language: en

Is the LIM-domain Protein HaWLIM1 Associated with Cortical Microtubules in Sunflower Protoplasts ?

Authors : Christian Brière 1 , Anne-Claire Bordel 1 , Henri Barthou 1 , Alain Jauneau 2 , André Steinmetz 3 , Gilbert Alibert 1 and Michel Petitprez 1
1 Laboratoire "Biotechnologie et Amélioration des Plantes", INP-ENSAT,
BP 107 Auzeville F-31326 Castanet-tolosan, France
2 IFR FR40,
18 chemin de Borderouge, BP 17 Auzeville, F-31326 Castanet-tolosan, France
3 Institut de Biologie Moléculaire des Plantes du CNRS,
12 rue du Général Zimmer, 67084 Strasbourg, France

AbstractFlowering plants express several LIM-domain proteins related to the animal CRP proteins. The expression of sunflower LIM genes was followed by RT-PCR in cultured sunflower protoplasts. A transcript was detected only for HaWLIM1, but not for the other two genes HaPLIM1 and HaPLIM2. Polyclonal antibodies raised against either full length recombinant HaWLIM1 protein or peptides recognized a 27 kDa polypeptide on western blots. Immunocytolocalization studies showed that HaWLIM1 is located in the cytoplasm and in the nucleus. In the cytoplasm, HaWLIM1 is localized in punctate structures, which finely decorate microtubule bundles. Depolymerising microtubules with oryzalin resulted in a strong modification of the HaWLIM1 cortical pattern. In contrast, treatment of protoplasts with latrunculin B, which disrupts actin filaments, had no effect on HaWLIM1 localization. HaWLIM1 was also located within the nucleus of interphase protoplasts. During mitosis, nuclear labelling was observed in prophase, which decreased in metaphase, disappeared in anaphase, and recovered in telophase. These results suggest a dual role for HaWLIM1: in the cytoplasm, as a component of molecular complexes which may interact with microtubules, and in the nucleus, as a partner of transcription factors during interphase.

Key words: LIM-domain protein, microtubule, protoplast, sunflower, Helianthus annuus

1 Introduction