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A 24-well growth assay was used to determine salt tolerance levels for Frankia strains.

Introduction

References Material and Methods

Results Results

ConclusionThese preliminary results are uncovering the mechanisms of salt stress tolerance in Frankia

Acknowledgement

Ornithine Biosynthesis is up regulated under salt stress

Salinization of soils and groundwater is a serious problem causing drastic reduction in agricultural production. Actinorhizal plants form a symbiotic association with the actinobacteria, Frankia, and are able to tolerate a variety of abiotic stresses including salt stress. Among the actinorhizal plants, some trees of the genus Casuarina have been shown to grow well under these conditions. The bacterial partner, Frankia, of the actinorhizal symbiosis plays a role in the ability of these plants to survive under harsh conditions. The aim of this study was to identify salt-tolerant Frankia strains and to determine the genes responsible for the molecular mechanisms of salt stress tolerance.

Rediet OSHONE1, Mariama NGOM2,3,5, Nathalie DIAGNE3,5, Diegane DIOUF3,5, Valérie HOCHER4,5, Mame Oureye SY2,5, Laurent LAPLAZE4,5, Antony CHAMPION3,4,5, and Louis S. TISA1

1. University of New Hampshire, USA 2. Laboratoire Campus de Biotechnologie Végétale, Faculté des Sciences & Techniques, Université Cheikh Anta Diop (UCAD), Dakar, Sénégal 3. Laboratoire Commun de Microbiologie IRD/ISRA/UCAD, Dakar, Sénégal 4. Equipe Rhizogenèse, UMR DIADE, IRD, Montpellier, France 5. Laboratoire mixte international Adaptation des Plantes et microorganismes associés aux Stress Environnementaux (LAPSE), Dakar, Sénégal

Identification and Molecular Characterization of Salt Stress Tolerance in Frankia Isolates from Casuarina Plants

COG category CcI6 CcI3 BMG5.23 Thr

Amino acid transport and metabolism 219 218 215 218

Carbohydrate transport and metabolism 133 132 130 135

Cell cycle control, cell division, chromosome partitioning 33 30 34 34

Cell motility 1 1 1 1

Cell wall/membrane/envelope biogenesis 142 139 143 134

Chromatin structure and dynamics 1 1 1 1

Coenzyme transport and metabolism 146 150 141 150

Defense mechanisms 41 39 35 39

Energy production and conversion 201 203 197 204

Function unknown 186 177 188 185

General function prediction only 378 369 365 366

Inorganic ion transport and metabolism 116 118 111 117

Intracellular trafficking, secretion, and vesicular transport 27 28 26 30

Lipid transport and metabolism 159 157 153 166

Nucleotide transport and metabolism 82 85 78 83

Posttranslational modification, protein turnover, chaperones 102 94 98 99

Replication, recombination and repair 180 212 183 169

RNA processing and modification 1 1 1 1

Secondary metabolites biosynthesis, transport and catabolism 113 105 112 116

Signal transduction mechanisms 147 145 147 147

Transcription 240 227 236 234

Translation, ribosomal structure and biogenesis 156 150 151 152

Not in COGs 2483 2183 2379 2406

Membrane composition changes under salt stress

RNA sequencing based differential gene expression analysis in CcI3 exposed to salt and

osmotic stress

Genomic synteny of CcI3 to CcI6, Thr, and BMG5.23CcI3 identified as the most salt sensitive strain, while Allo2, BMG5.23, CcI6, and CeD are salt tolerant

Trehalose biosynthesis is involved in the early response to salinity

Aldehyde detoxification is important in salt stress tolerance

RNA sequencing was performed in triplicate for cells under salt and osmotic stress.

The genomes of salt tolerant strains were sequenced and compared to the genome of the salt sensitive strain.

Quantitative PCR was performed on a sub set of the genes to confirm results of the RNA seq analysis.

Amino acid analysis was used to determine changes in the amino acid profile under salt stress.

A 24 well plate growth assay 2

Analysis of homologous coding sequences

Functional category comparison

Salt sensitive strain shows drastic change in amino acid profile under

stress

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pH homeostasis and Phospohate uptake are

important under salt stress

1. Benson DR and Silvester WB 1993 Biology of Frankia strains,actinomycete symbionts of actinorhizal plants

2. Furnholm T et al. 2012. Development of a semi-high-throughput growth assay for filamentous actinobacteria Frankia. Arch. Microbiol. 194 13–20

3. Hurst et al. 2014. Draft genome sequence of Frankia sp. Strain Thr. genomeA

4. Ghodhbane-Gtari F. et al. 2013 Draft Genome Sequence of Frankia sp. strain BMG5.23 genomeA

5. Mansour et al.2014. Draft genome sequence of Frankia sp. Strain CcI6. 2(1): e01205-13

6. Oshone R et al. 2013. Effect of salt stress on the physiology of Frankia sp. strain CcI6. J. Biosci. 38:699–702

7. Rengasamy P 2006 World salinization with emphasis on Australia. J. Exp. Bot. 57 1017–1023

This research is supported in part by Hatch NH585, JGI 2012 CSP585, and by the  College of Life Sciences and Agriculture at the University of New Hampshire, Durham. Travel support was obtained from the MCBS department, Graduate School, and the Zsigray Fund.