Sex reversal following deletion of a single distal enhancer of Sox9

Cell fate decisions require appropriate regulation of key genes. Sox9, a direct target of SRY, is pivotal in mammalian sex determination. In vivo high-throughput chromatin accessibility techniques, transgenic assays, and genome editing revealed several novel gonadal regulatory elements in the 2-megabase gene desert upstream of Sox9. Although others are redundant, enhancer 13 (Enh13), a 557–base pair element located 565 kilobases 5′ from the transcriptional start site, is essential to initiate mouse testis development; its deletion results in XY females with Sox9 transcript levels equivalent to those in XX gonads. Our data are consistent with the time-sensitive activity of SRY and indicate a strict order of enhancer usage. Enh13 is conserved and embedded within a 32.5-kilobase region whose deletion in humans is associated with XY sex reversal, suggesting that it is also critical in humans

The rhizosphere: Molecular interactions between microorganisms and roots.

The rhizosphere has a large impact on plant performance in several ways. A stand-specific, more or less high diversity of microorganisms not only supports the plant in the acquisition of water and nutrients, but also modulates its ability to cope with pathogens. This diversity, however, has to be maintained and thus causes a considerable drain of photoassimilates, which are then not available for shoot development. In this chapter, we try to explain why the considerable allocation of carbon to the root system is a “wise” decision by the plant. We thus focus on the function of root-associated bacteria and their relevance for plant growth and development of disease resistance, and deliver data on the molecular basis of the root–fungus symbiosis (mycorrhiza)