75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

153 Novel insights into cell separation, abscission, apical dominance, epinasty and meristem
arrest using dab4-1 (delayed abscission)
Joonyup Kim 1 , Bradely Dotson 2 , Camila Rey 2 , Sara Patterson 1
1
University of Wisconsin-Madison, Cellular and Molecular Biology, Department of Horticulture, 2 University of
Wisconsin-Madison, Department of Horticulture
Although remembered as one of the earliest traits selected by human being, it is not until recently that abscission has
been recognized as a model for cell separation process. Abscission is the developmental process that includes a series
of programmed events resulting in detachment of organs. We have been characterizing a novel floral organ abscission
mutant, dab4-1 (delayed abscission) in Arabidopsis. This mutant has several unique phenotypes including delayed floral
organ abscission, lack of anther dehiscence, delayed meristem arrest, epinastic leaf growth and strong apical dominance.
Recent observations indicate that dab4-1 has altered responses to several phytohormones. To further understand the
hormone interactions in dab4-1, expression of more than 20 plant hormone response genes were examined. Many of
these genes were differently regulated in the mutant background. Levels of auxin in dab4-1 were measured both in the
shoot apex and stem. In addition, the levels of methyl jasmonate (meJA) and jasmonic acid (JA) were measured for both
in dab4-1 and wild type. Genetic interactions with other hormone response mutants have also been observed and will be
discussed. We’ve cloned DAB4 using map-based cloning and it is an F-BOX gene on chromosome 2. Previous reports
on this gene indicate that it is involved in the JA pathway and characterized for its mutants insensitivity to meJA, male
sterility and mostly disease resistance. Here, we will demonstrate that dab4-1 has new additional phenotypes in specific
ecotypes indicating novel roles of DAB4 during plant development. We are continuing further studies on protein-protein
interactions along with downstream targets for DAB4 and believe this data will further elucidate novel functions of
original DAB4 in plant development.
154 Functional Characterization of NEVERSHED and IDA, Genes Essential For Floral Organ
Shedding in Arabidopsis
Michelle Leslie, Ji-Young Youn, Lalitree Darnielle, Michael Lewis, Emilee Glaub, Sarah Liljegren
University of North Carolina at Chapel Hill
Abscission is a specialized cell separation event that allows plants to shed mature organs, such as leaves, flowers
and fruit. Recent work has shown that NEVERSHED (NEV) and INFLORESCENCE DEFICIENT IN ABSCISSION
(IDA) are each required for floral organ abscission in Arabidopsis. IDA is the founding member of a new class of putative
signaling ligands (Butenko et al., 2003), and we have discovered that NEV is involved in vesicle trafficking. Currently,
we are taking genetic and molecular approaches to further define the roles of NEV and IDA, explore their relationship,
and elucidate the pathways that control cell separation. To identify additional components of the NEV pathway, we have
carried out a suppressor screen for mutations that restore abscission in nev mutant flowers. Further characterization of
these suppressors, including two allelic recessive suppressors that I am mapping, should identify proteins that interact
with or downstream of NEV. In addition to our genetic characterization of NEV, we have developed NEV-specific antisera
that we are using to test the co-localization of NEV with different endomembrane compartments. We are also testing
whether the proper localization of IDA, which is predicted to be a secreted signal, may be dependent on NEV activity.