scholarly journals Irradiance modulates thermal niche in a previously undescribed low-light and cold-adapted nano-diatom

2020 ◽  
Author(s):  
Joshua D. Kling ◽  
Kyla J. Kelly ◽  
Sophia Pei ◽  
Tatiana A. Rynearson ◽  
David A. Hutchins
Keyword(s):  
Light Stress ◽  
Early Spring ◽  
Narragansett Bay ◽  
Marine Phytoplankton ◽  
Low Light ◽  
Thermal Niche ◽  
Temperature Requirements ◽  
Future Warming ◽  
Polar Ocean ◽  
Temperature Levels

AbstractDiatoms have well-recognized roles in fixing and exporting carbon and supplying energy to marine ecosystems, but only recently have we begun to explore the diversity and importance of nano- and pico-diatoms. Here we describe a small (~5 μm) diatom from the genus Chaetoceros Isolated from a wintertime temperate estuary (2° C, Narragansett Bay, RI), with a unique obligate specialization for low-light environments (< 120 μmol photons m-2 sec-1). This diatom exhibits a striking interaction between irradiance and thermal responses whereby as temperatures increase, so does its susceptibility to light stress. Historical 18S rRNA amplicon data from our study site show this isolate was abundant throughout a six-year period, and its presence strongly correlates with winter and early spring months when light and temperature are low. Two ASVs matching this isolate had a circumpolar distribution in Tara Polar Ocean Circle samples, indicating its unusual light and temperature requirements are adaptations to life in a cold, dark environment. We expect this isolate’s low light, psychrophilic niche to shrink as future warming-induced stratification increases both light and temperature levels experienced by high latitude marine phytoplankton.

scholarly journals Compensation Mechanism of the Photosynthetic Apparatus in Arabidopsis thaliana ch1 Mutants

2020 ◽  
Vol 22 (1) ◽  
pp. 221
Author(s):  
Joanna Wójtowicz ◽  
Adam K. Jagielski ◽  
Agnieszka Mostowska ◽  
Katarzyna B. Gieczewska
Keyword(s):  
Light Stress ◽  
Photosynthetic Apparatus ◽  
Protein Composition ◽  
Mrna Levels ◽  
Chlorophyll B ◽  
Low Light ◽  
Plant Acclimation ◽  
Chlorophyll B Deficiency ◽  
Composition Changes

The origin of chlorophyll b deficiency is a mutation (ch1) in chlorophyllide a oxygenase (CAO), the enzyme responsible for Chl b synthesis. Regulation of Chl b synthesis is essential for understanding the mechanism of plant acclimation to various conditions. Therefore, the main aim of this study was to find the strategy in plants for compensation of low chlorophyll content by characterizing and comparing the performance and spectral properties of the photosynthetic apparatus related to the lipid and protein composition in four selected Arabidopsis ch1 mutants and two Arabidopsis ecotypes. Mutation in different loci of the CAO gene, viz., NW41, ch1.1, ch1.2 and ch1.3, manifested itself in a distinct chlorina phenotype, pigment and photosynthetic protein composition. Changes in the CAO mRNA levels and chlorophyllide a (Chlide a) content in ecotypes and ch1 mutants indicated their significant role in the adjustment mechanism of the photosynthetic apparatus to low-light conditions. Exposure of mutants with a lower chlorophyll b content to short-term (1LL) and long-term low-light stress (10LL) enabled showing a shift in the structure of the PSI and PSII complexes via spectral analysis and the thylakoid composition studies. We demonstrated that both ecotypes, Col-1 and Ler-0, reacted to high-light (HL) conditions in a way remarkably resembling the response of ch1 mutants to normal (NL) conditions. We also presented possible ways of regulating the conversion of chlorophyll a to b depending on the type of light stress conditions.

Does Astaxanthin Protect Haematococcus against Light Damage?

