Project description:We examine how the transcriptome of Prochlorococcus strain NATL2A changes in the presence of a naturally co-occurring heterotroph, Alteromonas macleodii MIT1002. Significant changes in the Prochlorococcus transcriptome were evident within six hours of co-culture, with groups of transcripts changing in different temporal waves. Many transcriptional changes persisted throughout the 48-hour experiment, indicating that the presence of the heterotroph affected a stable shift in Prochlorococcus physiology. These initial transcriptome changes largely correspond to reduced stress conditions within Prochlorococcus, as inferred from decreases in relative abundance for transcripts encoding DNA repair enzymes and many members of the âhigh-light inducibleâ family of stress response proteins. Notable changes were also seen in transcripts encoding components of the photosynthetic apparatus (particularly an increase in PSI subunits and chlorophyll synthesis enzymes), ribosomal proteins and biosynthetic enzymes. Changes in secretion-related proteins and transporters also highlight the potential for metabolic exchange between the two strains. At each of 7 timepoints, samples from 3 biological replicate co-cultures are compared to 3 biological replicate axenic Prochlorococcus cultures that serve as a control.
Project description:We examine how the transcriptome of Prochlorococcus strain NATL2A changes in the presence of a naturally co-occurring heterotroph, Alteromonas macleodii MIT1002. Significant changes in the Prochlorococcus transcriptome were evident within six hours of co-culture, with groups of transcripts changing in different temporal waves. Many transcriptional changes persisted throughout the 48-hour experiment, indicating that the presence of the heterotroph affected a stable shift in Prochlorococcus physiology. These initial transcriptome changes largely correspond to reduced stress conditions within Prochlorococcus, as inferred from decreases in relative abundance for transcripts encoding DNA repair enzymes and many members of the ‘high-light inducible’ family of stress response proteins. Notable changes were also seen in transcripts encoding components of the photosynthetic apparatus (particularly an increase in PSI subunits and chlorophyll synthesis enzymes), ribosomal proteins and biosynthetic enzymes. Changes in secretion-related proteins and transporters also highlight the potential for metabolic exchange between the two strains.
Project description:We examine how the transcriptome of Prochlorococcus strain NATL2A changes in response to extended light deprivation, both when grown alone and in the presence of a naturally co-occurring heterotroph, Alteromonas macleodii MIT1002.
Project description:Prochlorococcus is an obligate marine microorganism which are dominant autotroph in tropical and subtropical central oceans. However, what is the low salinity boundary and how Prochlorococcus would response to low salinity exposure is still unknown. In this study, we first tested the growing salinity range of two Prochlorococcus strains, NATL1A and MED4, and then compared the global transcriptome of their low salinity acclimated cells and cells growing in normal seawater salinity. We found that MED4 could be acclimated in the lowest salinity of 25% and NATL1A could be acclimated in the lowest salinity of 28%. Measurement of the effective quantum yield of PSII photochemistry (Fv/Fm) indicated that both strains were stressed when growing in salinity lower than 34%. The transcriptomic response of NATL1A and MED4 were approximately different, with much more genes having changed transcript abundance in NATL1A than in MED4. To cope with low salinity, NATL1A downregulated the transcript of most genes involved in translation, ribosomal structure and biogenesis, while MED4 upregulated those genes. Moreover, low salinity acclimated NATL1A cells suppressed ATP-producing genes and induced the expression of photosynthesis related genes, while low salinity acclimated MED4 upregulated ATP-producing genes and downregulated photosynthesis related genes. These results indicate that the response to low salinity stress of different Prochlorococcus strains could be distinct. The study provided the first glimpse into the growing salinity range of Prochlorococcus cells and their global gene expression changes due to low salinity stress.
Project description:Prochlorococcus contributes significantly to ocean primary productivity. The link between primary productivity and iron in specific ocean regions is well established and iron limitation of Prochlorococcus cell division rates in these regions has been shown. However, the extent of ecotypic variation in iron metabolism among Prochlorococcus and the molecular basis for differences is not understood. Here, we examine the growth and transcriptional response of Prochlorococcus strains, MED4 and MIT9313, to changing iron concentrations. During steady state, MIT9313 sustains growth at an order-of-magnitude lower iron concentration than MED4. To explore this difference, we measured the whole-genome transcriptional response of each strain to abrupt iron starvation and rescue. Only four of the 1159 orthologs of MED4 and MIT9313 were differentially expressed in response to iron in both strains. However, in each strain, the expression of over a hundred additional genes changed, many of which are in labile genomic regions, suggesting a role for lateral gene transfer in establishing diversity of iron metabolism among Prochlorococcus. Furthermore, we found that MED4 lacks three genes near the iron-deficiency-induced gene (idiA) that are present and induced by iron stress in MIT9313. These genes are interesting targets for studying the adaptation of natural Prochlorococcus assemblages to local iron conditions as they show more diversity than other genomic regions in environmental metagenomic databases.
Project description:Prochlorococcus is a cyanobacterium of abundance in open ocean environments and little is known of its iron requirements or iron metabolism. We used microarrays to measure the whole-genome expression response of Prochlorococcus MED4 and MIT9313 to iron stress and recovery from iron stress.
Project description:Histone acetylation and deposition of H2A.Z variant are integral aspects of active transcription. In Drosophila, the single DOMINO chromatin regulator complex is thought to combine both activities via an unknown mechanism. Here we show that two alternative splice isoforms of the DOMINO nucleosome remodeling ATPase, DOM-A and DOM-B, directly specify two distinct multi-subunit complexes. Both complexes are necessary for transcriptional regulation but through different mechanisms. The DOM-B complex incorporates H2A.V (the fly ortholog of H2A.Z) genome-wide in an ATP-dependent manner, like the yeast SWR1 complex. The DOM-A complex, instead, functions as an ATP-independent histone acetyltransferase complex similar to the yeast NuA4, targeting lysine 12 of histone H4. Our work provides an instructive example of how different evolutionary strategies lead to similar functional separation.