Root development is remarkably sensitive to variations in the supply and distribution of inorganic nutrients in the soil. Here we review examples of the ways in which nutrients such as N, P, K and Fe can affect developmental processes such as root branching, root hair production, root diameter, root growth angle, nodulation and proteoid root formation. The nutrient supply can affect root development either directly, as a result of changes in the external concentration of the nutrient, or indirectly through changes in the internal nutrient status of the plant. The direct pathway results in developmental responses that are localized to the part of the root exposed to the nutrient supply; the indirect pathway produces systemic responses and seems to depend on long-distance signals arising in the shoot. We propose the term 'trophomorphogenesis' to describe the changes in plant morphology that arise from variations in the availability or distribution of nutrients in the environment. We discuss what is currently known about the mechanisms of external and internal nutrient sensing, the possible nature of the long-distance signals and the role of hormones in the trophomorphogenic response.Abbreviations: ABA, abscisic acid; NR, nitrate reductase; P i , inorganic phosphate

No abstract

Background The use of dexamethasone in patients infected with Strongyloides stercoralis can cause severe complications. It is necessary to investigate the relationship between coronavirus disease 2019 (COVID-19) and strongyloidiasis infection. Methods A retrospective, longitudinal, descriptive study was undertaken to review all patients admitted with a diagnosis of COVID-19 infection at the Complejo Asistencial Universitario de Salamanca, Spain, during 1 March–31 December 2020. Results A total of 2567 patients received a diagnosis of COVID-19. Eighty-six patients from endemic areas were included. Seven patients had strongyloidiasis. Five patients were female. The mean age (±SD) was 39 (±10.8) y. Six patients were Latin-American and only one patient was from Africa. Six patients had previous symptoms compatible with strongyloidiasis infections. Only three patients received dexamethasone (6 mg once daily) for 10 d. In all cases, the clinical courses of the patients were satisfactory. No patient died or was admitted to the ICU. Conclusions Screening programmes using serological techniques should be implemented in COVID-19 patients to prevent strongyloidiasis. Our study suggested that drugs used against COVID-19 in patients with strongyloidiasis did not affect the evolution of the disease. However, more studies are necessary to elucidate the role of dexamethasone in COVID-19 patients infected with Strongyloides.

Ynt1 is the only high-affinity nitrate uptake system in Hansenula polymorpha. Nitrate uptake was directly correlated with the Ynt1 levels and shown to be independent of nitrate reductase (NR) activity levels. Ynt1 failed to transport chlorate and, as a result, strains lacking YNT1 were sensitive to chlorate, as is the wild-type. Nitrite uptake in a wild-type strain was partially inhibited by nitrate to levels shown by a YNT1-disrupted strain in which, in turn, nitrite transport was not inhibited by nitrate. It is concluded that nitrite uptake takes place by two different transport systems: Ynt1 and a nitrite-specific transporter(s). The nitrite-specific transport system was induced by nitrate; consistently, no induction was observed in strains lacking the transcription factor YNA1, which is involved in nitrate and nitrite induction of the nitrate assimilatory structural genes. Ynt1 presents its optimal rate for nitrite uptake at pH 6, while pH 4 was optimal for the specific nitrite uptake system(s). At pH 5.5, the contribution of Ynt1 to high-affinity nitrate and nitrite uptake was around 95% and 60%, respectively. The apparent K m of Ynt1 for nitrate and nitrite is in the µM range, as is the specific nitrite uptake system for nitrite. The analysis of the effect of the reduced nitrogen sources on nitrate assimilation revealed that glutamine inactivates nitrate and nitrite transport, dependent on Ynt1, but not the nitrite-specific system.