Cortical colonisation is not an absolute requirement for phosphorus transfer to plants in arbuscular mycorrhizas formed by Scutellospora calospora in a tomato mutant: evidence from physiology and gene expression
Maria Manjarrez A B , Helle M. Christophersen A , Sally E. Smith A and F. Andrew Smith AA School of Agriculture, Food and Wine, Waite Campus DX650 636, The University of Adelaide, Adelaide, SA 5005, Australia.
B Corresponding author. Email: ma.manjarrezmartinez@adelaide.edu.au
Functional Plant Biology 37(12) 1132-1142 https://doi.org/10.1071/FP09248
Submitted: 14 October 2009 Accepted: 21 August 2010 Published: 17 November 2010
Abstract
Arbuscules in Arum-type arbuscular mycorrhizas (AM), formed intracellularly in root cortical cells, are generally believed to be the most important and defining characteristics of the symbiosis as sites for phosphorus (P) and carbon (C) exchange. We used a Pen + Coi– phenotype (penetration of epidermal and exodermal root cells but not arbuscule formation) formed in rmc (reduced mycorrhizal colonisation) mutant tomato (Lycopersicon esculentum Mill.) by Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders to determine whether the fungus is capable of transferring P from soil to plant and whether there is concurrent upregulation of AM-inducible orthophosphate (Pi) transporter gene expression in the roots. Our physiological data showed that colonisation of outer root cell layers is sufficient for P transfer from S. calospora to tomato. This transfer of P was supported by increased expression of the Pi transporter genes, LePT3 and LePT5, known to be upregulated in AM interactions. We conclude that cortical colonisation and formation of arbuscules or arbusculate hyphal coils is not an absolute prerequisite for P transfer in this symbiosis.
Additional keywords: Coi– mycorrhizal phenotype, mycorrhizal fungi, reduced mycorrhizal colonisation P transfer, Pi transporters.
Acknowledgements
We thank the Australian Research Council (ARC) for financial support, Dr Evelina Facelli for statistical advice and Katrina Newman for technical help. We are grateful to Kathy Ophel-Keller, Alan McKay and Herdina from the Diagnostic Unit, SARDI, Adelaide, for the analysis of fungal DNA. Maria Manjarrez wishes to thank the Mexican Government (CONACyT and Colegio Postgraduados) for a Postgraduate Research Scholarship.
Barker SJ,
Stummer B,
Gao L,
Dispain I,
O’Connor PJ, Smith SE
(1998) A mutant in Lycopersicon esculentum Mill. with highly reduced VA mycorrhizal colonization: isolation and preliminary characterisation. The Plant Journal 15, 791–797.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
but has subsequently been shown to be an isolate of Glomus intraradices Schenck and Smith (from rDNA sequences) by J. Jansa (pers. comm.).
