Catastrophic costs incurred by tuberculosis affected households from Thailand's first national tuberculosis patient cost survey.

Tuberculosis (TB) causes an economic impact on the patients and their households. Although Thailand has expanded the national health benefit package for TB treatment, there was no data on out-of-pocket payments and income losses due to TB from patients and their household perspectives. This national TB patient cost survey was conducted to examine the TB-related economic burden, and assess the proportion of TB patients and their households facing catastrophic total costs because of TB disease. A cross-sectional TB patient cost survey was employed following WHO methods. Structured interviews with a paper-based questionnaire were conducted from October 2019 to July 2021. Both direct and indirect costs incurred from the patient and their household perspective were valued in 2021 and estimated throughout pre- and post-TB diagnosis episodes. We assessed the proportion of TB-affected households facing costs > 20% of household expenditure due to TB. We analyzed 1400 patients including 1382 TB (first-line treatment) and 18 drug-resistant TB patients (DR-TB). The mean total costs per TB episode for all study participants were 903 USD (95% confident interval; CI 771-1034 USD). Of these, total direct non-medical costs were the highest costs (mean, 402 USD, and 95%CI 334-470 USD) incurred per TB-affected household followed by total indirect costs (mean, 393 USD, and 95%CI 315-472 USD) and total direct medical costs (mean, 107 USD, and 95%CI 81-133 USD, respectively. The proportion of TB-affected households facing catastrophic costs was 29.5% (95%CI 25.1-34.0%) for TB (first-line), 61.1% (95%CI 29.6-88.1%) for DR-TB and 29.9% (95%CI 25.6-34.4%) overall. This first national survey highlighted the economic burden on TB-affected households. Travel, food/nutritional supplementation, and indirect costs contribute to a high proportion of catastrophic total costs. These suggest the need to enhance financial and social protection mechanisms to mitigate the financial burden of TB-affected households.

Comparing disease specific catastrophic cost estimates using longitudinal and cross-sectional designs: The example of tuberculosis.

BACKGROUND: There has been an increasing interest in assessing disease-specific catastrophic costs incurred by affected households as part of economic evaluations and to inform joint social/health policies for vulnerable groups. Although the longitudinal study design is the gold standard for estimating disease-specific household costs, many assessments are implemented with a cross-sectional design for pragmatic reasons. We aimed at identifying the potential biases of a cross-sectional design for estimating household cost, using the example of tuberculosis (TB), and exploring optimal approaches for sampling and interpolating cross-sectional cost data to estimate household costs. METHODS: Data on patient incurred costs, household income and coping strategies were collected from TB patients in Negros Occidental and Cebu in the Philippines between November 2018 and October 2020. The data collection tools were developed by adapting WHO Tuberculosis Patient Cost Surveys: A Handbook into a longitudinal study design. TB-specific catastrophic cost estimates were compared between longitudinal and simulated cross-sectional designs using different random samples from different times points in treatment (intensive and continuation phases). RESULTS: A total of 530 adult TB patients were enrolled upon TB diagnosis in this study. Using the longitudinal design, the catastrophic cost estimate for TB-affected households was 69 % using the output approach. The catastrophic cost estimates with the simulated cross-sectional design were affected by the reduction and recovery in household income during the episode of TB care and ranged from 40 to 55 %. CONCLUSION: Using longitudinally collected costs incurred by TB-affected households, we illustrated the potential limitations and implications of estimating household costs using a cross-sectional design. Not capturing changes in household income at multiple time points during the episode of the disease and estimating from inappropriate samples may result in biases that underestimates catastrophic cost.

An interlaboratory study on the detection method for Escherichia albertii in food using real time PCR assay and selective agars.

