Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

ISOLATION AND SEQUENCE ANALYSIS OF THE PROMOTER REGION OF A DEHYDRIN-ENCODING GENE OF SUNFLOWER

GIORDANI T., NATALI L., MAESTRINI P., CAVALLINI A.

Dipartimento di Biologia delle Piante Agrarie, Sezione di Genetica, Via Matteotti 1/B, 56124 Pisa

dehydrin, promoter, sunflower, water stress

Dehydrins are an immunologically distinct family of proteins, also known as the Lea D11 subgroup of late-embryogenesis-abundant (Lea) proteins and have been described in many angiosperm and gymnosperm species (Close 1997). They are characterized by typical domains, including one or more putative amphipatic a-helix forming consensus regions at the C-terminus, and, in the majority of dehydrins, a region at the N-terminus with homologies to a portion of the nucleotide binding site of chaperones of plants and bacteria. Dehydrins are usually produced by plants in the late stages of embryo development but also following any environmental stimulus involving dehydration, such as drought or cold stress and salinity, and are supposed to be key components of dehydration tolerance (Close 1996).

A dehydrin cDNA, HaDhn1, induced by drought stress, has been isolated and sequenced in sunflower (Ouvrard et al. 1996); the accumulation of HaDhn1 transcripts has been found to correlate to drought tolerance (Cellier et al. 1998). A sequence allelic to this gene, HaDhn1a, was found to be expressed in the latest stages of Helianthus annuus embryogenesis, depending on abscisic acid accumulation; HaDhn1a transcripts accumulated after drought stress even in ABA-deficient sunflower mutants (Giordani et al. 1999). Moreover, HaDhn1a is expressed also in plantlets exposed to low temperatures.

In subsequent experiments, we isolated the putative promoter sequence of the HaDhn1a gene using a RAGE (Rapid Amplification of Genomic Ends) protocol. After digestion of genomic DNA with Hind III, we added by terminal transferase a poly-C trait at 3’-ends; then, a 699 bp-long DNA sequence upstream the coding portion of the dehydrin gene was amplified by PCR, using primers homologous to poly-C and internal to the dehydrin coding sequence, and cloned.

Sequence analysis showed that different putative cis-elements recognizable by transcription factors occur in the isolated sequence: beside the putative TATA box (at -76 bp), one ABA-responsive element (ABRE), one dehydration responsive element (DRE), a G-box and some MYB- and MYC- related elements were found. Similar cis-elements were observed in promoter regions from other plant species, for example barley (Choi et al. 1999), and they may account for the complex regulation pattern of these genes, that are transcribed following different environmental stimula. The use of a construct including this promoter sequence and a reporter gene in transformation experiments will allow to evaluate the environmental changes to which this promoter responds.