Unravelling the regulatory network controlling lateral root hydropatterning

The 3-dimensional shape of a root system is of crucial importance to its ability to take up nutrients and water. As these resources are heterogeneously distributed in the soil, plants need to adapt their root growth to aid foraging. One such adaptive response is termed lateral root (LR) hydropatterning where roots branch towards areas with higher water availability. The main aim of this thesis is to investigate how plant roots sense water distribution and which regulatory pathways control lateral root branching towards available water using the model plant Arabidopsis thaliana. We observed that the choice of lateral root founder cells (LRFC) in the pericycle cell layer they originate from is influenced by external water availability. This allows lateral roots to angle towards water from the very first round of formative cell divisions. Additionally, the emerging lateral root primordium grows towards water availability through asymmetric rounds of cell division in its primordium flanks. LR hydropatterning is genetically regulated through a major regulator of LR initiation AUXIN RESPONSE FACTOR7 (ARF7). Knock-out mutants lose the ability to branch towards water and do not asymmetrically express the key transcription factor LBD16-GFP, a direct target for ARF7. This mechanism is regulated through post-translational regulation of ARF7. The ARF7 sequence contains four sites that can be SUMOylated. Transgenic lines expressing ARF7 with mutations in each of these four SUMO sites cannot rescue arf7-1 LR hydropatterning, revealing a key role for SUMOylation controlling water sensing by roots. ARF7 SUMO status appears to be controlled by SUMO protease OVERLY TOLERANT TO SALT1 (OTS1). Double knock-out mutants in OTS1 and its close homolog OTS2 have severely delayed root development and a LR hydropatterning defect. Additionally, ots1 ots2 mutants display reduced LR initiation and emergence defects that can be restored to Wild-Type levels by expressing an OTS1-Venus transgene. OTS1-Venus can be detected from the late elongation zone onwards in root pericycle cells and is stably expressed in the primordia. However, no asymmetrical localisation of OTS1-Venus is observed after a hydropatterning cue suggesting that SUMO protease activity, rather than stability, controls LR hydropatterning. This thesis highlights the early response of lateral roots to asymmetrical water distribution and role the deSUMOylation machinery plays in its molecular regulation

Unravelling the regulatory network controlling lateral root hydropatterning

The 3-dimensional shape of a root system is of crucial importance to its ability to take up nutrients and water. As these resources are heterogeneously distributed in the soil, plants need to adapt their root growth to aid foraging. One such adaptive response is termed lateral root (LR) hydropatterning where roots branch towards areas with higher water availability. The main aim of this thesis is to investigate how plant roots sense water distribution and which regulatory pathways control lateral root branching towards available water using the model plant Arabidopsis thaliana. We observed that the choice of lateral root founder cells (LRFC) in the pericycle cell layer they originate from is influenced by external water availability. This allows lateral roots to angle towards water from the very first round of formative cell divisions. Additionally, the emerging lateral root primordium grows towards water availability through asymmetric rounds of cell division in its primordium flanks. LR hydropatterning is genetically regulated through a major regulator of LR initiation AUXIN RESPONSE FACTOR7 (ARF7). Knock-out mutants lose the ability to branch towards water and do not asymmetrically express the key transcription factor LBD16-GFP, a direct target for ARF7. This mechanism is regulated through post-translational regulation of ARF7. The ARF7 sequence contains four sites that can be SUMOylated. Transgenic lines expressing ARF7 with mutations in each of these four SUMO sites cannot rescue arf7-1 LR hydropatterning, revealing a key role for SUMOylation controlling water sensing by roots. ARF7 SUMO status appears to be controlled by SUMO protease OVERLY TOLERANT TO SALT1 (OTS1). Double knock-out mutants in OTS1 and its close homolog OTS2 have severely delayed root development and a LR hydropatterning defect. Additionally, ots1 ots2 mutants display reduced LR initiation and emergence defects that can be restored to Wild-Type levels by expressing an OTS1-Venus transgene. OTS1-Venus can be detected from the late elongation zone onwards in root pericycle cells and is stably expressed in the primordia. However, no asymmetrical localisation of OTS1-Venus is observed after a hydropatterning cue suggesting that SUMO protease activity, rather than stability, controls LR hydropatterning. This thesis highlights the early response of lateral roots to asymmetrical water distribution and role the deSUMOylation machinery plays in its molecular regulation