Escherichia albertii is an emerging enteropathogen. Although E. albertii-specific detection and isolation methods have been developed, their efficiency on food samples have not yet been systematically studied. To establish a series of effective methods for detecting E. albertii in food, an interlaboratory study was conducted in 11 laboratories using enrichment with modified E. coli broth supplemented with cefixime and tellurite (CT-mEC), real-time PCR assay, and plating on four kinds of selective agars. This study focused on the detection efficiency of an E. albertii-specific real-time PCR assay (EA-rtPCR) and plating on deoxycholate hydrogen sulfide lactose agar (DHL), MacConkey agar (MAC), DHL supplemented with rhamnose and xylose (RX-DHL), and MAC supplemented with rhamnose and xylose (RX-MAC). Chicken and bean sprout samples were inoculated with E. albertii either at 17.7 CFU/25 g (low inoculation level) or 88.5 CFU/25 g (high inoculation level), and uninoculated samples were used as controls. The sensitivity of EA-rtPCR was 1.000 for chicken and bean sprout samples inoculated with E. albertii at low and high inoculation levels. The Ct values of bean sprout samples were higher than those of the chicken samples. Analysis of microbial distribution by 16S rRNA gene amplicon sequencing in enriched cultures of bean sprout samples showed that approximately >96 % of the population comprised unidentified genus of family Enterobacteriaceae and genus Acinetobacter in samples which E. albertii was not isolated. The sensitivity of the plating methods for chicken and bean sprout samples inoculated with a high inoculation level of E. albertii was 1.000 and 0.848-0.970, respectively. The sensitivity of the plating methods for chicken and bean sprout samples inoculated with a low inoculation level of E. albertii was 0.939-1.000 and 0.515-0.727, respectively. The E. albertii-positive rate in all colonies isolated in this study was 89-90 % in RX-DHL and RX-MAC, and 64 and 44 % in DHL and MAC, respectively. Therefore, the sensitivity of RX-supplemented agar was higher than that of the agars without these sugars. Using a combination of enrichment in CT-mEC and E. albertii isolation on selective agars supplemented with RX, E. albertii at an inoculation level of over 17.5 CFU/25 g of food was detected with a sensitivity of 1.000 and 0.667-0.727 in chicken and bean sprouts, respectively. Therefore, screening for E. albertii-specific genes using EA-rtPCR followed by isolation with RX-DHL or RX-MAC is an efficient method for E. albertii detection in food.

Costs incurred by people with co-morbid tuberculosis and diabetes and their households in the Philippines.

OBJECTIVE: Diabetes is a risk factor for TB mortality and relapse. The Philippines has a high TB incidence with co-morbid diabetes. This study assessed the pre- and post-TB diagnosis costs incurred by people with TB and diabetes (TB-DM) and their households in the Philippines. METHODS: Longitudinal data was collected for costs, income, and coping mechanisms of TB-affected households in Negros Occidental and Cebu, the Philippines. Data collection was conducted four times during TB treatment. The data collection tools were developed by adapting WHO's cross-sectional questionnaire in the Tuberculosis Patient Cost Surveys: A Handbook into a longitudinal study design. Demographic and clinical characteristics, self-reported household income, number of facility visits, patient costs, the proportion of TB-affected households facing catastrophic costs due to TB (>20% of annual household income before TB), coping mechanisms, and social support received were compared by diabetes status at the time of TB diagnosis. RESULTS: 530 people with TB were enrolled in this study, and 144 (27.2%) had TB-DM based on diabetes testing at the time of TB diagnosis. 75.4% of people with TB-DM were more than 45 years old compared to 50.3% of people with TB-only (p<0.001). People with TB-DM had more frequent visits for TB treatment (120 vs 87 visits, p = 0.054) as well as for total visits for TB-DM treatment (129 vs 88 visits, p = 0.010) compared to those with TB-only. There was no significant difference in the proportion of TB-affected households facing catastrophic costs between those with TB-DM (76.3%) and those with TB-only (68.7%, p = 0.691). CONCLUSION: People with TB-DM in the Philippines face extensive health service use. However, this does not translate into substantial differences in the incidence of catastrophic cost. Further study is required to understand the incidence of catastrophic costs due to diabetes-only in the Philippines.

Risk of peri­implant femoral fracture after cephalomedullary nailing in older patients with trochanteric fractures.

