3个干扰植株叶片上的菌斑均比对照明显。【结论】降低木薯叶片中MeUGT25基因的表达量会影响叶片抵抗Xam病菌侵染的能力,推测MeUGT25基因在木薯抗枯萎病中发挥正调控作用。

【Objective】Disease resistance to Xamthomonas axonopodis pv.Manihotis(Xam)of cassava related to MeUGT25,a UDP-glycosyltransferases(UGT)gene,was studied for breeding purposes.【Method】MeUGT25 was cloned from cassava leaves(SC124)by RT-PCR.Subsequently,virus-induced gene silencing(VIGS)and Xam infection challenge experiment were conducted to confirm the disease resistance of the plant.【Result】The expression of MeUGT25 was significantly induced by the presence of Xam.In 3 transgenic plants,qRT-PCR showed reductions in MeUGT25 expression by 71%,70%,and 69%.In 6 d after an Xam-inoculation,the bacterial counts on the leaves of MeUGT25V-2 and MeUGT25V-3 plants increased significantly,but not of MeUGT25V-1.On the other hand,apparent plaques appeared on the leaves of the MeUGT25 gene silencing plants indicating the lowered MeUGT25 expression had significantly reduced the resistance of cassava to Xam infection.【Conclusion】Reduction of MeUGT25 expression in cassava mitigated the ability of the leaves to resist invasion by Xam suggesting a positive regulatory role of the gene played in the disease resistance.