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United States Department of Agriculture

Agricultural Research Service

Title: Over-expression of a zeatin O-glucosylation gene in maize leads to growth retardation and tasselseed formation.

Authors
item Rodo, Albert - OSU
item Brugiere, Norbert - PIONEER HI-BRED INT IL
item Vankova, Radomira - ACAD SCIENCE CZECH REP
item Malbeck, Jiri - ACAD SCIENCE CZECH REP
item Olson, Jaleh - OSU
item Haines, Sara - OSU
item MARTIN, RUTH
item Habben, Jeffrey - PIONEER HI-BRET INT IL
item Mok, David - OSU
item Mok, Machteld - OSU

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 7, 2008
Publication Date: July 31, 2008
Citation: Rodo, A.P., Brugiere, N., Vankova, R., Malbeck, J., Olson, J.M., Haines, S.C., Martin, R.C., Habben, J.E., Mok, D.W., Mok, M.C. 2008. Over-expression of a zeatin O-glucosylation gene in maize leads to growth retardation and tasselseed formation. Journal of Experimental Botany. 59: 2673-2686.

Interpretive Summary: Cytokinins are plant hormones that are necessary for normal plant growth and development. Zeatin is a natural occurring cytokinin found in many plant tissues and can be metabolized to various forms. To study the effects of one of these metabolites in monocots, the gene from Phaseolus lunatus encoding an enzyme capable of O-glucosylating zeatin was constitutively expressed in maize (Ubi:ZOG1 transformants). As expected, the roots and leaves of these transformed plants had greatly increased levels of zeatin-O-glucoside. The hemizygous and homozygous Ubi:ZOG1 plants were shorter and had thinner stems, narrower leaves, smaller meristems, and increased root mass and branching similar to what one would see in cytokinin deficient plants. Leaves of the transformed plants were greener and had increased levels of active cytokinins compared with those of non-transformed sibs. The transformed plants also exhibited delayed senescence when grown in the spring/summer. While hemizygous transformants had reduced tassels with fewer spikelets and normal viable pollen, homozygotes had very small tassels and feminized tassel florets. Such modifications of the flowers were unexpected and demonstrate a link between cytokinins and sex-specific floral development in monocots. Over-expression of a zeatin O-glucosylation gene in maize leads to growth retardation and tasselseed formation.

Technical Abstract: To study the effects of cytokinin O-glucosylation in monocots, maize (Zea mays) transformants harboring the ZOG1 gene (encoding a zeatin O-glucosyltransferase from Phaseolus lunatus) under the control of the constitutive ubiquitin (Ubi) promoter were generated. The roots and leaves of the transformants had greatly increased levels of zeatin-O-glucoside. The vegetative characteristics of hemizygous and homozygous Ubi:ZOG1 plants resembled those of cytokinin deficient plants, including shorter stature, thinner stems, narrower leaves, smaller meristems, and increased root mass and branching. Transformant leaves had higher chlorophyll content and increased levels of active cytokinins compared with those of non-transformed sibs. The Ubi:ZOG1 plants exhibited delayed senescence when grown in the spring/summer. While hemizygous transformants had reduced tassels with fewer spikelets and normal viable pollen, homozygotes had very small tassels and feminized tassel florets, resembling tasselseed phenotypes. Such modifications of the reproductive phase were unexpected and demonstrate a link between cytokinins and sex-specific floral development in monocots.

Last Modified: 8/27/2014
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