ASGSB 2003 Annual Meeting Abstracts


CALCIUM SIGNALLING DURING POLARITY DEVELOPMENT IN Ceratopteris richardii.  S.C. Stout1, D.M. Porterfield2 and S.J. Roux11Section of Molecular Cell and Developmental Biology, University of Texas at Austin.  2Department of Biological Sciences, University of Missouri-Rolla.

   We are studying the role of calcium signaling during gravity directed polarity development in the single celled spores of the fern Ceratopteris richardii.  During the first 24 h after light initiation of germination, a calcium influx can be measured at the spore bottom, and a 20-fold larger efflux can be measured from the spore top.  When the spore is rotated, the bottom-to-top calcium current rapidly realigns parallel to the vector of gravity.  Previous measurements of the reorientation time had a minimum resolution of 10 minutes, by which time the calcium current had already reoriented.  Reorientation of the current could be accomplished by either movement of the current proteins through the membrane or by local activation of the current components at the spore top and bottom.  In this study, we were able to make measurements of the calcium current as quickly as 45 s after rotation of the spore.  In all cases (n=26), the calcium current had reoriented before the post-rotation measurements could be made.  The magnitude of the post-rotation top efflux was 101% relative to pre-rotation measurements.  Pre- and post-rotation measurements of the calcium flux at the side of the spore were 17% and 14% respectively, that of the efflux from the spore top before rotation.  Given an average spore diameter of 100 microns, the proteins responsible for the calcium current would have to move half the circumference, approximately 314 microns, in less than 45 s, or nearly 7 microns a second.  Given this data, it is more likely that the current proteins are locally activated at the spore top and bottom during rotation.

(Supported by NASA: NAG10-0295, NAG2-1347, and NGT5-50371)


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