Engineering starch accumulation by manipulation of phosphate metabolism of starch.
A new understanding of leaf starch degradation has emerged in the last 10 years. It has been shown that starch phosphorylation and dephosphorylation are critical components of this process. Glucan, water dikinase (GWD) (and phosphoglucan, water dikinase) adds phosphate to starch, and phosphoglucan phosphatase (SEX4) removes these phosphates. To explore the use of this metabolism to manipulate starch accumulation, Arabidopsis (Arabidopsis thaliana) plants were engineered by introducing RNAi constructs designed to reduce expression of AtGWD and AtSEX4. The timing of starch build-up was altered with ethanol-inducible and senescence-induced gene promoters. Ethanol induction of RNAi lines reduced transcript for AtGWD and AtSEX4 by 50%. The transgenic lines had seven times more starch than wild type at the end of the dark period but similar growth rates and total biomass. Elevated leaf starch content in maize leaves was engineered by making an RNAi construct against a gene in maize that appeared to be homologous to AtGWD. The RNAi construct was expressed using the constitutive ubiquitin promoter. Leaf starch content at the end of a night period in engineered maize plants was 20-fold higher than in untransformed plants with no impact on total plant biomass. We conclude that plants can be engineered to accumulate starch in the leaves with little impact on vegetative biomass.
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA.
Sean E
SE
Weise
Kimberly
K
Aung
Zach J
ZJ
Jarou
Payam
P
Mehrshahi
Ziru
Z
Li
Anna C
AC
Hardy
David J
DJ
Carr
Thomas D
TD
Sharkey
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018533:Biomass; D019295:Computational Biology; D054637:Dual-Specificity Phosphatases / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D010710:Phosphates / Q000378:metabolism*; D010766:Phosphorylation; D017866:Phosphotransferases (Paired Acceptors) / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D013213:Starch / Q000378:metabolism*; D003313:Zea mays / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D054637:Dual-Specificity Phosphatases; D010710:Phosphates; D017866:Phosphotransferases (Paired Acceptors); D013213:Starch; C500668:alpha-glucan, water dikinase, Arabidopsis; C553186:At3g52180 protein, Arabidopsis