871 research outputs found

    Reconsidering the nature and mode of action of metabolite retrograde signals from the chloroplast

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    Plant organelles produce retrograde signals to alter nuclear gene expression in order to coordinate their biogenesis, maintain homeostasis, or optimize their performance under adverse conditions. Many signals of different chemical nature have been described in the past decades, including chlorophyll intermediates, reactive oxygen species (ROS), and adenosine derivatives. While the effects of retrograde signaling on gene expression are well understood, the initiation and transport of the signals and their mode of action have either not been resolved, or are a matter of speculation. Moreover, retrograde signaling should be considered as part of a broader cellular network, instead of as separate pathways, required to adjust to changing physiologically relevant conditions. Here we summarize current plastid retrograde signaling models in plants, with a focus on new signaling pathways, SAL1-PAP, methylerythritol cyclodiphosphate (MEcPP), and β-cyclocitral (β-CC), and outline missing links or future areas of research that we believe need to be addressed to have a better understanding of plant intracellular signaling networks

    A Study On The Performances Of Mewma And Mcusum Charts For Skewed Distributions.

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    A multivariate chart, instead of separate univariate charts is used for a joint monitoring of several correlated variables

    Reconsidering the nature and mode of action of metabolite retrograde signals from the chloroplast

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    Plant organelles produce retrograde signals to alter nuclear gene expression in order to coordinate their biogenesis, maintain homeostasis, or optimize their performance under adverse conditions. Many signals of different chemical nature have been described in the past decades, including chlorophyll intermediates, reactive oxygen species (ROS), and adenosine derivatives. While the effects of retrograde signaling on gene expression are well understood, the initiation and transport of the signals and their mode of action have either not been resolved, or are a matter of speculation. Moreover, retrograde signaling should be considered as part of a broader cellular network, instead of as separate pathways, required to adjust to changing physiologically relevant conditions. Here we summarize current plastid retrograde signaling models in plants, with a focus on new signaling pathways, SALl-PAP, methylerythritol cyclodiphosphate (MEcPP), and beta-cyclocitral (beta-CC), and outline missing links or future areas of research that we believe need to be addressed to have a better understanding of plant intracellular signaling networks

    Development of strategies for genetic manipulation and fine-tuning of a chloroplast retrograde signal 3′-phosphoadenosine 5′-phosphate

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    Homeostasis of metabolism and regulation of stress-signaling pathways are important for plant growth. The metabolite 3'-phosphoadenosine-5'-phosphate (PAP) plays dual roles as a chloroplast retrograde signal during drought and high light stress, as well as a toxic by-product of secondary sulfur metabolism, and thus, its levels are regulated by the chloroplastic phosphatase, SAL1. Constitutive PAP accumulation in sal1 mutants improves drought tolerance but can impair growth and alter rosette morphology. Therefore, it is of interest to derive strategies to enable controlled and targeted PAP manipulation that could enhance drought tolerance while minimizing the negative effects on plant growth. We systematically tested the potential and efficiency of multiple established transgenic manipulation tools in altering PAP levels in Arabidopsis. Dexamethasone (dex)-inducible silencing of SAL1 via hpRNAi [pOpOff:SAL1hpRNAi] yielded reduction in SAL1 transcript and protein levels, yet failed to significantly induce PAP accumulation. Surprisingly, this was not due to insufficient silencing of the inducible system, as constitutive silencing using a strong promoter to drive hpRNAi and amiRNA targeting the SAL1 transcript also failed to increase PAP content or induce a sal1-like plant morphology despite significantly reducing the SAL1 transcript levels. In contrast, using dex-inducible expression of SAL1 cDNA to complement an Arabidopsis sal1 mutant successfully modulated PAP levels and restored rosette growth in a dosage-dependent manner. Results from this inducible complementation system indicate that plants with intermediate PAP levels could have improved rosette growth without compromising its drought tolerance. Additionally, preliminary evidence suggests that SAL1 cDNA driven by promoters of genes expressed specifically during early developmental stages such as ABA-Insensitive 3 (ABI3) could be another potential strategy for studying and optimizing PAP levels and drought tolerance while alleviating the negative impact of PAP on plant growth in sal1. Thus, we have identified ways that can allow future dissection into multiple aspects of stress and developmental regulation mediated by this chloroplast signal

