著者

Katsuhiro Kojima Tadashi Yokoyama Naoko Ohkama-Ohtsu Suwat Saengkerdsub Manabu Itakura Hisayuki Mitsui Kiwamu Minamisawa Yasuhiro Arima

出版者

Japanese Society of Soil Microbiology

雑誌

土と微生物 (ISSN:09122184)

巻号頁・発行日

vol.66, no.1, pp.12-21, 2012-04-01 (Released:2017-05-31)

参考文献数

35

---

Tetronic acid is a candidate for an inducer of nodulation (nod) gene expression in Mesorhizobium loti. However, there is no evidence that tetronic acid is secreted from Lotus species, the host plants of M. loti. This suggests that Lotus plants may produce other genuine nod gene inducers that differ from tetronic acid. In this study, M. loti cells harboring a nodA-lacZ fusion were enclosed in dialysis tubing and immersed in L. corniculatus culture solution. Significant β-galactosidase activities were detected in the M. loti cells, indicating that nod gene inducers were present in the seed and root exudates. β-galactosidase activities in M. loti cells were also determined after cells were exposed to seed and root exudates or tetronic acid in vitro. Seed and root exudates induced greater β-galactosidase activity in M. loti cells in 1 mM CaSO_4 solution than in YEM medium. In contrast, tetronic acid induced greater β-galactosidase activity in M. loti cells in YEM medium than in 1 mM CaSO_4 solution. Further, β-galactosidase activities induced by seed and root exudates and tetronic acid tended to decrease as the pH of the medium became neutral. In an LC-MS analysis, we could not detect tetronic acid in the concentrated seed and root exudates. These findings indicate that Lotus plants release genuine nod gene inducers for M. loti that differ from tetronic acid. Finally, seed exudates of L. corniculatus were fractionated according to molecular size and polarity, and it was clarified that a putative nod gene inducer in the seed exudates was a low molecular weight and high polarity substance.

著者

Sayed Ziauddin Hashami Hiroyuki Nakamura Naoko Ohkama-Ohtsu Katsuhiro Kojima Salem Djedidi Izumi Fukuhara Mohammad Daud Haidari Hitoshi Sekimoto Tadashi Yokoyama

出版者

Japanese Society of Microbial Ecology · The Japanese Society of Soil Microbiology

雑誌

Microbes and Environments (ISSN:13426311)

巻号頁・発行日

vol.34, no.1, pp.64-75, 2019 (Released:2019-03-30)

参考文献数

35

被引用文献数

9

---

Legumes form root nodules and fix atmospheric nitrogen by establishing symbiosis with rhizobia. However, excessive root nodules are harmful to plants because of the resulting overconsumption of energy from photosynthates. The delay of an inoculation of the soybean super-nodulation mutant NOD1–3 with Bradyrhizobium diazoefficiens USDA110T by 5 d after an inoculation with several soil bacteria confirmed that one bacterial group significantly decreased root nodules throughout the study period. Moreover, no significant changes were observed in nitrogen fixation by root nodules between an inoculation with USDA 110T only and co-inoculation treatments. To clarify the potential involvement of PR proteins in the restriction of nodule formation in the plants tested, the relative expression levels of PR-1, PR-2, PR-5, and PDF1.2 in NOD1–3 roots were measured using real-time PCR. One group of soil bacteria (Gr.3), which markedly reduced nodule numbers, significantly induced the expression of PR-1, PR-5 and PDF1.2 genes by day 5 after the inoculation. By days 7, 10, and 20 after the inoculation, the expression levels of PR-2 and PR-5 were lower than those with the uninoculated treatment. Inoculations with this group of soil bacteria resulted in lower root nodule numbers than with other tested soil bacteria exerting weak inhibitory effects on nodulation, and were accompanied by the induction of plant defense-related genes. Thus, PR genes appear to play important roles in the mechanisms that suppresses nodule formation on soybean roots.