Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 5.32

CHARACTERISATION OF DNA EPISOMES IN TUBER SPECIES

C. COSENTINO, B. LAZZARI, A. VIOTTI

Istituto Biologia e Biotecnologia Agraria, CNR, Milano

tuber species, episomes, T. borchii

Total DNAs from ascomata of different Tuber species were purified by CsCl gradient centrifugation and further treated with RNase and proteinase K. The analysis by agarose gel electrophoresis and ethidium bromide staining of eight different species displaies discrete size bands that migrate faster with respect to bulk DNA. Each species shows a specific band pattern with apparent electrophoretic mobility ranging between 0.7 and 11 kb. Among the various Tuber species, T. borchii was chosen as the elite one since in vitro liquid and solid cultures of hyphae can be obtained and as it is one of the best characterised at molecular level. T. borchii shows two main groups of faster migrating bands or episomes in the 7.0 (1Tb) and 2.5 (2Tb) kb region. Similarly, Tuber magnatum shows one major group of bands around 2.5 kb (1Tm). Episomes were found to be degraded by DNaseI while were resistant to both ExoIII and lambda-exo activities, suggesting a covalently circular closed feature for these episomes. In Southern blot analysis each group of episomes results to be specific within the same species and also among the other species. In particular, 1Tb and 2Tb were recovered in in vitro hyphae cultures. Preliminary data by northern blot analysis also indicate that episome probes hybridise to RNA molecules of different sizes suggesting a possible role in expressing their genetic information.

Currently, episome DNA fragments are under cloning and subsequent DNA sequences will allow a more precise identification of their functional roles.