    Estimating logged-over lowland rainforest aboveground biomass in Sabah, Malaysia using airborne LiDAR data

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    Unprecedented deforestation and forest degradation in recent decades have severely depleted the carbon storage in Borneo. Estimating aboveground biomass (AGB) with high accuracy is crucial to quantifying carbon stocks for Reducing Emissions from Deforestation and Forest Degradation-plus implementation (REDD+). Airborne Light Detection and Ranging (LiDAR) is a promising remote sensing technology that provides fine-scale forest structure variability data. This paper highlights the use of airborne LiDAR data for estimating the AGB of a logged-over tropical forest in Sabah, Malaysia. The LiDAR data was acquired using an Optech Orion C200 sensor onboard a fixed wing aircraft. The canopy height of each LiDAR point was calculated from the height difference between the first returns and the Digital Terrain Model (DTM) constructed from the ground points. Among the obtained LiDAR height metrics, the mean canopy height produced the strongest relationship with the observed AGB. This single-variable model had a root mean squared error (RMSE) of 80.02 t ha-1 or 22.31% of the mean AGB, which performed exceptionally when compared with recent tropical rainforest studies. Overall, airborne LiDAR did provide fine-scale canopy height measurements for accurately and reliably estimating the AGB in a logged-over forest in Sabah, thus supporting the state's effort in realizing the REDD+ mechanism

    A transfer learning algorithm to reduce brain-computer interface calibration time for long-term users

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    Current motor imagery-based brain-computer interface (BCI) systems require a long calibration time at the beginning of each session before they can be used with adequate levels of classification accuracy. In particular, this issue can be a significant burden for long term BCI users. This article proposes a novel transfer learning algorithm, called r-KLwDSA, to reduce the BCI calibration time for long-term users. The proposed r-KLwDSA algorithm aligns the user's EEG data collected in previous sessions to the few EEG trials collected in the current session, using a novel linear alignment method. Thereafter, the aligned EEG trials from the previous sessions and the few EEG trials from the current sessions are fused through a weighting mechanism before they are used for calibrating the BCI model. To validate the proposed algorithm, a large dataset containing the EEG data from 11 stroke patients, each performing 18 BCI sessions, was used. The proposed framework demonstrated a significant improvement in the classification accuracy, of over 4% compared to the session-specific algorithm, when there were as few as two trials per class available from the current session. The proposed algorithm was particularly successful in improving the BCI accuracy of the sessions that had initial session-specific accuracy below 60%, with an average improvement of around 10% in the accuracy, leading to more stroke patients having meaningful BCI rehabilitation

    Epidemiological analysis of typhoid fever in Kelantan from a retrieved registry

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    Aim: Despite the endemicity of typhoid in Kelantan, epidemiological data showing typhoid association to age, sex,ethnicity and district of patients is limited. This retrospective study investigated the statistical association of thesevariables from a retrieved registry.Methodology and results: Cross-tabulation using SPSS was used to analyze 1394 cases of confirmed typhoid patientsadmitted to various hospitals in Kelantan state over a six-year period. Fourteen age groups with a five-year rangeinterval were generated. There was a significant association between typhoid infection and sex of subjects, wherebyfemales were generally more susceptible than males. Ethnicity and district of typhoid patients did not show significantassociation.Conclusion, significance and impact of study: The observation of an increased number of typhoid cases with a malepredominance in the age group 5-14 and female predominance in the 20-60 age group calls for improved hygiene,continued public health education, together with better laboratory diagnostics to identify carriers, are some measures tocontrol this disease
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