Fighting Enemies in Every Which Way

Plants are subject to assault from numerous pathogens that colonize different tissues and organs that vary greatly in structure, nutrient availability, water status, and responsiveness to pathogens. Past research has focused on how plant immune receptors sense danger signals during infection and signaling mechanisms. How pathogens, particularly those that infect flowers and roots, breach physical barriers of different host tissues and establish niches for proliferation has received less attention. Recent advances indicate that different pathogens employ specialized mechanisms to manipulate the physiology, metabolism, growth, and development of specific host cells to breach various physical barriers and create a microenvironment suitable for pathogen proliferation and dissemination. Importantly, the plant immune system actively engages these processes to counter pathogenesis. Furthermore, emerging evidence increasingly points to different roles of specific plant cells in sensing the pathogen and cell–cell communication that is important for the establishment of immunity at the organism level.