Identification and molecular characterization of a β-1,4-endoglucanase gene (Rr-eng-1) from Rotylenchulus reniformis

β-1,4-endoglucanses, a.k.a. cellulases, are parasitism genes that facilitate root penetration and migration by plant-parasitic nematodes. Rotylenchulus reniformis is a sedentary semi-endoparasite for which little molecular data has been collected. In this report, we describe the isolation and characterization of a predicted glycosyl hydrolase family 5 cellulase from R. reniformis that we have named Rr-eng-1. The Rr-eng-1 cDNA was 1,341 bp long and was comprised of a 19 bp 5'-untranslated region (UTR), a 1,245 bp open reading frame (ORF), and an 80 bp 3'-UTR. The Rr-eng-1 genomic sequence was 2,325 bp. Alignment of the cDNA and genomic sequences revealed seven introns and eight exons for Rr-eng-1. BLASTN analysis showed the Rr-eng-1 cDNA was most homologous to the Hg-eng-6 mRNA from Heterodera glycines. Southern blot analysis indicated that at least three Rr-eng-1-like sequences were present in the R. reniformis genome. Translation of the Rr-eng-1 ORF yielded a 414 amino acid peptide (Rr-ENG-1) having an N-terminal signal sequence for secretion. No cellulose binding module (CBM) was detected in Rr-ENG-1; however, a putative CBM linker sequence N-terminal to the catalytic domain was present. Rr-ENG-1 was most homologous to Hg-ENG-6 but also shared a number of intron splice positions with Mi-ENG-2. Quantitative RT-PCR indicated that Rr-eng-1 was highly expressed in the J2 and adult vermiform life-stages with a sharp decline in expression detected in sedentary females.