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Drechslerella stenobrocha genome illustrates the mechanism of constricting rings and the origin of nematode predation in fungi.

Liu K, Zhang W, Lai Y, Xiang M, Wang X, Zhang X, Liu X - BMC Genomics (2014)

Bottom Line: The genome was 29.02 Mb in size and was found rare instances of transposons and repeat induced point mutations, than that of Arthrobotrys oligospora.In D. stenobrocha, the down-regulation of saprophytic enzyme genes and the up-regulation of infection-related genes during the capture of nematodes indicated a transition between dual life strategies of saprophagy and predation.It reveals the transition between saprophagy and predation of these fungi and also proves new insights into the mechanisms of mechanical trapping.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, No 3 1st Beichen West Rd,, Chaoyang District, Beijing 100101, China. liuxz@im.ac.cn.

ABSTRACT

Background: Nematode-trapping fungi are a unique group of organisms that can capture nematodes using sophisticated trapping structures. The genome of Drechslerella stenobrocha, a constricting-ring-forming fungus, has been sequenced and reported, and provided new insights into the evolutionary origins of nematode predation in fungi, the trapping mechanisms, and the dual lifestyles of saprophagy and predation.

Results: The genome of the fungus Drechslerella stenobrocha, which mechanically traps nematodes using a constricting ring, was sequenced. The genome was 29.02 Mb in size and was found rare instances of transposons and repeat induced point mutations, than that of Arthrobotrys oligospora. The functional proteins involved in nematode-infection, such as chitinases, subtilisins, and adhesive proteins, underwent a significant expansion in the A. oligospora genome, while there were fewer lectin genes that mediate fungus-nematode recognition in the D. stenobrocha genome. The carbohydrate-degrading enzyme catalogs in both species were similar to those of efficient cellulolytic fungi, suggesting a saprophytic origin of nematode-trapping fungi. In D. stenobrocha, the down-regulation of saprophytic enzyme genes and the up-regulation of infection-related genes during the capture of nematodes indicated a transition between dual life strategies of saprophagy and predation. The transcriptional profiles also indicated that trap formation was related to the protein kinase C (PKC) signal pathway and regulated by Zn(2)-C6 type transcription factors.

Conclusions: The genome of D. stenobrocha provides support for the hypothesis that nematode trapping fungi evolved from saprophytic fungi in a high carbon and low nitrogen environment. It reveals the transition between saprophagy and predation of these fungi and also proves new insights into the mechanisms of mechanical trapping.

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Characteristics of D. stenobrocha used in the sequenced nematode-trapping fungus, showing the amazing mechanical trapping process. The trapping process includes ring formation and ring constriction. A) The free living hyphae and spore; B) Ring without constriction; C) Ring induced to constrict; D) Nematode is capturing. Scale bar: A, D = 20 μm; B, C = 5 μm.
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Figure 1: Characteristics of D. stenobrocha used in the sequenced nematode-trapping fungus, showing the amazing mechanical trapping process. The trapping process includes ring formation and ring constriction. A) The free living hyphae and spore; B) Ring without constriction; C) Ring induced to constrict; D) Nematode is capturing. Scale bar: A, D = 20 μm; B, C = 5 μm.

Mentions: Traps are usually produced from hyphae in the presence of nematodes [4] or are induced by peptides, or nematode extracts from the nematodes [16]. Drechslerella stenobrocha (Ascomycota: Orbiliaceae) is a nematode-trapping species that forms constricting rings, the most sophisticated trapping structure, that consist of three ring cells capturing nematodes actively (Figure 1A, B) [17]. When a nematode enters the ring and contacts the inner surfaces of the ring cells, G protein-coupled receptors activate a down-stream signal pathway that includes cyclic adenosine monophosphate (cAMP), inositol-1, 4, 5-triphosphate (IP3), and Ca2+[18]. Subsequently, the ring cells rapidly (within 0.1 s) triple their volume and firmly lasso the nematode (Figure 1C, D) [19].


