Ten members of the Arabidopsis gene family encoding methyl-CpG-binding domain proteins are transcriptionally active and at least one,AtMBD11, is crucial for normal development

Animal proteins that contain a methyl-CpG-binding domain (MBD) are suggested to provide a link between DNA methylation, chromatin remodelling and gene silencing. However, some MBD proteins reside in chromatin remodelling complexes, but do not have specific affinity for methylated DNA. It has recently been shown that the Arabidopsis genome contains 12 putative genes encoding proteins with domains similar to MBD, of which at least three bind symmetrically methylated DNA. Using a bioinformatics approach, we have identified additional domains in a number of these proteins and, on this basis and extended sequence similarity, divided the proteins into subgroups. Using RT-PCR we show that 10 of the AtMBD genes are active and differentially expressed in diverse tissues. To investigate the biological significance of AtMBD proteins, we have transformed Arabidopsis with a construct aimed at RNA interference with expression of the AtMBD11 gene, normally active in most tissues. The resulting 35S::AtMBD11-RNAi plants displayed a variety of phenotypic effects, including aerial rosettes, serrated leaves, abnormal position of flowers, fertility problems and late flowering. Arabidopsis lines with reduced expression of genes involved in chromatin remodelling and transgene silencing show similar phenotypes. Our results suggest an important role for AtMBD proteins in plant development.     

Prediction of breeding values for group-recorded traits including genomic information and an individually recorded correlated trait

Records on groups of individuals could be valuable for predicting breeding values when a trait is difficult or costly to measure on single individuals, such as feed intake and egg production. Adding genomic information has shown improvement in the accuracy of genetic evaluation of quantitative traits with individual records. Here, we investigated the value of genomic information for traits with group records. Besides, we investigated the improvement in accuracy of genetic evaluation for group-recorded traits when including information on a correlated trait with individual records. The study was based on a simulated pig population, including three scenarios of group structure and size. The results showed that both the genomic information and a correlated trait increased the accuracy of estimated breeding values (EBVs) for traits with group records. The accuracies of EBV obtained from group records with a size 24 were much lower than those with a size 12. Random assignment of animals to pens led to lower accuracy due to the weaker relationship between individuals within each group. It suggests that group records are valuable for genetic evaluation of a trait that is difficult to record on individuals, and the accuracy of genetic evaluation can be considerably increased using genomic information. Moreover, the genetic evaluation for a trait with group records can be greatly improved using a bivariate model, including correlated traits that are recorded individually. For efficient use of group records in genetic evaluation, relatively small group size and close relationships between individuals within one group are recommended.Subject terms: Genetic markers, Animal breeding     

Skeletal muscle vascular responses in human limbs to isometric handgrip

Studies of whole limb blood flow have shown that static handgrip elicits a vasodilatation in the resting forearm and vasoconstriction in the resting leg. We asked if these responses occur in the skeletal muscle vascular bed, and if so, what is the relative contribution of local metabolic versus other mechanisms to these vascular responses. Blood flow recordings were made simultaneously in the skeletal muscle of the resting arm and leg using the Xenon-washout method in ten subjects during 3 min of isometric handgrip at 30% of maximal voluntary contraction. In the arm, skeletal muscle vascular resistance (SMVR) decreased transiently at the onset of exercise followed by a return to baseline levels at the end of exercise. In the leg SMVR remained unchanged during the 1st min of handgrip, but had increased to exceed baseline levels by the end of exercise. During exercise electromyography (EMG) recordings from nonexercising limbs demonstrated a progressive 20-fold increase in activity in the arm, but remained at baseline in the leg. During EMG-signal modelled exercise performed to mimic the inadvertent muscle activity, decreases in forearm SMVR amounted to 57% of the decrease seen with controlateral handgrip. The present study would seem to indicate that vascular tone in nonexercising skeletal muscle in the arm and leg are controlled differently during the early stages of static handgrip. Metabolic vasodilatation due to involuntary contraction could significantly modulate forearm skeletal muscle vascular responses, but other factors, most likely neural vasodilator mechanisms, must make major contributions. During the later stages of contralateral sustained handgrip, vascular adjustments in resting forearm skeletal muscle would seem to be the final result of reflex sympathetic vasoconstrictor drive, local metabolic vasodilator forces and possibly neurogenic vasodilator mechanisms.