EXPRESSED SEQUENCE TAGS OF FRUITS, PEELS, AND CARPELS AND ANALYSIS OFMESSENGER-RNA EXPRESSION LEVELS OF THE TAGGED CDNAS OF FRUITS FROM THE FUJI APPLE

In order to understand molecular events during fruit development and p rovide genetic resources for molecular breeding, 430 expressed sequenc e tags (ESTs) were generated from randomly selected clones of cDNA lib raries prepared from young fruits, peels of mature fruits, and carpels of the Fuji apple (Mabs domestica Borkh,), Database comparisons of th e ESTs revealed that 180 non-redundant clones showed a high similarity with previously identified genes. Among these, 138 clones exhibited a homology with previously identified plant genes and 12 were identical to genes that were previously identified from apples. The deduced ami no acid sequences of 42 clones had a homology to proteins that have no t been reported from plants. Eighteen cDNA clones from the young fruit library were selected for studying expression levels and patterns in reproductive organs and leaves. This study revealed that the clones ca n be classified into 3 different groups based on their expression leve ls. The first 9 clones were expressed strongly in at least one reprodu ctive organ. Eight of these clones (vacuolar processing protease, sucr ose phosphate synthase, arabinogalactan protein, UDP-glucose glucosyl transferase, major allergen D1, cystein proteinase inhibitor, lipoxyge nase, and protease subunit SUG2) were highly expressed in mature flowe rs and young fruits, whereas one clone (z-carotene desaturase protein precursor) was preferentially expressed in mature flowers but weakly i n young fruits. The second group includes 6 cDNA clones (glucose trans port protein, aminomethyl transferase precursor protein, dTDP-D-glucos e-4,6-dehydrogenase, 2 types of protein kinase, and selenium binding p rotein) that were weakly expressed. These clones were characterized by their preferential expression patterns in mature flowers and young fr uits. The transcripts of 3 cDNA clones in the third group (vacuolar am inopetidase, beta-galactosidase, and EREBP-4) were detectable only by RT-PCR and they were preferentially expressed in young fruits. These r esults indicate that most ESTs that were isolated from young fruits ar e preferentially expressed in reproductive organs and thereby play imp ortant roles during reproductive organ development.