Isolation and characterization of a candidate gene for resistance to cereal cyst nematode from Aegilops variabilis in China
Cereal cyst nematode (CCN) (Heterodera avenae Woll.) is one of the most economically damaging endoparasite pests of wheat worldwide. We isolated and characterized a novel cereal CCN resistance candidate gene, CreV8, from Aegilops variabilis (2n = 28, UUSvSv). The gene was 3,568 bp long and showed high nucleotide similarity with the known nematode resistance genes Cre3, CreZ, and go35. CreV8 consisted of two exons, one intron and a complete ORF of 2,763 bp. The deduced peptide sequence consisted of 920 amino acid residues and shared 97.83% amino acid identity with Cre3. The sequence harbored a signal peptide domain, a nucleotide-binding ARC (NB-ARC) domain, and a leucine-rich repeat (LRR) domain, all of which are typical characteristics of resistance genes. We proposed the resistance mechanism of CreV8 based on functional analysis and predictions from its conserved domains and tertiary structure. Real-time polymerase chain reaction (PCR) showed that CreV8 was expressed in CCN-inoculated roots of resistant plants, and its expression levels were 2.80 and 27.45 times higher than that in the untreated control at 3 and 11 days post-inoculation, respectively. These results indicate that CreV8 belongs to the nucleotide binding site (NBS)-LRR resistance gene family and that it is a candidate CCN-resistance gene.
Key words: Aegilops variabilis, CreV8, cereal cyst nematode (CCN), Heterodera avenae, tertiary structure.