INTRODUCTION: Despite the recent increase in the use of cephalomedullary nails for trochanteric hip fractures, factors that may be associated with peri­implant femoral fracture (PIFF) after cephalomedullary nailing for trochanteric fractures remain unknown. We investigated the factors associated with PIFF after cephalomedullary nailing of trochanteric hip fractures in older patients. METHODS: A nested case-control study was conducted using a database of patients aged ≥65 years who underwent surgery with cephalomedullary nails for trochanteric fractures caused by low-energy trauma during 2005-2021. The cases were defined as patients who developed PIFF after surgery, while controls were patients who did not develop PIFF and who were followed up for ≥3 years after surgery. Four controls were randomly matched to each case for sex and age. First, potential factors associated with PIFF were compared between cases and controls. Second, multivariable conditional logistic regression analysis was employed to assess factors possibly associated with PIFF, controlling for potential confounding factors. RESULTS: Of 1531 patients who underwent surgery with cephalomedullary nails because of trochanteric fractures, we assessed 34 cases and 136 controls (N = 170; mean age 85.7 ± 7 years; and females, 94 %). PIFF was significantly associated with patients having undergone total knee arthroplasty (adjusted odds ratios [95 % confidence intervals], 4.41 [1.16-16.8]) and those with AO/OTA classification 31A3 fracture (A3 fracture) (2.3 [1.12-4.76]), after adjusting for potential confounding factors. CONCLUSIONS: Our results showed that PIFF was more likely to develop among older patients with a clinical history of total knee arthroplasty and A3 fracture. These findings suggest that such patients may require careful follow-up with rigorous assessments after cephalomedullary nailing for trochanteric fractures.

Costs incurred by people receiving tuberculosis treatment in low-income and middle-income countries: a meta-regression analysis.

BACKGROUND: People accessing and completing treatment for tuberculosis can face large economic costs, even when treatment is provided free of charge. The WHO End TB Strategy targets the elimination of catastrophic costs among tuberculosis-affected households. While low-income and middle-income countries (LMICs) represent 99% of global tuberculosis cases, only 29 of 135 LMICs had conducted national surveys of costs for patients with tuberculosis by December, 2022. We estimated costs for patients with tuberculosis in countries that have not conducted a national survey, to provide evidence on the economic burden of tuberculosis in these settings and inform estimates of global economic burden. METHODS: We extracted data from 22 national surveys of costs faced by patients with tuberculosis that were completed across 2015-22 and met inclusion criteria. Using a Bayesian meta-regression approach, we used these data and covariate data for all 135 LMICs to estimate per-patient costs (2021 US$) by cost category (ie, direct medical, direct non-medical, and indirect), country, drug resistance, and household income quintile. We also estimated the proportion of households experiencing catastrophic total costs (defined as >20% of annual household income) as a result of tuberculosis disease. FINDINGS: Across LMICs, mean direct medical costs incurred by patients with tuberculosis were estimated as US$211 (95% uncertainty interval 154-302), direct non-medical costs were $512 (428-620), and indirect costs were $530 (423-663) per episode of tuberculosis. Overall, per-patient costs were $1253 (1127-1417). Estimated proportions of tuberculosis-affected households experiencing catastrophic total costs ranged from 75·2% (70·3-80·0) in the poorest quintile to 42·5% (34·3-51·5) in the richest quintile, compared with 54·9% (47·0-63·2) overall. INTERPRETATION: Tuberculosis diagnosis and treatment impose substantial costs on affected households. Eliminating these economic losses is crucial for removing barriers to accessing tuberculosis diagnosis and completing treatment among affected households and achieving the targets set in WHO's End TB Strategy. FUNDING: World Health Organization.

AO/OTA 31A3 fractures and postoperative complications in older patients.

