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United States Department of Agriculture

Agricultural Research Service

Title: Shoot Meristem Size Is Dependent on Inbred Background and Presence of the Maize Homeobox Gene, Knotted1

Authors
item Hake, Sarah
item Vollbrecht, E - PGEC, ALBANY, CA
item Reiser, L - PGEC, ALBANY, CA

Submitted to: Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 18, 2005
Publication Date: June 22, 2000
Citation: Hake, S.C., Vollbrecht, E., Reiser, L. 2000. Shoot meristem size is dependent on inbred background and presence of the maize homeobox gene, knotted1. Development, 127:3161-3172.

Interpretive Summary: The knotted (kn1) gene of maize is expressed in meristems and is absent from leaves, including the site of leaf initiation within the meristem. Analysis of limited shoot plants during embryogenesis indicated a role for kn1 in shoot meristem maintenance. We discuss a model for kn1 in maintenance of the morphogenetic zone of the shoot apical meristem.

Technical Abstract: The knotted (kn1) gene of maize is expressed in meristems and is absent from leaves, including the site of leaf initiation within the meristem. Recessive mutations of kn1 have been described that limit the capacity to make branches and result in extra carpels. Dominant mutations suggest that kn1 function plays a role in maintaining cells in an undifferentiated state. We took advantage of a Ds-induced dominant allele in order to scree for additional recessive alleles resulting from mobilization of the Ds element. Analysis of one such allele revealed a novel embryonic shoot phenotype in which the shoot initiated zero to few organs after the cotyledon was made, resulting in plants that arrested as seedlings. We refer to this phenotype as a limited shoot. The limited shoot phenotype reflected loss of kn1 function, but its penetrance was background dependent. We examined meristem size and found that plants lacking kn1 function had shorter meristems than non-mutant siblings. Furthermore, meristems of restrictive inbreds were significantly shorter than meristems of permissive inbreds, implying a correlation between meristem height and kn1 gene function in the embryo. Analysis of limited shoot plants during embryogenesis indicated a role for kn1 in shoot meristem maintenance. We discuss a model for kn1 in maintenance of the morphogenetic zone of the shoot apical meristem.

Last Modified: 10/22/2014
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