A picket fence function for adherens junctions in epithelial cell polarity

Impact of imidacloprid exposure on the biochemical responses, transcriptome, gut microbiota and growth performance of the Pacific white shrimp Litopenaeus vannamei

The widespread use of neonicotinoid insecticides, such as imidacloprid, in agriculture is one of the key factors for the drop in the survival of invertebrates, including decapod crustaceans. However, there is currently a lack of comprehensive studies on the chronic toxicity mechanisms in decapod crustaceans. Here, the concentration-dependent effects of imidacloprid on the physiology and biochemistry, gut microbiota and transcriptome of L. vannamei , and the interaction between imidacloprid, gut microbiota and genes were studied. Imidacloprid caused oxidative stress, leading to reduced growth and to immunity and tissue damage in L. vannamei . Imidacloprid increased the gut pathogenic microbiota abundance and broke the steady state of the gut microbiota interaction network, resulting in microbiota function disorders. Chronic imidacloprid exposure induced overall transcriptome changes in L. vannamei . Specifically, imidacloprid caused a large number of differentially expressed genes (DEGs) to be significantly downregulated. The inhibition of autophagy-related pathways revealed the toxic process of imidacloprid to L. vannamei . The changes in phase I and II detoxification gene expression clarified the formation of a detoxification mechanism in L. vannamei . The disturbance of circadian rhythm (CLOCK) caused by imidacloprid is one of the reasons for the increase in gut pathogenic microbiota abundance.

Anterior-posterior pattern formation in ciliates

As single cells, ciliates build, duplicate, and even regenerate complex cortical patterns by largely unknown mechanisms that precisely position organelles along two cell‐wide axes: anterior–posterior and circumferential (left–right). We review our current understanding of intracellular patterning along the anterior–posterior axis in ciliates, with emphasis on how the new pattern emerges during cell division. We focus on the recent progress at the molecular level that has been driven by the discovery of genes whose mutations cause organelle positioning defects in the model ciliate Tetrahymena thermophila. These investigations have revealed a network of highly conserved kinases that are confined to either anterior or posterior domains in the cell cortex. These pattern‐regulating kinases create zones of cortical inhibition that by exclusion determine the precise placement of organelles. We discuss observations and models derived from classical microsurgical experiments in large ciliates (including Stentor) and interpret them in light of recent molecular findings in Tetrahymena. In particular, we address the involvement of intracellular gradients as vehicles for positioning organelles along the anterior‐posterior axis.

Nonapoptotic role of caspase-3 in regulating Rho1GTPase-mediated morphogenesis of epithelial tubes of Drosophila renal system

BACKGROUND

Cells trigger caspase-mediated apoptosis to eliminate themselves from the system when tissue needs to be sculptured, or they detect any abnormality within them, thus preventing irreparable damage to the host. However, nonapoptotic activities of caspases are also involved in many cellular functions. Interestingly, Drosophila Malpighian tubules (MTs) express apoptotic proteins, without succumbing to cell death.

RESULTS

We show apoptosis-independent role of executioner caspase-3, Drice, in MT morphogenesis. Drice is required for precise cytoskeleton organization and convergent extension, failing which morphology, size, cell number, and arrangement get affected. Furthermore, characteristic stellate cell shape transformation in MTs is also governed by Drice. Genetic interaction study shows that Drice mediates its action by regulating Rho1GTPase functionally, and localization of polarity protein Disc large. Subsequently, downregulation of Rho1GTPase in Drice mutants significantly rescues the cystic MTs phenotype. The study shows a mechanism by which Drice governs tubulogenesis via Rho1GTPase-mediated coordinated organization of actin cytoskeleton and membrane stabilization.

CONCLUSION

Collectively our findings suggest a nonapoptotic function of caspase-3 in fine-tuning of cellular rearrangement during tubule development, and these results will add to the growing understanding of diverse roles of caspases during its evolution in metazoans.