Coralie Chuberre

Bruno Gügi

Azeddine Driouich

Maïté Muriel Bardor

Vicré Phaeodactylum

Phaeodactylum tricornutum: new source of

come

Coralie Chuberre 1 , Bruno Gugi 1 , Azzedine Driouich 1 , Muriel Bardor 1,2 , Maïté Vicré 1 et al., 2009). Plant were grown in 16-h-day/8-hnight cycles (120 µE m -2 s -1 , 21°C).

Arabidopsis root elicitation with P.tricornutum crude cell homogenate P.tricornutum was grown in water complemented with seasalt (33g.L - 1 ), Conway medium (1mL.L -1 ) and silicate (2mL.L -1 ). Culture were placed in 16-h-day/8-h-night cycles (50 µE m -2 s -1 , 19°C).

P.Tricornutum cells were harvested after 10 days of growth and ground via theFastPrep-24TMsystem

Introduction

Recently, the use of effective and eco-friendly substitutes to traditional agrochemicals has aroused great interest in agriculture. The development of these new products is based on studies on eliciting molecules, also called elicitors or stimulator of plant defense (SDP), that mimic pathogen aggression to trigger plant defense. Different storage and parietal polysaccharides such as β-glucan, chitin and chitosan oligomers, oligogalacturonides have been reported to induce plant immunity 1 . Among β-glucans, Laminarin extracted from the brown macroalga Laminaria digitata is a well-known elicitor of plant defense 2 .

Laminarin mimic pathogen aggression to trigger plant defense

Evaluation of crude cell homogenate efficiency to protect plant

Actual results have shown that the crude cell homogenate from P.tricornutum induce parietal remodeling and root growth inhibition. However, we need to further investigate the immune response triggered by Phaeodactylum tricornutum. To this end, we will study the impact of the elicitor on specific defense markers genes of root defense. Furthermore, a fine structural analysis of the active compound will be performed.

Some results illustrated

Effect on plant vigour :

Root growth was inhibited after microalgae crude cell homogenate for 2 days application on Arabidopsis roots.

Ability to induce parietal remodelling Effect on callose deposition in roots and in leaves :

Aniline blue staining showed callose deposition (white arrows) after microalgae crude cell homogenate application for two days.

Effect on parietal remodelling :

Immunolabelling of extensins with LM1 antibody showed a different distribution of labelling when microalgae crude cell homogenate was applied for two days on Arabidopsis roots.

1Sterilized

  Université de Rouen Normandie, Structure fédérative de Recherche "Normandie-Végétale", Laboratoire Glyco-MEV EA4358, Centre Universitaire de Recherche et d'Innovation en Biologie (CURIB), 25 rue Lucien Tesnière 76821 Mont-Saint-Aignan Cedex 2 Institut universitaire de France (I.U.F) 1 rue Descartes, 75231 Paris cedex 05 Phaeodactylum tricornutum as a of microalgae Promising candidate to identify new elicitor • Sequenced genome • Easy and cheap culture conditions • Pleiomorphic cells depending on environmental conditions 7 . • Production of allelopathic compounds 8-9 • Storage polysaccharide (chrysolaminarin 10 ) whose structure is related to laminarin Arabidopsis thaliana ecotype Columbia seeds are sown onto Murashige and Skoog medium containing 1% (w/v) Bacto Agar (Durand

  By contrast to macroalgae that require large natural culture areas and take a long time to develop, microalgae grow fast and in controlled restricted areas. They represent a highly diverse group with a wide range of metabolites which represents potential source of eliciting molecules. Image source : Dudek 2016 5 6 Tesson et al. 2009 Method to evaluate the potential elicitor effect of P.tricornutum extract performed on 7 days-old seedlings. Arabidopsis root treated with crude cell homogenate are harvested after different time according to the technique evaluated. Two control were used to evaluated the capacity of crude cell homogenate to induce plant defense. *Flg22 is a famous elicitor of plant defense used as reference in several studies. Neg. control : Water Pos. control :Flg22 (1μM) P.Tricornutum crude cell homogenate (10 8 cells.mL -1 )

  , S. et al. Frontiers in Plant Science 5, (2014). 2. Klarzynski, O. et al. Plant Physiol. 124, 1027-1038 (2000). 3. Norwegian seaweeds (consulted in 2017) : http://seaweeds.uib.no/?art=196 4. Goemar Etraining-Vacciplant (consulted in 2018) : http://etraining.vacciplant.fr/3 5. Dudek 2016, Aberystwyth university, 237p


Coralie Chuberre

Bruno Gügi

Azeddine Driouich

Maïté Muriel Bardor

Maïté Vicré

Bruno Gugi

Plant Immunity is compartimentalized and specialized in roots

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Conclusion

Root immunity is far from being fully understood and so many questions remain regarding mechanisms at the cellular and molecular levels. ). These biomarkers are not significantly induced in Arabidopsis roots 6,7,8 . Furthermore the antagonistic action between salicylic and jasmonic acid that occurs in leaves is not always reported in roots. ethylene seems to play a major role in root defense.

