Expression of an abscisic acid-responsive β-1,3-glucanase gene in autoregulation of nodulation

Abstract

Host legumes control nodule number by autoregulation of nodulation (AON), in which the presence of root nodules inhibits further root nodule formation. AON consist of at least two long-distance signals, i. e. a root-derived infection signal and a shoot-derived signal that inhibits nodulation. In Lotus japonicus, LjCLE-RS1 has been identified one of the strong candidates as the infection signal. However, it is still not clear how the nodulation is repressed in the roots. Abscisic acid (ABA) inhibits nodulation and antisense of LjGlu1 (ABA responsible β-1,3-glucanase) enhances nodulation and nitrogen fixation. We focused on the expression level of LjGlu1 under activating of AON. Split-root system was employed to investigate an involvement of LjGlu1 on AON in L. japonicus. The expression level of LjGlu1 was also analyzed in the transgenic hairy roots expressing LjCLE-RS1 constitutively.