Poster: Reproductive development
Abs #
372: ULTRAPETALA proteins are required for shoot apical meristem activity, floral patterning and flowering time in Arabidopsis
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Presenter: |
Carles, Cristel C, carles@uclink.berkeley.edu |
Authors | Carles, Cristel C (A) Choffnes, Dan (A) Fletcher, Jennifer C (A) | | Affiliations: |
(A): Plant Gene Expression Center - UC Berkeley
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Arabidopsis ult1 mutants have enlarged inflorescence meristems (IFMs) producing extra flowers and enlarged floral meristems producing extra floral organs. ULT1 encodes a novel cysteine-rich protein of unknown function. It is a member of a small, plant-specific family which shares 85% homology with a second protein (ULT2) in Arabidopsis.
ULT1 and ULT2 mRNA expression patterns fully overlap in IFMs, floral meristem and flowers: ULT transcripts are localized throughout inflorescence and young floral meristems and become restricted to the center of the flower (stamen and carpel primordia) as soon as the sepal primordia initiate. Both ULT genes are transcribed in the embryonic shoot apical meristem (SAM) and ULT2 is also expressed in the embryonic root apical meristem. Finally, ULT1 but not ULT2 mRNA can be detected in the vegetative SAM.
In addition to regulating stem cell proliferation in developing shoots and flowers, ULT proteins play a role in cell fate determination and flowering time. ULT1 and ULT2 overexpression lines show characteristics similar to the clf-2 mutant: upward curly leaves, mosaïcal floral organs and early flowering. These phenotypes are at least partially a consequence of AGAMOUS and APETALA3 transactivation. Antisense lines for both genes display a range of phenotypes, from reduced SAM activity to flowers with additional whorls of organs. Recent analysis of double mutants between ULT1 and ULT2 knockouts suggests that the absence of both proteins causes embryo lethality.
Altogether, these data suggest that ULT act in both vegetative and inflorescence meristem initiation and maintenance but also have a role in the later specific activation of homeotic genes.
