Freeze‐induced cyanide toxicity does not maintain the cyanogenesis polymorphism in white clover (Trifolium repens)
Year: 2018
Type: article
Abstract: PREMISE OF THE STUDY: The maintenance of adaptive polymorphisms within species requires fitness trade-offs reflecting selection for each morph. Cyanogenesis, the ability to produce hydrogen cyanide (HCN) after tissue damage, occurs in >3000 plant species and exists as a discrete polymorphism in white clover. This polymorphism is spatially distributed in recurrent clines, with higher frequencies of cyanogenic plants in warmer climates. The HCN autotoxicity hypothesis proposes that cyanogenic plants are selected against where frosts are common, as freezing liberates HCN and could impair cellular respiration. METHODS: We tested the HCN autotoxicity hypothesis using a freezing chamber to examine survival, tissue damage, and physiological recovery as assessed via chlorophyll fluorescence following mild and severe freezing treatments. We utilized 65 genotypes from a single polymorphic population to eliminate effects of population structure. KEY RESULTS: Cyanogenic plants did not differ from acyanogenic plants in survival, tissue damage, or recovery following freezing. However, plants producing either of the two required cyanogenic precursors had lower survival and tissue damage after freezing than plants lacking both precursors. CONCLUSIONS: These results suggest that freezing-induced HCN toxicity is unlikely to be responsible for the maintenance of the cyanogenesis polymorphism in white clover. However, energetic trade-offs associated with costs of producing the cyanogenic precursors may confer a fitness benefit to acyanogenic plants under stressful climatic conditions. The lack of evidence for HCN toxicity suggests that cyanogenic clover uses physiological mechanisms mediated by β-cyanoalanine synthase and alternative oxidase to maintain cellular function in the presence of HCN.
Source: American Journal of Botany
DOI: 10.1002/ajb2.1134
Language: English
Topic: Cassava research and cyanide
Subfield: Plant Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: bronze
Awards: Dissertation Research: Determining the Mechanisms of Recurrent Cline Evolution in White Clover (Trifolium repens), Collaborative Research: Genetic and Physiological Mechanisms of Local Climatic Adaptation in a Widespread Perennial Plant Species, CAREER -- Clover cyanogenesis: Integrating ecological and molecular genetics in the study of adaptation
OpenAlex ID: W2885456908