CAM Expression in the Homoploid Hybrid Yucca gloriosa

Yucca gloriosa is a homoploid hybrid cross between Y. aloifolia and Y. filamentosa, a CAM and C₃ species respectively. All three species are sympatric in the southeastern United States, overlapping particularly along the coast. Earlier work indicated that Y. gloriosa utilizes an intermediate form of CAM photosynthesis, with nighttime acid accumulation but without concurrent nighttime CO₂ uptake. The intermediacy of CAM expression in these hybrids paralleled molecular work, which showed Y. gloriosa segregates for parental alleles in the wild. While CAM has been in the spotlight recently for its evolutionary novelty and potential importance for improving drought tolerance of food and energy crops, little is still known about how a plant transitions to CAM. Using the system found in Y. gloriosa, we explored variation in the ability of genotypes from across the range to perform CAM under drought stress. We find that while the two parental species are fixed in their photosynthetic pathway, the hybrid shows segregation for the ability to utilize CAM. We paralleled physiological work with RNA sequencing across the three species at six time points over a 24 hour diel cycle. Here we present preliminary physiological and RNA expression data, as well as future plans for studies using the intermediate Yucca species.