Plants are exposed to various types of pathogens and pests throughout their life including viruses, bacteria, fungi, oomycetes, nematodes and insects. Plants have evolved for different strategies to combat pathogen entry and disease development. Pathogenic microorganisms have their own strategies to overcome plant defense responses. Pathogens secrete ‘effector’ molecules which manipulate host cell structure and function to facilitate successful infection and also trigger defense responses in host cells. New emerging concept of ‘effector’ has been put forth in this review.
