K+ AND Na+ HOMEOSTASIS IN FUNGI AND PLANTS

Personnel:

 

K+ and Na+ are chemically similar cations that have to be finely regulated in all organisms to maintain relatively high K+ and low Na+ concentrations in the cytosol. In fungi and plants this is achieved through the coordinated function of transporters. Our group is interested in the study of the ionic cellular fluxes and in the transporters that mediate K+ uptake, which is recognized as the most abundant cellular cation which fulfils important cellular functions; and in those transporters that could improve the Na+ efflux, which is considered as a toxic cellular cation. Especially we want to study of the role of the ion transporters that are relevant in salt tolerance and for K+ nutrition.

Soil salinity is a major environmental factor that prevents farming in many soils and limits crop productivity in others. Our group is interested on delimiting and quantifying the toxic causes of the plant growth inhibition by NaCl, characterizing the process of Na+ uptake and identifying the genes involved in this process. To address these aims, we have proposed different complementary approaches extending from genetic to molecular and cellular biology studies that will be carried out using three types of organisms, Arabidopsis thaliana, the model bryophyte Physcomitrella patens and some fungi like yeast Saccharomyces cerevisiae. For a long time our group has used the yeast Saccharomyces cerevisiae and other fungi as model organisms for the study of ionic homeostasis and salt tolerance and K+ nutrition of plants. Both fungi and plants have cell walls, they share K+ and Na+ transporters and they also share the systems of membrane energization.

At present three approaches are ongoing:

A genetic approach in Arabidopsis to characterize the Na+ uptake in plant roots and determinants involved in Na+ tolerance

This approach is based on RIL and GWA (genome-wide association) studies addressed to identify the genes involved in Na+ toxicity and osmotic inhibition, and root Na+ uptake. One line is directed to identify genetic determinants of NaCl tolerance through a GWA study (genome-wide association) exploiting the information obtained from the full genome sequencing of 1001 accessions of Arabidopsis (Cao et al. 2011, Nature Genetics. 43, 956-963). In other hand, QTL analysis will be also carried out based on RILs from parental accessions of Arabidopsis that differ significantly in low-affinity Na+ transport.

 
Study of the cellular toxicity of Na+. Ultra-structural study of plant cell changes upon salt treatments

Cellular root and shoot Na+ toxicities that we have observed in Arabidopsis are being studied with a microscopy approach to determine cellular Na+ accumulation using the Na+ specific fluorophore dye CoroNaGreen. Preliminary results indicate that Na+ accumulates in individual cells distributed in some regions of the plant root. To better understand the cellular effects of Na+, ultra-structural analysis of morphological cellular changes induced by salt treatment are also being studied by electron microscopy.

 

 

Regarding the Na+ accumulation at cellular level, it is assumed that the main strategy of plant cells to maintain a low Na+ concentration in the cytosol is its compartmentalization in the vacuole (Zhang and Blumwald, 2001, Nature Biotechnol. 19, 765-768). However, using CoronaGreen, we have observed that in Physcomitrella patens Na+ accumulates in chloroplasts and that this accumulation apparently does not affect the chloroplast function. Therefore we will study morphological changes in Physcomitrella cells by electron microscopy paying special attention to starch reserves.

A molecular approach to characterize genes involved in Na+ transport in plants

This approach has been initiated in the bryophyte Physcomitrella patens, a model plant that has become a tool for research in our group from which we have a large amount of physiological and genetic information regarding Na+ and K+ homeostasis. In parallel, we also are involved in the cloning, functional characterization, localization and expression analysis of fungal Na+ and K+ transporters that can be essential in Na+ uptake. Some examples of fungi used in our recent research are the basidiomycete Ustilago maydis, the ascomycetes Magnaporthe oryzae, and Yarrowia lypolitica.

 

 

Funding
  • Root Na+ uptake and NaCl tolerance in plants: functional and genetic analyses (2012-2015). National Project financed by the Ministerio de Economía y Competitividad (AGL2012-36174).
 
 

Representative Publications

Ruiz-Lau, N; Sáez, Á; Lanza, M; Benito, B. 2017. "Genomic and transcriptomic compilation of chloroplast ionic transporters of Physcomitrella patens. Study of NHAD transporters in Na+ and K+ homeostasis". Plant and Cell Physiology. DOI: 10.1093/pcp/pcx150".

Dominguez-Nuñez, JA; Benito, B; Berrocal-Lobo, M; Albanesi, A. 2016. "Mycorrhizal Fungi: Role in the Solubilization of Potassium", p. 77-98. In S. V. Meena, R. B. Maurya, P. J. Verma, and S. R. Meena (eds.), Potassium Solubilizing Microorganisms for Sustainable Agriculture. Springer India, New Delhi. DOI: 10.1007/978-81-322-2776-2_6".

Ruiz-Lau, N; Bojórquez-Quintal, E; Benito, B; Echevarría-Machado, I; Sánchez-Cach, LA; Medina-Lara, MdF; Martínez-Estévez, M. 2016. "Molecular cloning and functional analysis of a Na+-insensitive K+ transporter of Capsicum chinense Jacq". Frontiers in Plant Science. DOI: 10.3389/fpls.2016.01980".

Nieves-Cordones, M; Martinez, V; Benito, B; Rubio, F. 2016. "Comparison between Arabidopsis and rice for main pathways of K+ and Na+ uptake by roots". Frontiers in Plant Science. DOI: 10.3389/fpls.2016.00992".

Benito, B; González-Guerrero, M. 2014. "Unravelling potassium nutrition in ectomycorrhizal associations". New Phytologist. DOI: 10.1111/nph.12659".

Benito, B; Haro, R; Amtmann, A; Cuin, TA; Dreyer, I. 2014. "The twins K+ and Na+ in plants". Journal of Plant Physiology. DOI: 10.1016/j.jplph.2013.10.014".

 

 
 

 


 

Centro de Biotecnología y Genómica de Plantas UPM – INIA Parque Científico y Tecnológico de la U.P.M. Campus de Montegancedo
Autopista M-40, Km 38 - 28223 Pozuelo de Alarcón (Madrid) Tel.: +34 91 4524900 ext. 1806 / +34 91 3364539 Fax: +34 91 7157721. Contacto

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