Project description:We used RNA-Seq to compare the transcriptomes of Fe-replete vs. Fe-deficient vs. Fe-limited Chlamydomonas wild-type cells. Our RNA-Seq data revealed 90 and 49 genes to be specifically expressed under hetero-phototrophic and phototrophic conditions, respectively. Around 30 genes represent putative Fe-deficiency targets, independent of the carbon source used. Many of these Fe-specific responses are conserved between Chlamydomonas and land plants. We identified several transporters (NRAMP4, a CCC1-like proteins and a ferroportin homologue) all of them most likely being involved in intracellular Fe redistribution. RNA-seq of Chlamydomonas Fe-deficient and limited cells indicated that about 40% of differentially expressed genes represent proteins of unknown functions. Whereas Fe-deficiency gave us insides into putative Fe-specific responses, Fe-limitation revealed responses related to increased oxidative stress. Quantitative proteomics on the soluble Chlamydomonas extracts indicated a fair correlation between changes we detected at mRNA levels compared to changes in protein levels in Fe-deficient and Fe-limited Chlamydomonas. We found that Fe-deficient and Fe-limited cells have increased ascorbate levels, a major antioxidant molecule in plants. Ascorbate levels appear to be elevated by de novo synthesis via the L-Galactose pathway and recycling by monodehydroascorbate reductase. Fe-limited cells showed increased transcript and protein levels of enzymatic antioxidant components of the ascorbate-glutathione scavenging system (MSD3, MDAR1 or GSH1). Fe-limited cells showed the increase of several proteases indicative of elevated proteolitic activity under these severe nutrient limitation conditions. Sampling of Chlamydomonas CC-1021 (2137) cells cultivated photoheterotrophically (TAP) or phototrophically (minimal) under Fe-replete (20mM), Fe-deficient (1 mM) and Fe-limited (0.25 mM) conditions.
Project description:Microbial autotroph-heterotroph interactions influence biogeochemical cycles on a global scale, but the diversity and complexity of natural systems and their intractability to in situ manipulation make it challenging to elucidate the principles governing these interactions. The study of assembling phototrophic biofilm communities provides a robust means to identify such interactions and evaluate their contributions to the recruitment and maintenance of phylogenetic and functional diversity overtime. To examine primary succession in phototrophic communities, we isolated two unicyanobacterial consortia from the microbial mat in HotLake, Washington, characterizing the membership and metabolic function of each consortium. We then analyzed the spatial structures and quantified the community compositions of their assembling biofilms. The consortia retained the same suite of heterotrophic species, identified as abundant members of the mat and assigned to Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes. Autotroph growth rates dominated early in assembly, yielding to increasing heterotroph growth rates late in succession. The two consortia exhibited similar assembly patterns, with increasing relative abundances of members from Bacteroidetes and Alphaproteobacteria concurrent with decreasing relative abundances of those from Gamma proteobacteria. Despite these similarities at higher taxonomic levels, the relative abundances of individual heterotrophic species were substantially different in the developing consortial biofilms. This suggests that, although similar niches are created by the cyanobacterial metabolisms, the resulting webs of autotroph-heterotroph and heterotroph-heterotroph interactions are specific to each primary producer. The relative simplicity and tractability of the Hot Lake unicyanobacterial consortia make them useful model systems for deciphering interspecies interactions and assembly principles relevant to natural microbial communities.
Project description:We used RNA-Seq to compare the transcriptomes of Fe-replete vs. Fe-deficient vs. Fe-limited Chlamydomonas wild-type cells. Our RNA-Seq data revealed 90 and 49 genes to be specifically expressed under hetero-phototrophic and phototrophic conditions, respectively. Around 30 genes represent putative Fe-deficiency targets, independent of the carbon source used. Many of these Fe-specific responses are conserved between Chlamydomonas and land plants. We identified several transporters (NRAMP4, a CCC1-like proteins and a ferroportin homologue) all of them most likely being involved in intracellular Fe redistribution. RNA-seq of Chlamydomonas Fe-deficient and limited cells indicated that about 40% of differentially expressed genes represent proteins of unknown functions. Whereas Fe-deficiency gave us insides into putative Fe-specific responses, Fe-limitation revealed responses related to increased oxidative stress. Quantitative proteomics on the soluble Chlamydomonas extracts indicated a fair correlation between changes we detected at mRNA levels compared to changes in protein levels in Fe-deficient and Fe-limited Chlamydomonas. We found that Fe-deficient and Fe-limited cells have increased ascorbate levels, a major antioxidant molecule in plants. Ascorbate levels appear to be elevated by de novo synthesis via the L-Galactose pathway and recycling by monodehydroascorbate reductase. Fe-limited cells showed increased transcript and protein levels of enzymatic antioxidant components of the ascorbate-glutathione scavenging system (MSD3, MDAR1 or GSH1). Fe-limited cells showed the increase of several proteases indicative of elevated proteolitic activity under these severe nutrient limitation conditions.
Project description:Cryptomonas sp. was grown under phototrophic conditions, glucose supplemented phototrophic conditions and 3 different dissolved organic carbon (DOC) concentrations: 1.5, 30 and 90 mg C l−1. The objective was to study the adaptations that make Cryptomonas sp. thrive under high DOC conditions.
Project description:Wood maturation produces two distinct wood tissues: juvenile wood (JW) and mature wood (LW), which are the major cause of wood qaulity variation within a tree. We investigate transcriptome reorganization during wood maturation process in radiata pine using a newly developed 18k cDNA microarrays.
Project description:FtsH Zn-metalloproteinases are multimeric, membrane-intrinsic and universally conserved in bacteria, chloroplasts and mitochondria. FtsHs function in protein turnover and processing: activities that are essential in maintaining cellular homeostasis. In phototrophic organisms, FtsHs are additionally involved in the biogenesis and repair of the photosystem complexes. The cyanobacterium Synechocystis synthesizes 4 homologous FtsHs: FtsH1, 2, 3, and 4. While the first 3 are known to function as hetero-oligomers FtsH1/3 and FtsH2/3, interactions involving FtsH4 are not fully characterized. Here, we determined the relative amounts of the 4 FtsHs in wild-type Synechocystis thylakoid membranes using the iBAQ method. In conjunction with FLAG-affinity pulldown experiments, FtsH4 was found not to associate with the other FtsHs. However, the uncharacterized protein Sll1106 was identified as an FtsH interaction partner.