These authors contributed equally to this work. SUMMARYThe establishment of symbiotic interactions between mycorrhizal fungi, rhizobial bacteria and their legume hosts involves a common symbiosis signalling pathway. This signalling pathway is activated by Nod factors produced by rhizobia and these are recognised by the Nod factor receptors NFR1/LYK3 and NFR5/NFP. Mycorrhizal fungi produce lipochitooligosaccharides (LCOs) similar to Nod factors, as well as short-chain chitin oligomers (CO4/5), implying commonalities in signalling during mycorrhizal and rhizobial associations. Here we show that NFR1/LYK3, but not NFR5/NFP, is required for the establishment of the mycorrhizal interaction in legumes. NFR1/LYK3 is necessary for the recognition of mycorrhizal fungi and the activation of the symbiosis signalling pathway leading to induction of calcium oscillations and gene expression. Chitin oligosaccharides also act as microbe associated molecular patterns that promote plant immunity via similar LysM receptor-like kinases. CERK1 in rice has the highest homology to NFR1 and we show that this gene is also necessary for the establishment of the mycorrhizal interaction as well as for resistance to the rice blast fungus. Our results demonstrate that NFR1/LYK3/OsCERK1 represents a common receptor for chitooligosaccharide-based signals produced by mycorrhizal fungi, rhizobial bacteria (in legumes) and fungal pathogens. It would appear that mycorrhizal recognition has been conserved in multiple receptors across plant species, but additional diversification in certain plant species has defined other signals that this class of receptors can perceive.

Legumes form symbiotic associations with either nitrogen-fixing bacteria or arbuscular mycorrhizal fungi. Formation of these two symbioses is regulated by a common set of signalling components that act downstream of recognition of rhizobia or mycorrhizae by host plants. Central to these pathways is the calcium and calmodulin-dependent protein kinase (CCaMK)–IPD3 complex which initiates nodule organogenesis following calcium oscillations in the host nucleus. However, downstream signalling events are not fully understood. Here we show that Medicago truncatula DELLA proteins, which are the central regulators of gibberellic acid signalling, positively regulate rhizobial symbiosis. Rhizobia colonization is impaired in della mutants and we provide evidence that DELLAs can promote CCaMK–IPD3 complex formation and increase the phosphorylation state of IPD3. DELLAs can also interact with NSP2–NSP1 and enhance the expression of Nod-factor-inducible genes in protoplasts. We show that DELLA is able to bridge a protein complex containing IPD3 and NSP2. Our results suggest a transcriptional framework for regulation of root nodule symbiosis.

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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new virus recently isolated from humans. SARS-CoV-2 was discovered to be the pathogen responsible for a cluster of pneumonia associated with severe respiratory disease occurred in December 2019 in China. This novel pulmonary infection, formally called coronavirus disease 2019 (COVID-19), has spread rapidly in China and beyond. On 8 March 2020, the number of Italians with SARS-CoV-2 infection was 7375 with a 48% hospitalization rate. At present, chest computed tomography imaging is considered the most effective method for detection of lung abnormalities in early-stage disease and for quantitative assessment of severity and progression of COVID-19 infection. Although chest x-ray (CXR) is considered not sensitive for the detection of pulmonary involvement in the early stage of disease, we believe that, in the current emergency setting, CXR can be a useful diagnostic tool for monitoring the rapid progression of lung abnormalities in infected patients, particularly in intensive care units. In this article we present our experimental CXR scoring system that we are applying in hospitalized patients with COVID-19 pneumonia to quantify and monitor the severity and progression of this new infectious disease. We also present the results of our preliminary validation study on a sample of 100 hospitalized patients with SARS-CoV-2 infection for whom the final outcome (recovery or death) was available.

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Most land plants benefit from endosymbiotic interactions with mycorrhizal fungi, including legumes and some non-legumes that also interact with endosymbiotic nitrogen-fixing bacteria to form nodules. In addition to these helpful interactions, plants are continuously exposed to would-be pathogenic microbes: discriminating between friends and foes is a major determinant of plant survival. Recent breakthroughs have revealed how some key signals from pathogens and symbionts are distinguished. Once this checkpoint has been passed and a compatible symbiont is recognized, the plant coordinates the sequential development of two types of specialized structures in the host. The first serve to mediate infection, and the second, which appear later, serve as sophisticated intracellular nutrient exchange interfaces. The overlap in both the signaling pathways and downstream infection components of these symbioses reflects their evolutionary relatedness and the common requirements of these two interactions. However, the different outputs of the symbioses, phosphate uptake vs. nitrogen fixation, require fundamentally different components and physical environments and necessitated the recruitment of different master regulators, NLPs and PHRs, for nodulation and mycorrhization, respectively.

There are frequent population flow and complex spatial structures in suburban villages. Understanding the spatial characteristics of population activities in suburban villages helps to coordinate the relationship between urban and rural areas and guide the development of suburban villages and the formulation of sound policies. Taking the rural area of Qin and Han New City as the research object, this paper constructs a population time-space analysis framework of “population attribute-activity characteristics-spatial analysis” based on cellphone signaling data. According to the characteristics of the population activity curve, K-means clustering algorithm was used to classify rural space and analyze their characteristics. This study has shown that migrants, who are showed as young and energetic, account for 49.8% of the local registered population per day. Bidirectional flow of residents and commuters is generally presented in urban and rural areas. The urban-rural relation curve was characterized by “double peaks”. The changes in the population in each village and the intensity of urban-rural relation were affected by location, industry and land use. The village population activity curve was classified into three categories, and nine characteristic villages are formed combined with the activity function. The research results can provide a scientific basis for urban and rural planning, spatial planning, industrial guidance and the facility layout.