Abstracts

Reproduction

Program/Abstract # 57Examination of the role of the Arabidopsis MADS-boxtranscription factors AGL6 and AGL13 in reproductionStephen E. Schauer, Ramarmurthy Baskar, Lukas Brand,Arturo Bolaños, Monica Grobei, Michael Federer, Jauch,Valeria GagliardiniInstitute of Plant Biology, University of Zürich, Zürich,Switzerland

Screening enhancer detector lines has identified genes thatare specifically expressed in the diploid maternal sporophytictissue of the ovule. One such gene is the MADS-box trans-cription factor AGAMOUS-LIKE6 (AGL6), which is expressedasymmetrically in the endothelium layer of the ovule, adjacentto the developing haploid gametophyte. The closely relatedAGL13 has an overlapping expression pattern in the ovule andboth are likely to be functionally redundant, as neither nullmutant has a phenotype. For most AGL genes, the large firstintron contains key cis-regulatory elements. Analysis of thetranscriptional regulation of both AGL6 and AGL13 indicatesthat Intron 1 is critical for proper expression in the endothelium,enhancing AGL6 but repressing AGL13 expression. Modifiedforms of AGL6 (containing either a VP16 activation or a Dro-sophila Engrailed repression domain) were placed under thecontrol of an inducible two-component activation system. Thephenotypic effect of the modified forms implies that AGL6functions as a transcriptional repressor that does not regulate itsown expression, nor does it regulate AGL13's expression.While the role of some specific plant transcription factors hasbeen elucidated, the function of most of the ∼2000 Arabidopsistranscription factors are currently unknown. The tools andtechniques being developed to analysis AGL6 and AGL13 havebroad applications for the analysis of transcription factors inplant developmental biology.

doi:10.1016/j.ydbio.2007.03.110

Program/Abstract # 58Establishment of oocyte polarity in vertebratesTripti Gupta, Mary MullinsDept. of Cell and Dev. Biol., University of Pennsylvania,Philadelphia, PA, USA

A framework of oocyte polarity in vertebrates is established,however, genetic analysis has been lacking. Through amaternal-effect mutant screen, we isolated mutations in two genesrequired for animal–vegetal (AV) polarity of the zebrafishoocyte and egg. While wildtype eggs display an animal poleblastodisc and vegetal pole yolk cell, the blastodisc of bucky ballandmagellan mutant eggs surrounds the yolk indicating a loss ofvegetal and expansion of animal positional information. Duringoogenesis bucky ball and magellan mutants fail to localizevegetal transcripts, whereas animal transcripts are reciprocallyexpanded, revealing a defect in oocyte polarity. The firstindication of oocyte polarity is the formation of the Balbianibody, a highly conserved structure also found in mammalianoocytes, which marks the vegetal pole of early Xenopus oocytes.We identified the Balbiani body in zebrafish and found that itfails to form in bucky ball mutants. By stage II of oogenesis, theBalbiani body disassembles, leaving germinal granules andseveral localized mRNAs at the vegetal pole. In contrast, inmagellan mutants the Balbiani body fails to disassemble andinstead persists into late stages of oogenesis, also causing afailure in AV polarity. Thus, the bucky ball gene functions in theformation of the highly conserved Balbiani body, whereas themagellan gene functions to disassemble it, demonstrating thetransient role for the Balbiani body in establishing oocytepolarity. Furthermore, we show a role for these genes inestablishment of AV polarity in the surrounding follicle celllayer. The cloning progress for bucky ball will be discussed.

doi:10.1016/j.ydbio.2007.03.111

Program/Abstract # 59Formation of the female reproductive tract; a unique formof tubulogenesisGrant D. Orvis, Richard R. BehringerDept. of Molecular Genetics, UTM.D. Anderson Cancer Center,USA

Regardless of genetic sex, amniotes develop two sets ofgenital ducts, the Wolffian and Müllerian ducts. We show thatcells in the rostral region of the coelomic epithelium (CE) arespecified to a Müllerian duct fate beginning at Tail Somite Stage19 (TS19). The Müllerian duct (MD) invaginates from the CE

Developmental Biology 306 (2007) 312–314www.elsevier.com/locate/ydbio

doi:10.1016/j.ydbio.2007.03.109