Stomatal vs. genome size in angiosperms: the somatic tail wagging the genomic dog?

BACKGROUND AND AIMS

Genome size is a function, and the product, of cell volume. As such it is contingent on ecological circumstance. The nature of 'this ecological circumstance' is, however, hotly debated. Here, we investigate for angiosperms whether stomatal size may be this 'missing link': the primary determinant of genome size. Stomata are crucial for photosynthesis and their size affects functional efficiency.

METHODS

Stomatal and leaf characteristics were measured for 1442 species from Argentina, Iran, Spain and the UK and, using PCA, some emergent ecological and taxonomic patterns identified. Subsequently, an assessment of the relationship between genome-size values obtained from the Plant DNA C-values database and measurements of stomatal size was carried out.

KEY RESULTS

Stomatal size is an ecologically important attribute. It varies with life-history (woody species < herbaceous species < vernal geophytes) and contributes to ecologically and physiologically important axes of leaf specialization. Moreover, it is positively correlated with genome size across a wide range of major taxa.

CONCLUSIONS

Stomatal size predicts genome size within angiosperms. Correlation is not, however, proof of causality and here our interpretation is hampered by unexpected deficiencies in the scientific literature. Firstly, there are discrepancies between our own observations and established ideas about the ecological significance of stomatal size; very large stomata, theoretically facilitating photosynthesis in deep shade, were, in this study (and in other studies), primarily associated with vernal geophytes of unshaded habitats. Secondly, the lower size limit at which stomata can function efficiently, and the ecological circumstances under which these minute stomata might occur, have not been satisfactorally resolved. Thus, our hypothesis, that the optimization of stomatal size for functional efficiency is a major ecological determinant of genome size, remains unproven.

imProving Outcomes after STroke clinical pilot trial protocol

RATIONALE

One in three patients experience depression after stroke and this risk is consistent over time. A strategy to prevent depression that could be economically delivered to most stroke patients and ideally which also has a low likelihood of adverse events needs to be developed and evaluated. Aims POST aims to determine whether a simple intervention (postcards) prevents depression (Hospital Anxiety and Depression rating Scale, HADS depression subscale score > or =8) in patients with a recent stroke. Secondary end-points include reduced anxiety (HADS anxiety subscale score > or =8) and improved health-related quality of life in patients with a recent stroke.

DESIGN

A single-centre randomised, double-blind, pilot trial to prevent depression in patients with a recent (within 8 weeks) stroke presenting to hospital. Patients will be enrolled over 12 months and randomised to receive three trial-specific assessments (baseline, 3- and 6-month assessments of mood, HRQoL and social functioning), or three trial-specific assessments plus a postcard sent centrally in a sealed envelope at 1, 2, 3, 4 and 5 months after discharge from hospital. Blinded follow-up telephone assessments will be conducted for both groups. STUDY OUTCOMES AND SAMPLE SIZE: For the primary end-point the POST trial will have 80% power to detect a relative risk of 0.4 given an incidence of depression of 30%. For the secondary aims POST has 90% power to detect a difference of 3 points on the HADS depression subscale (assuming a standard deviation of 6 points) between randomised groups. This includes an inflation factor of 15% to account for patients lost to follow-up.

DISCUSSION

Evidence of efficacy will determine whether a multi-centre, international trial is warranted.

Developmentally spliced PKCbetaII provides a possible link between mTORC2 and Akt kinase to regulate 3T3-L1 adipocyte insulin-stimulated glucose transport

Functional adipocyte glucose disposal is a key component of global glucose homeostasis. PKCbetaII is involved in rat skeletal muscle cell ISGT. Western blot analysis and real-time PCR revealed 3T3-L1 cells developmentally regulated PKCbeta splicing such that PKCbetaI was downregulated and PKCbetaII was upregulated during the course of differentiation. An initial glucose uptake screen using PKC inhibitor LY379196 pointed to a PKC isozyme other than PKCzeta mediating 3T3-L1 adipocyte ISGT. Subsequent use of PKCbetaII inhibitor CGP53353 pointed to a role for PKCbetaII in ISGT. Western blot analysis showed that CGP53353 specifically inhibited phosphorylation of PKCbetaII Serine 660. Subcellular fractionation and immunofluorescence demonstrated that PKCbetaII regulates GLUT4 translocation. Further Western blot, immunofluorescence and co-immunoprecipitation analysis reveal that PKCbetaII inhibition does not affect mTORC2 activity yet abrogates phosphorylation of Akt Serine 473. PKCbetaII regulates GLUT4 translocation by regulating Akt phosphorylation and thus activity.