Temporal regulation of Dpp signaling output in the Drosophila wing

Mechanisms underlying the control of dynamic regulatory element activity and chromatin accessibility during metamorphosis

Cis-regulatory modules of metazoan genomes determine the when and where of gene expression during development. Here we discuss insights into the genetic and molecular mechanisms behind cis-regulatory module usage that have come from recent application of genomics assays to insect metamorphosis. Assays including FAIRE-seq, ATAC-seq, and CUT&RUN indicate that sequential changes in chromatin accessibility play a key role in mediating stage-specific cis-regulatory module activity and gene expression. We review the current understanding of what controls precisely coordinated changes in chromatin accessibility during metamorphosis and describe evidence that points to systemic hormone signaling as a primary signal to trigger genome-wide shifts in accessibility patterns and cis-regulatory module usage.

Anchor negatively regulates BMP signalling to control Drosophila wing development

G protein-coupled receptors play particularly important roles in many organisms. The novel Drosophila gene anchor is an orthologue of vertebrate GPR155. However, the roles of anchor in molecular functions and biological processes, especially in wing development, remain unknown. Knockdown of anchor resulted in an increased wing size and additional and thickened veins. These abnormal wing phenotypes were similar to those observed in BMP signalling gain-of-function experiments. We observed that the BMP signalling indicator p-Mad was significantly increased in wing discs in which anchor RNAi was induced in larvae and accumulated abnormally in intervein regions in pupae. Furthermore, the expression of target genes of the BMP signalling pathway was examined using a lacZ reporter, and the results indicated that omb and sal were substantially increased in anchor-knockdown wing discs. An investigation of genetic interactions between Anchor and the BMP signalling pathway revealed that the thickened and ectopic vein tissues were rescued by knocking down BMP levels. These results suggested that Anchor functions to negatively regulate BMP signalling during wing development and vein formation.

Auxin-induced degradation dynamics set the pace for lateral root development

Auxin elicits diverse cell behaviors through a simple nuclear signaling pathway initiated by degradation of Aux/IAA co-repressors. Our previous work revealed that members of the large Arabidopsis Aux/IAA family exhibit a range of degradation rates in synthetic contexts. However, it remained an unresolved issue whether differences in Aux/IAA turnover rates played a significant role in plant responses to auxin. Here, we use the well-established model of lateral root development to directly test the hypothesis that the rate of auxin-induced Aux/IAA turnover sets the pace for auxin-regulated developmental events. We did this by generating transgenic plants expressing degradation rate variants of IAA14, a crucial determinant of lateral root initiation. Progression through the well-established stages of lateral root development was strongly correlated with the engineered rates of IAA14 turnover, leading to the conclusion that Aux/IAAs are auxin-initiated timers that synchronize developmental transitions.