Non classical proteins in the apoplast of sunflower seedlings

QUIROGA IVANA; PINEDO MARCELA; REGENTE MARIANA; DE LA CANAL LAURA

Tucumán

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

The apoplast or extracellular matrix of plants is a dynamic compartment involved in biological functions as diverse as cell growth and defense. In order to identify sunflower apoplastic proteins, a 1D-SDS PAGE followed by MALDI/TOF mass spectrometric analysis was performed. Tentative identification was assigned using a sequence coverage of 20 %, a Mascott score of 62 and a peptide number of 4 as cut off. The analysis revealed novel proteins both in sunflower and the apoplastic fraction. Interestingly, a significant group of them was not expected to be extracellular since the sequences matched in the database lacked the typical signal peptide responsible for secretion. However, several controls allowed to discard a putative contamination of the apoplastic fraction with intracellular components. The group devoid of signal peptide or non–classically secreted proteins was subdivided into unfolded proteins, thus Secretome P positive, and proteins negative for both signal P and Secretome P by in silico analysis. As unfolded proteins have been observed in the extracellular matrix of animal cells, the implication of these findings in the plant secretion mechanisms is discussed.