PLANT PHYSIOLOGY , Vol 111, Issue 2 541-550, Copyright © 1996 by American Society of Plant Biologists
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CELL BIOLOGY AND SIGNAL TRANSDUCTION |
Tissue-Specific Expression of the Tobacco Mosaic Virus Movement Protein in Transgenic Potato Plants Alters Plasmodesmal Function and Carbohydrate Partitioning
A. A. Olesinski, E. Almon, N. Navot, A. Perl, E. Galun, W. J. Lucas and S. Wolf
Department of Field Crops Vegetables and Genetics and the Otto Warburg Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, Faculty of Agriculture, P.O. Box 12, Rehovot 76100, Israel (A.A.O., E.A., N.N., S.W.)
Transgenic potato (Solanum tuberosum) plants expressing the movement
protein (MP) of tobacco mosaic virus (TMV) under the control of the
promoters from the class I patatin gene (B33) or the nuclear photosynthesis
gene (ST-LS1) were employed to further explore the mode by which this viral
protein interacts with cellular metabolism to change carbohydrate
allocation. Dye-coupling experiments established that expression of the
TMV-MP alters plasmodesmal function in both potato leaves and tubers when
expressed in the respective tissues. However, whereas the size-exclusion
limit of mesophyll plasmodesmata was increased to a value greater than 9.4
kD, this size limit was smaller for plasmodesmata interconnecting tuber
parenchyma cells. Starch and sugars accumulated in potato leaves to
significantly lower levels in plants expressing the TMV-MP under the ST-LS1
promoter, and rate of sucrose efflux from petioles of the latter was higher
compared to controls. It is interesting that this effect was expressed only
in mature plants after tuber initiation. No effect on carbohydrate levels
was found in plants expressing this protein under the B33 promoter. These
results are discussed in terms of the mode by which the TMV-MP exerts its
influence over carbon metabolism and photoassimilate translocation, and the
possible role of plasmodesmal function in controlling these processes.
