Photoprotection in the Lichen Parmelia sulcata: The Origins of Desiccation-Induced Fluorescence Quenching1

Lichens, a symbiotic relationship between a fungus (mycobiont) and a photosynthetic green algae or cyanobacteria (photobiont), belong to an elite group of survivalist organisms termed resurrection species. When lichens are desiccated, they are photosynthetically inactive, but upon rehydration they can perform photosynthesis within seconds. Desiccation is correlated with both a loss of variable chlorophyll a fluorescence and a decrease in overall fluorescence yield. The fluorescence quenching likely reflects photoprotection mechanisms that may be based on desiccation-induced changes in lichen structure that limit light exposure to the photobiont (sunshade effect) and/or active quenching of excitation energy absorbed by the photosynthetic apparatus. To separate and quantify these possible mechanisms, we have investigated the origins of fluorescence quenching in desiccated lichens with steady-state, low temperature, and time-resolved chlorophyll fluorescence spectroscopy. We found the most dramatic target of quenching to be photosystem II (PSII), which produces negligible levels of fluorescence in desiccated lichens. We show that fluorescence decay in desiccated lichens was dominated by a short lifetime, long-wavelength component energetically coupled to PSII. Remaining fluorescence was primarily from PSI and although diminished in amplitude, PSI decay kinetics were unaffected by desiccation. The long-wavelength-quenching species was responsible for most (about 80%) of the fluorescence quenching observed in desiccated lichens; the rest of the quenching was attributed to the sunshade effect induced by structural changes in the lichen thallus

BRAHSS1415_Dataset_ALL

Measured response variables for migrating humpback whale baseline groups and groups exposed to control (vessel only) and full array seismic air gun trials

Genotypic fitness for hemizygotes and transgenic homozygotes relative to homozygous wild-type individuals over three developmental periods.

<p>In A) the fitness of the homozygous and hemizygous Phase-1 EE genotypes were compared to wild-type homozygotes; in B) the fitness of the homozygous and hemizygous Phase-2 EVida3 genotypes were compared to wild-type homozygotes. Boxplots were median, quartiles and min-maximum values. The significance levels of a pairwise Wilcoxon test are indicated - ns, not significant, *: <i>P</i><0.05, ** <i>P</i><0.01, *** <i>P</i><0.001.</p

Allelic fitness for transgene alleles relative to wild-type for three independent developmental periods.

<p>Boxplots were median, quartiles and min-maximum fitness from adult to 1^st instar larvae of the next generation (Adult - L₁ Larvae), larvae to pupae (L₁ Larvae - Pupae) and pupae to adult (Pupae - Adult). Significance levels of pairwise Wilcoxon tests are indicated - ns, not significant, *: <i>P</i><0.05, ** <i>P</i><0.01, *** <i>P</i><0.001.</p

Frequency of hemizygotes, homozygous transgenic and homozygous wild-type genotypes over 10 generations in three independent replicates.

<p>In A) the frequency of individuals homozygous (TT) and hemizygous (TW) for the Phase-1 EE docking construct are compared to homozygous wild-type (WW); in B) the frequency of homozygotes (TT) and heterozygotes (TW) for the Phase-2 EVida3 construct are compared to homozygous wild-type (WW). Significance levels of a Chi-square test of HWE are indicated - ns, not significant, *: <i>P</i><0.05, ** <i>P</i><0.01, *** <i>P</i><0.001.</p

Assortative mating and reproductive success of the transgenic and wild-type lines.

<p>In A) the frequency of the hemizygote (TW) and homozygous (WW, TT) genotypes were compared in both the Mopti vs EE and Mopti vs EVida3 comparisons. In B) the frequency of the transgenic (T) and wild-type (W) alleles in both the Mopti vs EE and Mopti vs EVida3 comparisons were compared. Error bars represent 95% confidence intervals. Significance levels of a Chi-square test are indicated - ns, not significant, *: <i>P</i><0.05, ** <i>P</i><0.01, *** <i>P</i><0.001.</p

Mean female and male body size, survival and insemination rate in relation to Genetic/Environmental treatment in the within-form mating experiment (1^st experiment).

<p>The insemination rate of females of each treatment exposed to Field/Field Mopti males.</p><p>Here the insemination rate of Field/Field Mopti females exposed to males of each treatment group.</p><p>Values in brackets are 95% confidence intervals and sample sizes are indicated in italics.</p

Mean wing length (mm) in females (dark bars) and males (light bars) from the 4 Genetic/Environmental treatments in the 2011 assortative mating experiment.

<p>For each gender, levels labelled with different letters differed significantly in pairwise statistical comparisons (Tukey test). Error bars are 95% confidence intervals.</p

Nominal logistic regressions of the effects of Year, Genetic/Environmental treatment, and Enclosure on female and male survival in within-form mating experiment (1^st experiment).

<p>Square brackets indicate effect nesting.</p><p>Sample sizes were 900 females and 900 males.</p

Survival rate of Field/Field Mopti form and Savanna form females and males mated to individuals of the 4 Gen/Env treatment groups in the assortative mating experiment (2^nd experiment).

<p>Values in brackets are 95% confidence intervals and sample sizes are indicated in italics.</p