HEAT-SHOCK INCREASES THE ACTIVITY OF THE GERMIN-LIKE PROTEASE INHIBITOR OF WHEAT LEAF APOPLAST

MANSILLA, A.; ORDOÑEZ, M.; SEGARRA, C.; CONDE, R.

Mar del Plata - Buenos Aires - Argentina

Congreso; XLIII Reunion Annual SAIB (Sociedad Argentina de Investigación en Bioquímica y Biología Molecular); 2007

SAIB

Previously, we found that leaf apoplast serine proteases take part in the wheat defence against the pathogenic fungus Septoria tritici. Their action either increases or decreases after inoculation with the fungus to plants of cultivars either resistant or susceptible to septoriosis, respectively. Also, we proved that these behaviours depend on the presence of an inhibitor, which was purified and partially sequenced. Its N-term sequence is homologous with germin-like proteins, being the first Germin Serine Protease Inhibitor (GPI) found. Its C-term was also determined by HPLC MS/MS. To know more about the control of its expression, the effect of high temperatures was explored. For it, 12d seedlings of the susceptible cv. ProINTA Molinero were put under 40ºC for 1, 2, 3 and 4 hours. After 3 hours, GPI activity increased ~30 %, while proteolytic activity decreased ~40%. These results suggest a link between GPI activation and heat-shock proteins induction (McElwain & Spiker. Plant Physiol 99: 1455, 1992). Also, whether GPI gene transcription changes under heat-shock or other stresses exist is explored. Thus, to earn GPI cDNA, primers based on its Nterm and C- term sequences were prepared. The cDNAthat encodes for GPI was isolated byRT-PCR and is used in Northern blot essays.