BACKGROUND: AO/OTA 31A3 fractures (A3 fractures) have risk for postoperative complications with major impact on morbidity and mortality. For older patients, limited information is available for factors associated with postoperative complications. We aimed to assess factors associated with postoperative complications after surgery using cephalomedullary nails. METHODS: A retrospective cohort study was conducted using the information on patients aged ≥65 years who underwent surgery using cephalomedullary nails for trochanteric fractures due to low-energy trauma in three hospitals. Postoperative complications were diagnosed when patients were identified as nonunion, cutout of lag screw, or nail breakage. First, we compared differences including age, sex, body mass index, American Society of Anesthesiologists physical status classification system, preoperative waking ability, fracture type, nail length, neck shaft angle, reduction method, reduction quality and tip apex distance between patients with and without postoperative complications. Second, multivariable logistic regression analysis was employed to assess factors associated with postoperative complications resulting from A3 fractures. RESULTS: Among 120 patients with A3 fractures, postoperative complications were identified in 12 patients (10.0%). Postoperative complications were significantly more likely to develop among patients with poor reduction quality (adjusted odds ratio [95% confidence interval], 35.0 [4.43-275.9]) and a tip-apex distance ≥25 mm (16.4 [1.92-140.3]). CONCLUSIONS: These findings suggest that surgeons should aim to perform appropriate postoperative reduction and to prevent postoperative complications when using a cephalomedullary nail for A3 fractures among older patients.

Anterior cruciate ligament reconstruction with retained internal fixation hardware for treating Schatzker type V tibial plateau fracture: Two case reports.

Despite the high incidence of anterior cruciate ligament injury in patients with tibial plateau fractures, we found no reports about anterior cruciate ligament reconstruction with retained internal fixation hardware for these fractures. Herein, we report 2 male patients with Schatzker type V tibial plateau fractures and describe the use of retained hardware for internal fixation in tibia. The patients underwent anterior cruciate ligament reconstruction using outside-in technique for the femoral tunnel. Throughout the follow-up, no radiological symptoms of suspected knee osteoarthritis were observed. Accordingly, surgical intervention can be reduced by creating an independent femoral tunnel.

Clinical Outcomes of Mirogabalin Treatment for Neuropathic Pain Due to Spinal Diseases in Patients Intolerant to Continuous Administration of Pregabalin.

Introduction: We often treat patients with peripheral neuropathic pain due to spine diseases with mirogabalin as an alternative to pregabalin because of adverse events or insufficient efficacy associated with pregabalin treatment. However, there have been few reports on the safety and efficacy of mirogabalin in such cases. This study aimed to evaluate the safety and efficacy of switching from pregabalin to mirogabalin in patients with peripheral neuropathic pain due to spine diseases. Methods: Between January 2019 and July 2021, we treated 106 patients (47 men and 59 women) with peripheral neuropathic pain due to spine diseases. All patients had switched from pregabalin to mirogabalin due to adverse events or lack of efficacy. We evaluated the retention rate, incidence of adverse events, and response rate of mirogabalin during the treatment course. Results: The mean age of the patients was 67.5 years (range, 33-93 years), and the average dose of mirogabalin was 13.8 mg (range, 2.5-30 mg) at the final follow-up. The average duration of mirogabalin treatment was 148.7 days (range, 3-463 days). The retention rate of mirogabalin was 78.3%, the incidence of adverse events after mirogabalin administration was 28.3%, and the response rate of mirogabalin was 66%. Somnolence with pregabalin or mirogabalin administration in the mirogabalin discontinuation group was increased compared with that in the mirogabalin continuation group (pregabalin: 52.2% vs. 19.3%, mirogabalin: 26.1% vs. 7.2%). The patients who responded to mirogabalin had a lower average age, higher retention rate, and longer drug administration period than those who did not respond to it. Conclusions: This study indicated that mirogabalin treatment might be continued in patients with peripheral neuropathic pain due to spinal diseases who could not continue pregabalin treatment.

Expansion of social protection is necessary towards zero catastrophic costs due to TB: The first national TB patient cost survey in the Philippines.