Early developmental plasticity of lateral roots in response to asymmetric water availability

© 2020, The Author(s), under exclusive licence to Springer Nature Limited. Root branching is influenced by the soil environment and exhibits a high level of plasticity. We report that the radial positioning of emerging lateral roots is influenced by their hydrological environment during early developmental stages. New lateral root primordia have both a high degree of flexibility in terms of initiation and development angle towards the available water. Our observations reveal how the external hydrological environment regulates lateral root morphogenesis

Qualitative study of practices and attitudes towards physical activity among prediabetic men and women in urban and rural Malawi.

OBJECTIVES: Given the decline in physical activity levels in Malawi, like other sub-Saharan African countries, and its implication for non-communicable disease (NCD) prevention, this study aimed to compare and contrast accounts of practices and attitudes towards physical activity among Malawian men and women (previously identified as having pre-diabetes) in urban and rural settings. SETTING: Two communities: one urban (Lilongwe) and one rural (Karonga). PARTICIPANTS: 14 men (urban N=6, rural N=8) and 18 women (urban N=9, rural N=9) classified as prediabetic during their participation in an NCD survey 3-5 years previously. DESIGN: A qualitative focus group study (N=4) and thematic analysis, with the ecological model used as a framework to characterise the types of physical activity people engaged in and potential ways to support them to exercise more. RESULTS: Participants reported undertaking different types of physical activity across all ecological model domains (household, occupational, transport, recreational). Rural participants reported more vigorous physical activities than urban participants, and women reported more household activities than men. Many participants recognised a need to promote physical activity in Malawi, and the health benefits of doing so, including the importance of physical activity in helping them stay strong to maintain physical functioning. Barriers to physical activity included competing priorities (especially urban men), societal expectations around wealth, use of motorised transport, lack of accessible facilities for women, ageing and ill health. CONCLUSIONS: Physical activity is declining in Malawi as working and transport practices change in response to economic development, making promotion of alternative forms of physical activity a public health priority. Multilevel interventions emphasising the personal benefits/value of physical activity for all ages, and routine and group-based exercising, as well as investment in accessible recreational facilities (including for women) and active travel infrastructure should be considered to improve physical activity levels in Malawi

The long term effect of pulmonary tuberculosis on income and employment in a low income, urban setting

Background Mitigating the socioeconomic impact of tuberculosis is key to the WHO End TB Strategy. However, ittle known about socioeconomic wellbeing beyond TB-treatment completion. In this mixed-methods study we describe socioeconomic outcomes after TB-disease in urban Blantyre, Malawi, and explore pathways and barriers to financial recovery. Methods Adults ≥15 years successfully completing treatment for a first episode of pulmonary TB under the National TB Control Programme were prospectively followed-up for 12-months. Socioeconomic, income, occupation, health-seeking and cost data were collected. Determinants and impacts of ongoing financial hardship were explored through illness narrative interviews with purposively selected participants. Results 405 participants were recruited from February 2016 - April 2017. Median age was 35-years (IQR: 28- 41), 67.9% (275/405) were male, and 60.6% (244/405) were HIV-positive. Employment and incomes were lowest at TB-treatment completion, with limited recovery in the following year: fewer people were in paid work (63.0% [232/368] vs. 72.4% [293/405], p=0.006), median incomes were lower ($44.13 [IQR:$0-106.15] vs. $72.20 [IQR:$26.71-173.29], p<0.001), and more patients were living in poverty (earning <$1.90/day: 57.7% [211/366] vs. 41.6% [166/399], p<0.001) 1-year after TB- treatment completion compared to before TB-disease onset. Half of the participants (50.5%, 184/368) reported ongoing dissaving (use of savings, selling assets, borrowing money) and 9.5% (35/368) reported school interruptions in the year after TB-treatment completion. Twenty-one participants completed in-depth interviews. Reported barriers to economic recovery included financial insecurity, challenges rebuilding business relationships, residual physical morbidity, and stigma. Conclusions TB-affected households remain economically vulnerable even after TB-treatment completion, with limited recovery in income and employment , persistent financial strain requiring dissaving, and school interruptions. Measures of the economic impact of TB-disease should include the post-TB period. Interventions to protect the long-term health and livelihoods of TB survivors must be explored

The long term effect of pulmonary tuberculosis on income and employment in a low income, urban setting.

