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Abstract

During early development, auxin controls cell division and differentiation through ARFs (auxin
response factors) and its repressors Aux/IAAs. In this project, we want to characterize one of the
most abundant Aux/IAAs found in Arabidopsis embryos, namely IAA8. Using reporter lines and in situ
hybridization, we showed that IAA8 is expressed broadly in the embryo. To assess its function we are
using a transactivated gain-of-function system. Ubiquitous overexpression leads to abnormal apical
divisions resulting in nonviable seeds. Tissue-specific overexpression suggests that IAA8 acts mainly
in apical cells since overexpression in suspensor cells does not seem to compromise the embryo
development. Preliminary results with cell identity markers indicate that IAA8 might be involved in
the establishment of apical/basal cell fate. Regarding interaction partners, dual-luciferase
experiments in protoplasts point out ARF5 as a potential interactor partner. Further validation
through phenotype rescue experiments is being conducted. Since IAA8 is found abundantly during
early embryogenesis, its characterization will help us understand more deeply how the embryo
pattern is formed.