Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2009
Publication Date: 6/30/2009
Publication URL: http://www.plantcell.org/cgi/rapidpdf/tpc.109.068221v1?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&author1=Hake%2C+Sarah&author2=Bolduc%2C+Nathalie&andorexacttitle=and&andorexacttitleabs=and&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT
Citation: Bolduc, N., Hake, S.C. 2009. The Maize Transcription Factor KNOTTED1 Directly Regulates the Gibberellin Catabolism Gene ga2ox1. The Plant Cell. 10.1105/tpc.109.068221. Interpretive Summary: KNOTTED 1 (KNl)-like homeobox (KNOX) transcription factors are involved in the establishment and maintenance of plant meristems. Few direct targets of KNOX proteins have been recognized, and their identification is necessary to understand how they function at the molecular level. Using a combination of double mutant analysis and biochemistry, we found that in maize, KNl negatively modulates the accumulation of gibberellin (GA) through the control of ga2oxl, which codes for an enzyme that inactivates GA.
Technical Abstract: ga2oxl mRNA level is elevated in immature leaves of dominant KNOX mutants and down-regulated in reproductive meristems of the null allele knl-el. KNl binds in vivo to an intron of ga2oxl through a cw-regulatory element containing two TGAC motifs. VP16-KN1 activates transcription inplanta from a chimeric promoter containing this binding site, knl and ga2oxl mRNA overlap at the base of the shoot apical meristem and the base of newly initiated leaves, suggesting that KNl-mediated activation of ga2ox 1 maintains a boundary between meristem cell identity and rapidly elongating cells of the shoot. The KNl binding site is conserved in ga2oxl genes of different grasses, suggesting that the local regulation of bioactive GA levels through KNOX proteins is a common theme in grasses.