In Science this week, an international research team led by investigators at the New York University School of Medicine reports that the "overall elongation rate of transcription is tightly controlled by the rate of translation," and that there is an inverse correlation between the rate of transcription and the number of rare codons in a gene. Cooperation between ribosome translation and RNA polymerase, they write, "ensure[s] that the transcriptional yield is always adjusted to translational needs at different genes and under various growth conditions."
In a paper published online in advance this week, researchers at the University of Cambridge present evidence that mobile small silencing RNAs in Arabidopsis "direct epigenetic modification in recipient cells." Using sRNA biogenesis-blocking mutants, the team shows that "transgene-derived and a substantial potion of endogenous sRNA has moved across the graft union." The team suggests that sRNA represents a mechanism through which epigenetic modification-related transmissions "could affect genome defense and responses to external stimuli" that affect plants.
In a related paper published in advance, online in Science, investigators in France and the US report that "small RNA duplexes function as mobile silencing signals between plant cells." Specifically, 21-nt duplexes of small interfering RNA are transformed from longer, double-stranded precursors by DCL4 in plants. "Using cell-specific rescue of DCL4 function and cell-specific inhibition of RNAi movement," the team demonstrates that both exogenous and endogenous siRNAs act as mobile silencing signals between plant cells.
Researchers in the US and Canada express that a complex set of modifiers influences phenotypic variation among individuals in their article "Genotype to Phenotype: A Complex Problem." Robin Dowell et al. generated a whole-genome sequence of Saccharomyces cerevisiae in which they deleted 5,100 genes. Then, by performing a "genome-wide comparison of deletion mutant phenotypes," they "identified a subset of genes that were conditionally essential by strain" of the model yeast. Further analysis revealed that "conditional phenotype was most often governed by complex genetic interactions, depending on multiple background-specific modifiers," the authors conclude.