A variety of regulatory mechanisms are involved in the nitrogen-dependent modulation of the nodule organogenesis program in legume roots

Abstract

Combined nitrogen (N) sources are known to strongly affect initiation, development and functioning of Nitrogen-Fixing-Nodules whose formation is triggered by lipochitin-oligosaccharide signals secreted in the rhizospere by the Rhizobium partner. The rapid effects of N supply on nodule initiation have been mainly described when N sources are present at the moment of Rhizobium inoculation or purified Nod Factors addition. We recently reported that high ammonium nitrate growth conditions might also strongly affect the nodulation competence of Lotus japonicus plants, prior to the Rhizobium inoculation. This is a long-term effect, which suggests a change of the general nutritional status as the signal controlling the reduced nodulation capacities. The mechanisms underlying these inhibitory pathways are apparently different and the identification of the molecular actors involved may provide new insights into the linkage between N environmental changes and root organogenesis programs.

Root Exudation of Phytochemicals in Arabidopsis Follows Specific Patterns That Are Developmentally Programmed and Correlate with Soil Microbial Functions

“…For example, to overcome nitrogen deficiency legumes release specific flavonols which attract and initiate symbiotic relationships with rhizobia [6]. However, when N fertilization is supplemented the symbiotic interaction is halted [7]. When Arabidopsis is attacked by the foliar pathogen Pseudomonas syringae pv tomato , roots release malic acid which recruits beneficial soil bacteria capable of triggering host defense responses against P. syringae [8].…”

Cropping systems sustainability: Inoculation and fertilisation effect on sulla performances in a new cultivation area

“…In fact, soil nitrate level may affect symbiotic N-fixation due to inhibitory action on nodule initiation and delay of N-fixation. A negative linear relationship between N rate and % Ndfa has been reported for legumes species, such as white clover (Trifolium repens L.), pea (Pisum sativum L.) and Lotus japonicus, when plants received fertiliser N at sowing (Mac Duff et al, 1996;Waterer and Vessey, 1993;Voisin et al, 2002;Omrane and Chiurazzi, 2009). In addition, the use of starter doses of N fertiliser aimed at alleviating N deficiency symptoms during legume early growth is still a disputed issue, regarding the balance between actual benefits and possible nodulation reduction (Van Kessel and Hartley, 2000).…”

Application of Natural Blends of Phytochemicals Derived from the Root Exudates of Arabidopsis to the Soil Reveal That Phenolic-related Compounds Predominantly Modulate the Soil Microbiome

“…For example, legumes exude specific flavonoids that act as signaling molecules to attract nitrogen-fixing bacteria (11). Yet when soil nitrogen is not limiting to the plant, this symbiosis does not occur (12). On the other hand, certain legumes release canavanine, an antimicrobial that acts against a broad range of microbes without affecting Rhizobia, which further cultures this beneficial microbe in the rhizosphere of legumes (13).…”