Transgenic rice grains expressing a heterologous ρ-hydroxyphenylpyruvate dioxygenase shift tocopherol synthesis from the c to the a isoform without increasing absolute tocopherol levels
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We generated transgenic rice plants overexpressing Arabidopsis thaliana q-hydroxyphenylpyruvate dioxygenase (HPPD), which catalyzes the first committed step in vitamin E biosynthesis. Transgenic grains accumulated marginally higher levels of total tocochromanols than controls, reflecting a small increase in absolute tocotrienol synthesis (but no change in the relative abundance of the a and c isoforms). In contrast, there was no change in the absolute tocopherol level, but a significant shift from the c to the a isoform. These data confirm HPPD is not rate limiting, and that increasing flux through the early pathway reveals downstream bottlenecks that act as metabolic tipping points.
Is part ofTransgenic Research, 2012, vol. 21, núm. 5, p. 1093-1097
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