Identification of pollination-induced genes from the ovary of apple (Malus domestica)

Abstract

 A set of fifteen cDNA clones from apple (Malus domestica Borkh) corresponding to fruit genes induced or enhanced by pollination have been identified by differential hybridization. Expression of corresponding mRNAs was induced in apple flowers by pollination, and in six clones mRNA levels also showed induction by gibberellin treatment of flowers. Sequence analysis and database searches showed that these cDNAs correspond to genes involved in defence responses, transport, protein and flavonoid synthesis, as well as cell division. One of the pollination-enhanced cDNAs was found to be similar to plant and animal genes encoding histone H2B. This mRNA was very highly expressed in flower buds and in fruit at early stages of development, but transcript levels were relatively low in young leaves and shoot tips. RNA in situ hybridization showed histone H2B mRNA detectable at high levels in the nucellus tissue of ovules in unopened flower buds. Five days after pollination, transcript levels decreased in the nucellus; however, weak signals were observed in the fleshy cortex tissue.