Comparative secretome analysis of Striga and Cuscuta species identifies candidate virulence factors for two evolutionarily independent parasitic plant lineages.

BACKGROUND: Many parasitic plants of the genera Striga and Cuscuta inflict huge agricultural damage worldwide. To form and maintain a connection with a host plant, parasitic plants deploy virulence factors (VFs) that interact with host biology. They possess a secretome that represents the complement of proteins secreted from cells and like other plant parasites such as fungi, bacteria or nematodes, some secreted proteins represent VFs crucial to successful host colonisation. Understanding the genome-wide complement of putative secreted proteins from parasitic plants, and their expression during host invasion, will advance understanding of virulence mechanisms used by parasitic plants to suppress/evade host immune responses and to establish and maintain a parasite-host interaction. RESULTS: We conducted a comparative analysis of the secretomes of root (Striga spp.) and shoot (Cuscuta spp.) parasitic plants, to enable prediction of candidate VFs. Using orthogroup clustering and protein domain analyses we identified gene families/functional annotations common to both Striga and Cuscuta species that were not present in their closest non-parasitic relatives (e.g. strictosidine synthase like enzymes), or specific to either the Striga or Cuscuta secretomes. For example, Striga secretomes were strongly associated with 'PAR1' protein domains. These were rare in the Cuscuta secretomes but an abundance of 'GMC oxidoreductase' domains were found, that were not present in the Striga secretomes. We then conducted transcriptional profiling of genes encoding putatively secreted proteins for the most agriculturally damaging root parasitic weed of cereals, S. hermonthica. A significant portion of the Striga-specific secretome set was differentially expressed during parasitism, which we probed further to identify genes following a 'wave-like' expression pattern peaking in the early penetration stage of infection. We identified 39 genes encoding putative VFs with functions such as cell wall modification, immune suppression, protease, kinase, or peroxidase activities, that are excellent candidates for future functional studies. CONCLUSIONS: Our study represents a comprehensive secretome analysis among parasitic plants and revealed both similarities and differences in candidate VFs between Striga and Cuscuta species. This knowledge is crucial for the development of new management strategies and delaying the evolution of virulence in parasitic weeds.

Genome-enabled discovery of candidate virulence loci in Striga hermonthica, a devastating parasite of African cereal crops.

Parasites have evolved proteins, virulence factors (VFs), that facilitate plant colonisation, however VFs mediating parasitic plant-host interactions are poorly understood. Striga hermonthica is an obligate, root-parasitic plant of cereal hosts in sub-Saharan Africa, causing devastating yield losses. Understanding the molecular nature and allelic variation of VFs in S. hermonthica is essential for breeding resistance and delaying the evolution of parasite virulence. We assembled the S. hermonthica genome and identified secreted proteins using in silico prediction. Pooled sequencing of parasites growing on a susceptible and a strongly resistant rice host allowed us to scan for loci where selection imposed by the resistant host had elevated the frequency of alleles contributing to successful colonisation. Thirty-eight putatively secreted VFs had very different allele frequencies with functions including host cell wall modification, protease or protease inhibitor and kinase activities. These candidate loci had significantly higher Tajima's D than the genomic background, consistent with balancing selection. Our results reveal diverse strategies used by S. hermonthica to overcome different layers of host resistance. Understanding the maintenance of variation at virulence loci by balancing selection will be critical to managing the evolution of virulence as part of a sustainable control strategy.

Development of competencies for advanced nursing practice in intensive care units across Europe: A modified e-Delphi study.

PURPOSE: The aim of this study was to identify and define core competencies for advanced nursing roles in adult intensive care units across Europe. METHODS: Three round electronic Delphi conducted between September 2018 and November 2019, with an expert panel of 184 nurses from 20 countries, supplemented by consensus meetings with 16 participants from 10 countries before each round. RESULTS: In Round 1, participants generated 275 statements across 4 domains (knowledge skills and clinical performance; clinical leadership, teaching and supervision; personal effectiveness; safety and systems management). These were re-worded as competency statements and refined at a consensus meeting resulting in 230 statements in 30 sub-domains. The expert panel rated the 'importance' of each statement in Round 2; further refinement at the consensus meeting and the addition of descriptors for sub-domains resulted in 95 competency statements presented to the panel in Round 3. These were all retained in the final set of competency statements. CONCLUSION: We have used consensus techniques to generate competencies for advanced practice in intensive care nursing that are relevant across European countries and available in eight languages. These have provided the basis for an outline curriculum from which education programmes can be developed within countries.

Identifying existing management practices in the control of Striga asiatica within rice-maize systems in mid-west Madagascar.

