|GAVILANO, LILY - Mississippi State University|
|BAUM, THOMAS - Iowa State University|
|PARROTT, WAYNE - University Of Georgia|
|DAVIS, ERIC - North Carolina State University|
Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2015
Publication Date: 6/1/2015
Citation: Wubben, M., Gavilano, L., Baum, T.J., Parrott, W.A., Davis, E.L. 2015. Sequence and spatiotemporal expression analysis of CLE-motif containing genes from the reniform nematode (Rotylenchulus reniformis Linford & Oliveira). Journal of Nematology. 47(2):159–165.
Interpretive Summary: Sedentary plant-parasitic nematodes express a large variety of genes that enable them to parasitize plants. Collectively, these genes are called ‘parasitism genes’ and the proteins they encode are known as ‘effectors.’ Cyst nematode effectors have been discovered that are able to mimic plant peptide hormones belonging to the CLE (CLAVATA3/ESR) family of genes. In plants, CLE peptides bind to receptor-kinase proteins and are involved in many aspects of plant development and physiology including the regulation of the shoot and root apical meristems. In this report, we describe effectors from the reniform nematode that appear to be homologous to cyst nematode CLE peptides. Three reniform nematode CLE genes were identified and were most similar to CLEs from soybean cyst and sugar beet cyst nematode. We also determined that maximum CLE gene expression occurred during the sedentary parasitic female life-stage and that this expression only happened in the dorsal esophageal gland cell of the female reniform nematodes. Previous research on cyst nematode CLE genes showed that CLE expression was required for the full parasitic capability of the nematode; therefore, future experiments will focus on attempts to silence reniform nematode CLE gene expression in an effort to increase host plant resistance.
Technical Abstract: The reniform nematode, Rotylenchulus reniformis, is a sedentary semi-endoparasitic species with a host range that encompasses more than 77 plant families. Nematode effector proteins containing plant-ligand motifs similar to CLAVATA3/ESR (CLE) peptides have been identified in the Heterodera, Globodera, and Meloidogyne genera of sedentary endoparasites. Here, we describe the isolation, sequence analysis, and spatiotemporal expression of three R. reniformis genes encoding putative CLE motifs named Rr-cle-1, Rr-cle-2, and Rr-cle-3. The Rr-cle cDNAs showed > 98% identity with each other and the predicted peptides were identical with the exception of a short stretch of residues at the carboxy(C)-terminus of the variable domain (VD). Aligning the Rr-cle cDNAs with their corresponding genomic sequences showed three exons with an intron separating the signal peptide from the VD and a second intron separating the VD from the CLE motif. Each RrCLE peptide possessed an amino-terminal signal peptide for secretion and a single C-terminal CLE motif that was most similar to Heterodera CLE motifs. An alignment of the RrCLE1 peptide with H. glycines and H. schachtii CLE proteins revealed a high level of homology within the VD region associated with regulating in planta trafficking of the processed CLE peptide. Quantitative RT-PCR showed similar expression profiles for each Rr-cle transcript across the life-cycle with the greatest transcript abundance being in sedentary parasitic female nematodes. In situ hybridization showed specific Rr-cle expression within the dorsal esophageal gland cell of sedentary parasitic females.