In Science this week, Chinese University of Hong Kong researchers published the discovery of a set of three genes that is responsible for hybrid sterility — the sterility that occurs in the offspring of two different species, such as in the case of a mule — in rice. They focused on the sterility that occurs between indica and japonica subspecies of cultivated rice,and pinpointed three closely associated genes that control fertility in the hybrids. One of the genes produces a molecule identified by another, which increases stress on a cells endoplasmic reticulum. That stress activates the third gene, which stabilizes and protects the endoplasmic reticulum, but triggers sterility in the process.
Also in Science, a Delft University of Technology team reported on their observation of movement within intertwined loops along a twisted molecule of DNA. The loops caused by the twisting, or supercoiling, are involved in transcription and protein binding, but have never been fully observed. Using novel magnetic tweezers, the researchers applied forced twists to fluorescently tagged DNA and directly visualized the loop dynamics. "The observations directly reveal the dynamics of plectonemes and identify a new mode of movement that allows long-distance reorganization of the conformation of the genome on a millisecond time scale," the researchers write.
Finally, investigators from the University of Toronto reported on the identification of genes involved in transformation process infectious yeast uses to invade human tissues and avoid immune responses. Comparing the genomes of the pathogen Candida albicans with the non-infectious model yeast Saccharomyces cerevisiae, they discovered certain genes that enable the former to switch from a single-cell budding yeast into a filamentous form and essential to its invasion strategies such as invasive growth and biofilm formation. "Systematic genetic analyses of diverse S. cerevisiae strains provides a powerful and general approach to identify not only the function of previously uncharacterized genes within this model system, but also the function of orthologous genes across distantly related yeast strains, including our understanding of filamentation in fungal pathogens," they conclude.