Phytoplasma associated diseases are long time know world wide as inducing severely economic losses in diverse low- and high-value crops worldwide. The increasing threat of phytoplasma diseases comes both from devastating diseases in emerging agricultural countries and from epidemics and or endemic situations in areas traditionally devoted to agriculture. Phytoplasmas usually do not kill in short time the host plant from which they are strongly metabolic dependent therefore increasing the possibility of epidemic spreading; phytoplasma-infected plants result also more susceptible to infection by other pathogens such as fungi and viruses. These still uncultured parasites are mollicutes with transkingdom habitats such as phloem of infected plants and hemolymph of insect vectors. In the last ten years several molecular biological findings involved in both the plant-phytoplasma and insect-phytoplasma interactions greatly increased the scientific knowledge about these pathogens. To now the complete genomes of four phytoplasmas were obtained and annotation is in progress. One of these genome shows to be linear that is a very uncommon feature. From annotation of ‘Candidatus Phytoplasma asteris’ (Japanese strain) sequence it was shown that the genome of this phytoplasma encodes very few metabolic functions confirming that phytoplasmas are highly dependent on metabolic compounds from their host cells. Moreover an approximately 30-kb region, including glycolytic genes, was found to be tandemly duplicated in the genome of a severely pathogenic strain of the same phytoplasma: the presence of two glycolytic gene clusters suggested that a higher consumption of the carbon source affects the growth rate of the phytoplasma and causes more severe symptoms directly or indirectly. Positive selection of Amp, a phytoplasma surface membrane protein, was also recognized and this may reflect an interaction between the phytoplasma and the host cytoplasm as indicated by the Amp complex with insect microfilament proteins identified in the leafhopper vectors. The phytoplasma genome encodes many membrane proteins whose functions are under study now to elucidate into more details the phytoplasma-plant-vector interactions
Phytoplasmas: the pathogenic mycoplasmas infecting plants and insects / Bertaccini A.; S. Namba.. - STAMPA. - (2009), pp. 43-43. (Intervento presentato al convegno Mycoplasmology: a review of developments over the last decade tenutosi a Gran Canaria, Spagna nel 10-12 giugno 2009).
Phytoplasmas: the pathogenic mycoplasmas infecting plants and insects.
BERTACCINI, ASSUNTA;
2009
Abstract
Phytoplasma associated diseases are long time know world wide as inducing severely economic losses in diverse low- and high-value crops worldwide. The increasing threat of phytoplasma diseases comes both from devastating diseases in emerging agricultural countries and from epidemics and or endemic situations in areas traditionally devoted to agriculture. Phytoplasmas usually do not kill in short time the host plant from which they are strongly metabolic dependent therefore increasing the possibility of epidemic spreading; phytoplasma-infected plants result also more susceptible to infection by other pathogens such as fungi and viruses. These still uncultured parasites are mollicutes with transkingdom habitats such as phloem of infected plants and hemolymph of insect vectors. In the last ten years several molecular biological findings involved in both the plant-phytoplasma and insect-phytoplasma interactions greatly increased the scientific knowledge about these pathogens. To now the complete genomes of four phytoplasmas were obtained and annotation is in progress. One of these genome shows to be linear that is a very uncommon feature. From annotation of ‘Candidatus Phytoplasma asteris’ (Japanese strain) sequence it was shown that the genome of this phytoplasma encodes very few metabolic functions confirming that phytoplasmas are highly dependent on metabolic compounds from their host cells. Moreover an approximately 30-kb region, including glycolytic genes, was found to be tandemly duplicated in the genome of a severely pathogenic strain of the same phytoplasma: the presence of two glycolytic gene clusters suggested that a higher consumption of the carbon source affects the growth rate of the phytoplasma and causes more severe symptoms directly or indirectly. Positive selection of Amp, a phytoplasma surface membrane protein, was also recognized and this may reflect an interaction between the phytoplasma and the host cytoplasm as indicated by the Amp complex with insect microfilament proteins identified in the leafhopper vectors. The phytoplasma genome encodes many membrane proteins whose functions are under study now to elucidate into more details the phytoplasma-plant-vector interactionsI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
