95 Comparative Apple-Tomato Genomics to Unravel the 1-MCP Effect on Apple Maturation and Ripening F. Costa 1, 6 , R. Alba 2 , V. Soglio 3 , H.J. Schouten 4 , L. Gianfranceschi 3 , G. Costa 1 , S. Sansavini 1 and J. Giovannoni 2, 5 1 Department of Fruit Tree and Woody Plant Science, University of Bologna, Viale Fanin 46, 40121 Bologna, Italy 2 Boyce Thompson Institute for Plant Research, Cornell Campus, 14850 Ithaca, New York, USA 3 Dept. of Biomolecular Sciences & Biotechnology, University of Milano, via Celoria 26, 20133 Milano, Italy 4 Plant Research International, Droevendaalsesteeg 1, 6700 AA Wageningen, The Netherlands 5 U.S. Department of Agriculture, Agricultural Research Service, Plant, Soil and Nutrition Laboratory, Ithaca, New York, 14853, USA 6 IASMA Research and Innovation Centre/Fondazione Edmund Mach- Genomics and Crop Biology Area, San Michele a/Adige, Trento, Italy Keywords: microarry, gene discovery, transcriptome profiling, heterologous hybridization, ethylene Abstract Ethylene is a gaseous hormone that in higher plants controls several physiological aspects. In climacteric species, like apple and tomato, this hormone plays a crucial role triggering and coordinating most of the ripening evolution. To identify the putative gene set impacting the apple fruit ripening, we have carried out a two-way microarray approach: performing homologous and heterologous hybridizations. In the cross species comparison we adopted the genomic resources available for tomato, to date recognized as the reference species for ripening investigation. In our experimental design we characterized the ethylene evolution and fruit softening dynamic over the fruit maturation and ripening of ‘Mondial Gala’ apple cultivar. To investigate the transcriptome ethylene regulation we applied 1-MCP at harvest, causing an evident distortion in the normal ripening physiology. Functional comparison between control and 1-MCP samples allowed the identification of an ethylene responsive gene set, specifically highlighting elements positively and negatively regulated by 1-MCP. The comparison between the two genomic platforms (homologous and heterologous) enable a preliminary investigation addressed to define a functional orthologous gene set commonly involved in the regulation of the climacteric ripening between the two species. INTRODUCTION Fruit undergo a complex changes during maturation and ripening, involving variation in colour, fruit texture and modification of important biochemical pathways enabling aroma formation. In climacteric fruits all these changes are triggered and coordinated by the presence of the hormone ethylene, a gas playing a fundamental role in the ripening control. Climacteric fruits, like apple, peach, banana, tomato and kiwifruit, despite the non-climacteric ones, has a typical hormone burst approximately coincident with the rise in respiration, and both phenomena occurs normally at the end of the ripening phase (Barry and Giovannoni, 2007; Cara and Giovannoni, 2008). However, it has been recently elucidated that in fruit are commonly present dependent and independent ethylene regulation (Lelievre et al., 1997). In non-climacteric fruits, ethylene normally doesn’t physiologically increase during maturation and the respiration rate continuously decreases. However, this hormone if exogenously applied is able to affect the normal physiology (Tesniere et al., 2004), Proc. XI th IS on Plant Bioregulators in Fruit Production Ed.: G. Costa Acta Hort. 884, ISHS 2010