Abstract
Five Aphelenchoides besseyi isolates collected from bird’s-nest ferns or rice possess different parasitic capacities in bird’s-nest fern. Two different glycoside hydrolase (GH) 45 genes were identified in the fern isolates, and only one was found in the rice isolates. A Abe GH5-1 gene containing an SCP-like family domain was found only in the fern isolates. Abe GH5-1 gene has five introns suggesting a eukaryotic origin. A maximum likelihood phylogeny revealed that Abe GH5-1 is part of the nematode monophyletic group that can be clearly distinguished from those of other eukaryotic and bacterial GH5 sequences with high bootstrap support values. The fern A. besseyi isolates were the first parasitic plant nematode found to possess both GH5 and GH45 genes. Surveying the genome of the five A. besseyi isolates by Southern blotting using an 834 bp probe targeting the GH5 domain suggests the presence of at least two copies in the fern-origin isolates but none in the rice-origin isolates. The in situ hybridization shows that the Abe GH5-1 gene is expressed in the nematode ovary and testis. Our study provides insights into the diversity of GH in isolates of plant parasitic nematodes of different host origins.
Highlights
The nematode Aphelenchoides besseyi is the causal nematode of rice white tip disease, and is one of the most destructive problems in many rice-producing areas[1, 2]
This study is the first report on the co-existence of both candidate glycoside hydrolase family 5 (GH5) and GH45 cellulase-coding genes in a single Plant parasitic nematodes (PPNs) species
We have identified a candidate GH5 and two GH45 cellulase genes in all three A. besseyi isolates that were originally collected from the bird’s-nest fern but only one GH45 cellulase-coding gene was currently identified from the two rice-origin isolates
Summary
The nematode Aphelenchoides besseyi is the causal nematode of rice white tip disease, and is one of the most destructive problems in many rice-producing areas[1, 2]. Rice fields with A. besseyi infection rates of 34–58% were associated to a 35–45% reduction in yield in Taiwan [3], while 60% of rice cultivars in India were found to be infested [4]. Seed samples from 41% of Iranian fields were infested by A. besseyi [5]. This nematode has been found on a wide range of plants, including bird’s-nest fern, strawberry, and sweet corn [2, 6]
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