A high-quality genome of the mass-blooming desert plant Cistanthe longiscapa and its photosynthetic behavior related to drought and life history

Abstract

O_LICrassulacean acid metabolism (CAM) photosynthesis has independently evolved many times in arid-adapted plant lineages. Cistanthe longiscapa (Montiaceae), a desert mass-blooming annual, can upregulate CAM facultatively upon stress such as drought. Few studies, however, consider life history stages when measuring CAM activity or its facultative onset. C_LIO_LITo test the effect of drought and flowering on photosynthetic activity, we assayed Cistanthe individuals in fully-watered and drought conditions, as well as fully-watered individuals at pre-flowering and flowering life stages. We assembled and annotated a chromosome-scale genome of C. longiscapa and compared it with the genome of Portulaca amilis and analyzed differential gene expression. C_LIO_LIResults show significantly upregulated CAM in drought conditions as compared to fully-watered conditions; furthermore, flowering individuals showed slightly higher CAM activity as compared to pre-flowering plants, even when fully-watered. Differential gene expression analyses provide preliminary support for the possible co-regulation of CAM expression and reproduction. C_LIO_LIWe emphasize the potentially missed significance of life history in the CAM literature, and consider how the CAM biochemical module could become co-opted into other plant behaviors and responses, such as the shift to reproduction or flowering in annuals. C_LI