Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/27/2008
Publication Date: N/A
Technical Abstract: Cell wall invertases (CWI) are ionically bound to the cell wall in plant cells. A major CWI, INCW2, encoded by the Mn1 gene, provides the gateway to sucrose metabolism in developing seeds as it is entirely and exclusively localized to the BETCs that juxtapose the pedicel. The loss of INCW2 protein is the causal basis of the mn1 seed phenotype with a loss of > 70% seed weight at maturity. A ubiquitous feature of all transfer cells is labyrinth wall, the WIGs, that increases the plasma membrane area – a feature believed to confer greater solute transport capacity to these cells. To better understand the roles of the INCW2, the WIGs and various cellular details of transport functions in the BETCs, 12 DAP Mn1 and mn1 kernels were examined by confocal, microscopy SEM and TEM approaches with the following noteworthy observations: Direct fluorescence by Alexafluor 488, a marker for intracellular membranes, showed that WIGs were unique to the BETCs, and no major differences were seen in the architecture of WIGs in the two genotypes. Indirect immuno-fluorescence using the same dye conjugated to a secondary antibody and maize INCW2 as the primary showed, as expected, a positive signal in the Mn1 but not in mn1 kernels. More importantly, the signal was intensely localized to WIGs inside the BETCs and very little or no immuno-signal was seen on the primary cell wall. Confocal imaging of the Mn1 RNA after in situ hybridization and backscatter SEM imaging of INCW2 immuno-gold particles confirmed the immuno-fluorescence experiment results. Localization of the INCW2 protein in high-pressure frozen samples by immuno-electron microscopy is in progress. Possible significance of the collective data in sugar transport will be discussed.