小菜蛾幼虫血淋巴中β-1,3-葡聚糖结合蛋白的分离及其对根虫瘟霉侵染的免疫活性

Extraction of β-1,3-Glucan Binding Proteins From The Lymphocytes of Plutella xylostella larvae and Their Immune Response to Zoophthora radicans Infection

用亲和沉淀法从小菜蛾 (Plutellaxylostella)幼虫血淋巴中分离获得 2种β 1,3 葡聚糖结合蛋白 ,分子质量分别为 75 9ku和 83 2ku ,主要存在于幼虫血浆中 ,但血细胞中未检出 .研究表明 ,β 1,3 葡聚糖结合蛋白能特异性地识别β 1,3 葡聚糖 ,并显著激活幼虫血淋巴中的酚氧化酶原 (ProPO) ,与昆布多糖共存时所激活的酚氧化酶 (PO)活性显著高于两者单独存在时的PO活性 .与 4株根虫瘟霉 (Zoophthoraradicans)菌丝裂解液共存时 ,β 1,3 葡聚糖结合蛋白能激活幼虫血淋巴中的ProPO ,使PO活力显著高于该菌原生质体裂解液所激活的PO活性 .显然 ,β 1,3 葡聚糖结合蛋白只有特异性地识别根虫瘟霉细胞壁中的β 1,3 葡聚糖后才能激活幼虫血淋巴中的ProPO ,表明虫霉原生质体可逃避寄主免疫反应 .此外 ,β 1,3 葡聚糖结合蛋白对不同菌株所激活的PO活性存在差异 ,各菌株所激活的PO活性由高到低依次为 :ARSEF1342 >ARSEF2 6 99>F9910 1>ARSEF110 0 ,这与各菌株对小菜蛾的毒力强弱相一致 。

Two major β-glucan binding proteins (β-GBPs), 75 9 ku and 83 2 ku, were extracted from the hemolymph of Plutella xylostella larvae by using β-1,3-glucan affinity precipitation method. The proteins were present in plasma but absent in haemocytes. The β-GBPs had a specific affinity to β-1,3-glucan, a prophenoloxidase (ProPO) trigger in P.xylostella hemolymph. The phenoloxidase (PO) activity induced by the coexistence of both β-GBPs and β-1,3-glucan was significantly higher than that by the β-GBPs or β-1,3-glucan alone. Moreover, the PO activities induced by mycelial lysates of four Zoophthora radicans isolates at the presence of β-GBPs were much higher than that triggered by their protoplast lysates. The results indicate that the β-GBPs may trigger the ProPO activity in P.xylostella hemolymph only if they specifically recognized β-1,3-glucan from Z.radicans cell walls. This is a proof for a hypothesis that entomophthoralean protoplasts may evade from insect host immune defense. The protoplast or mycelial lysates of different Z.radicans isolates differed in ability to trigger the PO activities in the following order: ARSEF1342>ARSEF2699>F99101>ARSEF1100. This trend was in accordance with that of their virulence to P.xylostella larvae, suggesting a possible relationship between host immune defense and fungal virulence.