Chitinases in root nodules
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 biotechnology
Plant biotechnology 25(3), 299-307, 2008-06-01
Japanese Society for Plant Cell and Molecular Biology