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

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 1.03

THE AtRHA1 GENE OF ARABIDOPSIS: STRUCTURE AND POSSIBLE FUNCTIONS

S. PICONESE, C. ROSI, F. MIGLIACCIO

Institute of Agroenvironmental and Forest Biology; Consiglio Nazionale delle Ricerche, Via Salaria Km 29.300, 00016 Monterotondo (Roma), Italy

Arabidopsis, gravitropism, auxin, HSFs

The mutant Atrha1 shows in the roots reduced gravitropic response, reduced slanting toward the right-hand, and increased resistance to the auxinic hormones, their inhibitors, and ethylene. Taking advantage of a T-DNA tag inserted in AtRHA1, the gene was cloned through the TAIL-PCR technique. The gene appears to be a new heat shock factor (HSF) of Arabidopsis, made up of three EXONS, two of which translated, and two INTRONS. It maps on chromosome 5, close and above the RFLP marker mi61. Through RT-PCR it was confirmed that the gene is expressed in the wild-type, but not in the mutant. Complementation of the Atrha1 mutants with the wild type gene abolished the mutated phenotype.

AtRHA1 shows notable homology in the DNA binding motif, at the level of the aminoacid sequence, with other HSFs from plants (Arabidopsis, Licopersicum peruvianum, maize), Coenorhabdites, Drosophila, mouse, yeast, and humans. It belongs to the A group of plant HSFs. We suggest that AtRHA1, apart its function in the activation of Heat Shock Proteins, could be involved in the transduction of signals coming from gravity and auxin.. Possibly, as shown for the HSF2 from humans (Hong and Sargent, 1999 J. Biol. Chem. 274, 12967- 70), it could be involved in the regulation of the PP2A phosphatase, which has been demonstrated to regulate the transport of auxin in Arabidopsis (Garbers et al. 1996 EMBO J. 15, 2115-24).