BACKGROUND: Tuberculosis (TB) is a disease associated with poverty. Moreover, a significant proportion of TB patients face a substantial financial burden before and during TB care. One of the top targets in the End TB strategy was to achieve zero catastrophic costs due to TB by 2020. To assess patient costs related to TB care and the proportion of TB-affected households that faced catastrophic costs, the Philippines National TB Programme (NTP) conducted a national TB patient cost survey in 2016-2017. METHODS: A cross-sectional survey of 1,912 TB patients taking treatment in health facilities engaged with the NTP. The sample consists of 786 drug-sensitive TB (DS-TB) patients in urban facilities, 806 DS-TB patients in rural facilities, and 320 drug-resistant TB (DR-TB) patients. Catastrophic cost due to TB is defined as total costs, consisting of direct medical and non-medical costs and indirect costs net of social assistance, exceeding 20% of annual household income. RESULTS: The overall mean total cost including pre- and post-diagnostic costs was US$601. The mean total cost was five times higher among DR-TB patients than DS-TB patients. Direct non-medical costs and income loss accounted for 42.7% and 40.4% of the total cost of TB, respectively. More than 40% of households had to rely on dissaving, taking loans, or selling their assets to cope with the costs. Overall, 42.4% (95% confidence interval (95% CI): 40.2-44.6) of TB-affected households faced catastrophic costs due to TB, and it was significantly higher among DR-TB patients (89.7%, 95%CI: 86.3-93.0). A TB enabler package, which 70% of DR-TB patients received, reduced catastrophic costs by 13.1 percentage points (89.7% to 76.6%) among DR-TB patients, but only by 0.4 percentage points (42.4% to 42.0%), overall. CONCLUSIONS: TB patients in the Philippines face a substantial financial burden due to TB despite free TB services provided by the National TB Programme. The TB enabler package mitigated catastrophic costs to some extent, but only for DR-TB patients. Enhancing the current social and welfare support through multisectoral collaboration is urgently required to achieve zero catastrophic costs due to TB.

Economic evaluation of patient costs associated with tuberculosis diagnosis and care in Solomon Islands.

BACKGROUND: Tuberculosis (TB) care can be costly for patients and their families. The End TB Strategy includes a target that zero TB affected households should experience catastrophic costs associated with TB care. Costs are catastrophic when a patient spends 20% or more of their annual household income on their TB diagnosis and care. In Solomon Islands the costs of TB care are unknown. The aim of this study was to determine the costs of TB diagnosis and care, the types of costs and the proportion of patients with catastrophic costs. METHODS: This was a nationally representative cross-sectional survey of TB patients carried out between 2017 and 2019. Patients were recruited from health care facilities, from all ten provinces in Solomon Islands. During an interview they were asked about the costs of TB diagnosis and care. These data were analysed using descriptive statistics to describe the costs overall and the proportions of different types of costs. The proportion of patients with catastrophic costs was calculated and a multivariate logistic regression was undertaken to determine factors associated with catastrophic costs. RESULTS: One hundred and eighty-three TB patients participated in the survey. They spent a mean of 716 USD (inter quartile range: 348-1217 USD) on their TB diagnosis and care. Overall, 62.1% of costs were attributable to non-medical costs, while income loss and medical costs comprised 28.5 and 9.4%, respectively. Overall, 19.7% (n = 36) of patients used savings, borrowed money, or sold assets as a financial coping mechanism. Three patients (1.6%) had health insurance. A total of 92.3% (95% CI: 88.5-96.2) experienced catastrophic costs, using the output approach. Being in the first, second or third poorest wealth quintile was significantly associated with catastrophic costs (adjusted odds ratio: 67.3, 95% CI: 15.86-489.74%, p <  0.001). CONCLUSION: The costs of TB care are catastrophic for almost all patients in Solomon Islands. The provision of TB specific social and financial protection measures from the National TB and Leprosy Programme may be needed in the short term to ameliorate these costs. In the longer term, advancement of universal health coverage and other social and financial protection measures should be pursued.

First national tuberculosis patient cost survey in Lao People's Democratic Republic: Assessment of the financial burden faced by TB-affected households and the comparisons by drug-resistance and HIV status.

