Using the Genome of the Orchid Erycina pusilla as a Model to Study Crassulacean Acid Metabolism in Monocots

Photosynthesis is a foundational process supporting the vast majority of life on Earth. However, for plants living under water-limited conditions, photosynthetic productivity can be reduced by hotter and drier climatic conditions. Some plants employ modified forms of photosynthesis that increase their water-use efficiency under extreme environmental conditions. Crassulacean acid metabolism (CAM) is one such innovation that has facilitated diversification in a widearray of plant lineages. We are actively studying the independent development of CAM in the orchid family, wherein many species with an array of vegetative forms thrive in epiphytic and lithophytic niches. We are using the species Erycina pusilla (a CAM species) and Erycina crista-galli (a closely related C3 species) of subtribe Oncidiinae as a model species for functional research, with stable genetic transformation possible in E. pusilla and time to the T1 generation in as few as 18 months. Using our complete nuclear genome sequence, we have classified gene families in Erycina relative to another model CAM species, Phalaenopsis equestris, as well as to several other sequenced plant genomes. We have performed transcriptome analysis throughout the 24 hour light-dark growth cycle, and correlated results with physiological evidence for CAM activity. We have initiated transformation studies after mining these transcripome resources for differentially expressed genes. Here, we will report our initial progress with these various experiments. Coauthors: Ming-Tsair Chan, Agricultural Biotechnology Research Center, Taiwan; Choun-Sea Lin, Agricultural Biotechnology Research Center, Taiwan; Jeremy J. W. Chen, National Chung Hsing University, Taiwan; Yao-Ting Huang, National Chung Cheng University, Taiwan; Tianying Lan, University at Buffalo, USA, Kimberley Farr, University at Buffalo, USA; Tien-Hao Chang, University at Buffalo, USA; Jim Leebens-Mack, University of Georgia, USA; Karolina Heyduk, University of Georgia, USA; Michelle C. Hwang, University of Georgia, USA; Katia Silvera, University of California, Riverside, USA.