Poster: Cell Walls

Abs # 1254: Altered expression of the tomato LeAGP-1 arabinogalactan-protein affects lateral branching and fruit production

Presenter:	Sun, Wenxian , ws341890@ohiou.edu
Authors	Sun, Wenxian  (A) (C)  Kieliszewski, Marcia  (B) (C)  Showalter, Allan  (A) (C)
Affiliations:	(A): Dept. of Environmental and Plant Biology, Ohio University (B): Dept. of Chemistry and Biochemistry, Ohio University (C): Molecular and Cellular Biology Program, Ohio University

LeAGP-1 represents a glycosylphosphatidylinositol(GPI)-anchored arabinogalactan-protein (AGP) in tomato (Lycopersicon esculentum). The patterns of mRNA expression and protein localization for LeAGP-1 indicate that this AGP likely functions in certain aspects of plant growth and development. To more specifically elucidate LeAGP-1 function(s), transgenic tomato plants expressing enhanced green fluorescence protein (GFP) fused to LeAGP-1 [GFP-LeAGP-1] or an LeAGP-1 variant, lacking the GPI-anchor domain [GFP-LeAGP-1DC], under the control of the CaMV35S promoter were produced using Agrobacterium-mediated transformation. Transgenic lines with high levels of both GFP-LeAGP-1 mRNA and LeAGP-1 protein: 1) were significantly shorter (some were only one-third as tall as GFP-transformed plants); 2) were highly branched (1.5-3 times as much branching as control plants); 3) produced more flower buds, but most of these flowers did not mature, resulting in less fruit production; and 4) produced seeds that were significantly smaller than normal seeds. Transgenic plants overexpressing GFP-LeAGP-1DC showed a similar phenotype except that these plants produced seeds of normal size. The second generation of the GFP-LeAGP-1 transgenic plants revealed that the mutant phenotypes correlated with high levels of LeAGP-1 mRNA. Since the phenotype of the GFP-LeAGP-1 overexpressing transgenic plants is similar to that of cytokinin-overproducing plants, the mRNA expression patterns of LeAGP-1 under different hormone treatments were studied. Cytokinins were found to up-regulate LeAGP-1 mRNA expression, while auxins and ABA were found to down-regulate LeAGP-1 mRNA expression. Based on the above results, we speculate that the GPI-anchored LeAGP-1 might be an extracellular mediator of cytokinin action.