Evolution of GHF5 endoglucanase gene structure in plant-parasitic nematodes: no evidence for an early domain shuffling eventReportar como inadecuado




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BMC Evolutionary Biology

, 8:305

First Online: 03 November 2008Received: 17 October 2007Accepted: 03 November 2008

Abstract

BackgroundEndo-1,4-beta-glucanases or cellulases from the glycosyl hydrolase family 5 GHF5 have been found in numerous bacteria and fungi, and recently also in higher eukaryotes, particularly in plant-parasitic nematodes PPN. The origin of these genes has been attributed to horizontal gene transfer from bacteria, although there still is a lot of uncertainty about the origin and structure of the ancestral GHF5 PPN endoglucanase. It is not clear whether this ancestral endoglucanase consisted of the whole gene cassette, containing a catalytic domain and a carbohydrate-binding module CBM, type 2 in PPN and bacteria or only of the catalytic domain while the CBM2 was retrieved by domain shuffling later in evolution. Previous studies on the evolution of these genes have focused primarily on data of sedentary nematodes, while in this study, extra data from migratory nematodes were included.

ResultsTwo new endoglucanases from the migratory nematodes Pratylenchus coffeae and Ditylenchus africanus were included in this study. The latter one is the first gene isolated from a PPN of a different superfamily Sphaerularioidea; all previously known nematode endoglucanases belong to the superfamily Tylenchoidea order Rhabditida. Phylogenetic analyses were conducted with the PPN GHF5 endoglucanases and homologous endoglucanases from bacterial and other eukaryotic lineages such as beetles, fungi and plants. No statistical incongruence between the phylogenetic trees deduced from the catalytic domain and the CBM2 was found, which could suggest that both domains have evolved together. Furthermore, based on gene structure data, we inferred a model for the evolution of the GHF5 endoglucanase gene structure in plant-parasitic nematodes. Our data confirm a close relationship between Pratylenchus spp. and the root knot nematodes, while some Radopholus similis endoglucanases are more similar to cyst nematode genes.

ConclusionWe conclude that the ancestral PPN GHF5 endoglucanase gene most probably consisted of the whole gene cassette, i.e. the GHF5 catalytic domain and the CBM2, rather than that it evolved by domain shuffling. Our evolutionary model for the gene structure in PPN GHF5 endoglucanases implies the occurrence of an early duplication event, and more recent gene duplications at genus or species level.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2148-8-305 contains supplementary material, which is available to authorized users.

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Autor: Tina Kyndt - Annelies Haegeman - Godelieve Gheysen

Fuente: https://link.springer.com/article/10.1186/1471-2148-8-305



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