Phytoplasmas of the stolbur group infect a wide range of wild and cultivated plants in several areas worldwide. In Europe they are transmitted by polyphagous planthoppers of the Cixiidae family. Based on actual and in silico RFLP analyses of 16S rDNA nucleotide sequences subgroups have been described in the stolbur group. In vineyards, grapevine-affecting stolbur phytoplasmas are associated with bois noir (BN) disease and are transmitted by Hyalesthes obsoletus Signoret, but in wine-growing areas where H. obsoletus is absent, the presence of stolbur phytoplasmas could implies the existence of alternative vectors. Taxonomy of stolbur phytoplasmas on 16S rDNA gene is still poorly studied, and from virtual RFLP analyses there is growing evidence of a discrete amount of variability suggesting delineation of a number of subgroups. Selecting 16Sr DNA sequences from 26 stolbur phytoplasmas infecting diverse plant species such as grapevine, potatoes, corn, and rhododendron in different areas worldwide, and sharing 99% sequence identity, made it possible to distinguish at least 6 different clusters, and many subclusters, based upon nucleotide sequences within the ca. 1,240 bp; actual RFLP patterns confirmed the presence of nine new subgroups in grapevine plants with BN from Northern and Central Italy, Hungary, Serbia and Iran. Key enzymes for distinguishing among these subgroups were AluI, BfaI, BstUI, together with MboII, FauI, Tsp509I, and Hpy188I. However when compared to its closest relatives, stolbur phytoplasma 16Sr DNA is 97.6% identical to the 16Sr DNA of ‘Candidatus Phytoplasma australiense’, 96.5% and 95.3% identical to ‘Ca. P. graminis’ and ‘Ca. P. caricae’, respectively. Due to its 16S identity with ‘Ca. P. australiense’, the designation of stolbur phytoplasma as a ‘Candidatus’ species will be not possible without a comparative analysis of non ribosomal loci. Biological complexity of stolbur phytoplasmas, indicated by the existence of numerous herbaceous hosts and diverse insect vectors, has stimulated studies on molecular markers of stolbur phytoplasma strains. Characterization of stolbur phytoplasmas in Italian vineyards was performed by multilocus sequence analysis of tuf, hlyC, trxA-truB, cbiQ-glyA, and rplS-csdB genes based on PCR-RFLP assays. Tuf gene was selected since two tuf gene sequence variants of stolbur phytoplasmas were found consistently associated with different herbaceous hosts and natural ecologies in Italian vineyards. For each of the other genes it was possible to define two distinct SNP lineages: hlyC SNP genetic lineages were consistent with those identified on the basis of tuf gene sequences; SNP lineages of trxA-truB, cbiQ-glyA, and rplS-csdB were not consistent with tuf-hlyC SNP lineages. Several SNPs of tuf, hlyC, trxA-truB, cbiQ-glyA, and rplS-csdB genes were positioned within recognition sites of restriction enzymes, and were employed for multilocus sequence analyses that grouped the stolbur phytoplasma strains from grapevines in six SNP genetic lineages. Intriguingly, distribution patterns indicated a different prevalence of these SNP lineages in the geographic areas investigated. Furthermore, the finding that the host specificities of stolbur phytoplasma lineages delineated based on hlyC and tuf genes, points to their possible involvement in the interaction of phytoplasmas with specific hosts. Moreover genotyping of the SecY locus revealed 27 stolbur genotypes in the Euro-Mediterranean areas, that formed two major clusters which are congruent with the two tuf groups. The interaction between phytoplasma membrane proteins and host proteins may influence biological and ecological properties of phytoplasmas such as specificity of plants host and insect vectors or symptom induction in plants. Such phytoplasma proteins can be highly variable; therefore their study should present opportunities for further development of phytoplasma genomic markers. Recently, PCR-sequencing and PCR-RFLP genotyping ...

