INTERACTIONS BETWEEN PLANTS AND PATHOGEN MICROORGANISMS: FROM STRESS PERCEPTION TO DEFENSE RESPONSES


SALADIN Gaëlle

INTRODUCTION

Phytopathogenic microorganisms (fungi, oomycetes and bacteria) cause each year a yield loss of 10 – 15 % in the world. Around 70 % of plant diseases are related to fungi, these microorganisms representing with oomycetes more than 100 000 phytopathogenic species whereas there are approximately 100 species of phytopathogenic bacteria.Phytopathogenic species can have three modes of trophy depending on the species[1]:

– they can grow in living plant tissues (biotrophy) such as Ustilago, Puccinia and Agrobacterium species,

– they can lyse plant cells to obtain nutrients and thus grow in dead tissues such as Botrytis or Fusarium (necrotrophy),

– they can be first biotrophic and then switch to a necrotrophic mode (hemibiotrophy) such as Phytophtora and most of phytopathogenic bacteria.

Phytopathogens can infect plant organs after penetration by stomata for leaves (that is the most frequent mode for bacteria), after wounding or after adhesion on an aboveground or an underground organ. The adhesion requires the secretion of lytic enzymes (lipases, cutinases) by phytopathogen to remove cuticle and the secretion of adhesive substances containing polysaccharides, lipids and proteins such as hydrophobins [2].

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