Gibberellin guidance is required for the spatial regulation of symbiosis gene expression and infection of arbuscular mycorrhizal fungi in Lotus japonicus
N. TAKEDA (1), M. Nagae (2), M. Kojima (3), H. Sakakibara (3), M. Kawaguchi (4) (1) Natl Inst of Basic Biology/SOKENDAI, Japan; (2) Natl Inst of Basic Biology, Japan; (3) RIKEN CSRS, Japan; (4) Natl Inst of Basic Biology/SOKENDAI, Japan

Arbuscular mycorrhiza (AM) is a plant-fungi interaction that confers great advantages for plant growth by supplying nutrients. AM colonization of the host root is controlled by symbiotic factors in both host plant and AM fungi. Recent studies revealed that biosynthesis of gibberellins (GAs) is enhanced during AM development and disturbance of the GA signaling influences AM colonization. We found that GA level in the host root is maintained by a GRAS transcription regulator NSP1. The nsp1 mutant showed the lower AM colonization but the mutant phenotype was suppressed by the adjustment of GA signaling conditions. We also found that GA signaling interacts with the symbiotic signaling and positively or negatively regulates expression of AM-induced genes. Promoter analysis of the AM-induced genes revealed that the promoters contain AM- and GA-response cis-acting regions and these regions coordinately regulate spatiotemporal expression of the symbiotic genes during AM development. In the infected roots, the symbiosis genes showed unequal distribution of the expression levels: some cortical cells contain the stronger expression than the neighboring cells. The characteristic pattern formation requires both AM- and GA-response regions and the loss of the GA-response region caused disappearance of the expression pattern. These results indicated that the GA is a symbiotic signaling factor that regulates the spatial expression of symbiosis genes and guides AM fungal infection in the host root.

Abstract Number: P2-51
Session Type: Poster