title: Common and divergent shoot-root signalling in legume symbioses.
abstract: The role of shoot-root signals in the control of nodulation and arbuscular mycorrhizal (AM) development were examined in the divergent legume species pea and blue lupin. These species were chosen as pea can host both symbionts, whereas lupin can nodulate but has lost the ability to form AM. Intergeneric grafts between lupin and pea enabled examination of key long-distance signals in these symbioses. The role of strigolactones, auxin and elements of the autoregulation of nodulation (AON) pathway were investigated. Grafting studies were combined with loss-of-function mutants to monitor symbioses (nodulation, AM) and hormone effects (levels, gene expression and application studies). Lupin shoots suppress AM colonization in pea roots, in part by downregulating strigolactone exudation involving reduced expression of the strigolactone biosynthesis gene PsCCD8. By contrast, lupin shoots enhance pea nodulation, independently of strigolactones, possibly due to a partial incompatibility in AON shoot-root signalling between pea and lupin. This study highlights that nodulation and AM symbioses can be regulated independently and this may be due to long-distance signals, a phenomenon we were able to uncover by working with divergent legumes. We also identify a role for strigolactone exudation in determining the status of non-AM hosts.
authors.affiliation: School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia.
authors.forename: Eloise
authors.initials: E
authors.lastname: Foo
authors.affiliation: School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia.|Applied Biology, HAS University of Applied Sciences, 5200 MA, 's-Hertogenbosch, the Netherlands.
authors.forename: Eveline M H
authors.initials: EM
authors.lastname: Heynen
authors.affiliation: School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia.
authors.forename: James B
authors.initials: JB
authors.lastname: Reid
mesh_terms: D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D007783:Lactones / Q000378:metabolism; D031297:Lupinus / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D008954:Models, Biological; D038821:Mycorrhizae / Q000502:physiology; D018532:Pisum sativum / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000378:metabolism* / Q000382:microbiology; D018520:Plant Shoots / Q000378:metabolism*; D030821:Plants, Genetically Modified; D015398:Signal Transduction; D013559:Symbiosis; D014316:Tritium
chemical_list: D007210:Indoleacetic Acids; D007783:Lactones; D014316:Tritium
keywords: arbuscular mycorrhizal (AM); autoregulation of nodulation (AON); auxin; grafting; lupin; pea; shoot-root signalling; strigolactones