Search

Potassium (K+) is an essential mineral nutrient for plant growth and development, with numerous membrane transporters and channels having been implicated in the maintenance and regulation of its homeostasis. The cation cesium (Cs+) is toxic for plants but shares similar chemical properties to the K+ ion and hence competes with its transport. Here, we report that K+ and Cs+ homeostasis in Arabidopsis thaliana also requires the action of ZIFL2 (Zinc-Induced Facilitator-Like 2), a member of the Major Facilitator Superfamily (MFS) of membrane transporters. We show that the Arabidopsis ZIFL2 is a functional transporter able to mediate K+ and Cs+ influx when heterologously expressed in yeast. Promoter–reporter, reverse transcription–PCR and fluorescent protein fusion experiments indicate that the predominant ZIFL2.1 isoform is targeted to the plasma membrane of endodermal and pericyle root cells. ZIFL2 loss of function and overexpression exacerbate and alleviate plant sensitivity, respectively, upon Cs+ and excess K+ supply, also influencing Cs+ whole-plant partitioning. We propose that the activity of this Arabidopsis MFS carrier promotes cellular K+ efflux in the root, thereby restricting Cs+/K+ xylem loading and subsequent root to shoot translocation under conditions of Cs+ or high K+ external supply. [ABSTRACT FROM AUTHOR]

Genomic information and tools are beginning to be used to increase our understanding of how organisms of all types interact with their environment. The study of the expression of all genes, at the genome, transcriptome, proteome and metabolome level, in response to exposure to a toxicant, is known as toxicogenomics. Here, we show how this new field of environmental genomics has enhanced the development of fundamental knowledge on the mechanisms behind the toxicity of and resistance to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Although 2,4-D is one of the most successfully and widely used herbicides, its intensive use has led to the emergence of resistant weeds and might give rise to several toxicological problems when present in concentrations above those recommended. This review summarizes recent mechanistic insights into 2,4-D toxicity and the corresponding adaptive responses based on studies carried out using Saccharomyces cerevisiae and Arabidopsis thaliana as model organisms. [Copyright &y& Elsevier]