Interacting partners of the BSL protein phosphatases in plants

GUSTAVO MASELLI; JAVIER BIANCHI; SANTIAGO MORA-GARCIA

Tucuman, Argentina

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The BSL protein phosphatases belong to a novel family of the PPP phosphatases found in several organisms. The only member of the family characterised to date is involved in the modulation of the brassinosteroid signalling pathway in Arabidopsis thaliana. BSL phosphatases are formed by a characteristic catalytic domain at the C-terminus, linked to a b-propeller domain at the N-terminus by a connecting region. Protein phosphatases are modular proteins, whose functional properties and/or subcellular localisation are defined by disparate interacting partners. To gain more insight on the processes these enzymes may act on in plants and to further precise their regulatory properties, we searched for interacting partners of one of the paralogs in Arabidopsis through yeast two-hybrid screens, using both domains separately. We found that the catalytic domain is able to homodimerise, which is an unusual feature among Ser/Thr phosphatases. We report the validation of this interaction and dissect its requirements, and show that it is common to all the members of the family in Arabidopsis, in a combinatorial way. Moreover, extending the assay to a broader phylogenetic range, including homologs in mosses and green algae, we show that this interaction appears to be a feature of this whole group of phosphatases. The functional consequences of this interaction are being explored.