Abstract
To prevent excessive nodulation, leguminous plants have a systemic regulatory system called "autoregulation" of nodulation (AON). In Lotus japonicus, Har1 has been shown to be involved in AON and the har1 mutants display hyper-nodulation phenotype by the lack of AON. The har1 mutants are also hyper-infected by symbiotic AM fungi and parasitic nematodes in roots, suggesting that AON signal(s) also play the inhibitory role against other kinds of infections. Here, we report that Har1 also participates in the defense mechanism against Pseudomonas syringae.
Leaves of wild type L. japonicus were susceptible to Pseudomonas syringae pv. pisi but not to pv. glycinea. In contrast to the wild type plants, leaves of har1 mutants were severely infected by P. syringae pv. glycinea. In addition, har1 mutants were more susceptible to P. syringae pv. pisi than wild type. These findings suggest that Har1 participates in shoot defense mechanisms.
