Arabidopsis homeotic gene APETALA3 ectopic expression: Transcriptional and posttranscriptional regulation determine floral organ identity
APETALA3 (AP3) specifies the development of petals and stamens in the Arabidopsis flower. We constructed a transgenic line, 35S-AP3, that ectopically expresses AP3 under the control of a constitutive promoter. The resulting flowers exhibit a replacement of carpels by stamens and resemble flowers homozygous for the previously described Arabidopsis mutation superman. Although AP3 RNA is detected at high levels throughout the flower and stem in 35S-AP3, AP3 protein is detected at high levels only in the second, third, and fourth floral whorls, demonstrating that AP3 is posttranscriptionally regulated. Ectopic expression of AP3 causes a second floral homeotic gene, PISTILLATA (PI), to function in the fourth whorl of 35S-AP3 flowers. AP3 and PI also activate an AP3 promoter-reporter gene fusion, demonstrating that AP3 positively autoregulates.
© 1994 Cell Press. Received 5 October 1993, Revised 23 November 1993. We thank Beth Krizek, Leslie Sieburth, Koji Goto, and Detlef Weigel for allowing us to mention their unpublished data and Laura Brockman for doing AP3 in situ hybridizations in ap3 mutants. We also thank Leslie Sieburth for the pCGN18 plaamid, members of the Meyerowitz lab (both past and present) for comments on the manuscript, and Pat Koen of the California Institute of Technology electron microscope facility for advice on use of the scanning electron microscope. During the period of this work, T.J. was supported by the National Institutes of Health postdoctoral fellowship GM13667-5. This work was supported by National Science Foundation grant MCB-9204839 to E.M.M.