BACKGROUND: Mitigating the socioeconomic impact of tuberculosis (TB) is key to the WHO End TB Strategy. However, little known about socioeconomic well-being beyond TB-treatment completion. In this mixed-methods study, we describe socioeconomic outcomes after TB-disease in urban Blantyre, Malawi, and explore pathways and barriers to financial recovery. METHODS: Adults ≥15 years successfully completing treatment for a first episode of pulmonary TB under the National TB Control Programme were prospectively followed up for 12 months. Socioeconomic, income, occupation, health seeking and cost data were collected. Determinants and impacts of ongoing financial hardship were explored through illness narrative interviews with purposively selected participants. RESULTS: 405 participants were recruited from February 2016 to April 2017. Median age was 35 years (IQR: 28-41), 67.9% (275/405) were male, and 60.6% (244/405) were HIV-positive. Employment and incomes were lowest at TB-treatment completion, with limited recovery in the following year: fewer people were in paid work (63.0% (232/368) vs 72.4% (293/405), p=0.006), median incomes were lower (US$44.13 (IQR: US$0-US$106.15) vs US$72.20 (IQR: US$26.71-US$173.29), p<0.001), and more patients were living in poverty (earning <US$1.90/day: 57.7% (211/366) vs 41.6% (166/399), p<0.001) 1 year after TB-treatment completion compared with before TB-disease onset. Half of the participants (50.5%, 184/368) reported ongoing dissaving (use of savings, selling assets, borrowing money) and 9.5% (35/368) reported school interruptions in the year after TB-treatment completion. Twenty-one participants completed in-depth interviews. Reported barriers to economic recovery included financial insecurity, challenges rebuilding business relationships, residual physical morbidity and stigma. CONCLUSIONS: TB-affected households remain economically vulnerable even after TB-treatment completion, with limited recovery in income and employment, persistent financial strain requiring dissaving, and ongoing school interruptions. Measures of the economic impact of TB disease should include the post-TB period. Interventions to protect the long-term health and livelihoods of TB survivors must be explored

Hydraulic flux–responsive hormone redistribution determines root branching

Plant roots exhibit plasticity in their branching patterns to forage efficiently for heterogeneously distributed resources, such as soil water. The xerobranching response represses lateral root formation when roots lose contact with water. Here, we show that xerobranching is regulated by radial movement of the phloem-derived hormone abscisic acid, which disrupts intercellular communication between inner and outer cell layers through plasmodesmata. Closure of these intercellular pores disrupts the inward movement of the hormone signal auxin, blocking lateral root branching. Once root tips regain contact with moisture, the abscisic acid response rapidly attenuates. Our study reveals how roots adapt their branching pattern to heterogeneous soil water conditions by linking changes in hydraulic flux with dynamic hormone redistribution

Critical Loss of the Balance between Th17 and T Regulatory Cell Populations in Pathogenic SIV Infection

Chronic immune activation and progression to AIDS are observed after SIV infection in macaques but not in natural host primate species. To better understand this dichotomy, we compared acute pathogenic SIV infection in pigtailed macaques (PTs) to non-pathogenic infection in African green monkeys (AGMs). SIVagm-infected PTs, but not SIVagm-infected AGMs, rapidly developed systemic immune activation, marked and selective depletion of IL-17-secreting (Th17) cells, and loss of the balance between Th17 and T regulatory (Treg) cells in blood, lymphoid organs, and mucosal tissue. The loss of Th17 cells was found to be predictive of systemic and sustained T cell activation. Collectively, these data indicate that loss of the Th17 to Treg balance is related to SIV disease progression

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead