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 - 1.21

INVOLVEMENT OF AtMYB41 GENE IN OSMOTIC STRESS RESPONSE IN ARABIDOPSIS THALIANA

E. COMINELLI, D. CALVI, T. SALA, C. TONELLI

Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Via Celoria 26, 20133 Milano

R2R3MYB, drought, salt stress, abi mutants

In the last years it has been demonstrated that overexpression of some transcription factors in transgenic plants activates many stress tolerance genes and improves plant tolerance to osmotic stresses. This shows that characterization of transcription factors that control the coordinate expression of multiple genes involved in stress response is very important in the perspective of improving plants tolerance.

Analysis of the expression of dehydration-inducible genes in Arabidopsis have indicated that at least four independent signal pathways function in the induction of these genes. Two are abscisic acid (ABA) -dependent and two are ABA-independent.

In this study we analyzed the expression pattern of AtMYB41 gene, belonging to the R2R3 MYB family of Arabidopsis, in response to different osmotic stresses in wild type and abi mutants plants. Then we analyzed molecularly and phenotipically plants overexpressing this gene.

AtMYB41 is not expressed in any organs and at any developmental stages in wild type plants grown in normal conditions, while its transcript is accumulated in a specific manner in response to drought, PEG and NaCl treatments, but not after ABA supply. Expression pattern of AtMYB41 gene in response to ABA treatment in wild type plants has been compared to that obtained in ABA-insensitive mutants abi1-1 and abi2-1. In this cases AtMYB41 m-RNA is accumulated during the treatment, suggesting a role for ABI1 and ABI2 phosphatases in the regulation of this gene activity.

The overexpression of AtMYB41 in transgenic plants (35S::AtMYB41) results in severe growth retardation under control conditions. A phenotypic characterization of 35S::AtMYB41 plants is in progress to understand if reduced plants dimensions are a consequence of problems in cell expansion or in cell division.

The expression patterns of some stress induced genes were compared between wild type and 35S::AtMYB41 plants in normal growth conditions and in response to PEG and NaCl treatments. Since so far no differences have been detected, we decided to do a large scale analysis through the hybridization of macroarrays containing 8000 Arabidopsis ESTs.

35S::AtMYB41 plants did not show improved tolerance in response to drought and salt stresses. Probably AtMYB41 constitutive expression is too dangerous for the plants. Transgenic plants harbouring AtMYB41 fused downstream the drought inducible promoter of RD29A gene, are now under analysis.

Transgenic plants for a construct harbouring a 1kb sequence of the putative AtMYB41 promoter fused upstream the GUS reporter gene are also under analysis.