Short‐chain chitin oligomers from arbuscular mycorrhizal fungi trigger nuclear Ca2+ spiking in Medicago truncatula roots and their production is enhanced by strigolactone. Issue 1 (6th February 2013)

• Record Type: Journal Article
• Authors: Genre, Andrea; Chabaud, Mireille; Balzergue, Coline; Puech‐Pagès, Virginie; Novero, Mara; Rey, Thomas; Fournier, Joëlle; Rochange, Soizic; Bécard, Guillaume; Bonfante, Paola; Barker, David G.
• Is Part Of: New phytologist. Volume 198:Issue 1(2013)
• Page Start: 190
• Page End: 202
• Publication Date: 2013-02-06
• Subjects: Botany -- Periodicals; 580
• DOI: 10.1111/nph.12146
• Languages: English
• ISSNs: 0028-646X

Abstract

<abstract abstract-type="main" id="nph12146-abs-0001"> <title>Summary</title> <p> <list id="nph12146-list-0001" list-type="bullet"> <list-item> <p>The primary objective of this study was to identify the molecular signals present in arbuscular mycorrhizal (AM) germinated spore exudates (GSEs) responsible for activating nuclear Ca<sup>2+</sup> spiking in the <italic>Medicago truncatula</italic> root epidermis.</p> </list-item> <list-item> <p> <italic>Medicago truncatula</italic> root organ cultures (ROCs) expressing a nuclear‐localized cameleon reporter were used as a bioassay to detect AM‐associated Ca<sup>2+</sup> spiking responses and LC‐MS to characterize targeted molecules in GSEs.</p> </list-item> <list-item> <p>This approach has revealed that short‐chain chitin oligomers (COs) can mimic AM GSE‐elicited Ca<sup>2+</sup> spiking, with maximum activity observed for CO4 and CO5. This spiking response is dependent on genes of the common SYM signalling pathway (<italic>DMI1</italic>/<italic>DMI2</italic>) but not on NFP, the putative <italic>Sinorhizobium meliloti </italic>Nod factor receptor. A major increase in the CO4/5 concentration in fungal exudates is observed when <italic>Rhizophagus irregularis</italic> spores are germinated in the presence of the synthetic strigolactone analogue GR24. By comparison with COs, both sulphated and nonsulphated Myc lipochito‐oligosaccharides (LCOs) are less efficient elicitors of Ca<sup>2+</sup> spiking in <italic>M. truncatula </italic>ROCs.</p> </list-item> <list-item> <p>We propose that short‐chain COs secreted by AM fungi are part of a molecular exchange with the host plant and that their perception in the epidermis leads to the activation of a SYM‐dependent signalling pathway involved in the initial stages of fungal root colonization.</p> </list-item> </list> </p> </abstract>