Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/6/2008
Publication Date: N/A
Technical Abstract: Cell wall invertases (CWI) are ionically bound to the plant cell walls. A major CWI, INCW2, provides the gateway to sucrose metabolism in developing maize seeds as it is entirely 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 which confers 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 various cellular approaches including confocal microscopy SEM and TEM approaches that led to the following noteworthy observations: Direct fluorescence by Alexafluor 488, a marker for intracellular membranes, showed that WIGs were unique to the BETCs, and the two genotypes showed no major differences in the architecture of WIGs. Indirect immuno-fluorescence with the same dye and maize INCW2 as the primary antibody showed, as expected, a positive signal in the Mn1 but not in mn1 kernels. The signal was intensely localized to WIGs inside the BETCs and little or no immuno-signal was seen on the primary cell wall. Confocal imaging of the Mn1 RNA and backscatter SEM imaging of INCW2 immuno-gold particles confirmed the immuno-fluorescence results. Most importantly, immuno-electron microscopy on high-pressure frozen samples of 12 DAP Mn1 kernels has confirmed that the INCW2 protein was localized to the WIGs. Possible significance of these data in sugar transport and a potential role of the INCW2 in non-sucrolytic function and metabolic signaling during seed development will be discussed.