BACKGROUND: Tuberculosis (TB) patients incur large costs for care seeking, diagnosis, and treatment. To understand the magnitude of this financial burden and its main cost drivers, the Lao People's Democratic Republic (PDR) National TB Programme carried out the first national TB patient cost survey in 2018-2019. METHOD: A facility-based cross-sectional survey was conducted based on a nationally representative sample of TB patients from public health facilities across 12 provinces. A total of 848 TB patients including 30 drug resistant (DR)-TB and 123 TB-HIV coinfected patients were interviewed using a standardised questionnaire developed by the World Health Organization. Information on direct medical, direct non-medical and indirect costs, as well as coping mechanisms was collected. We estimated the percentage of TB-affected households facing catastrophic costs, which was defined as total TB-related costs accounting for more than 20% of annual household income. RESULT: The median total cost of TB care was US$ 755 (Interquartile range 351-1,454). The costs were driven by direct non-medical costs (46.6%) and income loss (37.6%). Nutritional supplements accounted for 74.7% of direct non-medical costs. Half of the patients used savings, borrowed money or sold household assets to cope with TB. The proportion of unemployment more than doubled from 16.8% to 35.4% during the TB episode, especially among those working in the informal sector. Of all participants, 62.6% of TB-affected households faced catastrophic costs. This proportion was higher among households with DR-TB (86.7%) and TB-HIV coinfected patients (81.1%). CONCLUSION: In Lao PDR, TB patients and their households faced a substantial financial burden due to TB, despite the availability of free TB services in public health facilities. As direct non-medical and indirect costs were major cost drivers, providing free TB services is not enough to ease this financial burden. Expansion of existing social protection schemes to accommodate the needs of TB patients is necessary.

Intensified research on tuberculosis in the Western Pacific Region: a bibliometric analysis, 2000-2019.

"Intensified TB research and innovation" is one of the three pillars of the End TB Strategy. To assess achievements and gaps in tuberculosis (TB) research productivity in countries and areas of the Western Pacific Region quantitatively, a bibliometric analysis was carried out by examining trends in the numbers of publications on TB indexed in PubMed between 2000 and 2019 and by comparing them with trends in publications on other selected major infectious diseases for the same period. The number of publications on TB in the Region increased by 3.2 times during the period, from 534 in 2000-2004 to 1714 in 2015-2019, as compared with 2.9 times each for HIV, hepatitis and malaria. The number increased by 46% in 2005-2009, 79% in 2010-2014 and 23% in 2015-2019, as compared with each previous 5-year period. The average annual growth rate between 2000 and 2018 was 8.8%. China accounted for 34.8% of the total number of publications on TB in the Region. Increases in TB research were observed in most countries and areas in the Region, particularly in those with a high TB burden. The number of publications on TB remained low, however, in the Lao People's Democratic Republic, Mongolia and Pacific island countries. Countries are encouraged to implement the set of actions proposed in the Global Strategy for TB Research and Innovation to accelerate progress towards ending TB.

Plasma membrane protein OsMCA1 is involved in regulation of hypo-osmotic shock-induced Ca2+ influx and modulates generation of reactive oxygen species in cultured rice cells.

