Regulatory nodD1 and nodD2 genes of Rhizobium tropici strain CIAT 899 and their roles in the early stages of molecular signaling and host-legume nodulation

BACKGROUND: Nodulation and symbiotic nitrogen fixation are mediated by several genes, both of the host legume and of the bacterium. The rhizobial regulatory nodD gene plays a critical role, orchestrating the transcription of the other nodulation genes. Rhizobium tropici strain CIAT 899 is an effective symbiont of several legumes—with an emphasis on common bean (Phaseolus vulgaris)—and is unusual in carrying multiple copies of nodD, the roles of which remain to be elucidated. RESULTS: Phenotypes, Nod factors and gene expression of nodD1 and nodD2 mutants of CIAT 899 were compared with those of the wild type strain, both in the presence and in the absence of the nod-gene-inducing molecules apigenin and salt (NaCl). Differences between the wild type and mutants were observed in swimming motility and IAA (indole acetic acid) synthesis. In the presence of both apigenin and salt, large numbers of Nod factors were detected in CIAT 899, with fewer detected in the mutants. nodC expression was lower in both mutants; differences in nodD1 and nodD2 expression were observed between the wild type and the mutants, with variation according to the inducing molecule, and with a major role of apigenin with nodD1 and of salt with nodD2. In the nodD1 mutant, nodulation was markedly reduced in common bean and abolished in leucaena (Leucaena leucocephala) and siratro (Macroptilium atropurpureum), whereas a mutation in nodD2 reduced nodulation in common bean, but not in the other two legumes. CONCLUSION: Our proposed model considers that full nodulation of common bean by R. tropici requires both nodD1 and nodD2, whereas, in other legume species that might represent the original host, nodD1 plays the major role. In general, nodD2 is an activator of nod-gene transcription, but, in specific conditions, it can slightly repress nodD1. nodD1 and nodD2 play other roles beyond nodulation, such as swimming motility and IAA synthesis. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12864-015-1458-8) contains supplementary material, which is available to authorized users

Aortic stiffness and distensibility in elite athletes: impact of discipline and gender

Abstract Background Aortic remodeling in athletes is variable among sports disciplines with more ascending aorta (Asc Ao) dilatation in endurance (EAs) as compared to power athletes (PAs). Nevertheless, the impact of this differential remodeling on the Asc Ao functional properties is not well established. The aim of this study was to assess the distensibility and stiffness of the ascending aorta in endurance and power elite athletes in order to evaluate if this aortic remodeling implies functional changes. Methods 119 elite athletes (61 EA and 58 PA, 49% female sex, mean age: 18.7±7.1 years) underwent standardized pre-participation screening with 12 lead ECG, transthoracic echocardiography and maximum stress test. Asc Ao diameter was measured from parasternal long axis views in 2D echocardiography. The aortic distensibility index (ADi) was calculated as 2 × (systolic Asc Ao diameter − diastolic Asc Ao diameter) / (diastolic Asc Ao diameter) × (pulse pressure) (cm–2 dyn–1 10–6). Aortic stiffness (AS) index was defined as Ln (systolic blood pressure/diastolic blood pressure) / (systolic Asc Ao diameter − diastolic Asc Ao diameter)/diastolic proximal Asc Ao diameter. Results Globally, EA presented larger AscAO, both in absolute and indexed values, than PA (28±3.0 vs 26±3.0cm, p&amp;lt;0.001 and 16.4±1.5 vs 15.7±1.9cm, p&amp;lt;0.05, while were no differences in AS or ADi) (Figure 1A). Nevertheless, ADi in male EAs was higher than in male PAs (ADi: 4.3±1.7 vs 3.2±1.3 cm2/dyn/10–6, p&amp;lt;0.05) and AS was lower (AS: 4.7±1.7 vs 6.3±3.8, P&amp;lt;0.005) (Figure 1B and 1C). Female athletes presented higher ADi (ADi: 4.7±1.9 vs 4.0±1.6 cm, p&amp;lt;0.05) and a trend towards lower AS (4.8±2.9 vs 5.1±2.6, p: 0.4) than male athletes. There were no differences in AS or ADi between female EAs and PAs. Conclusion Male EAs showed an increased aortic distensibility with lower stiffness as compared to that observed in male PAs. This difference was not observed in female EAs and PAs, potentially due to better baseline distensibility with less room for improvement with endurance training. Funding Acknowledgement Type of funding source: None </jats:sec