Avr/Cf互作诱发番茄Pto互作因子Pti编码基因的表达

植物抗病基因Pto和Cf产物具完全不同的结构域,其细胞定位也不同.二者决定的抗病性产生机制的异同令人关注.采用两种过敏性反应(hypersensitive response,HR)产生系统研究了Pto互作蛋白Pti4、Pti5和Pti6编码基因在Avr/Cf互作中的时序表达:(1)通过杂交方法获取同含互补基因对Avr4/Cf-4和Avr9/Cf-9的番茄(Lycopersicon esculentum Mill.)种子.常温下这些种子发芽后形成的苗产生HR坏死斑.(2)先将Avr/Cf苗置于33 ℃下培养,此时番茄苗生长正常,不形成HR坏死斑.然后将温度降至25 ℃,数小时内这些苗即形成HR坏死斑.不同方法研究结果均表明,随Avr/Cf苗中HR坏死斑的形成,Pti4、Pti5和Pti6均受显著诱导表达.但它们的表达水平和动态不同.这些结果表明,这些Pti在功能上互补,可能同时涉及Pto和Cf决定性抗性的调节作用.

Avr/Cf Interaction Induce the Expression of Ptis,Genes Encoding Pto-interactors

Products of plant resistance (R) genes Pto and Cf contain distinct domains, and have different cellular localization. It is intriguing to compare the development mechanisms of resistance conferred by the two R genes. In the present report, two hypersensitive response (HR) initiation systems were employed to study the time course expression induced by Avr/Cf interaction of the genes encoding Pti4, Pti5 and Pti6 which interact directly with Pto: (1) Seeds of tomato (Lycopersicon esculentum Mill.) containing complementary gene pairs Avr4/Cf 4 and Avr9/Cf9 were obtained through crossing. Their seedlings developed HR under room temperature. (2) Avr/Cf seedlings grew normally at 33℃. When the temperature was shifted down to 25℃, HR occurred within hours in the seedlings. Results of both experiments showed that expression of Pti4, Pti5 and Pti6 was induced upon development of hypersensitive necrosis in Avr/Cf seedlings. However, the expression levels and patterns of these Ptis differed. This finding indicated that these Ptis function complementarily, and might be involved in regulation of both Pto and Cf conferred resistance.