Role of Surface Factors in Plant-Microbe Interactions: Involvement of Rhizobium Meliloti Exopolysaccharide During Early Infection Events in Alfalfa
Substances secreted by bacteria play important roles in their interactions with plants. For example, in the N2-fixing symbiosis involving legumes and rhizobia, secreted signals are now known to be essential for eliciting certain key steps in root nodulation. In pathogenic interactions, one expects to find secreted toxins and degradative enzymes, as well as factors that protect the bacteria from plant defense responses. In both types of interactions, polymers or substances that adhere to cell surfaces might also participate in physical interactions such as the disruption of plant tissues or attachment. Substances that remain associated with the cell surface would act in the immediate vicinity of the bacterial cell, while those that diffuse away from the cell could act at a distance. This article discusses secreted substances that are often termed “surface factors”, including both exopolysaccharides (EPSs) and lipopolysaccharides (LPSs). While these substances probably do function in many cases as cell-associated factors, they can also be found in the intercellular milieu and so could also function at a distance. Surface factors involved in plant-microbe interactions have been discussed in several review articles [1-4].
KeywordsCell Surface Plant Pathology Plant Tissue Bacterial Cell Defense Response
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