Clusia genomes shed light on the evolution and diversity of CAM physiotypes (GEO series)

Here, we de novo sequenced the genomes of three Clusia species to capture genetic snapshots along an evo-ecophysiological continuum from weak over inducible to strong CAM. Through a combination of chromosome level assembly and annotation, comparative multiomics, and physiological phenotyping, we identify a strong association between diploidization of polyploids and the physiotype diversity of CAM. We illustrate that Clusia major, a plant that seems to exhibits a C3-type mode of photosynthesis, retained almost all hallmarks of CAM.

Transposon-mediated genic diploidization, however, acted upon homoeologs in CAM-related gene families, particularly those involved in phosphoenolpyruvate (PEP) recycling via phosphorolytic leaf starch metabolization. In effect, this rendered a plant capable of C3+CAM with open stomata during the day by shifting carbohydrate supply (PEP) to viable soluble sugars. Our findings indicate that polyploidization during genus evolution and subsequent diploidization shaped the emergence of extant physiotypes in Clusia.