Submitted to: Plant Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/1998
Publication Date: N/A
Interpretive Summary: Understanding the structural organization of genes is one of the most essential components of the Plant Genome research. Such structural details, including the DNA sequences, are essential because they provide clues to structure - function relationship, and potential basis for their precise regulation at appropriate time and space in the plant. Here we describe the results of collaborative research done by scientists at the ARS, Crop Genetics & Environmental Research Unit, University of Florida, Gainesville, FL, and Institut de Biotechnologie des Plantes, Orsay, France. Briefly, we describe the first molecular architecture of two invertase genes in maize. The two genes encode two separate forms of the enzyme invertases that are associated with plant cell walls and are essential for breakdown of sucrose to simple sugars - a critical step in the normal utilization of photosynthesized sucrose. For example, our previous ARS research has shown that a loss of one of these two invertases in a developing seed by mutation leads to a reduction of ~ 75% of the total seed weight. Thus, the molecular knowledge obtained in this study provides us the essential genetic tool kit to better understand how to modify these genes to attain greater productivity.
Technical Abstract: Acid invertases are glycoproteins that catalyze the hydrolysis of sucrose to glucose and fructose and are associated with metabolic sink tissues in a variety of plant species. Acid invertases are divided into cell wall-bound invertases (INCW) and soluble invertases based on their location in the cell. We describe here the isolation and characterization of two cell wall invertase cDNA (Incw1 and Incw2) and genomic (respectively, pC3 and pC1 clones. Both pC3 and pC1 genomic clones have six introns and seven exons typical of most other acid invertase genes. Since the deduced amino acid sequence of Incw1 and Incw2 cDNA clones are more similar to several cell wall invertases from other species than they are to maize soluble invertase; we conclude Incw1 and Incw2 represent cell wall-bound invertases. Incw1 mRNA is present in cell suspension culture, etiolated shoots, roots and, at much reduced steady state levels, in developing endosperm. In contrast, Incw2 mRNA is present in developing endosperm, but lacking in the miniature-1(mn1-1) seed mutant endosperm, and etiolated shoots. In situ hybridization studies show that the Incw2 mRNA is confined to the basal endosperm transfer cells in a developing kernel.