Isolation of disease resistance related genes in mulberry plant by gene-tagging method

桑树芽枯病是桑树茎部最具破坏性的病害之一。它是由红土镰刀菌引起的。桑，在死桑茎表面产生孢子。而非致病性镰刀菌侵染的桑树则无此症状。非致病性真菌通过寄主细胞的抗病反应而不能在桑树组织中传播。为探讨桑树抗病机理，本项目拟对经dna标记法分离的桑树抗病相关基因进行鉴定。首先，利用桑树培养细胞建立了一种快速简便的抗枯萎病能力评估方法，这是选择转化突变细胞的必要条件。研究了农杆菌介导的桑树愈伤组织转化获得T-DNA标记基因的有效方法。最后，过氧化物酶和多酚氧化酶可能参与了非致病性镰刀菌感染桑树愈伤组织褐变的过程。感染组织的快速和局部褐变是典型的抗病性超敏反应。这两种酶可能在桑树对真菌的抗性反应中起重要作用。本研究建立的方法为桑树抗病相关基因的分离提供了可能。

The bud blight of mulberry trees is one of the most destructive disease of mulberry stems. It is caused by Fusarium lateritium f.sp.mori, that produces sporodochia on the surface of dead mulberry stems. However, no such symptom appears in mulberry plant infected by non-pathogenic Fusarium to the host. Non-pathogenic fungi could not spread in the tissues of mulberry plant by disease resistance response of host cells. In order to investigate the mechanism of disease resistance in mulberry plant, this project is planned to characterize resistance-related gene that is isolated by DNA-tagging method. First of all, rapid and convenient method to estimate the ability to resist to Fusarium was established using mulberry cultured cells, that is necessary to select the transformed mutant cells. The efficient methods for Agrobacterium-mediated transformation in mulberry callus was investigated to obtain T-DNA tagged genes. Finally, peroxidase and polyphenol oxidase might be involved in tissue browning in the non-pathogenic Fusarium infected mulberry callus. The rapid and local browning in the infected tissue is the typical hypersensitive response in disease resistance. Both enzymes may play the important role in resistance response of mulberry plant against to fungi. It may be possible to isolate disease resistance-related genes of mulberry plant by the method established by the present study.