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Plant Physiology Preview Published on April 16, 2008; 10.1104/pp.107.115634
OPEN ACCESS ARTICLE
Received December 28, 2007 Two GATA transcription factors are downstream effectors of floral homeotic gene action in Arabidopsis
Department of Molecular, Cellular and Developmental Biology, Yale University, 266 Whitney Ave., New Haven, CT 06520-8104, USA * Corresponding author; email: Vivian.irish{at}yale.edu.
Floral organogenesis is dependent on the combinatorial action of MADS box transcription factors, which in turn control the expression of suites of genes required for growth, patterning, and differentiation. In Arabidopsis, the specification of petal and stamen identity depends on the action of two MADS box gene products, APETALA3 (AP3) and PISTILLATA (PI). In a screen for genes whose expression was altered in response to the induction of AP3 activity, we identified GNC (GATA, nitrate-inducible, carbon-metabolism-involved) as being negatively regulated by AP3 and PI. The GNC gene encodes a member of the Arabidopsis GATA transcription factor family and has been implicated in the regulation of chlorophyll biosynthesis as well as carbon and nitrogen metabolism. In addition, we found that the GNC paralog, GNL (GNC-like), is also negatively regulated by AP3 and PI. Using chromatin immunoprecipitation, we showed that promoter sequences of both GNC and GNL are bound by PI protein, suggesting a direct regulatory interaction. Analyses of single and double gnc and gnl mutants indicated that the two genes share redundant roles in promoting chlorophyll biosynthesis, suggesting that in repressing GNC and GNL, AP3/PI have roles in negatively regulating this biosynthetic pathway in flowers. In addition, co-expression analyses of genes regulated by AP3, PI, GNC and GNL indicate a complex regulatory interplay between these transcription factors in regulating a variety of light and nutrient responsive genes. Together, these results provide new insights into the transcriptional cascades controlling the specification of floral organ identities.
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