Drechslerella stenobrocha genome illustrates the mechanism of constricting rings and the origin of nematode predation in fungi.

Liu K, Zhang W, Lai Y, Xiang M, Wang X, Zhang X, Liu X - BMC Genomics (2014)

Characteristics of D. stenobrocha used in the sequenced nematode-trapping fungus, showing the amazing mechanical trapping process. The trapping process includes ring formation and ring constriction. A) The free living hyphae and spore; B) Ring without constriction; C) Ring induced to constrict; D) Nematode is capturing. Scale bar: A, D = 20 μm; B, C = 5 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3924618&req=5

Figure 1: Characteristics of D. stenobrocha used in the sequenced nematode-trapping fungus, showing the amazing mechanical trapping process. The trapping process includes ring formation and ring constriction. A) The free living hyphae and spore; B) Ring without constriction; C) Ring induced to constrict; D) Nematode is capturing. Scale bar: A, D = 20 μm; B, C = 5 μm.
Mentions: Traps are usually produced from hyphae in the presence of nematodes [4] or are induced by peptides, or nematode extracts from the nematodes [16]. Drechslerella stenobrocha (Ascomycota: Orbiliaceae) is a nematode-trapping species that forms constricting rings, the most sophisticated trapping structure, that consist of three ring cells capturing nematodes actively (Figure 1A, B) [17]. When a nematode enters the ring and contacts the inner surfaces of the ring cells, G protein-coupled receptors activate a down-stream signal pathway that includes cyclic adenosine monophosphate (cAMP), inositol-1, 4, 5-triphosphate (IP3), and Ca2+[18]. Subsequently, the ring cells rapidly (within 0.1 s) triple their volume and firmly lasso the nematode (Figure 1C, D) [19].

Bottom Line: The genome was 29.02 Mb in size and was found rare instances of transposons and repeat induced point mutations, than that of Arthrobotrys oligospora.In D. stenobrocha, the down-regulation of saprophytic enzyme genes and the up-regulation of infection-related genes during the capture of nematodes indicated a transition between dual life strategies of saprophagy and predation.It reveals the transition between saprophagy and predation of these fungi and also proves new insights into the mechanisms of mechanical trapping.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, No 3 1st Beichen West Rd,, Chaoyang District, Beijing 100101, China. liuxz@im.ac.cn.

ABSTRACT

Background: Nematode-trapping fungi are a unique group of organisms that can capture nematodes using sophisticated trapping structures. The genome of Drechslerella stenobrocha, a constricting-ring-forming fungus, has been sequenced and reported, and provided new insights into the evolutionary origins of nematode predation in fungi, the trapping mechanisms, and the dual lifestyles of saprophagy and predation.

Results: The genome of the fungus Drechslerella stenobrocha, which mechanically traps nematodes using a constricting ring, was sequenced. The genome was 29.02 Mb in size and was found rare instances of transposons and repeat induced point mutations, than that of Arthrobotrys oligospora. The functional proteins involved in nematode-infection, such as chitinases, subtilisins, and adhesive proteins, underwent a significant expansion in the A. oligospora genome, while there were fewer lectin genes that mediate fungus-nematode recognition in the D. stenobrocha genome. The carbohydrate-degrading enzyme catalogs in both species were similar to those of efficient cellulolytic fungi, suggesting a saprophytic origin of nematode-trapping fungi. In D. stenobrocha, the down-regulation of saprophytic enzyme genes and the up-regulation of infection-related genes during the capture of nematodes indicated a transition between dual life strategies of saprophagy and predation. The transcriptional profiles also indicated that trap formation was related to the protein kinase C (PKC) signal pathway and regulated by Zn(2)-C6 type transcription factors.

Conclusions: The genome of D. stenobrocha provides support for the hypothesis that nematode trapping fungi evolved from saprophytic fungi in a high carbon and low nitrogen environment. It reveals the transition between saprophagy and predation of these fungi and also proves new insights into the mechanisms of mechanical trapping.

Show MeSH
Related in: MedlinePlus