Project description:We identified 174 miRNAs expressed in Volvox carteri. Some of Volvox miRNAs are highly enriched in gonidia or somatic cells. Subsequently, we predicted the targets of Volvox miRNAs and found many of target genes were regulated through mRNA degradation. Conservation analysis suggests the common origin of miRNA between Volvox and Chlamydomonas and high frequency of birth and death of Volvox miRNAs. Identification of miRNAs in multicellular green Volvox
Project description:We identified 174 miRNAs expressed in Volvox carteri. Some of Volvox miRNAs are highly enriched in gonidia or somatic cells. Subsequently, we predicted the targets of Volvox miRNAs and found many of target genes were regulated through mRNA degradation. Conservation analysis suggests the common origin of miRNA between Volvox and Chlamydomonas and high frequency of birth and death of Volvox miRNAs.
Project description:Small RNAs (21-24 nt) are pivotal regulators of gene expression that guide both transcriptional and post-transcriptional silencing mechanisms in diverse eukaryotes, including most if not all plants. MicroRNAs (miRNAs) and short interfering RNAs (siRNAs) are the two major types, both of which have a demonstrated and important role in plant development, stress responses and pathogen resistance. In this work, we used a deep sequencing approach (Sequencing-By-Synthesis, or SBS) to develop sequence resources of small RNAs from cultures of Volvox carteri (in control, phosphate starvation and sulphate starvation conditions). The high depth of the resulting datasets enabled us to examine in detail critical small RNA features as size distribution, tissue-specific regulation and sequence conservation between different organs in this species. We also developed database resources and a dedicated website (http://smallrna.udel.edu/) with computational tools for allowing other users to identify new miRNAs or siRNAs involved in specific regulatory pathways, verify the degree of conservation of these sequences in other plant species and map small RNAs on genes or larger regions of the genome under study.
Project description:Small RNAs (21-24 nt) are pivotal regulators of gene expression that guide both transcriptional and post-transcriptional silencing mechanisms in diverse eukaryotes, including most if not all plants. MicroRNAs (miRNAs) and short interfering RNAs (siRNAs) are the two major types, both of which have a demonstrated and important role in plant development, stress responses and pathogen resistance. In this work, we used a deep sequencing approach (Sequencing-By-Synthesis, or SBS) to develop sequence resources of small RNAs from cultures of Volvox carteri (in control, phosphate starvation and sulphate starvation conditions). The high depth of the resulting datasets enabled us to examine in detail critical small RNA features as size distribution, tissue-specific regulation and sequence conservation between different organs in this species. We also developed database resources and a dedicated website (http://smallrna.udel.edu/) with computational tools for allowing other users to identify new miRNAs or siRNAs involved in specific regulatory pathways, verify the degree of conservation of these sequences in other plant species and map small RNAs on genes or larger regions of the genome under study. Small RNA libraries were derived from cultures of Volvox carteri in control, phosphate starvation and sulphate starvation conditions. Total RNA was isolated using the TriReagent (Molecular Research Center), and submitted to Illumina (Hayward, CA, http://www.illumina.com) for small RNA library construction using approaches described in (Lu et al., 2007) with minor modifications. The small RNA libraries were sequenced with the Sequencing-By-Synthesis (SBS) technology by Illumina. PERL scripts were designed to remove the adapter sequences and determine the abundance of each distinct small RNA. We thank Kan Nobuta and Gayathri Mahalingam for assistance with the computational methods.
Project description:The green alga Volvox carteri is a model organism for the development of multicellularity. It has a spherical shape with a complete division of labor between around 2000 somatic cells and 16 reproductive cells. When comparing Volvox with its unicellular relative Chlamydomonas rheinhardtii, one striking observation is the similarity in the protein coding genes [1]. Additionally, Baulcombe and colleagues showed that Chlamydomonas contains functional RNAi and miRNA machineries [2]. We deep sequenced small RNAs of the female Volvox strain HK10 in different life stages (asexual reproduction to sexual reproduction), each time dividing the samples into somatic cells and reproductive cells. This allowed for the observation not only of differences in individual life stages, but also for monitoring sRNA content in the two cell types. We show that Volvox expresses miRNAs and that they are 2’-O-methylated at the 3’ end. The expression profiles of several miRNAs were validated by Northern blotting showing a differential expression both between cell types and between life stages. Intriguingly, most miRNAs do not seem to be conserved between Volvox and Chlamydomonas, raising the interesting question if this changed miRNome leads to differently targeted mRNAs thus resulting in cell differentiation. Since only little is known about the transcriptome of Volvox, we performed RNASeq in order to analyze potential miRNA targets. In conclusion, most miRNA in Volvox are not conserved in Chlamydomonas although the two species are evolutionary close together. This suggests that dramatic changes in the miRNA expression might be one of the driving forces for the development of multicellularity. 1. Prochnik, S.E., et al., Genomic analysis of organismal complexity in the multicellular green alga Volvox carteri. Science, 2010. 329(5988): p. 223-6. 2. Molnar, A., et al., miRNAs control gene expression in the single-cell alga Chlamydomonas reinhardtii. Nature, 2007. 447(7148): p. 1126-9.
Project description:BackgroundBacteria of the family Rickettsiaceae are principally associated with arthropods. Recently, endosymbionts of the Rickettsiaceae have been found in non-phagotrophic cells of the volvocalean green algae Carteria cerasiformis, Pleodorina japonica, and Volvox carteri. Such endosymbionts were present in only C. cerasiformis strain NIES-425 and V. carteri strain UTEX 2180, of various strains of Carteria and V. carteri examined, suggesting that rickettsial endosymbionts may have been transmitted to only a few algal strains very recently. However, in preliminary work, we detected a sequence similar to that of a rickettsial gene in the nuclear genome of V. carteri strain EVE.Methodology/principal findingsHere we explored the origin of the rickettsial gene-like sequences in the endosymbiont-lacking V. carteri strain EVE, by performing comparative analyses on 13 strains of V. carteri. By reference to our ongoing genomic sequence of rickettsial endosymbionts in C. cerasiformis strain NIES-425 cells, we confirmed that an approximately 9-kbp DNA sequence encompassing a region similar to that of four rickettsial genes was present in the nuclear genome of V. carteri strain EVE. Phylogenetic analyses, and comparisons of the synteny of rickettsial gene-like sequences from various strains of V. carteri, indicated that the rickettsial gene-like sequences in the nuclear genome of V. carteri strain EVE were closely related to rickettsial gene sequences of P. japonica, rather than those of V. carteri strain UTEX 2180.Conclusion/significanceAt least two different rickettsial organisms may have invaded the V. carteri lineage, one of which may be the direct ancestor of the endosymbiont of V. carteri strain UTEX 2180, whereas the other may be closely related to the endosymbiont of P. japonica. Endosymbiotic gene transfer from the latter rickettsial organism may have occurred in an ancestor of V. carteri. Thus, the rickettsiae may be widely associated with V. carteri, and likely have often been lost during host evolution.