Expression of a modified ADP-glucose pyrophosphorylase large subunit in wheat seeds stimulates photosynthesis and carbon metabolism |
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Authors: | Eric D Smidansky Fletcher D Meyer Beth Blakeslee Thaddeus E Weglarz Thomas W Greene Michael J Giroux |
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Institution: | (1) Department of Plant Sciences and Plant Pathology, Montana State University-Bozeman, Ag. BioSci. Fac., Bozeman, MT 59717, USA;(2) Dow AgroSciences, 9330 Zionsville Road, Building 306, C1-249, Indianapolis, IN 46268, USA;(3) Present address: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA |
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Abstract: | ADP-glucose pyrophosphorylase (AGP) is the rate-limiting step in seed starch biosynthesis. Expression of an altered maize
AGP large subunit (Sh2r6hs) in wheat (Triticum aestivum L.) results in increased AGP activity in developing seed endosperm and seed yield. The yield phenotype involves increases
in both seed number and total plant biomass. Here we describe stimulation of photosynthesis by the seed-specific Sh2r6hs transgene. Photosynthetic rates were increased in Sh2r6hs-expressing plants under high light but not low light growth conditions, peaking at roughly 7 days after flowering (DAF).
In addition, there were significant increases in levels of fructose, glucose, and sucrose in flag leaves at both 7 and 14
DAF. In seeds, levels of carbon metabolites at 7 and 14 DAF were relatively unchanged but increases in glucose, ADP-glucose,
and UDP-glucose were observed in seeds from Sh2r6hs positive plants at maturity. Increased photosynthetic rates relatively early in seed development appear to be key to the
Sh2r6hs enhanced yield phenotype as no yield increase or photosynthetic rate changes were found when plants were grown in a suboptimal
light environment. These findings demonstrate that stimulation of biochemical events in both source and sink tissues is associated
with Sh2r6hs expression. |
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Keywords: | ADP-glucose pyrophosphorylase Endosperm Gene up regulation Photosynthesis Source– sink relations Wheat Yield |
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