Expansins as agents in hormone action

Expansins are wall-loosening proteins implicated in plant responses to most of the major plant hormones. These include cell enlargement, cell proliferation, fruit softening, abscission, senescence, and adaptation to water stress - all hormone-controlled responses in which the cell wall is modified so as to make it more extensible or softer or more easily separated from other walls. In this chapter ¹ we summarize the current evidence implicating expansins in the action of various hormones, beginning with a short summary of the characteristics of this protein and its likely mechanism of action.