Olea Europaea Geminivirus: A Novel Bipartite Geminivirid Infecting Olive Trees

Michela Chiumenti,Giuliana Loconsole,Vincenzo Cavalieri,Pasquale Saldarelli,Claudia Greco,Stefania Zicca,Angelo De Stradis,Giuseppe Altamura,Maria Saponari

doi:10.3390/v13030481

Abstract

In 2014, high-throughput sequencing of libraries of total DNA from olive trees allowed the identification of two geminivirus-like contigs. After conventional resequencing of the two genomic DNAs, their analysis revealed they belonged to the same viral entity, for which the provisional name of Olea europaea geminivirus (OEGV) was proposed. Although DNA-A showed a genome organization similar to that of New World begomoviruses, DNA-B had a peculiar ORF arrangement, consisting of a movement protein (MP) in the virion sense and a protein with unknown function on the complementary sense. Phylogenetic analysis performed either on full-length genome or on coat protein, replication associated protein (Rep), and MP sequences did not endorse the inclusion of this virus in any of the established genera in the family Geminiviridae. A survey of 55 plants revealed that the virus is widespread in Apulia (Italy) with 91% of the samples testing positive, although no correlation of OEGV with a disease or specific symptoms was encountered. Southern blot assay suggested that the virus is not integrated in the olive genome. The study of OEGV-derived siRNA obtained from small RNA libraries of leaves and fruits of three different cultivars, showed that the accumulation of the two genomic components is influenced by the plant genotype while virus-derived-siRNA profile is in line with other geminivirids reported in literature. Single-nucleotide polymorphism (SNP) analysis unveiled a low intra-specific variability.

Highlights

IntroductionOlive (Olea europaea L.) is an important crop in Italy in terms of olives and oil productions, cultivated area, and cultural heritage
Two olive trees were sampled: one Xylella-infected tree was selected in the outbreak area and used to recover the sample identified as PC, and one Xylella-free tree, identified as “OS”, was sampled in the repository of olive cultivars maintained at the research center “Centro di Ricerca, Sperimentazione e Formazione in Agricoltura”, Palagiano, Italy
high throughput sequencing (HTS) approaches were used to identify a novel species in the Geminiviridae family, to characterize its intraspecific diversity and to get insights on the defense mechanisms triggered by this novel geminivirid in olive

Summary

Introduction

Olive (Olea europaea L.) is an important crop in Italy in terms of olives and oil productions, cultivated area, and cultural heritage. As for other vegetatively propagated crops, olive can be affected by several viruses and virus-like diseases. Sixteen (16) viruses belonging to eight genera have been described on olive so far [1,2,3], most of them from symptomless plants or detected in a very limited number of trees [4,5,6,7,8,9,10,11], and in most cases with no clear evidence of their etiological involvement in a disease. An exception is olive leaf yellowing-associated virus (OLYaV; [12]), whose detection in plants with yellowing and woody cylinder symptoms strongly advocate its involvement in the disease

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Conclusion