Tissue-specific defense responses in Arabidopsis thaliana root

Introduction 1 .

 1 Watt et al., 2006 Ann. Bot. 97, 839-855 2. Mendes et al., 2013 FEMS Microbiol. Rev. 37, 634-663 3. Perrine-Walker et al., 2007 J. Exp. Bot. 58, 3343-3350 4. Sesma et al., 2004 Nature 431, 582-586 Acknowledgement: The authors would like to thank the Region Normandie (Fellowship for C. Chuberre) and the University of Rouen for their funding. References: 5. Okubara et al., 2005 Root Physiology: from Gene to Function, 215-226 7. Attard et al., 2010 New Phytol. 187, 449-460 8. Badri et al., 2008 New Phytol. 179, 209-223 9. Lyons et al., 2015 PLoS One 10:e0121902

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  Root defense response to elicitors and/or pathogen attacks exhibit tissue specificity. How such compartmentalization occurs in root defense as compared to leaves is still unclear. Is it due to distinct localization of signal receptors or only due to differences in the amplitude of responses in each tissue? Root border cells are particularly important in root defense against pathogens. In A. thaliana, root border-like cells (BLCs) are likely to be key elements in defense as they perceive elicitors and display defense mechanisms responses.

  found in leaves are SA markers (pathogenesis related proteins PR-1), JA markers (plant defensin: PDF1.2), ET markers (amino-cyclopropane-carboxylate oxidase myrosinase binding protein: ACCO), glucosinolate markers (enzyme involved in glucosinolate biosynthesis: CYP79B2

  Promotors of defense gene in fusion to GUS were used to evaluate defense gene expression in the different root zone after elicitor treatments. In response to chitin, gene expression occurred in the entire mature zones(DZ and PZ). In contrast, with Flg22 and PGN, the response is restricted to EZ (idem callose). In root caps, expression of defense genes (WRKY11/HEL) was restricted to the peripheral RC cells. This compartmentalized response suggest tissue-specific elicitor receptors localization or difference in the amplitude of response within tissue 12 . DZ, differentiation zone; PZ, root hair zone; EZ, elongation zone; MZ, meristematic zone; RC and BLCs, root cap and border-like cells CYP71A12, Cytochrome P450 family 71 polypeptide; MYB51, Transcription factor involved in indoleglucosinolate biosynthesis; WRKY11, Negative regulator of basal resistance; AT5G25260, Nodulin-like protein of unknown function; ACS6 : 1-aminocyclopropane-1-carboxylate synthase 6; HEL, Hevein-like protein; ZAT12, Zinc-finger protein; PER5, Peroxidase superfamily protein; Flg22, Flagellin ; PGN, peptidoglycan Barley roots infected by M. grisea (a). Once inside the root M. grisea progressed from the cortical cells through the endodermis and into the root stele (b-c) 4 . Confocal imaging of radial and longitudinal sections of a three-week-old rice seedling (cultivar Nipponbare) infected with GFP-tagged M. grisea 1. Colonization of natural apertures (epidermal cracks) (a, c) and within the entire (b) root tissue of rice forming intercellular lines of GFPlabelled Rhizobium bacteria 3 . Aerial disease can be related to root infection 3. Cotton root infection with Fusarium sp (a). Once inside the root, Fusarium sp. infect the aerial part of the plant (hypocotyl) through the vascular tissue (b-c) 5 . Gene biomarkers differ both according to the plant species and the organs (e.g., aerial or belowground organs) PTI induction is restricted to specific root zones that are critical for successful infection by invading pathogens Fungal hyphae growth (green) is limited and at distance from root tips (red). (C) In root treated with DNase I, fungal hyphae (double white arrow) proliferate among border cells (white arrow) and penetrate the root tip epidermis (black arrows) 11 . A Root extracellular trap (RET) is formed by border cells and root secretions (mucilage). Experimental evidences indicate that RET is able to alter microbial behavior in many ways to ensure root protection and create stable changes within the rhizosphere. Inhibition of RET formation results in root infection 9 . BC, border cells; ExDNA, extracellular DNA; PR proteins, pathogenesis-related proteins; PGPR, plant growth promoting rhizobacteria; RC, root cap. et al., 2013 Curr. Opin. Plant Biol. 16, 489-495 11. Tran et al., 2016 PLoS Pathogens 12(6):e1005686 12.Chuberre et al., 2018, Front. Plant Sci. 9:1692