Mapping non-targeted-site resistance to herbicides in Spirodela polyrhiza (MapNTSR)
Evolution and Systematics of Plants and Fungi
Final Report Abstract
Adaptive evolution of plants to environmental stresses – either natural or human-mediated – shaped the global biodiversity and can profoundly affect the development of human societies. One example is the rapid expansion of weeds and their evolution to herbicide resistances, which threatens worldwide crop yields. However, it remains unclear how do weeds expand their habitats and evolve resistance to herbicides rapidly. In this project, we aimed to address this challenge using the giant duckweed, Spirodela polyrhiza as a model system. We first tested the hypothesis that herbicide resistance via the non-target site resistance (NTSR) mechanisms evolved from ecological pleiotropy - standing genetic variations that are associated with adaptation to natural stresses. To this end, we assessed the variations and heritability of diquat resistance among 138 globally distributed S. polyrhiza genotypes, which have not be subjected to herbicide applications in nature. We found that diquat resistance in the duckweed is highly heritable and the resistance level varied 8.5 folds. Further experiments suggested that diquat uptake and antioxidant-related processes, two processes that also mediate tolerance to natural stresses, jointly contributed to diquat resistance in S. polyrhiza. We then sequenced the genomes of globally distributed genotypes and identified several candidate genes, including a homolog of dienelactone hydrolase that is involved in the degradation of xenobiotics, are associated with diquat resistance using a genome-wide association approach. These results are consistent with the ecological pleiotropy hypothesis. Further population genomic and epigenomic analysis suggested that natural selection acting on asexual reproduction likely facilitated its rapid habitat expansion, which in turn also affected genomic diversity in populations. Together, the results from this project provide not only new insight into how herbicide resistance evolved weeds, but also shed light on the processes of plant adaptation to novel environment in general.
Publications
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Return of the Lemnaceae: duckweed as a model plant system in the genomics and postgenomics era. The Plant Cell, 33(10), 3207-3234.
Acosta, Kenneth; Appenroth, Klaus J.; Borisjuk, Ljudmilla; Edelman, Marvin; Heinig, Uwe; Jansen, Marcel A. K.; Oyama, Tokitaka; Pasaribu, Buntora; Schubert, Ingo; Sorrels, Shawn; Sree, K. Sowjanya; Xu, Shuqing; Michael, Todd P. & Lam, Eric
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Genetic Mechanism of Non-Targeted-Site Resistance to Diquat in Spirodela polyrhiza. Plants, 13(6), 845.
Höfer, Martin; Schäfer, Martin; Wang, Yangzi; Wink, Samuel & Xu, Shuqing
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Population genomics and epigenomics of Spirodela polyrhiza provide insights into the evolution of facultative asexuality. Communications Biology, 7(1).
Wang, Yangzi; Duchen, Pablo; Chávez, Alexandra; Sree, K. Sowjanya; Appenroth, Klaus J.; Zhao, Hai; Höfer, Martin; Huber, Meret & Xu, Shuqing
