45:	A transposon insertion in the LACERATA gene of Arabidopsis thaliana, a cytochrome P450 enzyme, results in ectopic postgenital organ fusions.

Authors:	Wellesen, Kirsten(A)Saedler, Heinz(A)Wisman, Ellen(A)Yephremov, Alexander(A)
Affiliations:	(A): MAX-PLANCK Institut fuer Zuechtungsforschung, Molek. Pflanzengenetik (B): MSU-DOE Plant Research Laboratory, Michigan State University
Presenter:	Yephremov, Alexander , efremov@mpiz-koeln.mpg.de

Epidermal cells of aerial organs of plants usually do not respond to contact with other cells, even through grafting or after the cuticle has been removed. Several mutants have been described to date which exhibit ectopic fusion of organs. The lacerata mutant was isolated from an A.thaliana population mutagenized with the En/Spm transposon. The rosette leaves of this mutant show strong postgenital fusions, which can cause the leaves or pedicels to be torn during later growth. Weak fusions of floral organs were also observed in some mutant plants. The leaf shape of lacerata mutants is abnormal, and plants show reduced apical dominance and reduced size. The mutant phenotype co-segregates with a stable transposon insertion of 1.2 kb in a non-transcribed region upstream of an ORF encoding a cytochrome P450 enzyme. Corresponding transcripts were detected in all parts of wild type plants, predominantly in 2 week old whole seedlings and inflorescences. Northern blot analysis and RT-PCR demonstrate that the transposon insertion results in reduced expression of this gene. Lacerata plants, transformed with a construct containing a 4.0 kb genomic region of this cytochrome P450 gene, including the promoter and 3' UTR, restored the wild-type phenotype. Ectopic expression of antisense RNA using the 35S CaMV promoter in wild-type plants resulted in lacerata phenocopies. Sequence similarity suggests a putative function of the LACERATA cytochrome P450 enzyme in hydroxylation of lipids.