Stress induced and nuclear localized HIPP26 from Arabidopsis thaliana interacts via its heavy metal associated domain with the drought stress related zinc finger transcription factor ATHB29.
Barth, Olaf; Vogt, Sebastian; Uhlemann, Ria; Zschiesche, Wiebke; Humbeck, Klaus
[Article] Plant Molecular Biology. 69(1-2):213-226, January 2009.

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HIPP26 from Arabidopsis thaliana belongs to a novel class of plant proteins, characterized by a heavy metal associated domain and an additional isoprenylation motif. It is induced during cold, salt and drought stress. The nuclear localization of HIPP26, predicted by a NLS motif, could be confirmed in onion epidermal cells overexpressing GFP-HIPP26. Experiments with modified HIPP26 indicate that the isoprenylation plays a role in the spatial distribution in the nucleus. Using promoter-GUS constructs, a tissue specific expression pattern of HIPP26 could be shown, with high expression in the vascular tissue. By a yeast-two-hybrid approach a strong interaction of HIPP26 with the zinc finger homeodomain transcription factor ATHB29, which is known to play a role in dehydration stress response could be detected. This was confirmed by GST pull-down assays. When using a modified HIPP26 lacking the two central cysteines of the heavy metal associated domain, ATHB29 was not bound in the GST pull-down assay, indicating that this structure is necessary for the interaction. Further yeast-two-hybrid analyses testing interaction of different members of the HIPP family with related zinc finger transcription factors revealed a specific interaction of ATHB29 with several HIPP proteins. A functional relationship between HIPP26 and ATHB29 is also indicated by experiments with mutants of HIPP26 showing altered expression levels of such genes known to be regulated by ATHB29.

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