Infection of Soybean and Pea Nodules by \u3cem\u3eRhizobium\u3c/em\u3e spp. Purine Auxotrophs in the Presence of 5-aminoimidazole-4-Carboxamide Riboside

Purine auxotrophs of various Rhizobium species are symbiotically defective, usually unable to initiate or complete the infection process. Earlier studies demonstrated that, in the Rhizobium etli-bean symbiosis, infection by purine auxotrophs is partially restored by supplementation of the plant medium with 5-amino-imidazole-4-carboxamide (AICA) riboside, the unphosphorylated form of the purine biosynthetic intermediate AICAR. The addition of purine to the root environment does not have this effect. In this study, purine auxotrophs of Rhizobium fredii HH303 and Rhizobium leguminosarum 128C56 (bv. viciae) were examined. Nutritional and genetic characterization indicated that each mutant was blocked in purine biosynthesis prior to the production of AICAR. R. fredii HH303 and R. leguminosarum 128C56 appeared to be deficient in AICA riboside transport and/or conversion into AICAR, and the auxotrophs derived from them grew very poorly with AICA riboside as a purine source. All of the auxotrophs elicited poorly developed, uninfected nodules on their appropriate hosts. On peas, addition of AICA riboside or purine to the root environment led to enhanced nodulation; however, infection threads were observed only in the presence of AICA riboside. On soybeans, only AICA riboside was effective in enhancing nodulation and promoting infection. Although AICA riboside supplementation of the auxotrophs led to infection thread development on both hosts, the numbers of bacteria recovered from the nodules were still 2 or more orders of magnitude lower than in fully developed nodules populated by wild-type bacteria. The ability to AICA riboside to promote infection by purine auxotrophs, despite serving as a very poor purine source for these strains, supports the hypothesis that AICAR plays a role in infection other than merely promoting bacterial growth

The 2021 EULAR/American College of Rheumatology points to consider for diagnosis, management and monitoring of the interleukin-1 mediated autoinflammatory diseases: cryopyrin-associated periodic syndromes, tumour necrosis factor receptor-associated periodic syndrome, mevalonate kinase deficiency, and deficiency of the interleukin-1 receptor antagonist

BACKGROUND: The interleukin-1 (IL-1) mediated systemic autoinflammatory diseases, including the cryopyrin-associated periodic syndromes (CAPS), tumour necrosis factor receptor-associated periodic syndrome (TRAPS), mevalonate kinase deficiency (MKD) and deficiency of the IL-1 receptor antagonist (DIRA), belong to a group of rare immunodysregulatory diseases that primarily present in early childhood with variable multiorgan involvement. When untreated, patients with severe clinical phenotypes have a poor prognosis, and diagnosis and management of these patients can be challenging. However, approved treatments targeting the proinflammatory cytokine IL-1 have been life changing and have significantly improved patient outcomes. OBJECTIVE: To establish evidence-based recommendations for diagnosis, treatment and monitoring of patients with IL-1 mediated autoinflammatory diseases to standardise their management. METHODS: A multinational, multidisciplinary task force consisting of physician experts, including rheumatologists, patients or caregivers and allied healthcare professionals, was established. Evidence synthesis, including systematic literature review and expert consensus (Delphi) via surveys, was conducted. Consensus methodology was used to formulate and vote on statements to guide optimal patient care. RESULTS: The task force devised five overarching principles, 14 statements related to diagnosis, 10 on therapy, and nine focused on long-term monitoring that were evidence and/or consensus-based for patients with IL-1 mediated diseases. An outline was developed for disease-specific monitoring of inflammation-induced organ damage progression and reported treatments of CAPS, TRAPS, MKD and DIRA. CONCLUSION: The 2021 EULAR/American College of Rheumatology points to consider represent state-of-the-art knowledge based on published data and expert opinion to guide diagnostic evaluation, treatment and monitoring of patients with CAPS, TRAPS, MKD and DIRA, and to standardise and improve care, quality of life and disease outcomes

The Requirements for Purine and Exopolysaccharide Biosynthesis in the Symbioses of \u3cem\u3eRhizobium leguminosarum\u3c/em\u3e

Purine auxotrophs of Rhizobium leguminosarum strain CFN42 (biovar phaseoli) induce bean nodules lacking infection threads. Only purine and pyrimidine auxotrophs had this particular symbiotic phenotype on bean. Transfer of mutant alleles affecting purine or pyrimidine synthesis into R. leguminosarum strains which nodulate pea (bv. viciae) or clover (bv. trifolii) had a similar effect on pea and clover nodulation. Several experiments showed that the mutants grew in the rhizosphere as well as the wild-type strain. The addition of 5-aminoimidazole-4-carboxamide riboside (AICAR) enhanced nodule development of the auxotrophs on all of the respective host plants. It is possible that AICAR or the subsequent precursor of inosine, or a derivative of one of them, is an essential factor in promoting nodule development. Ten exopolysaccharide (Exo-) mutants of strain CFN42 were isolated after Tn5 mutagenesis and were grouped into three classes (Class A1, A2 and B). The Class A1 and A2 strains induced normal nitrogen-fixing nodules on beans. The A1 strains contained Tn5 inserts on the same chromosomal EcoRI fragment and could be complemented to Exo+ with cosmids of the CFN42 library carrying this fragment. The A2 strains harbored Tn5 insertions on another chromosomal EcoRI fragment but could not be complemented to Exo+ with cosmids of the CFN42 library. Both classes of mutants did not produce any acidic exopolysaccharide (EPS) but, unlike the wild-type strain excreted lipopolysaccharide (LPS) into the media. The Class B strains induced underdeveloped nodules (Ndv-) on bean. They lacked acidic EPS and were deficient in lipopolysaccharide synthesis (Exo- Lps- Ndv-). These mutants were complemented to Exo+ Lps+ Ndv+ by either of two overlapping cosmids and the Tn5 inserts were found on adjacent chromosomal EcoRI fragments. The exo::Tn5 alleles were transferred to bv. viciae and bv. trifolii strains. The resulting transconjugants were Exo- and failed to induce normal nodules on pea and clover. When these Exo- mutants were complemented to Exo+ by cosmids from the CFN42 library, normal nodulation on pea and clover was restored. Thus, exo mutations which did not affect bean nodulation prevented normal nodule development on pea and clover. Acidic EPS appears to be a compatibility factor on pea and clover, but is unnecessary for symbiosis with bean