NoxA activation by the small GTPase RacA is required to maintain a mutualistic symbiotic association between Epichloe festucae and perennial ryegrass
NoxA activation by the small GTPase RacA is required to maintain a mutualistic symbiotic association between Epichloe festucae and perennial ryegrass
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DOI：
10.1111/j.1365-2958.2008.06217.x
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发表时间：
2008-06-01
影响因子：
3.6
通讯作者：
Scott, Barry
中科院分区：
文献类型：
--
作者：
Tanaka, Aiko;Takemoto, Daigo;Scott, Barry
在哺乳动物和植物中，Rac组的小gtpase在NADPH氧化酶催化活性氧（ROS）的产生中起着关键的调节作用，但很少有证据表明真菌中也有相应的作用。我们最近发现，在Epichloe festucae和多年生黑麦草的共生互作中，由一种特定的真菌NADPH氧化酶异构体NoxA产生的ROS在调控菌丝形态发生和生长中起着至关重要的作用。我们在这里证明了E. festucae RacA是NoxA激活和调节ROS产生以维持共生相互作用所必需的。缺失racA导致ROS生成减少，菌丝径向生长减少，菌丝超分枝。相反，在植物中，racA突变体表现出对寄主植物的广泛定植，导致寄主植物发育迟缓和过早衰老。表达RacA显性活性（DA）等位基因的菌株ROS产量增加，气生菌丝增多，径向生长减慢。这些结果表明，RacA在调控NoxA产生ROS，从而控制植物菌丝形态发生和内生菌生长中起着至关重要的作用。
Small GTPases of the Rac group play a key regulatory role in NADPH oxidase catalysed production of reactive oxygen species (ROS) in mammals and plants, but very little evidence is available for a corresponding role in fungi. We recently showed that ROS produced by a specific fungal NADPH oxidase isoform, NoxA, are crucial in regulating hyphal morphogenesis and growth in the mutualistic symbiotic interaction between Epichloe festucae and perennial ryegrass. We demonstrate here that E. festucae RacA is required for NoxA activation and regulated production of ROS to maintain a symbiotic interaction. Deletion of racA resulted in decreased ROS production, reduction of radial growth and hyper-branching of the hyphae in culture. In contrast, in planta the racA mutant showed extensive colonization of the host plant, resulting in stunting and precocious senescence of the host plants. Strains expressing a dominant active (DA) allele of RacA had increased ROS production, increased aerial hyphae and reduced radial growth. These results demonstrate that RacA plays a crucial role in regulating ROS production by NoxA, in order to control hyphal morphogenesis and growth of the endophyte in planta.