Analysis of Expressed Sequence Tags from Japanese pear (Pyrus pyrifolia). Pears (Pyrus spp.) are member of the family Rosaceae, subfamily Maloideae, same as apples (Malus spp.). Recently, over 10,000 pear cDNAs were analyzed by microarray and some novel important genes relating to fruit development and parthenocarpy were extracted (Nishitani et al., 2010, Nishitani et al., 2012). However, apple whole genome analysis showed that the predicted number of apple genes is 57,386 by using Sanger method and pyrosequencing method (Velasco 2010). It is known that though the genome sizes of pear and apple are different each other (approximately 500 Mb and 750 Mb in pear and apple, respectively), they are related species and their genomic structures are very similar to each other, so it is predicted that the number of the pear genes might be the same level as apple. So as to increase our understanding of the genetic control of pear development, to correct the wide range of genetic information from pear is needed. In addition, because pears are the second major Maloideae fruit following to apples, its genetic information is very useful to understand the unique phenomenon in Maloideae or Rosaceae crops. Recently, in many plant species, the comprehensive genomic analyses make it possible to establish the overall picture of the information contained in the genomes of populous (Tuskan et al., 2006), grapes (The French–Italian Public Consortium for Grapevine Genome Characterization, 2007), papaya (Ming et al., 2008), apple (Velasco et al., 2010), strawberry (Shulaev et al., 2011), citrus (Gmitter et al., 2012), tomato (The Tomato Genome Consortium, 2012) and so on. The accumulation of the whole genome information in a variety of species has made it possible, not only to analyze the individual species, but also to perform the comparative genomic analysis to extract the common or specific genes related to each phenomenon, like fruits enlargement and tree development. As with these species, appearance of the next-generation sequencer would make it possible to complete pear whole genome sequencing in the future. In the absence of complete genome sequences, the ESTs (expressed sequence tags) originated from cDNAs provide a robust sequence resource that can be exploited for gene discovery, genome annotation and comparative genomics (Rudd, 2003). And even if pear whole genome sequence information is fully available, the sources of information based on actual cDNA are indispensable. Currently, in the NCBI EST database, approximately 2000 pear ESTs are published. This number is too few compared to the number of the genes in the other plant species. In this study, the EST data set for various tissues of Japanese pear is generated by using both of Sanger and pyrosequencing method
Less...