1998 ◽  
Vol 53 (1-2) ◽  
pp. 93-100 ◽  
Author(s):  
Lu Fan ◽  
Avigad Vonshak ◽  
Aliza Zarka ◽  
Sammy Boussiba
Keyword(s):  
Light Intensity ◽  
Light Stress ◽  
Phosphate Starvation ◽  
High Light Intensity ◽  
High Irradiance ◽  
High Light ◽  
Protective Agent ◽  
Light Damage ◽  
Low Light ◽  
Very High

Abstract The photoprotective function of the ketocarotenoid astaxanthin in Haematococcus was questioned. When exposed to high irradiance and/or nutritional stress, green Haematococcus cells turned red due to accumulation of an immense quantity of the red pigment astaxanthin. Our results demonstrate that: 1) The addition of diphenylamine, an inhibitor of astaxanthin biosynthesis, causes cell death under high light intensity; 2) Red cells are susceptible to high light stress to the same extent or even higher then green ones upon exposure to a very high light intensity (4000 μmol photon m-2 s-1); 3) Addition of 1O2 generators (methylene blue, rose bengal) under noninductive conditions (low light of 100 (μmol photon m-2 s-1) induced astaxanthin accumulation. This can be reversed by an exogenous 1O2 quencher (histidine); 4) Histidine can prevent the accumulation of astaxanthin induced by phosphate starvation. We suggest that: 1) Astaxanthin is the result of the photoprotection process rather than the protective agent; 2) 1O2 is involved indirectly in astaxanthin accumulation process.

scholarly journals Metabolomic indicators for low-light stress in seagrass

2020 ◽  
Vol 114 ◽  
pp. 106316
Author(s):  
L.L. Griffiths ◽  
S.D. Melvin ◽  
R.M. Connolly ◽  
R.M. Pearson ◽  
C.J. Brown
Keyword(s):  
Light Stress ◽  
Low Light ◽  
Low Light Stress

scholarly journals Metatranscriptome analyses indicate resource partitioning between diatoms in the field

2015 ◽  
Vol 112 (17) ◽  
pp. E2182-E2190 ◽  
Author(s):  
Harriet Alexander ◽  
Bethany D. Jenkins ◽  
Tatiana A. Rynearson ◽  
Sonya T. Dyhrman
Keyword(s):  
Resource Utilization ◽  
Resource Partitioning ◽  
Niche Partitioning ◽  
The United States ◽  
Narragansett Bay ◽  
Marine Phytoplankton ◽  
Transcriptional Responses ◽  
Gene Sets ◽  
Nutrient Amendment

Diverse communities of marine phytoplankton carry out half of global primary production. The vast diversity of the phytoplankton has long perplexed ecologists because these organisms coexist in an isotropic environment while competing for the same basic resources (e.g., inorganic nutrients). Differential niche partitioning of resources is one hypothesis to explain this “paradox of the plankton,” but it is difficult to quantify and track variation in phytoplankton metabolism in situ. Here, we use quantitative metatranscriptome analyses to examine pathways of nitrogen (N) and phosphorus (P) metabolism in diatoms that cooccur regularly in an estuary on the east coast of the United States (Narragansett Bay). Expression of known N and P metabolic pathways varied between diatoms, indicating apparent differences in resource utilization capacity that may prevent direct competition. Nutrient amendment incubations skewed N/P ratios, elucidating nutrient-responsive patterns of expression and facilitating a quantitative comparison between diatoms. The resource-responsive (RR) gene sets deviated in composition from the metabolic profile of the organism, being enriched in genes associated with N and P metabolism. Expression of the RR gene set varied over time and differed significantly between diatoms, resulting in opposite transcriptional responses to the same environment. Apparent differences in metabolic capacity and the expression of that capacity in the environment suggest that diatom-specific resource partitioning was occurring in Narragansett Bay. This high-resolution approach highlights the molecular underpinnings of diatom resource utilization and how cooccurring diatoms adjust their cellular physiology to partition their niche space.

Distinction and characterisation of submergence tolerant and sensitive rice cultivars, probed by the fluorescence OJIP rise kinetics

2009 ◽  
Vol 36 (3) ◽  
pp. 222 ◽  
Author(s):  
Ramani Kumar Sarkar ◽  
Debabrata Panda
Keyword(s):  
Photosynthetic Rate ◽  
Oryza Sativa L ◽  
Indica Rice ◽  
Light Stress ◽  
Elongation Growth ◽  
Rice Cultivars ◽  
Low Light ◽  
Test Parameters ◽  
Fluorescence Characteristics ◽  
Low Light Stress

