Cyanobacteria are phototrophic microorganisms able to establish nitrogen-fixing symbiotic associations with representatives of all four of the major phylogenetic divisions of terrestrial plants. Despite increasing knowledge on the beneficial effects of cyanobacteria in rice fields, the information about the interaction between these microorganisms and rice at the molecular and structural levels is still limited. We have used the model nitrogen-fixing cyanobacterium Nostoc punctiforme to promote a long-term stable endophytic association with rice. Inoculation with this strain of hydroponic cultures of rice produces a fast adherence of the cyanobacterium to rice roots. At longer times, cyanobacterial growth in the proximity of the roots increased until reaching a plateau. This latter phase coincides with the intracellular colonization of the root epidermis and exodermis. Structural analysis of the roots revealed that the cyanobacterium use an apoplastic route to colonize the plant cells. Moreover, plant roots inoculated with N. punctiforme show both the presence of heterocysts and nitrogenase activity, resulting in the promotion of plant growth under nitrogen deficiency, thus providing benefits for the plant.

蓝细菌是能够与陆生植物的所有四个主要系统发育分支的代表建立固氮共生联系的光养微生物。尽管人们对蓝细菌在稻田中的有益作用的认识不断提高，但是有关这些微生物与稻在分子和结构水平上相互作用的信息仍然有限。我们已经使用了模型固氮蓝细菌点状菌促进与水稻长期稳定的内生联系。用这种水稻的水培培养物接种会产生蓝细菌对水稻根的快速粘附。在更长的时间里，根附近的蓝细菌生长增加，直到达到平稳。后一个阶段与根表皮和外皮的细胞内定殖相吻合。根的结构分析表明，蓝细菌使用质外生途径定殖于植物细胞。此外，接种点状猪笼草的植物根部同时显示了异胞藻和氮酶的活性，从而在缺氮的情况下促进了植物的生长，从而为植物带来了好处。