SUMMARY The sequences of the N-terminal 132 nucleotides of the coat protein genes of eleven Portuguese isolates of Zucchini yellow mosaic virus (ZYMV) were determined. The nucleotide sequence similarities among the eleven isolates suggested two groups, based on different codon usage for the amino acid residues in seven positions. Comparisons among the encoded amino acid sequences and those previously reported indicated that in this re- gion the Portuguese isolates were identical to isolates from the USA (California), Germany, Italy and France. A monoclonal antibody was produced against a Por- tuguese isolate that recognized the epitope SGTQPT and cross-reacted with particles of other potyviruses. Key words: ZYMV, monoclonal antibody, nucleotide sequence, epitope, phage display library. Zucchini yellow mosaic virus (ZYMV) is a member of the Potyviridae family, the largest group of plant-infect- ing viruses (Shukla and Ward, 1989). ZYMV coat pro- tein (CP) is composed of a 214-amino acid core domain flanked by 43- to 45-amino acid N-terminal domain and a 20-amino acid C-terminal domain (Shukla and Ward, 1989). Different domains have been associated with dis- tinct functions of the CP during the virus life cycle. The conserved core, but not the N- or C-terminus, is re- quired for virus assembly (Jagadish et al., 1991; Dolja et al., 1995; Varrelmann and Maiss, 2000), plasmodesmatal gating (Rojas et al., 1997), and cell-to-cell movement (Dolja et al., 1995). The N-terminus has been shown to assist aphid transmission via its DAG motif (Atreya et al., 1991; Gal-On et al., 1992). Several monoclonal anti- bodies (Mabs) have been obtained for ZYMV particles that recognise epitopes in the N-terminal region of the CP and in the core region (Kundu et al., 1998; Desbiez et al., 2002). Corresponding author: C. Novo Fax: + 35.121.7163636 E-mail: carlos.novo@ineti.pt ZYMV was maintained in C. sativa as a propagation host in an insect proof greenhouse and purified from systemically infected leaves according to Fribourg et al. (1984). The band containing virus particles was collect- ed and the absence of protein other than CP was checked by SDS-PAGE. BALB/c mice were immunized with purified ZYMV virus particles and monoclonal antibodies were pro- duced according to Somowiyarjo et al. (1988), using Sp2/0 Ag14 myeloma cells. Mabs were isotyped by ELISA using the Mab-based Mouse Ig Isotyping Kit (BD Biosciences Pharmingen, San Diego, CA, USA) and purified by chromatographic methods. The selected Mab 71E2 was used for the detection of virus in infect- ed plant material extracts by ELISA as described by So- mowiyarjo et al. (1988). Immunocapture RT-PCR was used for CP amplifications using the primers ZY-1 and ZY-2 described by Thomson et al. (1995). The RT-PCR products were analysed by electrophoresis in 1% agarose gel and stained with ethidium bromide. The ex- cised DNA band was sequenced on both strands using the Terminator Cycle Sequencing Ready Reaction Kit (Applied Biosystem, Foster City, CA, USA). The ex- pected 300 bp band was amplified from samples of all the Portuguese isolates after the IC-RT-PCR reaction. The nucleotide sequences coding for the C-terminus of the polymerase and for the N-terminus of the coat pro- tein (N-CP) were deposited in GenBank (accession numbers AY648578 to AY648588). Although the deduced amino acid sequences for all the tested Portuguese isolates have the same amino acid sequence in the 44 amino acids of the N-CP, there are nucleotide differences in codons for V7, A8, D9, A12, D26, S30 and V37. Four of the isolates use the codons GTT (V7), GCC (A8), GAC (D9), GCC (A12), GAT (D26) and GTG (V37) in contrast with the other seven isolates which use the codons GTG (V7), GCA (A8), GAT (D9), GCT (A12), GAC (D26) and GTA (V37). The codon usage of GTA for Val seems be specific for this group and position as no similar codon was found for the other Val residues of the sequenced N-CP from both groups. Journal of Plant Pathology (2005), 87 (3), 229-232 Edizioni ETS Pisa, 2005 229 SHORT COMMUNICATION SEQUENCES OF THE N-TERMINI OF COAT PROTEINS OF PORTUGUESE ZUCCHINI YELLOW MOSAIC VIRUS ISOLATES AND OF AN EPITOPE RECOGNIZED BY A MONOCLONAL ANTIBODY F.H. Cardoso 1 , A. Armada 1 , A.M. Fonseca 2 , M.T. Santos 3 , J. Sequeira 3 , A. Clemente 1 , O. Sequeira 3 and C. Novo 1 1 Instituto Nacional de Engenharia, Tecnologia e Inovaçao, Departamento de Biotecnologia, Unidade de Tecnologias de Proteínas e Anticorpos Monoclonais, Edifício F, Estrada do Paço do Lumiar 22, 1649-038, Lisboa, Portugal 2 Universidade do Algarve, Campus de Gambelas, Faro, Portugal 3 Estação Agronómica Nacional, Quinta do Marquês 2784-505 Oeiras, Portugal