In Planta Regulation of Extension of an Endophytic Fungus and Maintenance of High Metabolic Rates in Its Mycelium in the Absence of Apical Extension
In Planta Regulation of Extension of an Endophytic Fungus and Maintenance of High Metabolic Rates in Its Mycelium in the Absence of Apical Extension
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DOI：
10.1128/aem.67.12.5377-5383.2001
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发表时间：
2001-12
影响因子：
4.4
通讯作者：
Yong Y. Tan;M. J. Spiering;Vicki Scott;G. Lane;M. Christensen;J. Schmid
中科院分区：
文献类型：
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作者：
Yong Y. Tan;M. J. Spiering;Vicki Scott;G. Lane;M. Christensen;J. Schmid
摘要：lolii新伤寒菌是一种内生共生体。它生长在多年生黑麦草（Lolium perenne）的细胞间隙中，产生次生代谢物，与未感染的l相比，增加了结合体的适合度。为。我们报告说，在叶子的一生中，叶子的一个给定部分的菌丝链的平均数量保持不变，这表明叶子和菌丝延伸的同步性，包括当叶子延伸停止时菌丝延伸的停止。我们使用组成型表达的报告基因作为菌丝延伸期间和之后的代谢活性指标。报告基因活性在液体培养基中随着菌丝的停止伸展而下降，而在植物中则没有。这表明，在植物中，当伸展停止时，内生菌丝仍保持高度的代谢活性，并且在叶片的整个生命周期中它们都在定植。真菌在植物中的行为表明，在不降低菌丝代谢活性的情况下，存在通过调节菌丝延伸来同步叶片和菌丝延伸的信号通路，抑制菌丝分支，阻止真菌菌丝的顶端延伸。这些信号可能对共生关系至关重要，通过允许内生菌将其代谢活动的重点从扩展转移到次生代谢物的生产。
ABSTRACT The fungus Neotyphodium lolii is an endophytic symbiont. It grows in the intercellular spaces of the perennial ryegrass Lolium perenne, producing secondary metabolites which enhance the fitness of the association over that of uninfectedL. perenne. We report that the average number of hyphal strands in a given section of a leaf remains constant during the life of a leaf, indicating synchrony of leaf and hyphal extension, including cessation of hyphal extension when leaf extension ceases. We used a constitutively expressed reporter gene as an indicator of the mycelium's metabolic activity during and after hyphal extension. Reporter gene activity decreased when the mycelium stopped extending in liquid culture but not in planta. This indicates that in planta endophyte hyphae remain metabolically highly active when extension has ceased and throughout the life of the leaf they are colonizing. The behavior of the fungus in planta indicates the existence of signaling pathways which (i) synchronize the extension of leaf and hypha by regulating hyphal extension, (ii) suppress hyphal branching, and (iii) stop apical extension of fungal hyphae, without reducing the mycelium's metabolic activity. These signals may be crucial for the symbiosis, by allowing the endophyte to switch the focus of its metabolic activity from extension to the production of secondary metabolites.