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Genetic and physiological mechanisms of freezing tolerance in locally adapted populations of a winter annual

bioRxiv, ISSN: 2692-8205
2019
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Article Description

Premise of the study Despite myriad examples of local adaptation, the phenotypes and genetic variants underlying such adaptive differentiation are seldom known. Recent work on freezing tolerance and local adaptation in ecotypes of Arabidopsis thaliana from Sweden and Italy provides the essential foundation for uncovering the genotype-phenotype-fitness map for an adaptive response to a key environmental stress. Methods Here we examine the consequences of a naturally occurring loss of function (LOF) mutation in an Italian allele of the gene that encodes the transcription factor CBF2, which underlies a major freezing tolerance locus. We used four lines with a Swedish genetic background, each containing a LOF CBF2 allele. Two lines had introgression segments containing of the Italian CBF2 allele, and two were created using CRISPR-Cas9. We used a growth chamber experiment to quantify freezing tolerance and gene expression both before and after cold acclimation. Key results Freezing tolerance was greater in the Swedish (72%) compared to the Italian (11%) ecotype, and all four experimental CBF2 LOF lines had reduced freezing tolerance compared to the Swedish ecotype. Differential expression analyses identified ten genes for which all CBF2 LOF lines and the IT ecotype showed similar patterns of reduced cold responsive expression compared to the SW ecotype. Conclusions We identified ten genes that are at least partially regulated by CBF2 that may contribute to the differences in cold acclimated freezing tolerance between the Italian and Swedish ecotypes. These results provide novel insight into the molecular and physiological mechanisms connecting a naturally occurring sequence polymorphism to an adaptive response to freezing conditions.

Bibliographic Details

Sanderson, Brian J.; Park, Sunchung; Jameel, M. Inam; Kraft, Joshua C.; Thomashow, Michael F.; Schemske, Douglas W.; Oakley, Christopher G.

Cold Spring Harbor Laboratory

Biochemistry, Genetics and Molecular Biology; Agricultural and Biological Sciences; Immunology and Microbiology; Neuroscience; Pharmacology, Toxicology and Pharmaceutics

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