Central Tuber Crops Research Institute, Thiruvananthapuram 695017, Kerala, India.
Microbiol Res. 2010 Feb 28;165(2):97-107. doi: 10.1016/j.micres.2008.10.002. Epub 2009 Feb 20.
The rapid and effective activation of disease resistance responses is essential for plant defense against pathogen attack. These responses are initiated when pathogen-derived molecules (elicitors) are recognized by the host. A cDNA encoding elicitor, the major secreted extracellular glycoprotein of Phytophthora colocasiae, a pathogen of taro (Colocasia esculenta) plants, was isolated, sequenced and characterized. The expression of the corresponding elicitor gene during the disease cycle of P. colocasiae was analyzed. Elicitor was shown to be expressed in mycelium grown in culture media, whereas it was not expressed in sporangiospores and zoospores. In planta, during infection of taro, particularly during the biotrophic stage, expression of elicitor was down-regulated compared to in vitro. The highest levels of expression of elicitor were observed in in vitro grown mycelium and in late stages of infection when profuse sporulation and leaf necrosis occur. The elicitation of the suspension-cultured taro cells was effective in the induction of the enzyme activity of l-phenylalanine-ammonia lyase, peroxidase and lipoxygenase as well as the expression of defense-related endochitinase gene. All these biological activities were exerted within a low concentration range. The glycoprotein represents a powerful tool to investigate further the signals and their transduction pathways involved in induced disease resistance. It may also be useful to engineer broad disease protection in taro plant against Phytophthora leaf blight.
快速有效地激活疾病抗性反应对于植物抵御病原体攻击至关重要。当病原体衍生的分子（激发子）被宿主识别时，这些反应就会启动。从芋（Colocasia esculenta）病原体芋疫病（Phytophthora colocasiae）的主要分泌细胞外糖蛋白中分离、测序并表征了一个编码激发子的 cDNA。分析了 P. colocasiae 疾病周期中相应激发子基因的表达。结果表明，在培养的菌丝体中表达激发子，而在游动孢子和休止孢子中不表达。在植物体内，在芋的感染过程中，特别是在生物营养阶段，与体外相比，激发子的表达受到下调。在体外生长的菌丝体和大量孢子形成和叶片坏死发生的感染后期观察到激发子表达水平最高。悬浮培养的芋细胞的激发有效地诱导了 l-苯丙氨酸-氨裂解酶、过氧化物酶和脂氧合酶的酶活性以及防御相关内切几丁质酶基因的表达。所有这些生物活性都在低浓度范围内发挥作用。该糖蛋白代表了一种强大的工具，可以进一步研究参与诱导抗病性的信号及其转导途径。它也可能有助于对芋植物的广泛的叶疫病进行工程保护。
