The diatom Phaeodactylum tricornutum adjusts nonphotochemical fluorescence quenching capacity in response to dynamic light via fine‐tuned Lhcx and xanthophyll cycle pigment synthesis

Abstract

Diatoms contain a highly flexible capacity to dissipate excessively absorbed light by nonphotochemical fluorescence quenching (NPQ) based on the light-induced conversion of diadinoxanthin (Dd) into diatoxanthin (Dt) and the presence of Lhcx proteins. Their NPQ fine regulation on the molecular level upon a shift to dynamic light conditions is unknown. We investigated the regulation of Dd + Dt amount, Lhcx gene and protein synthesis and NPQ capacity in the diatom Phaeodactylum tricornutum after a change from continuous low light to 3 d of sine (SL) or fluctuating (FL) light conditions. Four P. tricornutum strains with different NPQ capacities due to different expression of Lhcx1 were included. All strains responded to dynamic light comparably, independently of initial NPQ capacity. During SL, NPQ capacity was strongly enhanced due to a gradual increase of Lhcx2 and Dd + Dt amount. During FL, cells enhanced their NPQ capacity on the first day due to increased Dd + Dt, Lhcx2 and Lhcx3; already by the second day light acclimation was accomplished. While quenching efficiency of Dt was strongly lowered during SL conditions, it remained high throughout the whole FL exposure. Our results highlight a more balanced and cost-effective photoacclimation strategy of P. tricornutum under FL than under SL conditions.

Ocean acidification stimulates particulate organic carbon accumulation in two Antarctic diatom species under moderate and high natural solar radiation

“…This was likely due to light stress under these high irradiances. Hence, as previously observed, the amount of variability in light, including constant, sine and more dynamic light conditions, impact how much of the absorbed photons are converted into biomass with substantial differences between light regimes (Wagner et al 2006, Arrigo et al 2010, Hoppe et al 2015, Lepetit et al 2016, Lin et al 2016. The lowered POC contents from MSR to HSR in the two tested species were further accompanied by increased maximum electron transport rates under current pCO 2 (ETR m ; Table 4), indicating no light saturation of absETRs.…”

“…, 90 μmol photons · m −2 · s −1 ; Lepetit et al. , 40, 80 and 158 μmol photons · m −2 · s −1 ). Under dynamic compared to sine light of the same daily integrated irradiance, growth and cellular POC quotas remained unaltered in the Antarctic diatom Chaetoceros brevis (Boelen et al.…”

Morpho‐anatomical and physiological differences between sun and shade leaves in Abies alba Mill. (Pinaceae, Coniferales): a combined approach

“…Also, it was generally quite low, even taking into account that for measuring rapid light curves we used photosynthetically more active blue light while other studies mostly rely on white or red light. Because of the unusual stable E 50NPQ value, being independent of incident light amount, and the typical increase of Ek in sun leaves, the ratio E 50NPQ /Ek dropped to a value of about 1 in sun leaves, a feature not observed in angiosperm plants (Serôdio & Lavaud, ) and even not recorded in severely light stressed diatoms, which can build up a huge NPQ (Lepetit et al, ). Also the values for NPQ (Ek) /NPQmax, at about 30% in shade and about 50% in sun leaves, were largely higher than the average value for plants/algae with a violaxanthin cycle (25–75% percentile between 8 and 20% (Serôdio & Lavaud, )).…”

Diurnal fluctuations in chloroplast GSH redox state regulate susceptibility to oxidative stress and cell fate in a bloom‐forming diatom

“…These include ROS-scavenging enzymes and small molecules such as ascorbate, NADPH, and glutathione (reduced GSH, oxidized GSSG). Nonphotochemical chlorophyll fluorescence quenching (NPQ) is another fundamental photoprotective mechanism to prevent ROS formation by energy dissipation of excess excitation energy (Lepetit et al 2017). Glutathione is the most abundant small peptide in cells, its concentration typically reaches the millimolar range and it accounts for~90% of the nonprotein thiols in plant and algal cells (Rijstenbil andWijnholds 1996, Ahner et al 2002).…”