Abstract Detail


Nissenbaum, Matthew [1], Burke, Sean [2], Orton, Lauren [3], Holthuijzen, Wieteke [1], Duvall, M [4].

Dispelling the Mirage of C4 Driven Drought Tolerance in Poaceae: A Phylogenomic Study.

Climate change has been considered a key driver for adaptations in water usage efficiency (WUE) in plants. Perceptions persist that C4 photosynthesis is indicative of some level of WUE.  Here, we examined the interaction and evolution of WUE within the grass family, Poaceae, as it pertains to photosynthetic pathway. Unique to this study is the magnitude of taxa sampled, presence of intrageneric sampling, and use of complete plastid genomes (plastomes) for phylogenomic analyses.310 species were sampled including 26 with newly sequenced plastomes, which were  assembled de novo from next-generation sequencing data. Additional plastomes were downloaded (https://www.ncbi.nlm.nih.gov/), increasing taxonomic and molecular sampling. Critical  leaf water potentials were available in the literature for 88 taxa. Key classifiers for the other taxa were also obtained from the literature to infer WUE.Phylogenetic analyses of complete plastomes were conducted with maximum likelihood and Bayesian inference methods. Character state transitions were determined using Mesquite software, and analyzed to determine the relationship between photosynthetic pathway and WUE using Pagel’s Correlation Method.The ancestral condition of Poaceae was determined to be drought intolerant + C3. There was no statistically significant correlation between C4 photosynthesis and increased WUE within C4 lineages. Analyses across Poaceae indicated that both variables were significantly correlated regardless of the dependent variable. We found 66 occurrences of WUE state transitions and state reversals accounted for >70%. Transitions became increasingly prevalent towards the branch tips.Our analyses indicated that C4 photosynthesis, however correlative, is not a driver of increased WUE, but an attribute that likely arose as a result of tertiary evolutionary pressure(s). Multiple state transitions in WUE among lineages also suggests a degree of WUE plasticity. 

1 - Northern Illinois University, Biological Sciences, 1425 W. Lincoln Hwy., Dekalb, IL, 60115, USA
2 - University of Chicago, Center for Translational Data Science, 5454 S Shore Dr , #2b, Chicago, Illinois, 60615, USA
3 - 251 Ashwood Drive, Sycamore, IL, 60178, United States
4 - Northern Illinois University, Plant Molecular And Bioinformatics Center And Department Of Biology, 1425 W Lincoln Hwy, Dekalb, IL, 60115, United States

C4 photosynthesis
drought tolerance
Ancestral character state reconstruction.

Presentation Type: Oral Paper
Session: PHYL4, Phylogenomics IV
Location: Virtual/Virtual
Date: Friday, July 31st, 2020
Time: 3:45 PM
Number: PHYL4004
Abstract ID:810
Candidate for Awards:None

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