Beyond toxicity

Abstract

In non-cyanogenic plants, cyanide is a co-product of ethylene and camalexin biosynthesis. To maintain cyanide at non-toxic levels, Arabidopsis plants express the mitochondrial β-cyanoalanine synthase CYS-C1. CYS-C1 knockout leads to an increased level of cyanide in the roots and leaves and a severe defect in root hair morphogenesis, suggesting that cyanide acts as a signaling factor in root development. During compatible and incompatible plant-bacteria interactions, cyanide accumulation and CYS-C1 gene expression are negatively correlated. Moreover, CYS-C1 mutation increases both plant tolerance to biotrophic pathogens and their susceptibility to necrotrophic fungi, indicating that cyanide could stimulate the salicylic acid-dependent signaling pathway of the plant immune system. We hypothesize that CYS-C1 is essential for maintaining non-toxic concentrations of cyanide in the mitochondria to facilitate cyanide’s role in signaling.

Keywords: :

• cell signaling
• cyanide
• mitochondria
• plant immune response
• root hair
• β-cyanoalanine synthase

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Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

We would like to thank the European Regional Development Fund, the Ministerio de Economía y Competitividad of Spain (grant no. BIO2010–15201 and CSD2007–00057), and Junta de Andalucía of Spain (grant no. CVI-7190) for their financial support.