Dimethylsulfoniopropionate (
While light limitation can inhibit bloom formation in dinoflagellates, the potential for high‐intensity photosynthetically active radiation (
- NSF-PAR ID:
- 10459614
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Phycology
- Volume:
- 55
- Issue:
- 5
- ISSN:
- 0022-3646
- Page Range / eLocation ID:
- p. 1082-1095
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
DMSP ) is produced by many species of marine phytoplankton and has been reported to provide a variety of beneficial functions including osmoregulation. Dinoflagellates are recognized as majorDMSP producers; however, accumulation has been shown to be highly variable in this group. We explored the effect of hyposaline transfer inGambierdiscus belizeanus between ecologically relevant salinities (36 and 31) onDMSP accumulation, Chla , cell growth, and cell volume, over 12 d. Our results showed thatG. belizeanus maintained an intracellularDMSP content of 16.3 pmol cell−1and concentration of 139mM in both salinities. Although this intracellular concentration was near the median reported for other dinoflagellates, the cellular content achieved byG. belizeanus was the highest reported of any dinoflagellate thus far, owing mainly to its large size.DMSP levels were not significantly affected by salinity treatment but did change over time during the experiment. Salinity, however, did have a significant effect on the ratio ofDMSP :Chla , suggesting that salinity transfer ofG. belizeanus induced a physiological response other thanDMSP adjustment. A survey ofDMSP content in a variety ofGambierdiscus species and strains revealed relatively highDMSP concentrations (1.0–16.4 pmol cell−1) as well as high intrageneric and intraspecific variation. We conclude that, althoughDMSP may not be involved in long‐term (3–12 d) osmoregulation in this species,G. belizeanus and otherGambierdiscus species may be important contributors toDMSP production in tropical benthic microalgal communities due to their large size and high cellular content. -
Photopigment, Absorption, and Growth Responses of Marine Cryptophytes to Varying Spectral Irradiance
The underwater light field of lakes, estuaries, and oceans may vary greatly in spectral composition. Phytoplankton in these environments must contain pigments that absorb the available colors of light. If spectral quality changes, acclimation to the new spectral environment would confer an ecological advantage in terms of photosynthesis and growth. Here, we explored the capacity of eight marine cryptophytes to adjust pigmentation in response to changes in spectral irradiance and related effects on light absorption, photosynthetically useable radiation (
PUR ), and growth rate. The pigment composition of all species changed in some way in response to shifts in spectral irradiance, but not all pigment changes could be considered advantageous in the context of chromatic acclimation. For most species, absorption by chl‐a and chl‐c 2 resulted in highest absorption in the blue region, highestPUR values for blue‐light grown cells, and highest growth rates in blue light. The exception wasChroomonas mesostigmatica (CCMP 1168), which contains a high percentage of Cryptophyte‐Phycocyanin (Cr‐PC ) 645, absorbs strongly in the orange‐to‐red region of the spectrum, and grew fastest under red light. The position and magnitude of the maximum and secondary absorption peak of Cr‐PC 569, the phycobiliprotein pigment ofHemiselmis cryptochromatica , varied with spectral irradiance. The underlying cause remains unknown, but may represent a mechanism by which cryptophytes optimize photon capture. -
Abstract With the high variability of natural growth environments, plants exhibit flexibility and resilience in regard to the strategies they employ to maintain overall fitness, including maximizing light use for photosynthesis, while simultaneously limiting light‐associated damage. We measured distinct parameters of photosynthetic performance of
