H a linker peptide. The GHF5 endoglucanase genes isolated from plant parasitic nematodes have also different structures: all have a signal peptide and catalytic domain, some have an additional linker and CBD and others only have a linker but no CBD [25,67]. However, neither peptide linkers nor CBD domains were present in the two GHF5 endoglucanases isolated from A. avenae. Expansins from cyst nematodes have also been shown to contain a CBD,Page 10 of(page number not for citation purposes)BMC Genomics 2009, 10:http://www.biomedcentral.com/1471-2164/10/but no such domains were Staurosporine predicted in other sequences within the EST dataset, including the putative expansins. A phylogenetic tree was generated from an alignment of the -1,4-endoglucanase protein sequences from AAENG-1, AA-ENG-2, cyst and root-knot nematodes, the migratory plant-parasitic nematodes R. similis, Pratylenchus penetrans, Pratylenchus coffeae and Ditylenchus africanus and GHF5 cellulases from phytophagous beetles, bacteria and protists (Fig. 6). AA-ENG-1 and AA-ENG-2 clustered into a larger group of protein sequences including all nematode GHF5 cellulases, indicating that A. avenae cellulases are closely related to those of the Tylenchida. This analysis supports the idea that all nema-tode GHF5 cellulases evolved from a GHF5 sequence acquired by a common ancestor of this group. The -1,4-endoglucanases are the largest family of cellwall-degrading enzymes that have been identified in parasitic nematodes to date. Over the last decade, a large number of GHF5 endoglucanases have been identified and extensively studied in plant parasitic Tylenchida including cyst and root-knot nematodes [20-25]. Genes encoding -1,4-endoglucanases have also been found in Bursaphelenchus spp but these enzymes are most similar to GHF45 cellulases from fungi [16]. The presence of GHF5 cellulases within A. avenae (as opposed to GHF45 cellulases) provides further support for the suggestion that thisDA-ENG-1 [ABY52965]100 93 37GR-ENG-1 [AAC48325] GR-ENG-2 [AAC48341]HG-ENG-2 [AAC48327] HG-ENG-4 [AAP88024]100 39RS-ENG-3 [ABV54449] MI-ENG-4 [AAR37375]MI-ENG-1 [AF323087] MI-ENG-3 [AAR37374]Nematodes79 98 87 97MJ-ENG- 3 [CAJ77137]PP-ENG-2 [BAB68523] PP-ENG-1 [BAB68522] PC-ENG-1 [ABX79356]GR-ENG-4 [AAN03647] HG-ENG-5 [AAN32884] RS-ENG-1B [BABV54447]90 82RS-ENG-2 [ABV54448] RS-ENG-1A [ABV54446] HG-ENG-6 [AAO25506]13MI-ENG-2 [AAK21883] AA-ENG-100 AA-ENG-Psacothea hilaris EG [BAB86867]BeetlesApriona germari EG [AAX18655]Bacillus licheniformis Bglc [YP091670] Bacillus subtilis Egls [CAA976101]Cytophaga hutchinsonii EG [YP678708]13 81 100BacteriaPseudomonas sp AclA [BAB79288] Erwinia chrysanthemi Cel5A [CAA68604] Protist from Cryptocereus [BAF57332] Protist from Reticulitemes [BAF57329]Protists0.Figure 6 Unrooted phylogenetic tree of GHF5 catalytic domains based on the protein sequences using the maximum likelihood method Unrooted phylogenetic tree of GHF5 catalytic domains based on the protein sequences using the maximum likelihood method. The GHF5 proteins from A. avenae (AA-ENG-1 and AA-ENG-2) are labeled in bold. GenBank accession numbers of GHF5 proteins from Meloidogyne incognita (MI-ENG-1, MI-ENG-2, MI-ENG-3 and MI-ENG-4), Pratylenchus PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/17139194 penetrans (PP-ENG-1 and PP-ENG-2), Pratylenchus coffeae (PC-ENG-1), Radopholus similis (RS-ENG-1A, RS-ENG-1B, RS-ENG-2 and RS-ENG-3), Globodera rostochiensis (GR-ENG-1, GR-ENG-2 and GR-ENG-4), Heterodera glycines (HG-ENG-2, HG-ENG-4, HGENG-5 and HG-ENG-6), Ditylenchus africanus.