Infestations by the parasitic weed genus Striga result in significant losses to cereal crop yields across sub-Saharan Africa. The problem disproportionately affects subsistence farmers who frequently lack access to novel technologies. Effective Striga management therefore requires the development of strategies utilizing existing cultural management practices. We report a multiyear, landscape-scale monitoring project for Striga asiatica in the mid-west of Madagascar, undertaken over 2019-2020 with the aims of examining cultural, climatic, and edaphic factors currently driving abundance and distribution. Long-distance transects were established across the middle-west region of Madagascar, over which S. asiatica abundance in fields was estimated. Analysis of the data highlights the importance of crop variety and legumes in driving Striga density. Moreover, the dataset revealed significant effect of precipitation seasonality, mean temperature, and altitude in determining abundance. A composite management index indicated the effect of a range of cultural practices on changes in Striga abundance. The findings support the assertion that single measures are not sufficient for the effective, long-term management of Striga. Furthermore, the composite score has potential as a significant guide of integrated Striga management beyond the geographic range of this study.

Sustainability in critical care practice: A grounded theory study.

BACKGROUND: Sustaining high-quality, critical care practice is challenging because of current limits to financial, environmental, and social resources. The National Health Service in England intends to be more sustainable, although there is minimal research into what sustainability means to people working in critical care, and a theoretical framework is lacking that explains the social processes influencing sustainability in critical care. AIMS AND OBJECTIVES: This study aimed to explain the concept of sustainability from the perspective of practitioners caring for critically ill patients. DESIGN: The qualitative research followed a Charmazian constructivist grounded theory approach, including concurrent data collection and interpretation through constant comparison analysis. METHODS: In-depth interviews were conducted online or by telephone with 11 health care professionals working in critical care in the South of England (8 nurses, 2 physiotherapists, and 1 technician). Schatzman's dimensional analysis and Straussian grounded theory techniques supplemented the data analysis. RESULTS: Sustainability was defined as maintaining financial, environmental, and social resources throughout the micro, meso, and macro systems of critical care practice. The most pertinent social process enabling sustainability of critical care was satisficing (satisfaction of achieving a goal of quality care while sufficing within the limits of available resources). Increased satisficing enabled practitioners to fulfil their sense of normative, responsible, sustainable, and flourishing practice. Satisficing was bounded by the cognitive and environmental influences on decisions and an ethical imperative to ensure resources were used wisely through stewarding. CONCLUSIONS: An explanation of the concept of sustainability and significant social processes, in relation to critical care, are presented in a theoretical framework, with implications for how financial, environmental, and social resources for critical care practice can be maintained. RELEVANCE TO CLINICAL PRACTICE: This theory offers clinicians, managers, educators, and researchers a definition of sustainability in critical care practice and provides a structured approach to addressing critical care sustainability issues.

SMAX1-dependent seed germination bypasses GA signalling in Arabidopsis and Striga.

Parasitic plant infestations dramatically reduce the yield of many major food crops of sub-Saharan Africa and pose a serious threat to food security on that continent1. The first committed step of a successful infestation is the germination of parasite seeds primarily in response to a group of related small-molecule hormones called strigolactones (SLs), which are emitted by host roots2. Despite the important role of SLs, it is not clear how host-derived SLs germinate parasitic plants. In contrast, gibberellins (GA) acts as the dominant hormone for stimulation of germination in non-parasitic plant species by inhibiting a set of DELLA repressors3. Here, we show that expression of SL receptors from the parasitic plant Striga hermonthica in the presence of SLs circumvents the GA requirement for germination of Arabidopsis thaliana seed. Striga receptors co-opt and enhance signalling through the HYPOSENSITIVE TO LIGHT/KARRIKIN INSENSITIVE 2 (AtHTL/KAI2) pathway, which normally plays a rudimentary role in Arabidopsis seed germination4,5. AtHTL/KAI2 negatively controls the SUPPRESSOR OF MAX2 1 (SMAX1) protein5, and loss of SMAX1 function allows germination in the presence of DELLA repressors. Our data suggest that ligand-dependent inactivation of SMAX1 in Striga and Arabidopsis can bypass GA-dependent germination in these species.

Publisher Correction: Farming with crops and rocks to address global climate, food and soil security.

In the version of this Perspective originally published, 'acidification' was incorrectly spelt as 'adification' in Fig. 4. This has now been corrected.

Farming with crops and rocks to address global climate, food and soil security.

The magnitude of future climate change could be moderated by immediately reducing the amount of CO2 entering the atmosphere as a result of energy generation and by adopting strategies that actively remove CO2 from it. Biogeochemical improvement of soils by adding crushed, fast-reacting silicate rocks to croplands is one such CO2-removal strategy. This approach has the potential to improve crop production, increase protection from pests and diseases, and restore soil fertility and structure. Managed croplands worldwide are already equipped for frequent rock dust additions to soils, making rapid adoption at scale feasible, and the potential benefits could generate financial incentives for widespread adoption in the agricultural sector. However, there are still obstacles to be surmounted. Audited field-scale assessments of the efficacy of CO2 capture are urgently required together with detailed environmental monitoring. A cost-effective way to meet the rock requirements for CO2 removal must be found, possibly involving the recycling of silicate waste materials. Finally, issues of public perception, trust and acceptance must also be addressed.