BACKGROUND: Mechanosensing and its downstream responses are speculated to involve sensory complexes containing Ca2+-permeable mechanosensitive channels. On recognizing osmotic signals, plant cells initiate activation of a widespread signal transduction network that induces second messengers and triggers inducible defense responses. Characteristic early signaling events include Ca2+ influx, protein phosphorylation and generation of reactive oxygen species (ROS). Pharmacological analyses show Ca2+ influx mediated by mechanosensitive Ca2+ channels to influence induction of osmotic signals, including ROS generation. However, molecular bases and regulatory mechanisms for early osmotic signaling events remain poorly elucidated. RESULTS: We here identified and investigated OsMCA1, the sole rice homolog of putative Ca2+-permeable mechanosensitive channels in Arabidopsis (MCAs). OsMCA1 was specifically localized at the plasma membrane. A promoter-reporter assay suggested that OsMCA1 mRNA is widely expressed in seed embryos, proximal and apical regions of shoots, and mesophyll cells of leaves and roots in rice. Ca2+ uptake was enhanced in OsMCA1-overexpressing suspension-cultured cells, suggesting that OsMCA1 is involved in Ca2+ influx across the plasma membrane. Hypo-osmotic shock-induced ROS generation mediated by NADPH oxidases was also enhanced in OsMCA1-overexpressing cells. We also generated and characterized OsMCA1-RNAi transgenic plants and cultured cells; OsMCA1-suppressed plants showed retarded growth and shortened rachises, while OsMCA1-suppressed cells carrying Ca2+-sensitive photoprotein aequorin showed partially impaired changes in cytosolic free Ca2+ concentration ([Ca2+]cyt) induced by hypo-osmotic shock and trinitrophenol, an activator of mechanosensitive channels. CONCLUSIONS: We have identified a sole MCA ortholog in the rice genome and developed both overexpression and suppression lines. Analyses of cultured cells with altered levels of this putative Ca2+-permeable mechanosensitive channel indicate that OsMCA1 is involved in regulation of plasma membrane Ca2+ influx and ROS generation induced by hypo-osmotic stress in cultured rice cells. These findings shed light on our understanding of mechanical sensing pathways.

Involvement of the putative Ca²âº-permeable mechanosensitive channels, NtMCA1 and NtMCA2, in Ca²âº uptake, Ca²âº-dependent cell proliferation and mechanical stress-induced gene expression in tobacco (Nicotiana tabacum) BY-2 cells.

To gain insight into the cellular functions of the mid1-complementing activity (MCA) family proteins, encoding putative Ca²âº-permeable mechanosensitive channels, we isolated two MCA homologs of tobacco (Nicotiana tabacum) BY-2 cells, named NtMCA1 and NtMCA2. NtMCA1 and NtMCA2 partially complemented the lethality and Ca²âº uptake defects of yeast mutants lacking mechanosensitive Ca²âº channel components. Furthermore, in yeast cells overexpressing NtMCA1 and NtMCA2, the hypo-osmotic shock-induced Ca²âº influx was enhanced. Overexpression of NtMCA1 or NtMCA2 in BY-2 cells enhanced Ca²âº uptake, and significantly alleviated growth inhibition under Ca²âº limitation. NtMCA1-overexpressing BY-2 cells showed higher sensitivity to hypo-osmotic shock than control cells, and induced the expression of the touch-inducible gene, NtERF4. We found that both NtMCA1-GFP and NtMCA2-GFP were localized at the plasma membrane and its interface with the cell wall, Hechtian strands, and at the cell plate and perinuclear vesicles of dividing cells. NtMCA2 transcript levels fluctuated during the cell cycle and were highest at the G1 phase. These results suggest that NtMCA1 and NtMCA2 play roles in Ca²âº-dependent cell proliferation and mechanical stress-induced gene expression in BY-2 cells, by regulating the Ca²âº influx through the plasma membrane.

MCA1 and MCA2 that mediate Ca2+ uptake have distinct and overlapping roles in Arabidopsis.

