Does Chloroplast Thylakoid Membrane Organization Influence Desiccation Tolerance in Green Algae?
EMSL Project ID
48938
Abstract
A key step in the evolution and diversification of advanced life on Earth was the transition from aquatic to terrestrial habitats. Organisms making the leap from water to land faced high light levels, temperature swings, and desiccation. The green plant clade (including higher plants and green algae) is by far the largest lineage of photosynthetic eukaryotes to have become established on land, but desiccation threatens terrestrial photosynthetic organisms with photooxidative damage. We are studying photoprotection during desiccation in multiple, evolutionarily independent terrestrial green algal lineages found in desert microbiotic crusts of the Southwestern U.S. Our preliminary data indicate many of these desert algae exhibit extremely efficient, desiccation-induced photoprotection reminiscent of protection previously described in a handful of lichens and mosses. The details of the mechanism remain unknown, but signatures of photoprotection during desiccation can be detected using analyses of chlorophyll fluorescence produced from Photosystem II (PSII). One hypothesis suggests that spillover of energy from PSII to Photosystem I (PSI) is the dominant mechanism underlying this desiccation-induced photoprotection, and spillover requires that PSII and PSI be near one another. We therefore hypothesize that desiccation-induced photoprotection facilitated by spillover should be inhibited by stacking of thylakoid membranes into grana stacks within chloroplasts, because, in grana stacks, PSII is dominantly localized to internal membrane regions of grana, and PSI to external edges of, or between, stacks. We aim to work with EMSL personnel to examine whether thylakoids stack into grana in chloroplasts of a diverse range of green algae, all isolated from desert microbiotic crusts, but demonstrated in our assays to have a repeatable difference in their ability to recover photosynthesis during rehydration after desiccation. The diversity of techniques available at EMSL is critical for this effort. Structured illumination microscopy, TEM, and confocal fluorescence imaging will all be applied to a suite of ten diverse desert green algal taxa to discern whether thylakoids are stacked in grana, and whether the presence/absence/extent of stacking correlates with the strength of observed desiccation-induced photoprotection.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2015-10-01
End Date
2017-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Cardon Z.G., E. Peredo, A. Dohnalkova, G. Hannah, and M. Bazanilla. 2018. "A model suite of green algae within the Scenedesmaceae for investigating contrasting desiccation tolerance and morphology." Journal of Cell Science 131, no. 7. PNNL-SA-133995. doi:10.1242/jcs.212233