Inhibition of protein synthesis: a basis for tunicamycin-induced decrease in rat liver cytochrome P-450

Tunicamycin caused a dose and time dependent decrease in cytochrome P-450 in rat liver. A dose of 50 micrograms/kg caused a decrease of about 50% in 72 hours. A similar decrease in the activities of rat liver microsomal aniline hydroxylase, aminopyrine N-demethylase and ethoxycoumarin O-deethylase were also seen after the tunicamycin treatment. Tunicamycin also suppressed food and water intake but the decrease in cytochrome P-450 was not related to these effects. NADPH cytochrome c reductase was not markedly decreased by tunicamycin. A decrease in cytochrome P-450 was also observed in cultured rat hepatocytes treated with tunicamycin. It decreased incorporation of [35S]-methionine into total proteins as well as into various cytochrome P-450 isozymes of rat hepatocytes. This indicates that a decrease in protein synthesis may be responsible for the tunicamycin-induced decrease in cytochrome P-450 and drug metabolism.     

Long-term trends of subtidal macrobenthos in North Inlet,South Carolina

Analyses of seasonal and yearly trends in subtidal macrobenthic samples collected bi-weekly at a sandy site (1981–1984) and a muddy site (1981–1985) in North Inlet, South Carolina, show large fluctations in abundance and high variability between replicate samples. Sampling variability at the sandy site, thought to be influenced more by physical disturbance than by biotic interactions, was especially high and prevented the interpretation of seasonal trends in abundance. Increased replication at the muddy site in 1985 revealed abundance patterns of winter/spring maxima and summer minima. Despite short-term (seasonal) and high year-to-year variability, the fauna at both sites were characterized by long-term stability in abundance. That is, although abundances varied considerably between seasons or years only 9 of 22 taxa analyzed showed a directional change in abundance. These 9 taxa increased in abundance over the four (sandy site) or five (muddy site) years of examination while the other 13 taxa fluctuated about a mean value. The taxonomic composition of benthic fauna at both sites was also very stable through time, with the sandy site always numerically dominated, in order, by polychaetes, amphipods, and bivalves and the muddy site by polychaetes, oligochaetes, and bivalves.     

Parallel reverse genetic screening in mutant human cells using transcriptomics

Reverse genetic screens have driven gene annotation and target discovery in model organisms. However, many disease‐relevant genotypes and phenotypes cannot be studied in lower organisms. It is therefore essential to overcome technical hurdles associated with large‐scale reverse genetics in human cells. Here, we establish a reverse genetic approach based on highly robust and sensitive multiplexed RNA sequencing of mutant human cells. We conduct 10 parallel screens using a collection of engineered haploid isogenic cell lines with knockouts covering tyrosine kinases and identify known and unexpected effects on signaling pathways. Our study provides proof of concept for a scalable approach to link genotype to phenotype in human cells, which has broad applications. In particular, it clears the way for systematic phenotyping of still poorly characterized human genes and for systematic study of uncharacterized genomic features associated with human disease.     

Precocious reproduction increases at the leading edge of a mangrove range expansion

Climate change‐driven shifts in species ranges are ongoing and expected to increase. However, life‐history traits may interact with climate to influence species ranges, potentially accelerating or slowing range shifts in response to climate change. Tropical mangroves have expanded their ranges poleward in the last three decades. Here, we report on a shift at the range edge in life‐history traits related to reproduction and dispersal. With a common garden experiment and field observations, we show that Rhizophora mangle individuals from northern populations reproduce at a younger age than those from southern populations. In a common garden at the northern range limit, 38% of individuals from the northernmost population were reproductive by age 2, but less than 10% of individuals from the southernmost population were reproductive by the same age, with intermediate amounts of reproduction from intermediate latitudes. Field observations show a similar pattern of younger reproductive individuals toward the northern range limit. We also demonstrate a shift toward larger propagule size in populations at the leading range edge, which may aid seedling growth. The substantial increase in precocious reproduction at the leading edge of the R. mangle range could accelerate population growth and hasten the expansion of mangroves into salt marshes.