Insight into the Genetic Diversity among Phytoplasmas in the Stolbur Group

CONTALDO, NICOLETTA;DUDUK, BOJAN;BERTACCINI, ASSUNTA
2010

Abstract

Phytoplasmas of the stolbur group infect a wide range of wild and cultivated plants in several areas worldwide. In Europe they are transmitted by polyphagous planthoppers of the Cixiidae family. Based on actual and in silico RFLP analyses of 16S rDNA nucleotide sequences subgroups have been described in the stolbur group. In vineyards, grapevine-affecting stolbur phytoplasmas are associated with bois noir (BN) disease and are transmitted by Hyalesthes obsoletus Signoret, but in wine-growing areas where H. obsoletus is absent, the presence of stolbur phytoplasmas could implies the existence of alternative vectors. Taxonomy of stolbur phytoplasmas on 16S rDNA gene is still poorly studied, and from virtual RFLP analyses there is growing evidence of a discrete amount of variability suggesting delineation of a number of subgroups. Selecting 16Sr DNA sequences from 26 stolbur phytoplasmas infecting diverse plant species such as grapevine, potatoes, corn, and rhododendron in different areas worldwide, and sharing 99% sequence identity, made it possible to distinguish at least 6 different clusters, and many subclusters, based upon nucleotide sequences within the ca. 1,240 bp; actual RFLP patterns confirmed the presence of nine new subgroups in grapevine plants with BN from Northern and Central Italy, Hungary, Serbia and Iran. Key enzymes for distinguishing among these subgroups were AluI, BfaI, BstUI, together with MboII, FauI, Tsp509I, and Hpy188I. However when compared to its closest relatives, stolbur phytoplasma 16Sr DNA is 97.6% identical to the 16Sr DNA of ‘Candidatus Phytoplasma australiense’, 96.5% and 95.3% identical to ‘Ca. P. graminis’ and ‘Ca. P. caricae’, respectively. Due to its 16S identity with ‘Ca. P. australiense’, the designation of stolbur phytoplasma as a ‘Candidatus’ species will be not possible without a comparative analysis of non ribosomal loci. Biological complexity of stolbur phytoplasmas, indicated by the existence of numerous herbaceous hosts and diverse insect vectors, has stimulated studies on molecular markers of stolbur phytoplasma strains. Characterization of stolbur phytoplasmas in Italian vineyards was performed by multilocus sequence analysis of tuf, hlyC, trxA-truB, cbiQ-glyA, and rplS-csdB genes based on PCR-RFLP assays. Tuf gene was selected since two tuf gene sequence variants of stolbur phytoplasmas were found consistently associated with different herbaceous hosts and natural ecologies in Italian vineyards. For each of the other genes it was possible to define two distinct SNP lineages: hlyC SNP genetic lineages were consistent with those identified on the basis of tuf gene sequences; SNP lineages of trxA-truB, cbiQ-glyA, and rplS-csdB were not consistent with tuf-hlyC SNP lineages. Several SNPs of tuf, hlyC, trxA-truB, cbiQ-glyA, and rplS-csdB genes were positioned within recognition sites of restriction enzymes, and were employed for multilocus sequence analyses that grouped the stolbur phytoplasma strains from grapevines in six SNP genetic lineages. Intriguingly, distribution patterns indicated a different prevalence of these SNP lineages in the geographic areas investigated. Furthermore, the finding that the host specificities of stolbur phytoplasma lineages delineated based on hlyC and tuf genes, points to their possible involvement in the interaction of phytoplasmas with specific hosts. Moreover genotyping of the SecY locus revealed 27 stolbur genotypes in the Euro-Mediterranean areas, that formed two major clusters which are congruent with the two tuf groups. The interaction between phytoplasma membrane proteins and host proteins may influence biological and ecological properties of phytoplasmas such as specificity of plants host and insect vectors or symptom induction in plants. Such phytoplasma proteins can be highly variable; therefore their study should present opportunities for further development of phytoplasma genomic markers. Recently, PCR-sequencing and PCR-RFLP genotyping ...
2010
18th Congress of the International Organization for Mycoplasmology
246
246
Quaglino F.; N. Contaldo; B. Duduk; D. Pacifico; C. Marzachì; X. Foissac; Y. Zhao; P.A. Bianco; W. Wei; P. Casati; R.E. Davis; A. Bertaccini
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/93772
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