THE PLANT CELL, Vol 6, Issue 5 601-612, Copyright © 1994 by American Society of Plant Biologists
A Truncated Version of an ADP-Glucose Pyrophosphorylase Promoter from Potato Specifies Guard Cell-Selective Expression in Transgenic Plants
B. Muller-Rober, U. L. Cognata, U. Sonnewald and L. Willmitzer
Institut fur Genbiologische Forschung Berlin GmbH, Ihnestrasse 63, 14195 Berlin, Germany
ADP-glucose pyrophosphorylase (AGPase) is a key regulatory enzyme in starch
biosynthesis in higher plants. A 3.2-kb promoter of the large subunit gene
of the AGPase from potato has been isolated and its activity analyzed in
transgenic potato and tobacco plants using a promoter-[beta]-glucuronidase
fusion system. The promoter was active in various starch-containing cells,
including guard cells, tuber parenchyma cells, and the starch sheath layer
of stems and petioles. No expression was observed in mesophyll cells.
Analysis of various promoter derivatives showed that with respect to
expression in petioles and stems, essential elements must be located in the
5[prime] distal region of the promoter, whereas elements important for
expression in tuber parenchyma cells are located in an internal fragment
comprising nucleotides from positions -500 to -1200. Finally, a 0.3-kb
5[prime] proximal promoter fragment was identified that was sufficient to
obtain exclusive expression in guard cells of transgenic potato and tobacco
plants. The implications of our observations are discussed with respect to
starch synthesis in various tissues and the use of the newly identified
promoter as a tool for stomatal biology.
