Abstract Detail

Genomics / Proteomics

Heyduk, Karolina [1], Ray, Jeremy [1], Leebens-Mack, Jim [1].

Comparative transcriptomics of Crassulacean acid metabolism in Yucca .

Crassulacean acid metabolism (CAM) is an adaptation to water-stressed environments whereby plants modify the central process of carbon fixation. In CAM plants, stomata open at night when transpiration rates are lowest, and incoming CO₂ is fixed and stored temporarily as malic acid in the vacuoles. During the day, stomata close, malic acid is decarboxylated, and RuBisCO is flooded with a high concentration of carbon in the leaf cells. This carbon concentrating mechanism increases the efficiency of RuBisCO while simultaneously decreasing the amount of water lost per carbon molecule gained. In the genus Yucca (Asparagaceae), in which half of the species use C₃ photosynthesis and half use CAM, a natural C₃-CAM hybrid, Yucca gloriosa, shows intermediate physiological phenotypes; during periods of ample water, Y. gloriosa will conduct C₃ photosynthesis, with low levels of concomitant nighttime CO₂ uptake presumably via the CAM pathway. Under drought stress, daytime CO₂ fixation disappears in the C₃-CAM hybrid and it converts to full CAM, until re-watering returns them to a largely C₃ state. Yucca gloriosa is native to the Southeastern U.S., and marker data suggests it is a later generational hybrid (greater than F1) that is potentially segregating for CAM function. Here we use Yucca as an emerging model for the study of CAM evolution by an in-depth exploration of the transcriptomes from the C₃ and CAM parental species, Y. filamentosa and Y. aloifolia respectively, and the hybrid Y. gloriosa. We sequenced 3-4 genotypes of each parental species, with samples taken every four hours over a 24-hour period from both well-watered and drought-stressed samples. Additionally, we sequenced 7 genotypes of Y. gloriosa that segregate for the ability to use the CAM pathway under drought stress. We find that the C₃ parent has CAM-like expression of a number of central CAM pathway genes, but without the corresponding CAM phenotype (as measured by gas exchange and leaf acid accumulation). Allele specific gene expression of CAM genes was examined in the hybrid genotypes to determine whether cis or trans elements play a larger role in the expression of CAM photosynthesis.

1 - University Of Georgia, Plant Biology, 2502 Miller Plant Sciences, Athens, GA, 30602, USA

Keywords:
photosynthesis
Transcriptomics
comparative transcriptome
RNAseq.

Presentation Type: Oral Paper
Session: 19, Genomics & Proteomics I
Location: 105/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 8:15 AM
Number: 19002
Abstract ID:380
Candidate for Awards:Margaret Menzel Award