PLANT PHYSIOLOGY , Vol 104, Issue 2 535-540, Copyright © 1994 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
Temporal and Spatial Expression Pattern of Sucrose Synthase during Tomato Fruit Development
F. Wang, A. G. Smith and M. L. Brenner
Departments of Horticultural Science (F.W., A.G.S., M.L.B) and Plant Biology (M.L.B), University of Minnesota, St. Paul, Minnesota 55108
Sucrose synthase is proposed to play an important role in the early stages
of tomato fruit (Lycopersicon esculentum Mill.) growth. In this work, the
temporal and spatial expression patterns of sucrose synthase during tomato
fruit development were investigated. Fruit contained the majority of the
sucrose synthase protein and mRNA relative to other organs. Only trace
levels of sucrose synthase protein and mRNA were detected in the stem,
petiole, and roots. Sucrose synthase mRNA was detected in pistils prior to
anthesis, reached peak levels in fruit 5 to 7 d after anthesis (DAA), and
was not detectable after 35 DAA. Sucrose synthase protein levels reached a
maximum at 20 to 25 DAA and then declined to nondetectable levels after 45
DAA. The lack of coordination between protein and mRNA levels suggests that
sucrose synthase expression may be controlled at the levels of both
transcription and translation. Sucrose synthase mRNA was differentially
localized in the fruit, being most abundant in the mesocarp cells adjacent
to the placenta, the columella, and the cells surrounding the vascular
bundle. Except around the vascular tissue, the localization of sucrose
synthase mRNA positively correlates with starch granule accumulation at the
cellular level.
