Jourand Philippe, Renier Adeline, Rapior Sylvie, Miana de Faria Sergio, Prin Yves, Galiana Antoine, Giraud Eric, Dreyfus Bernard
Laboratoire des Symbioses Tropicales et Méditerranéennes, UMR 113 AgroM/CIRAD/INRA/IRD/UMII, TA 10/J, Campus International de Baillarguet, Montpellier, France.
Mol Plant Microbe Interact. 2005 Oct;18(10):1061-8. doi: 10.1094/MPMI-18-1061.
Some rare leguminous plants of the genus Crotalaria are specifically nodulated by the methylotrophic bacterium Methylobacterium nodulans. In this study, the expression and role of bacterial methylotrophy were investigated during symbiosis between M. nodulans, strain ORS 2060T, and its host legume, Crotalaria podocarpa. Using lacZ fusion to the mxaF gene, we showed that the methylotroph genes are expressed in the root nodules, suggesting methylotrophic activity during symbiosis. In addition, loss of the bacterial methylotrophic function significantly affected plant development. Indeed, inoculation of M. nodulans nonmethylotroph mutants in C. podocarpa decreased the total root nodule number per plant up to 60%, decreased the whole-plant nitrogen fixation capacity up to 42%, and reduced the total dry plant biomass up to 46% compared with the wild-type strain. In contrast, inoculation of the legume C. podocarpa with nonmethylotrophic mutants complemented with functional mxa genes restored the symbiotic wild phenotype. These results demonstrate the key role of methylotrophy during symbiosis between M. nodulans and C. podocarpa.
猪屎豆属的一些稀有豆科植物会被甲基营养型细菌甲基杆菌特异性地结瘤。在本研究中，对甲基杆菌菌株ORS 2060T与其宿主豆科植物长叶猪屎豆共生期间细菌甲基营养的表达及作用进行了研究。利用与mxaF基因的lacZ融合，我们发现甲基营养型基因在根瘤中表达，表明共生期间存在甲基营养活性。此外，细菌甲基营养功能的丧失显著影响植物发育。事实上，用甲基杆菌非甲基营养突变体接种长叶猪屎豆，与野生型菌株相比，每株植物的根瘤总数减少了60%，全株固氮能力降低了42%，植物总干生物量减少了46%。相反，用携带功能性mxa基因的非甲基营养突变体接种豆科长叶猪屎豆，恢复了共生野生表型。这些结果证明了甲基营养在甲基杆菌与长叶猪屎豆共生过程中的关键作用。
