Peanut seed cultivars with contrasting resistance to Aspergillus parasiticus colonization display differential temporal response of protease inhibitors.

MÜLLER, V; BONACCI, G; BATTHYANY C; AMÉ MV; CARRARI F; GIECO, J; ASIS, R

PHYTOPATHOLOGY

AMER PHYTOPATHOLOGICAL SOC

Año: 2016

0031-949X

Significant efforts are being made to minimize aflatoxin contamination in peanut seeds and one possible strategy is to understand and exploit the mechanisms of plant defense against  fungal  infection.  In  this  study  we  have  identified  and  characterized,  at biochemical and molecular levels, plant protease inhibitors (PPIs) produced in peanut seeds  of  the  resistant  PI337394  and  the  susceptible Forman  cultivar  during  A. parasiticus  colonization.  With  chromatographic  methods  and 2D electrophoresis-mass spectrometry  we  have  isolated  and  identified  four  variants  of  Bowman-Birk  trypsin inhibitor (BBTI) and a novel Kunitz-type protease inhibitor (KPI) produced in response to A.  parasiticus  colonization.  KPI  was  detected  only  in  the  resistant  cultivar  while  BBTI was produced in the resistant cultivar in a higher concentration than susceptible cultivar and with different isoforms. The kinetic expressionof  KPI  andBBTI  genes along with trypsin  inhibitory  activity  was  analyzed  in  both  cultivars  during  infection.  In  the susceptible  cultivar  an  early  PPI  activity  response was  associated  with  BBTI occurrence. Meanwhile in the resistant cultivar a later response with a larger increase in PPI activity was associated with BBTI and KPI occurrence. The biological significance of  PPI  in  seed defense  against fungal  infection  was analyzed  and  linked  to  inhibitory properties  on  enzymes  released  by  the  fungus  during infection,  and  to  the  antifungal effect of KPI.