USING PETUNIA HYBRIDA AS A MODEL SYSTEM TO STUDY THE ROLE OF EXPANSINS IN PLANT DEVELOPMENT

In plants, organ shape is determined by organised and regulated control of cell expansion and division. 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. Studies of expansin gene expression indicate that the different expansin genes are expressed in different organs, tissues and cell type, and they respond distinctively to such treatments as hormones, light, pollination. The reverse genetics approach based on transposon mutagenesis was used to study the function of Petunia hybrida expansin genes. An insertion allele was isolated in the promoter region of the PhEXP1. The plants with the homozygous insertion of dTph1 transposon element show morphological alterations affecting the flowers. PhEXP1 expression levels in mutant plants was characterised by by Real-Time RTPCR. The PhEXP1 promoter region was also studied by fusion with the reporter genes β-glucoronidase (GUS) and GFP.