Expansins: Cell Wall Remodeling Proteins with a Potential Function in Plant Defense

Cell wall (CW) performs a number of important functions. This distinctive feature of plants determines cell structure, and plays major roles in intercellular communication and plant-microbe interactions, including defense responses against potential pathogens. Expansins are novel plant CW loosening proteins, are mainly involved in the pH-dependent extension of plant CWs that is called acid growth [1,2]. These plant CW remodeling proteins have important roles in plant cell growth, fruit softening, abscission, and emergence of root hairs, pollen tube invasion of the stigma and style, meristem function, pathogenicity and developmental processes. Expansins are linked with cell growth and CW changes that are induced by a number of plant hormones.