The role of strigolactone signaling in rice-endophytic bacterium interaction
H. NAKASHITA (1), M. Kusajima (1), T. Asami (2), H. Yamakawa (3) (1) Fukui Prefectural University, Japan; (2) The University of Tokyo, Japan; (3) NARO Agricultural Research Center, Japan

Various kinds of fungus and bacterial endophytes are isolated form plants. Some endophytes have the useful functions, such as growth promotion, disease resistance, and drought tolerance, to the host plant. Azospirillum sp. B510, isolated from rice in Japan, can induce disease resistance and promote the growth in rice plants. Endophytic colonization of rice by Azospirillum sp. B510 increased tiller number and yield. To elucidate the mechanism of plant growth promotion by Azospirillum sp. B510, the mode of tillering acceleration was characterized. Colonization with Azospirillum sp. B510 has no influence on plastochron of the host plant, suggesting that the increase in tiller number is due to the tiller bud outgrowth that is inhibited by strigolactone (SL). The involvement of SL in the plant growth promoting effect of Azospirillum sp. -colonization was examined by using synthetic SL biological analog 4-Br debranone (4BD). One-weak-old rice seedlings (Oryza sativa cv. Nipponbare) were pretreated with Azospirillum sp. B510 (2x10^7 cfu/ml) 3 d before a soil drenching with 4BD (30 μM). Measurment of tiller number, leaf number and plant height indicated that treatment with 4BD suppressed the tillering in control plants but not in Azospirillum-colonized plants. It is possible that SL signaling may function in the disease resistance induced by Azospirillum–colonization.  These results suggest that signal perception of SL plays an important role in the plant growth promoting effect of the interaction with an endophytic bacterium Azospirillum sp. B510.  

Abstract Number: P16-462
Session Type: Poster