OTC and AUL1, two convergent and overlapping genes in the nuclear genome of Arabidopsis thaliana

In contrast to bacterial, fungal and, vertebrate ornithine transcarbamylase s (OTCs; EC 2.1.3.3), very little is known about the enzyme in plants, We r eport here the isolation of a T-DNA-tagged mutant displaying sensitivity to ornithine, whose characterization has allowed for the identification of se veral complementary and genomic DNA clones encoding the OTC and auxilin-lik e 1 (AUL1) proteins of the crucifer Arabidopsis thaliana. Transcript mappin g revealed that at least 22 bp within the OTC-A UL1 interceding region are transcribed from both strands, which makes this one of the rarely described cases of convergent and overlapping transcription units in the nuclear gen ome of a multicellular eukaryote, Transcription of the OTC gene was shown t o be ubiquitous in aerial organs of adult plants, whereas that of AUL1 was obscured by the existence of a putative second copy of the gene. The OTC-AU L1 locus maps at the bottom of chromosome 1. (C) 1999 Federation of Europea n Biochemical Societies.