http://http://dspace.unitus.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sat, 18 May 2013 16:29:00 GMT 2013-05-18T16:29:00Z http://hdl.handle.net/2067/1611 Title: Phloem cytochemical modification and gene expression following the recovery of apple plants from apple proliferation Authors: Musetti, Rita; Paolacci, Anna Rita; Ciaffi, Mario; Tanzarella, Oronzo A.; Polizzotto, Rachele; Tubaro, Franco; Mizzau, Michela; Ermacora, Paolo; Badiani, Maurizio; Osler, Ruggero Abstract: Recovery of apple trees from apple proliferation was studied by combining ultrastructural, cytochemical, and gene expression analyses to possibly reveal changes linked to recovery-associated resistance. When compared with either healthy or visibly diseased plants, recovered apple trees showed abnormal callose and phloem-protein accumulation in their leaf phloem. Although cytochemical localization detected Ca2+ ions in the phloem of all the three plant groups, Ca2+ concentration was remarkably higher in the phloem cytosol of recovered trees. The expression patterns of five genes encoding callose synthase and of four genes encoding phloem proteins were analyzed by quantitative real-time reverse transcription- polymerase chain reaction. In comparison to both healthy and diseased plants, four of the above nine genes were remarkably upregulated in recovered trees. As in infected apple trees, phytoplasma disappear from the crown during winter, but persist in the roots, and it is suggested that callose synthesis/deposition and phloem-protein plugging of the sieve tubes would form physical barriers preventing the recolonization of the crown during the following spring. Since callose deposition and phloem-protein aggregation are both Ca2+-dependent processes, the present results suggest that an inward flux of Ca2+ across the phloem plasma membrane could act as a signal for activating defense reactions leading to recovery in phytoplasma-infected apple trees. Description: L'articolo é disponibile sul sito dell'editore: http://www.apsjournals.apsnet.org Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/2067/1611 2009-12-31T23:00:00Z http://hdl.handle.net/2067/1620 Title: ‘Recovery’ from apple proliferation disease: an integrated approach. Authors: Musetti, Rita; Paolacci, Anna Rita; Ciaffi, Mario; Tanzarella, Oronzo A.; Polizzotto, Rachele; Tubaro, Franco; Mizzau, Michela; Ermacora, Paolo; Badiani, Maurizio; Osler, Ruggero Abstract: Recovery is the spontaneous remission, sometimes permanent, from disease symptoms. Phytoplasmas surviving in the roots are not able to recolonise the plant crown. The causes that induce recovery remain still unknown and its physiological bases are poorly understood. In this research the modifications in the phloem tissue related to recovery-induced resistance in apple have been investigated through ultrastructural, chemical, cytochemical and gene expression analyses of leaf tissues from recovered, healthy and apple proliferation-diseased plants. Ultrastructural observations detected abnormal callose and P-protein accumulations in the phloem of recovered apple plants. Callose synthesis and Pprotein plugging, which are Ca2+-dependent, would form physical barriers preventing the in planta movement. The cytochemical localization by potassium pyroantimonate detected the presence of Ca2+ ions in the phloem in all the three groups of plants; however the Ca2+ concentration was remarkably higher in the cytosol of the recovered apple plants. This observation would support the hypothesis that resistance mechanisms would be related to an increased Ca2+- dependent signaling activities. Apple genes coding for callose synthases and phloem proteins were identified by an in silico approach. The expression patterns of five genes encoding callose synthases (MDCALS1/5) and of four genes encoding phloem proteins (MDPP2-1/3 and MDERG1) were analysed by quantitative real time RT-PCR. Four of the nine analysed genes were up-regulated in recovered plants in comparison to healthy and diseased ones, supporting the hypothesis that recovered apple plants were able to develop resistance mechanisms dependent from Ca2+ signal activities. Wed, 31 Dec 2008 23:00:00 GMT http://hdl.handle.net/2067/1620 2008-12-31T23:00:00Z