Photosynthetic Acclimation Mediates Exponential Growth of a Desert Plant in Death Valley Summer

Heat waves, now more frequent and longer due to climate change, devastate plant productivity. Although rare, thermophilic plants could hold keys to engineering heat resilience in crop plants. Tidestromia oblongifolia is a thermophilic flowering plant that thrives at temperatures above 45°C. When exposed to Death Valley summer conditions, T. oblongifolia increased its thermal optimum of photosynthesis within a day and accelerated growth within 10 days. The physiological changes were accompanied by morphological, anatomical, and gene expression changes revealed by a newly sequenced genome. In bundle sheath cells where Rubisco fixes CO 2 , mitochondria relocated to chloroplasts and novel, cup-shaped chloroplasts appeared. Understanding how this plant acclimates under heat may afford new ways of engineering heat tolerance in crop plants. One-Sentence Summary Tidestromia oblongifolia ’s acclimation to Death Valley is accompanied by changes in gene expression, organellar dynamics, and photosynthesis.