Congress Abstracts - Society for Developmental Biology

downregulated by polycomb-group proteins, and that such regulation is suppressed after a vernalization treatment. Polycomb-group
protein CLF methylates chromatin in the AGL19 locus, with the first intron being the most frequent target. Thus, it has been proposed
that CLF jointly with other PRC2 proteins silences AGL19 expression by methylation. It is not known if this silencing occurs in the
root, the organ where AGL19 shows the highest expression. On the other hand, our data from fusions of AGL19 promotor region and
reporter genes suggests that AGL19 is upregulated by auxin. Studies on CLF mutants show that its role in the RAM is not linked to
changes in auxin concentration. Based on this data, we ask ourselves whether the AGL19 regulatory pathway involving polycombgroup
proteins and the one involving auxin are connected. In this work we characterized AGL19 molecular and cellular functions
through analysis of a loss-of-function mutant. We found that AGL19 silencing by polycomb-group proteins also occurs in the root.
Finally, we propose experiments involving auxin induction of AGL19 expression in CLF and LHP1 mutants in order to find out
whether its epigenetic regulation is independent to auxin regulation.
This work is supported by CONACyT (180098; 180380; 167705; 152649; 105678) and DGAPA, UNAM (IN204011-3; IN203113-3;
IN226510-3; IB201212-2) grants.
Program/Abstract # 135
The SWI2/SNF2 Chromatin Remodeling Factor CHR9 Regulates Floral Meristem Identity in Cooperation with LEAFY
Lamb, Rebecca S.; Kovach, Jeffrey; Habina, Matthew; Siriwardana, Nirodhini (Ohio State University, USA)
In angiosperms the flower is the unit of reproduction and is considered to be a modified shoot. The floral meristem identity genes are
required to specify meristems as flowers rather than as shoots. In the model plant species Arabidopsis thaliana as well as other
flowering plants the LEAFY (LFY) transcription factor is a key regulator of floral development, regulating expression of other floral
meristem identity genes and floral homeotic genes that control floral organ identity. We have identified CHR9, a member of the
SWI2/SNF2 family of chromatin remodeling factors, as an LFY-interacting protein. chr9 loss-of-function mutations have mild
meristem identity defects while CHR9 overexpression lines flower early with shoots converted to flowers. Physical and genetic
interactions between LFY and CHR9 indicate that these factors act together. Evidence will be presented that CHR9 acts with LFY to
regulate expression of floral meristem identity genes, including TERMINAL FLOWER 1 (TFL1), and thus CHR9 is involved in the
control of plant reproductive architecture.
Program/Abstract # 136
Paternal contributions to early embryogenesis of Arabidopsis thaliana: A functional genetic approach
Del Toro, Gerardo Del Toro; García-Aguilar, Marcelina; Gillmor, Stewart (CINVESTAV-IPN, Mexico)
In animals, zygotic genome activation and maternal product decay are prerequisites for transfer of developmental control from the
mother to the zygote, a phenomenon known as the Maternal to Zygotic Transition (MZT). In plants, the existence of a MZT is
controversial. Two recent studies have reported allele-specific transcriptome profiles of early embryogenesis, one providing support
for maternal dominance with significant paternal input (Autran et al., Cell 2011), and the other study arguing for equivalent parental
contribution (Nodine and Bartel, Nature 2012). However, neither study tested the biological relevance of this phenomenon. Here we
report the first systematic functional genetic analysis of paternal gene activity in early plant embryogenesis. Our assay consists of
testing the timing of the ability of wild type paternal alleles to complement pre-globular embryo phenotypes conditioned by mutant
maternal alleles. In our analysis of 50 embryo defective mutants (emb), we found that 82% of genes showed delayed
complementation, while 18% showed immediate complementation. In addition, we used GCT/MED13 and CCT/MED12, two genes
that show delayed phenotypic complementation, to correlate delayed paternal function with delayed paternal expression. Thus,
activation of many paternal alleles in early embryogenesis is gradual, while a significant proportion of paternal alleles show
immediate activity. Our results demonstrate that plants do not have discrete step for zygotic gene activation, and suggest that the
maternal and paternal genomes make unequal contributions to early plant embryogenesis.
Program/Abstract # 137
Expression of Aminopeptidase N Genes During Sea Urchin Development
Ingersoll, Eric P.; Drab, Diana L. (Penn State, USA)
Aminopeptidase N (APN) is an exopeptidase that has been shown to play a role in the development of nematodes and fruit files.
Recent advances in genome sequencing have made available information allowing the identification of genes in the sea urchin
genome. We have searched the sea urchin genome and found a number of APN genes. In this study, we are determining which of
these APN genes is expressed during embryonic development. We used reverse transcription PCR to detect gene-specific mRNAs
throughout development. Our studies have identified several APN genes that are expressed in embryos. We will present data on the
temporal expression of these genes throughout the entirety of sea urchin embryonic development. In the future, we hope to determine
the spatial expression patterns and developmental functions of these genes.
Program/Abstract # 138
Repulsive guidance molecules expression pattern during chicken embryogenesis suggested new roles for these molecules
during notochord formation, somitogenesis and myogenesis
Jorge, Erika; Ahmed, Mohi (Mount Sinai School of Medicine, USA); Bothe, Ingo (Sloan Kettering Institute, USA); Coutinho, Luiz
(Universidade de São Paulo, Brazil); Dietrich, Susanne (University of Portsmouth, UK)
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