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A comprehensive picture of phloem loading strategies.

ABSTRACT: Mechanisms of phloem loading in the minor veins of leaves are known for only a few species. We propose that there are a limited number of loading strategies for the primary photoassimilates, sucrose and sugar alcohols. These strategies can be predicted based on thermodynamic and anatomical considerations and identified by autoradiography of veins following uptake of (14)C-labeled compounds, analysis of leaf solute composition and concentrations, and plasmodesmatal counting. Experiments on 45 dicotyledonous species identified the predicted loading patterns. Over 50-fold differences in concentrations of sucrose and sugar alcohols in leaves were measured. The cumulative concentrations of transport compounds in leaves correlated with loading mechanisms, a previously unrecognized association. Comparisons of solute concentrations and osmotic potentials of whole leaves suggest that sucrose and sugar alcohols are more concentrated in the cytosol than in the vacuoles of mesophyll cells, thus increasing the driving force for passive loading in species that employ this strategy. Passive loading is more widespread than previously thought, especially in trees. The results indicate that plants have exploited all thermodynamically feasible and structurally compatible loading strategies and that these strategies can be identified with straightforward protocols.

SUBMITTER: Rennie EA

PROVIDER: S-EPMC2729037 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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A comprehensive picture of phloem loading strategies.

Rennie Emilie A EA Turgeon Robert R

Proceedings of the National Academy of Sciences of the United States of America 20090730 33

Mechanisms of phloem loading in the minor veins of leaves are known for only a few species. We propose that there are a limited number of loading strategies for the primary photoassimilates, sucrose and sugar alcohols. These strategies can be predicted based on thermodynamic and anatomical considerations and identified by autoradiography of veins following uptake of (14)C-labeled compounds, analysis of leaf solute composition and concentrations, and plasmodesmatal counting. Experiments on 45 dic ...[more]

PMID: 19666555

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Project description:Introduction Scabies is a neglected disease stablished worldwide with a fairy well determined incidence. In high-income countries, it often causes outbreaks affecting the residents and staff of institutions and long-term facilities, usually hard to detect and control due to the difficult diagnosis and notification delay. This study aim at characterizing the affected population, geographical distribution, and evolution of scabies in Spain from 1997–2019 as well as to describe the main environments of transmission using different data sources. Methods We carried out a nationwide retrospective study using four databases, which record data from different perspectives: hospital admissions, patients attended at primary healthcare services, outbreaks, and occupational diseases. We described the main characteristics from each database and calculated annual incidences in order to evaluate temporal and geographical patterns. We also analyzed outbreaks and occupational settings to characterize the main transmission foci and applied Joinpoint regression models to detect trend changes. Results The elderly was the most frequent collective among the hospital admitted patients and notified cases in outbreaks, while children and young adults were the most affected according to primary care databases. The majority of the outbreaks occurred in homes and nursing homes; however, the facilities with more cases per outbreak were military barracks, healthcare settings and nursing homes. Most occupational cases occurred also in healthcare and social services settings, being healthcare workers the most common affected professional group. We detected a decreasing trend in scabies admissions from 1997 to 2014 (annual percentage change -APC- = -11.2%) and an increasing trend from 2014 to 2017 (APC = 23.6%). Wide geographical differences were observed depending on the database explored. Discussion An increasing trend in scabies admissions was observed in Spain since 2014, probably due to cutbacks in social services and healthcare in addition to worsen of living conditions as a result of the 2008 economic crisis, among other reasons. The main transmission foci were healthcare and social settings. Measures including enhancing epidemic studies and national registries, reinforcing clinical diagnosis and early detection of cases, hygiene improvements and training of the staff and wide implementation of scabies treatment (considering mass drug administration in institutions outbreaks) should be considered to reduce the impact of scabies among most vulnerable groups in Spain.

Dataset Information

A comprehensive picture of phloem loading strategies.

Publications

A comprehensive picture of phloem loading strategies.

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