Apple messenger RNAs related to bacterial lignostilbene dioxygenase and plant SAUR genes are preferentially expressed in flowers

In an attempt to use a differential display procedure to identify organ-specific genes in apple, cDNA fragments of two transcripts preferentially expressed in flowers were isolated and corresponding full-length cDNA inserts were subsequently obtained. One of these clones, Md-FS1, belongs to the SAUR gene family, originally identified as a set of auxin-inducible genes in soybean. The second one, Md-FS2, encodes a polypeptide with sequence similarities to bacterial lignostilbene-alpha,beta-dioxygenase isozymes, which are thought to be involved in lignin biodegradation. Northern blot analysis confirmed that both genes are preferentially expressed in floral organs at full bloom, while being expressed at lower or undetectable levels in vegetative organs (leaves, shoots or roots) as well as in immature, green and unopened blossoms. Furthermore, Md-FS1 transcripts also appeared to accumulate in vegetative tissues after auxin treatment of micropropagated apple shoots.