Extending the Genotype in Brachypodium by Including DNA Methylation Reveals a Joint Contribution with Genetics on Adaptive Traits.

Epigenomic changes have been considered a potential missing link underlying phenotypic variation in quantitative traits but is potentially confounded with the underlying DNA sequence variation. Although the concept of epigenetic inheritance has been discussed in depth, there have been few studies attempting to directly dissect the amount of epigenomic variation within inbred natural populations while also accounting for genetic diversity. By using known genetic relationships between Brachypodium lines, multiple sets of nearly identical accession families were selected for phenotypic studies and DNA methylome profiling to investigate the dual role of (epi)genetics under simulated natural seasonal climate conditions. Despite reduced genetic diversity, appreciable phenotypic variation was still observable in the measured traits (height, leaf width and length, tiller count, flowering time, ear count) between as well as within the inbred accessions. However, with reduced genetic diversity there was diminished variation in DNA methylation within families. Mixed-effects linear modeling revealed large genetic differences between families and a minor contribution of DNA methylation variation on phenotypic variation in select traits. Taken together, this analysis suggests a limited but significant contribution of DNA methylation toward heritable phenotypic variation relative to genetic differences.

Determination of line tension in lipid monolayers by Fourier analysis of capillary waves.

In the past decade, intense interest has focused on the phase separation and lateral organization of two-dimensional lipid systems. In this manuscript, we describe a method for extracting the interfacial line tension between coexisting monolayer phases through direct observations of thermal fluctuations using fluorescence microscopy and digital image processing. We demonstrate that the interfacial line tension calculated from the capillary wave spectrum is in good agreement with previous measurements employed using other experimental techniques. A distinct advantage of this method is that line tensions can be extracted directly from acquired images. In addition, small line tensions are measured, enabling characterization of phase separated membranes near critical points. Future applications of this method are briefly discussed.