Abstract Detail



Mycology & Phycology

Peredo, Elena L [1], Austin, Jotham [2], Bezanilla, Madgalena [3], Dohnalkova, Alice [4], Cardon, Zoe [1].

Characterization at cellular and subcellular level of desert-evolved and aquatic green microalgae within the Scendesmaceae.

Multiple lineages of microalgae have successfully completed the leap to land and adapted to a variety of terrestrial environments, including deserts where they often are found inhabiting microbial soil crusts. All these algal lineages independently acquired traits to survive the harsh abiotic conditions of land, characterized by temperature swings, high light, and low water availability. In desert-evolved algae, one key trait is desiccation tolerance in the vegetative state. In Embryophytes, it has long been established that a series of major innovations in plant body plans, anatomy, and biochemistry correlate with terrestrial colonization. Much less is known of the consequences of the transition to land in microalgae as the extremely small size of these green plants, often around 5-10 ┬Ám, has hindered our ability to observe their adaptations. Here we used a suite of independently desert-evolved microalgae within the family Scenedesmaceae and their close aquatic relatives to investigate cellular and physiological traits that correlate with adaptation to land in this group of algae. We worked with two aquatic species (Enallax costatus, Tetradesmus obliquus), and three desert species (Tetradesmus deserticola, Fletchneria rotunda, Tetradesmus bajacalifornicus.) First, we investigated the commonalities and differences in the cellular processes during asexual reproduction. We coupled fluorescence confocal imaging of live cell staining and transmission electron microscopy to determine the fate of the nuclei and organelles during different stages of cellular karyo and cytokinesis. All desert and aquatic species divided by multiple (rather than binary) fission. We recorded the release of daughter cells with live time-lapse confocal imaging on polydimethylsiloxane (PDMS) microfluidic chambers specially designed to maintain the cells in aerobic conditions over long periods of time. We identified in all species a dynamic rotation of the daughter cell masses within the mother cell wall during cytokinesis. The progeny of the aquatic taxa were multicellular (with daughter cells joined in a sheet-like coenobium) as is characteristic of algae within the Scendesmaceae. Progeny in the three desert-evolved species were unicellular upon release. Live imaging also revealed an intriguing morphological change after division in the desert-evolved taxon T. deserticola. Each newly-released, lemon-shaped daughter cell extruded one flexible bristle from each pole. Bristles tended to attach to surfaces and continued extrusion propelled the cells across the PDMS. We speculate that bristle growth may aid daughter cell dispersal, and adhesion to substrate may tether cells against advective flow during rain. We also explored the consequences of water loss in desert-evolved and aquatic microalgae. Using confocal imaging and a dye sensitive to intracellular ROS, we identified a statistically significant differential accumulation of intracellular reactive oxygen species (ROS) in desert-evolved and aquatic species upon rehydration after desiccation. We also successfully implemented cryo-FIB (focused ion beam) milling of T. deserticola cells desiccated on electron microscopy grids, producing 150-200 nm lamellae that can be imaged to produce 1-3 nm resolution 3D cryo-tomograms. Future comparisons of desiccation tolerant and intolerant algae using this technique should provide an excellent window into thylakoid conformational changes protecting photosynthetic capacity during desiccation and rehydration of desiccation tolerant algae.


Related Links:
Elena L Peredo


1 - Marine Biological Laboratory (USA), 7 MBL st, Woods Hole, Massachusetts, 02543, United States
2 - University of Chicago
3 - Dartmouth College
4 - Pacific Northwest National Laboratory

Keywords:
dessication tolerance
confocal imaging
Live imaging
cryo-FIB.

Presentation Type: Oral Paper
Number: MP1003
Abstract ID:349
Candidate for Awards:None


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