根瘤菌HH103效应子NopT影响大豆结瘤固氮及共生早期防御反应

Effects of HH103 effector NopT of rhizobium on nodule fixation and symbiotic early defense response of soybean

[目的]研究根瘤菌HH103中Ⅲ型效应子NopT对不同大豆品种结瘤的影响及共生早期参与的植物防御反应。[方法]将根瘤菌HH103及ΔnopT接种在10种大豆上测定大豆的农艺性状及固氮酶活性,确定其对不同大豆结瘤的影响。对共生早期的大豆根系进行SA、JA和SOD水平测定,最后通过qRT-PCR测定植物防御反应基因表达量。[结果]ΔnopT突变体使大豆黑科86的根瘤数、根瘤鲜重、根瘤干重和固氮酶活提升了110%、103.57%、268.00%和33.42%。接种ΔnopT 72 h、12 h后大豆SA、JA水平达到最高,为(804.84±16.36)pmol/L、(485.90±1.37)pmol/L,且大部分时间内接种HH103的大豆黑科86根中植物激素水平和SOD活性低于接种ΔnopT的大豆根部。接种ΔnopT 12 h后大豆防御反应基因PR1、PR5相对表达量是对照组的5.31±0.78倍、13.29±1.52倍。[结论]nopT缺失可促进黑科86结瘤,NopT通过抑制植物激素和防御基因表达抑制大豆防御反应。

[Objective] To study the effect of type Ⅲ effector NopT from rhizobium HH1103 on nodulation of different soybean varieties and the plant defense response involved in the early symbiosis.[Method]10 kinds of soybeans were inoculated with rhizobium HH103 and ΔnopT to determine the agronomic traits and nitrogenase activities of soybeans, and to determine their effects on nodulation of different soybeans.The levels of SA,JA and SOD in soybean roots at the early stage of symbiosis were measured.Finally, the expression of plant defense response gene was determined by qRT-PCR.[Result]The nodule number, fresh nodule weight, dry nodule weight and nitrogenase activity of soybean Nodule 86 were increased by 110%,103.57%,268.00% and 33.42% by ΔnopT mutant.The highest levels of SA and JA were(804.84±16.36) pmol/L and(485.90±1.37) pmol/L after 72 hours, 12 hours inoculation with ΔnopT.Moreover, the level of plant hormone and SOD activity in 86 roots of soybean black family inoculated with HH103 were lower than those inoculated with ΔnopT for most of the time.After 12 hours inoculation with ΔnopT,the relative expressions of PR1 and PR5 in soybean were 5.31±0.78 folds and 13.29±1.52 folds of those in control group.[Conclusion] nopT deletion can promote nodule formation in Heike 86 soybean, and NopT inhibits soybean defense response by inhibiting plant hormone and defense gene expression.