Overexpression of tomato LeAGP-1 arabinogalactan-protein promotes lateral branching and hampers reproductive development.
LeAGP-1 is a glycosylphosphatidylinositol (GPI)-anchored arabinogalactan-protein (AGP) in tomato (Lycopersicon esculentum). Patterns of mRNA expression and protein localization for LeAGP-1 indicate that it likely functions in certain aspects of plant growth and development. To elucidate LeAGP-1 function(s), transgenic tomato plants expressing enhanced green fluorescent protein (GFP) fused to LeAGP-1 [GFP-LeAGP-1] or two LeAGP-1 variants, one lacking the C-terminal GPI-anchor domain [GFP-LeAGP-1DeltaC] and the other lacking the lysine-rich domain [GFP-LeAGP-1DeltaK], under the control of the CaMV35S promoter were produced using Agrobacterium-mediated transformation. Transgenic T0 and T1 lines with high levels of both GFP-LeAGP-1 mRNA and protein: (i) were significantly shorter; (ii) were highly branched; (iii) produced more flower buds, but most of these flowers did not mature, resulting in less fruit production; and (iv) produced seeds that were significantly smaller than normal seeds. Overexpression of LeAGP-1DeltaK had a similar or even more pronounced effect on plant vegetative and reproductive growth, while the effect of LeAGP-1DeltaC overexpression on plant reproduction was minimal. These results indicate that the GPI anchor is critical for LeAGP-1 function. As the phenotype of GFP-LeAGP-1 overexpressing transgenic plants is similar to that of cytokinin-overproducing plants, mRNA expression patterns of LeAGP-1 under different hormone treatments were examined. Cytokinins upregulated LeAGP-1 mRNA expression, while auxins and ABA inhibited LeAGP-1 mRNA expression. Based on these results, GPI-anchored LeAGP-1 most likely functions in plant growth and development in concert with auxin/cytokinin signaling.
Sun
Wenxian
W
Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701-2979, USA.
Kieliszewski
Marcia J
MJ
Showalter
Allan M
AM
D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D009088:Mucoproteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
D009088:Mucoproteins; D010940:Plant Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C006619:arabinogalactan proteins