Rice (Oryza sativa L.) plants experience multiple abiotic stresses when they are submerged. In addition to the effects of submergence on gas exchange, water also creates shading of submerged plants. It is believed that responses to submergence are actually responses to low light stress, although during complete submergence in addition to low light other environmental factors like reduce movement of gases affect the plant growth, and therefore, the consequences of submergence are not always alike to shade. We monitored the extent to which shade and submergence change the plant height, chlorophyll a fluorescence characteristics and CO2 photosynthetic rate in three Indica rice cultivars, namely Sarala, Kalaputia and Khoda, which differed in submergence tolerance. There were both similarities and dissimilarities between the consequence of shade and submergence on rice plants. Under shade conditions, elongation growth was greater in submergence tolerant cultivars than the sensitive cultivar, whereas elongation growth was greater under submergence in sensitive cultivar. The reduction in chlorophyll content, damage to PSII, and decrease in CO2 photosynthetic rate was more notable under submergence than the shade conditions. Our results show that several JIP-test parameters clearly distinguish between submergence tolerant and sensitive cultivars, and responses to submergence among different rice cultivars differ depending on their sensitivity to submergence. There were different interactions between cultivar and shade (~low light) and cultivar and submergence.

Effects of low-light stress on maize ear development and endogenous hormones content of two maize hybrids (Zea maysL.) with different shade-tolerance

2013 ◽  
Vol 33 (14) ◽  
pp. 4315-4323 ◽  
Author(s):  
周卫霞 ZHOU Weixia ◽  
李潮海 LI Chaohai ◽  
刘天学 LIU Tianxue ◽  
王秀萍 WANG Xiuping ◽  
闫志广 YAN Zhiguang
Keyword(s):  
Shade Tolerance ◽  
Light Stress ◽  
Endogenous Hormones ◽  
Low Light ◽  
Ear Development ◽  
Maize Hybrids ◽  
Low Light Stress ◽  
Maize Ear

Inhibition of Photosystems I and II in Chilling-Sensitive and Chilling-Tolerant Plants under Light and Low-Temperature Stress

1999 ◽  
Vol 54 (9-10) ◽  
pp. 645-657 ◽  
Author(s):  
Carina Barth ◽  
G. Heinrich Krause
Keyword(s):  
Low Temperature ◽  
Xanthophyll Cycle ◽  
Spinacia Oleracea ◽  
Light Stress ◽  
Fluorescence Emission ◽  
Early Spring ◽  
Psii Efficiency ◽  
Chl A ◽  
Leaf Discs

The responses of photosystems (PS) I and II to light stress at 4 °C and 20 °C were studied in leaf discs from three chilling-sensitive plant species, Cucumis sativus, Cucurbita maxima and Nicotiana tabacum, and in the chilling-tolerant Spinacia oleracea. The chilling-sensitive plants were grown at 24 °C under 80 -120 μmol photons m-2 s-1 (Cucumis and Cucurbita) or 30 μmol photons m-2 s-1 (Nicotiana). Spinacia was cultivated outdoors during winter and early spring. The P700 absorbance change around 820 nm served as a relative measure of PSI activity. The potential efficiency of PSII was determined in dark-adapted leaf discs by means of the ratio of variable to maximum chlorophyll (Chl) a fluorescence emission (Fv/Fᴍ). In Cucurbita, Nicotiana and Spinacia, PSI was not or only slightly inhibited by 2 h illumination with 200 μmol m-2 s-1 at 4 °C or with 2000 μmol m-2 s-1 at 20 °C. In leaves of Cucurbita and Nicotiana, exposure to 2000 μmol photons m-2 s-1 at 4 °C resulted in a decline in PSI activity and potential PSII efficiency approximately to the same extent (about 50% within 2 h). In contrast, in Cucumis, both moderate and high light at low temperature caused a PSI inhibition that proceeded considerably faster than the decline in PSII efficiency. Such preferential photoinhibition of PSI was not observed in the other three species tested. In Spinacia, a lower susceptibility of PSI and PSII to photoinhibition at 4 °C was associated with a faster de-epoxidation kinetics of violaxanthin, as compared to the three chilling-sensitive species. In addition, leaves of Spinacia were characterized by a significantly larger pool of xanthophyll-cycle pigments and a higher content of β-carotene based on Chi a+b. When leaves of Cucurbita were preincubated with methylviologen, which catalyzes formation of superoxide anion radicals at the acceptor side of PSI, the decline in potential PSII efficiency under 2000 μmol photons m-2 s-1 at 20 °C and 4 °C was strongly enhanced, whereas the P700 signal was less affected. Our data demonstrate that in the species tested, PSI may be inhibited in vivo besides PSII under light stress, but preferential photoinhibition of PSI is not a general phenomenon in chilling-sensitive plants. At low temperatures, a reduced function of the xanthophyll cycle and of the antioxidative scavenging system might account for enhanced PSI and PSII inhibition in vivo

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