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

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 3.39

CHANGING THE SHAPE OF PETUNIA COROLLA

ZENONI S.*, REALE L.**, TORNIELLI G.B.*, LANFALONI L.***, MORETTI C.**, FERRARINI A.*, ZAMBONI A.*, ROMANO B.**, FERRANTI F.**, PEZZOTTI M.*

*) Dip. Scientifico e Tecnologico, Università degli Studi di Verona

**) Dip. di Biologia Vegetale e Biotecnologie Agroambientali, Università degli Studi di Perugia

***) Dip. di Biologia Cellulare e Molecolare Università degli Studi di Perugia

expansin, antisense, transposon mutagenesis, flower, Petunia hybrida

Plant cells do not migrate during development as do animal cells, and organ shape is determined by organised and regulated control of cell expansion together with cell division. For plant organs to attain their final morphology and function properly, constituent cells must regulate tightly the way in which they expand. Emerging data support the view that the direction and magnitude of the enlargement of the primary cell wall largely determine the expansion pattern and thereby the final shape and size of the cells.

Cell wall proteins are believed to play important roles in regulating cell wall extensibility which is a key parameter determining cell expansion. Among cell wall proteins studied to date, expansins are unique in the ability to induce immediate cell wall extension in vitro and cell expansion in vivo. Expansins are classified as “primary wall loosening agents” referring to their capacity to induce stress relaxation of cell wall. Expansin proteins have been identified in many plant species and organs on the basis of the activity assay and immunoblotting.

During flower development, floral organs typically assume their final shape after mitotic activity has basically ceased, indicating that cell expansion plays an important role in determining organ shape. To initiate the investigation on the function of expansins in vivo and during plant development, we cloned PhExp1, a Petunia hybrida a-expansin-like gene, determined its pattern of spatial and temporal expression in plant and flower organs and generated transgenic Petunia lines that express the cDNA encoding PhExp1 in the antisense orientation under control of the strong and constitutively expresses cauliflower mosaic virus (CaMV) 35S promoter. This approach allowed us to analyse the phenotypes of plants that showed significantly reduced expression of PhExp1 in comparison to wild type plants. PhExp1 insertion mutants were also isolated in two dTph1 mutagenised populations.