Microscopic green algae shed light on desiccation tolerance in green plants
Deserts of the southwestern U.S. are extreme habitats for most plants, but, remarkably, there are highly diverse communities of microscopic green algae living there that are extraordinarily desiccation tolerant. These tiny green algae (many just a few microns in size) live embedded in microbiotic soil crust. After drying out completely, algae can become active and start photosynthesizing again within seconds of receiving a drop of water.
How are they so resilient? That question is at the core of MBL Scientists Elena Lopez Peredo and Zoe Cardon’s research, published today in the Proceedings of the National Academy of Sciences of the United States of America. Working with two particularly resilient species (Acutodesmus deserticola and Flechtneria rotunda), they studied up- and down-regulation of gene expression during desiccation, and they added a twist. They also analyzed gene expression in a close aquatic relative (Enallax costatus) as it dried (and ultimately died). Surprisingly, all three algae – desiccation tolerant or not – upregulated expression of groups of genes well known to protect even seed plants during drought. But the desiccation tolerant algae also ramped down expression of genes coding for many other basic cellular processes, seemingly putting the brakes on their metabolism. The aquatic relative did not.
Peredo’s and Cardon’s research suggests this new perspective on desiccation tolerance warrants investigation in green plants more broadly. Upregulation of gene expression coding for protective proteins may be necessary but not sufficient; downregulation of diverse metabolic genes may also be key to survival. Given expected intensification droughts and the altered precipitation patterns in much of the world with climate change, understanding the bases of such adaptations facilitating green plant survival in arid environments becomes even more pressing.