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Title: Characterization of three novel fatty acid- and retinoid-binding protein genes (Ha-far-1, Ha-far-2 and Hf-far-1) from the cereal cyst nematodes Heterodera avenae and H. filipjevi

Author
item QIAO, FEN - Chinese Academy Of Agricultural Sciences
item LUO, LILIAN - Chinese Academy Of Agricultural Sciences
item PENG, HUAN - Chinese Academy Of Agricultural Sciences
item HUANG, WENKUN - Chinese Academy Of Agricultural Sciences
item CUI, JIANGKUAN - Chinese Academy Of Agricultural Sciences
item LUO, SHUJIE - Chinese Academy Of Agricultural Sciences
item LI, XIN - Chinese Academy Of Agricultural Sciences
item KONG, LINGAN - Huazhong Agricultural University
item Chitwood, David
item PENG, DELIANG - Chinese Academy Of Agricultural Sciences

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2016
Publication Date: 8/1/2016
Publication URL: http://handle.nal.usda.gov/10113/63010
Citation: Qiao, F., Luo, L., Peng, H., Huang, W., Cui, J., Luo, S., Li, X., Kong, L., Chitwood, D.J., Peng, D. 2016. Characterization of three novel fatty acid- and retinoid-binding protein genes (Ha-far-1, Ha-far-2 and Hf-far-1) from the cereal cyst nematodes Heterodera avenae and H. filipjevi. PLoS One. 11(8):e0160003. doi: 10.1371/journal.pone.0160003.

Interpretive Summary: Cereal cyst nematodes are microscopic soil worms that cause major crop losses to wheat globally. Environmentally safe methods to control these losses are urgently needed. One approach for developing novel controls is by exploiting fundamental differences between the biological processes of nematodes and their host plants. In this paper, scientists describe the discovery of important nematode genes essential for the transport of fats and other important molecules from the nematode host plant to the nematode. The DNA sequences of the genes and the amino acid sequences of the proteins were determined and compared to those of similar genes in other nematodes. The results are significant because they provide the first report that two different types of this gene can occur in the same plant-feeding nematode species and because they reveal a natural target that can be used to develop naturally based control strategies. Therefore, the results will be used by researchers developing safe and effective methods for controlling nematode-induced crop losses.

Technical Abstract: Heterodera avenae and H. filipjevi are major parasites of wheat, reducing production worldwide. Both are sedentary endoparasitic nematodes, and their development and parasitism depend strongly on nutrients obtained from hosts. Secreted fatty acid- and retinoid-binding (FAR) proteins are nematode-specific lipid carrier proteins used for nutrient acquisition as well as suppression of plant defenses. In this study, we discovered three novel FAR genes (Ha-far-1, Ha-far-2, Hf-far-1). Ha-far-1 and Ha-far-2 were cloned from H. avenae, encoding proteins of 191 and 280 amino acids with molecular masses about 17 and 30 kDa, respectively and sequence identity of 28%. Protein Blast in NCBI revealed that the Ha-FAR-1 sequence is 78% similar to the Gp-FAR-1 protein from G. pallida, while Ha-FAR-2 is 30% similar to Rs-FAR-1 from Radopholus similis. Only one FAR protein Hf-FAR-1was indentified in H. filipjevi; it had 96% sequence identity to Ha-FAR-1. The three proteins are alpha-helix-rich and contain the conserved domain of Gp-FAR-1, but Ha-FAR-2 had a remarkable peptide at the C-terminus which was random-coil-rich. Both Ha-FAR-1 and Hf-FAR-1 had casein kinase II phosphorylation sites, while Ha-FAR-2 had predicted N-glycosylation sites. Phylogenetic analysis showed that the three proteins clustered together, though Ha-FAR-1 and Hf-FAR-1 adjoined each other in a plant-parasitic nematode branch, but Ha-FAR-2 was distinct from the other proteins in the group. Fluorescence-based ligand binding analysis showed the three FAR proteins bound to a fluorescent fatty acid derivative and retinol and with dissociation constants similar to FARs from other species, though Ha-FAR-2 binding ability was weaker than that of the two others. In situ hybridization detected mRNAs of Ha-far-1 and Ha-far-2 in the hypodermis. The qRT-PCR results showed that the Ha-far-1and Ha-far-2 were expressed in all developmental stages; Ha-far-1 expressed 100 times more than Ha-far-2 in all stages. The highest expression level of Ha-far-1 was observed in J4, whereas the highest expression level of Ha-far-2 occurred in J2. In conclusion, we have identified two novel far genes from H. avenae and one from H. filipjevi and have provided further indication that nematode far genes are present in a variety of nematode species, where the FAR proteins share similar basic structure, expression pattern and biochemical activities.