小麦穗组织中脱氧镰刀菌烯醇毒素的免疫细胞化学定位

 采用免疫细胞化学技术对禾谷镰刀菌(Fusarium graminearum)在侵染小麦穗部过程中产生的脱氧镰刀菌烯醇毒素(deoxynivalenol,DON)进行了定位分析。在接种后24h,当菌丝在外稃、内稃的内侧表面扩展而尚未侵入寄主细胞前,病菌已分泌DON,并且DON已扩散到寄主组织内。在菌丝细胞内,DON主要被定位于细胞质、线粒体及细胞壁上;在寄主细胞中DON主要分布于细胞壁、叶绿体、细胞质和内质网上。在侵染初期(接种后2 d),菌丝仅能在寄主细胞间隙扩展,随寄主组织中DON浓度的升高,寄主细胞相应发生了一系列病理变化。随寄主细胞坏死(接种后3~4d),病菌进入坏死的寄主细胞。上述结果表明,DON在禾谷镰刀菌的侵染、致病和定殖过程中起着重要的作用。毒素标记结果表明病菌产生的毒素可通过穗轴微管束组织从侵染部位向上、向下转输,毒素向上的转输量明显高于向下转输

Immunocytochemical localization of deoxynivalenol in infected wheat spikes by Fusarium graminearum

Fusarium toxin deoxynivalenol (DON) was localized in wheat spikes during infection process of Fusarium graminearum by means of immunocytochemical labeling technique. Hyphae of the pathogen produced toxin when they grew on inner surfaces of lemma and palea as early as 24 h after inoculation, and the toxin was detected inside of host tissues at this time. In hyphal cells, the toxin was localized in cytoplasm, mitochondria and cell wall, while the toxin was detected in cell wall, chloroplasts, plasmalemma and endoplasmic reticulum in host cells. At the earlier infection stage (2 days after inoculation), the hyphae extended only intercellularly in the host tissues. With increase in concentration of the toxin in host tissues, a series of pathogenic changes in host cells occurred and the hyphae then co lonized degenerated host cells intracellularly (3-4 days after inoculation). These results suggested that DON might play an important role in infection, pathogenesis and colonization for Fusarium graminearum on wheat spikes. In addition, labeling for DON demonstrated that toxin can be translocated upwards and downwards through vascular bundle of rachis from the infected floret, much toxin was detected in the upper florets than in the lower florets.