15th International Conference on Arabidopsis Research - TAIR

T04-031
Functional Analysis of Arabidopsis Group III and IV
GSK-3/shaggy-like Kinases
Elena Petutschnig(1), Wilfried Rozhon(1), Claudia Jonak(1)
1-Insitute of Microbiology and Genetics, University of Vienna
GSK-3/shaggy-like genes code for a group of highly conserved protein
kinases that can be found in all eukaryotes and are involved in a variety of biological
processes (Jonak and Hirt, 2002, TIPS, 7, 457). Arabidopsis thaliana
contains ten GSK-3/shaggy-like kinases (ASKs) that can be divided into four
groups according to their sequence similarity. Group I and II ASKs have been
shown to function in hormone and stress signalling as well as floral and leaf
development. However, to date there are no functional data available on the
Arabidopsis members of groups III and IV. Therefore, we have isolated these
ASKs and generated a range of tools to elucidate their biological function.
Transgenic plants overexpressing epitope-tagged versions of the ASKs have
been produced and will be characterised in the near future. Transient expression
assays in protoplasts revealed highly different protein levels and kinase
activities between closely related ASKs. Furthermore, T-DNA insertion lines
have been obtained and the T-DNA insertions have been characterised by
PCR and southern blotting. Functional analysis of these lines is in progress.
Group III ASKs are predicted to posses a mitochondrial targeting sequence,
whereas Group IV members are expected to be cytosolic. Thus, we are presently
analysing the localisation by expression of YFP-tagged versions of the
ASKs in Arabidopsis protoplasts and Agrobacterium infiltrated tobacco leaves.
T04 Interaction with the Environment 1 (Abiotic)
T04-032
Genetic analysis of zig suppressor 3 suppressing
AtVti11 deficiency
Tetsuya Takahashi(1), Mitsuru Niihama(1), Miyo Terao Morita(1), Masao Tasaka(1)
1-Graduate School of Biological Sciences Nara Institute of Science and Technology (NAIST), Japan
To elucidate the molecular mechanism of the shoot gravitropism, we have
isolated many shoot gravitropism (sgr) mutants in Arabidopsis. zig/sgr4 mutant
exhibits abnormal shoot gravitropism and morphological defects in stems
and leaves. ZIG encodes AtVTI11, a Qb-SNARE that is likely to function in the
trans Golgi Network-Vacuole vesicle transport pathway. Actually, dysfunctional
vacuoles were formed in the gravity-sensing endodermal cells, and the
fragmented vacuoles or abnormal vesicles were observed in other tissues in
zig-1 mutant. Thus, the vesicle transport mediated by ZIG may have pleiotropic
functions in planta. To understand ZIG ¯related genetic network involving
gravitropism and/or morphology, we performed a screening for the second
mutation that can suppress defects of zig-1. Previously, we reported zip1, a
dominant mutation in AtVTI12 which encodes a homologue of ZIG/AtVTI11,
suppresses defects of zig-1 almost completely. Here we will report another
suppressor mutant zip3 which can partially suppress both abnormal gravitropism
and morphology of zig-1. The amyloplasts in endodermal cells were
sedimented to the direction of gravity in zig-1 zip3-1, suggesting that ZIP3
functions in the vacuole formation or function. The molecular cloning of the
ZIP3 gene and its functional analysis are in progress.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin