Sequence and expression studies of A-, B-, and E-class MADS-box homologues in Eupomatia (Eupomatiaceae): Support for the bracteate origin of the calyptra

Sangtae Kim, Jin Koh, Hong Ma, Yi Hu, Peter K. Endress, Bernard A. Hauser, Matyas Buzgo, Pamela S. Soltis, Douglas E. Soltis

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Abstract

Eupomatia (Magnoliales, Eupomatiaceae) has flowers that bear a calyptra, an unusual organ that encloses the floral bud. The structural homology and evolutionary derivation of the calyptra are unknown, although some have proposed that it is a bract, while others favor a derivation from the perianth. To address the evolutionary origin of the calyptra, we isolated, sequenced, and characterized the expression of A-, B-, and E-class MADS-box homologues from Eupomatia bennettii and a close relative, Magnolia grandiflora (Magnoliaceae). The expression patterns of organ identity genes in floral organs of Eupomatia and Magnolia were very similar. However, the expression patterns of these MADS-box genes indicated that the ABC model is not strictly applicable to either Eupomatia or Magnolia. For example, A-class homologues were expressed in carpels and leaves of both Eupomatia and Magnolia. In the calyptra, expression levels of B- and E-class homologues were low and almost identical to those observed in leaf tissue. In contrast, high levels of expression for B- and E-class homologues were observed in the stamens, staminodes, and carpels. These gene expression data agree with recent developmental data and the interpretation of the calyptra as a bract. We also report the presence of various forms of alternatively spliced mRNAs in the cDNA pool from floral organs, and the implications of these mRNAs are discussed.

Original languageEnglish (US)
Pages (from-to)185-198
Number of pages14
JournalInternational journal of plant sciences
Volume166
Issue number2
DOIs
StatePublished - Mar 2005

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Plant Science

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