CONICET | Buscador de Institutos y Recursos Humanos

Transcription initiation by RNA polymerase II is unidirectional from most genes. In plants, divergent genes, defined as nonoverlapping genes organized head-to-head, are highly represented in the Arabidopsis genome. Nevertheless, functional analyses of these intergenic regions are lacking. The At5g06290 and At5g06280 loci are head-to-head oriented and they encode a chloroplast located 2-Cys peroxyredoxin B (2CPB) and a protein of unknown function (PUF), respectively. In the present study, we characterized the transcriptional activity of a small intergenic region (351 bp) shared by At5g06290 and At5g06280 in both orientation in Arabidopsis thaliana. This activity was analyzed by driving the GUS reporter gene during development and growth of Arabidopsis plants under physiological and stressful conditions. Results showed that this region drives expression either of 2cpb or puf in photosynthetic or vascular tissues, respectively. The promoter in both orientations showed similar regulation of GUS expression by temperature and other stress conditions such as mannitol, oxidative stress or fungal elicitor. Our results provide the first evidences of an intergenic region that in opposite orientation directs GUS expression in different spatially localized Arabidopsis tissues in a mutually exclusive manner. Additionally, this is the first demonstration of a small intergenic region that drives expression of a gene whose product is involved in the chloroplast antioxidant defense such as 2cpb