Smidansky Eric D, Meyer Fletcher D, Blakeslee Beth, Weglarz Thaddeus E, Greene Thomas W, Giroux Michael J
Department of Plant Sciences and Plant Pathology, Montana State University-Bozeman, Ag. BioSci. Fac., Bozeman, MT 59717, USA.
Planta. 2007 Mar;225(4):965-76. doi: 10.1007/s00425-006-0400-3.
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.
ADP - 葡萄糖焦磷酸化酶（AGP）是种子淀粉生物合成中的限速步骤。在小麦（Triticum aestivum L.）中表达改变的玉米AGP大亚基（Sh2r6hs）会导致发育中的种子胚乳中AGP活性增加以及种子产量提高。产量表型包括种子数量和植株总生物量的增加。在此我们描述了种子特异性Sh2r6hs转基因对光合作用的刺激作用。在高光而非低光生长条件下，表达Sh2r6hs的植株光合速率增加，在开花后约7天（DAF）达到峰值。此外，在7天和14天DAF时，旗叶中的果糖、葡萄糖和蔗糖水平均显著增加。在种子中，7天和14天DAF时的碳代谢物水平相对未变，但在成熟时，Sh2r6hs阳性植株的种子中观察到葡萄糖、ADP - 葡萄糖和UDP - 葡萄糖增加。在种子发育相对早期光合速率的增加似乎是Sh2r6hs增强产量表型的关键，因为当植株在次优光照环境中生长时未发现产量增加或光合速率变化。这些发现表明，源组织和库组织中生化事件的刺激都与Sh2r6hs的表达相关。
