Abstract
The green unicellular alga Chlamydomonas reinhardtii lives in temperate soils, a highly variable habitat, and is gene-rich compared with algae occupying more homogeneous habitats, suggesting that it possesses a particularly rich repertoire of adaptive responses to stress. We have combined RNA-Seq and other gene-expression technologies with quick-freeze deep-etch electron microscopy, which visualizes cells in their native state, to compare two of these responses: the adjustments made when an essential nutrient (nitrogen) is abruptly withdrawn from cycling cells, and the adjustments made when nutrients are "naturally" depleted to trigger entrance into stationary phase. The two conditions elicit very different gene-expression patterns, vacuole populations, and starch/triacylglycerol storage profiles, but both generate fully viable quiescent cells that, in nature, presumably await improved circumstances. When applied to additional stress responses in the future, this omics/ultrastructure approach should yield an informative catalogue of Chlamydomonas versatility.