Chitinases in root nodules
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The abundance of chitinases in plants is surprising in view of the fact that plants do not contain chitin. However, plant chitinases have been shown to play a role in defense, growth and developmental processes. They are also involved in plant-bacterial symbioses. Two groups of plants, legumes and actinorhizal plants, are able to enter root-nodule symbioses with nitrogen fixing bacteria, rhizobia and <i>Frankia</i> strains, respectively, and plant chitinases are involved in these interactions. None of these bacteria contain chitin in their cell walls but rhizobia produce chitinaceous signal factors. To find out whether symbiosis-related chitinases belonged to phylogenetically distinct subgroups, a phylogenetic analysis was performed including all chitinases of one dicot, Arabidopsis, and one monocot, rice. The results show that conserved class I- and class III-chitinases were recruited in both types of root nodule symbioses. Since no chitinaceous signal molecules are formed by <i>Frankia</i>, a role of chitinases in the control of microbial signaling is unlikely. Alternative roles of chitinases in root nodules are discussed.
- Plant tissue culture letters
Plant tissue culture letters 25(3), 299-307, 2008-06-01
Japanese Society for Plant Cell and Molecular Biology