plants under dynamic light regimes. Plants were grown to maturity then subjected to the following 5‐day (16 h light, 8 h dark) regime: Day 1 at constant light (CL) intensity during light period, representative of a common lab growth condition; Day 2 under sinusoidal variation in light intensity (SL) during the light period that is representative of changes occurring during a clear sunny day; Day 3 under fluctuating light (FL) intensity during the light period that simulates sudden changes that might occur with the movements of clouds in and out of the view of the sun; Day 4, repeat of CL; and Day 5, repeat of FL. We also examined the global transcriptome profile in these growth conditions based on obtaining RNA‐sequencing (RNA‐seq) data for whole plant rosettes. Our transcriptomic analyses indicated downregulation of photosystem I (PSI) and II (PSII) associated genes, which were correlated with elevated levels of photoinhibition as indicated by measurements of nonphotochemical quenching (NPQ), energy‐dependent quenching (qE), and inhibitory quenching (qI) under both SL and FL conditions. Furthermore, our transcriptomic results indicated downregulation of tetrapyrrole biosynthesis associated genes, coupled with reduced levels of chlorophyll under both SL and FL compared with CL, as well as downregulation of photorespiration‐associated genes under SL. We also noticed an enrichment of the stress response gene ontology (GO) terms for genes differentially regulated under FL when compared with SL. Collectively, our phenotypic and transcriptome analyses serve as useful resources for probing the underlying molecular mechanisms associated with plant acclimation to rapid light intensity changes in the natural environment.Arabidopsis thaliana -
Abstract Synonymous codons are not used at equal frequency throughout the genome, a phenomenon termed codon usage bias (
CUB ). It is often assumed that interspecific variation in the intensity ofCUB is related to species differences in effective population sizes (N e), with selection onCUB operating less efficiently in species with smallN e. Here, we specifically ask whether variation inN epredicts differences inCUB in mammals and report two main findings. First, across 41 mammalian genomes,CUB was not correlated with two indirect proxies ofN e(body mass and generation time), even though there was statistically significant evidence of selection shapingCUB across all species. Interestingly, autosomal genes showed higher codon usage bias compared to X‐linked genes, and high‐recombination genes showed higher codon usage bias compared to low recombination genes, suggesting intraspecific variation inN epredicts variation inCUB . Second, across six mammalian species with genetic estimates ofN e(human, chimpanzee, rabbit, and three mouse species:Mus musculus, M. domesticus, andM. castaneus ),N eandCUB were weakly and inconsistently correlated. At least in mammals, interspecific divergence inN edoes not strongly predict variation inCUB . One hypothesis is that each species responds to a unique distribution of selection coefficients, confounding any straightforward link betweenN eandCUB . -
Abstract Sigma factor (
SIG ) proteins contribute to promoter specificity of the plastid‐encodedRNA polymerase during chloroplast genome transcription. All six members of theSIG family, that is,SIG 1–SIG 6, are nuclear‐encoded proteins targeted to chloroplasts. Sigma factor 2 (SIG 2) is a phytochrome‐regulated protein important for stoichiometric control of the expression of plastid‐ and nuclear‐encoded genes that impact plastid development and plant growth and development. AmongSIG factors,SIG 2 is required not only for transcription of chloroplast genes (i.e., anterograde signaling), but also impacts nuclear‐encoded, photosynthesis‐related, and light signaling‐related genes (i.e., retrograde signaling) in response to plastid functional status. AlthoughSIG 2 is involved in photomorphogenesis in Arabidopsis, the molecular bases for its role in light signaling that impacts photomorphogenesis and aspects of photosynthesis have only recently begun to be investigated. Previously, we reported thatSIG 2 is necessary for phytochrome‐mediated photomorphogenesis specifically under red (R) and far‐red light, thereby suggesting a link between phytochromes and nuclear‐encodedSIG 2 in light signaling. To explore transcriptional roles ofSIG 2 in R‐dependent growth and development, we performedRNA sequencing analysis to compare gene expression insig2‐2 mutant and Col‐0 wild‐type seedlings at two developmental stages (1‐ and 7‐day). We identified a subset of misregulated genes involved in growth, hormonal cross talk, stress responses, and photosynthesis. To investigate the functional relevance of these gene expression analyses, we performed several comparative phenotyping tests. In these analyses, strongsig2 mutants showed insensitivity to bioactiveGA 3, high intracellular levels of hydrogen peroxide (H2O2) indicative of a stress response, and specific defects in photosynthesis, including elevated levels of cyclic electron flow (CEF ) and nonphotochemical quenching (NPQ ). We demonstrated thatSIG 2 regulates a broader range of physiological responses at the molecular level than previously reported, with specific roles in red‐light‐mediated photomorphogenesis.