Ca(2+) is important for plant growth and development as a nutrient and a second messenger. However, the molecular nature and roles of Ca(2+)-permeable channels or transporters involved in Ca(2+) uptake in roots are largely unknown. We recently identified a candidate for the Ca(2+)-permeable mechanosensitive channel in Arabidopsis (Arabidopsis thaliana), named MCA1. Here, we investigated the only paralog of MCA1 in Arabidopsis, MCA2. cDNA of MCA2 complemented a Ca(2+) uptake deficiency in yeast cells lacking a Ca(2+) channel composed of Mid1 and Cch1. Reverse transcription polymerase chain reaction analysis indicated that MCA2 was expressed in leaves, flowers, roots, siliques, and stems, and histochemical observation showed that an MCA2 promoter::GUS fusion reporter gene was universally expressed in 10-d-old seedlings with some exceptions: it was relatively highly expressed in vascular tissues and undetectable in the cap and the elongation zone of the primary root. mca2-null plants were normal in growth and morphology. In addition, the primary root of mca2-null seedlings was able to normally sense the hardness of agar medium, unlike that of mca1-null or mca1-null mca2-null seedlings, as revealed by the two-phase agar method. Ca(2+) uptake activity was lower in the roots of mca2-null plants than those of wild-type plants. Finally, growth of mca1-null mca2-null plants was more retarded at a high concentration of Mg(2+) added to medium compared with that of mca1-null and mca2-null single mutants and wild-type plants. These results suggest that the MCA2 protein has a distinct role in Ca(2+) uptake in roots and an overlapping role with MCA1 in plant growth.

Transcriptome profiling of the mangrove plant Bruguiera gymnorhiza and identification of salt tolerance genes by Agrobacterium functional screening.

To identify key genes in the regulation of salt tolerance in the mangrove plant Bruguiera gymnorhiza, transcriptome profiling in the lateral and main roots under conditions of salt stress was performed. Statistical analysis revealed that 175 and 403 of 11,997 genes shoewd significantly increased high expression in the lateral and main roots respectively. One hundred and sixty genes were up-regulated in both types of roots in the early time period, 1 to 12 h after salt treatment. Expression vectors for 28 selected salt responsive genes were constructed and transformed in Agrobacterium tumefaciens, and then screened for salt tolerance. A. tumefaciens transformed with genes for lipid transfer, zinc finger, and ankyrin repeat proteins showed enhanced salt tolerance. Transgenic Arabidopsis plants expressing these three genes also exhibited increased tolerance to NaCl. These results indicate that Agrobacterium functional screening is an effective supplemental method of pre-screening genes involved in abiotic stress tolerance.

Arabidopsis plasma membrane protein crucial for Ca2+ influx and touch sensing in roots.

Plants can sense and respond to mechanical stimuli, like animals. An early mechanism of mechanosensing and response is speculated to be governed by as-yet-unidentified sensory complexes containing a Ca(2+)-permeable, stretch-activated (SA) channel. However, the components or regulators of such complexes are poorly understood at the molecular level in plants. Here, we report the molecular identification of a plasma membrane protein (designated Mca1) that correlates Ca(2+) influx with mechanosensing in Arabidopsis thaliana. MCA1 cDNA was cloned by the functional complementation of lethality of a yeast mid1 mutant lacking a putative Ca(2+)-permeable SA channel component. Mca1 was localized to the yeast plasma membrane as an integral membrane protein and mediated Ca(2+) influx. Mca1 also increased [Ca(2+)](cyt) upon plasma membrane distortion in Arabidopsis. The growth of MCA1-overexpressing plants was impaired in a high-calcium but not a low-calcium medium. The primary roots of mca1-null plants failed to penetrate a harder agar medium from a softer one. These observations demonstrate that Mca1 plays a crucial role in a Ca(2+)-permeable SA channel system that leads to mechanosensing in Arabidopsis. We anticipate our findings to be a starting point for a deeper understanding of the molecular mechanisms of mechanotransduction in plants.

Tobamovirus-resistant tobacco generated by RNA interference directed against host genes.

Two homologous Nicotiana tabacum genes NtTOM1 and NtTOM3 have been identified. These genes encode polypeptides with amino acid sequence similarity to Arabidopsis thaliana TOM1 and TOM3, which function in parallel to support tobamovirus multiplication. Simultaneous RNA interference against NtTOM1 and NtTOM3 in N. tabacum resulted in nearly complete inhibition of the multiplication of Tomato mosaic virus and other tobamoviruses, but did not affect plant growth or the ability of Cucumber mosaic virus to multiply. As TOM1 and TOM3 homologues are present in a variety of plant species, their inhibition via RNA interference should constitute a useful method for generating tobamovirus-resistant plants.