1. Front Cover.cdr - CORE

Session 8.Signalling
A B S T R A C T B O O K – A B S T R A C T S O F T A L K S
MEMBERS OF THE GIBBERELLIN RECEPTOR GENE FAMILY (GIBBERELLIN
INSENSITIVE DWARF1) PLAY DISTINCT ROLES DURING LEPIDIUMSATIVUM
AND ARABIDOPSIS THALIANA SEED GERMINATION
Antje Voegele, Ada Linkies, Kerstin Müller, Gerhard Leubner
Institute for Biology II, Faculty of Biology, Albert-Ludwigs-University, Biology II, Freiburg, Germany
E-mail: antje.voegele@biologie.uni-freiburg.de
A plant species survival depends on appropriate timing of seed germination. The seeds of
Arabidopsis thaliana and its close relative Lepidium sativum are highly similar in physiology
and structure, with Lepidium seeds being much bigger, facilitating tissue-specific
analyses. Both species possess a thin endosperm layer surrounding the embryo, which
regulates germination by acting as constraint to radicle protrusion. Gibberellin (GA)
signaling controls germination at least partly by regulating endosperm weakening by cellwall
modifying proteins. Arabidopsis has three known GA receptors: GID1a, GID1b and
GID1c. Using phylogenetic analysis we have shown that the angiosperm GID1s cluster in
two eudicot (GID1ac, GID1b) groups, indicating their distinct roles during plant
development. We used a comparative Brassicaceae approach, combining gid1 mutants
and whole-seed analyses in Arabidopsis with seed-tissue-specific analyses in Lepidium to
show that GA signaling via GID1ac is required for Arabidopsis seed germination and that
GID1 transcript expression patterns differed, with GID1b being distinct from GID1ac. We
identified putative cell-wall modifying expansins and xyloglucanendotransglycosylases/hydrolases
(XTHs) in a SSH cDNA library from Lepidium endosperm
tissue. Their transcript expression patterns strongly suggest their regulation by distinct
GID1-mediated GA signaling pathways: the GID1b and the GID1ac pathway, fulfilling
distinct regulatory roles in Brassicaceae seed germination.
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