水稻白叶枯病菌蛋白质激发子HarpinXoo诱导植物的防卫反应

摘要：含质粒pHRF4的表达菌株BLHR4在培养基中经IPTG诱导，16 h Harpin表达接近最高量。用不同浓度的HarpinXoo喷雾处理烟草(Nicotiana tabacum L.)、油菜(Brassica campestris L.)和番茄(Lycopersicon esculentum Mill.)，对烟草花叶病毒(TMV)、油菜菌核病(Sclerotinia sclerotiorum (lib.) de Bary)和番茄灰霉病(Botrytis cinerea Pers.)均表现较好的诱导抗病效果。以浓度为100μg/mL的HarpinXoo处理烟草后，分别测定叶片中与防卫反应相关的一些生理指标的变化，结果表明，处理叶片中苯丙氨酸解氨酶（PAL）、过氧化物酶（PO）和多酚氧化酶（PPO）活性都有不同程度的增强。三种酶活性高峰分别在处理后24、12和3 h出现，分别比清水对照增加110.1%、211.2%和273.0%；同时，两个病程相关蛋白（pathogenesis-related protein，PR）基因PR-1b和PR-1a在HarpinXoo处理24 h后被诱导显著表达，36 h时达到最高表达水平。这表明HarpinXoo与HarpinEa一样能够诱导烟草不同抗病信号通路的启动，从而使植株获得抗病性。

Defense Response in Plants Induced by Harpinxoo, An Elicitor of Hypersensitive Response From Xanthomonas oryzae pv. oryzae

Abstract: Harpin proteins with the elicitor activity are encoded by particular genes in hrp gene clusters of Gram negtive plant pathogenic bacteria. As HarpinEa of Erwinia amylovora, HarpinXoo (15.6 kD) is encoded by gene hrfAXoo (420 bp) positioned in hrp cluster of Xanthomonas oryzae pv. oryzae and shows the ability for induction of hypersensitive reaction of plants. HarpinXoo could induce plant resistance against some diseases and the relevant mediated mechanisms by the expressed product of hrfAxoo. HarpinXoo was expressed in recombinant bacteria E.coli BLHR4/pHRF4(pET30a(+)::hrfAxoo) and the protein expression was at peak level after IPTG induction for 16 h. After applying HarpinXoo to tobacco (Nicotiana tabacum L), rape (Brassica campestris L.) and tomato (Lycopersicon esculentum Mill.), the resistance was induced with remarkable control effects to tobacco mosaic virus (TMV), sclerotinia stem blight of rape (Sclirotinia sclerotiorum (Lib.) de Bary) and tomato gray mold rot (Botrytis cinerea Pers.) respectively. Comparing with water treatment control, 66.5% for TMV control efficiency, 79.39% for contol of Sclerotinia sclerotiarum of rape and more than 75% for control of Botrytis fruit rot of tomato were achieved. Biochemical and molecular technologies were used to reveal resistance mechanisms in tobacco (Xanthi) as model plant. The activities of defense-related enzymes involving phenylalanine ammonia lyase (PAL), peroxidase (PO) and polyphenoloxidase (PPO) were determined in tobacco leaves treated with HarpinXoo and the result showed that their activites were 110.1%, 211.2% and 273.0% higher than that treated with water control respectively. Two pathogenesis-related genes PR-1b and PR-1a were expressed conspicuously at 24 h after induction with HarpinXoo and showed the highest level of expression at 36 h after treatments by RT-PCR methodology. These results indicated that HarpinXoo similar to HarpinEa could induce the resistance of plants by various signal transduction pathways.