Anna Fusconi1. 1. Department of Life Sciences and Systems Biology, Università di Torino, Viale Mattioli 25, 10125 Turin, Italy.
Abstract
BACKGROUND: Arbuscular mycorrhizae (AMs) form a widespread root-fungus symbiosis that improves plant phosphate (Pi) acquisition and modifies the physiology and development of host plants. Increased branching is recognized as a general feature of AM roots, and has been interpreted as a means of increasing suitable sites for colonization. Fungal exudates, which are involved in the dialogue between AM fungi and their host during the pre-colonization phase, play a well-documented role in lateral root (LR) formation. In addition, the increased Pi content of AM plants, in relation to Pi-starved controls, as well as changes in the delivery of carbohydrates to the roots and modulation of phytohormone concentration, transport and sensitivity, are probably involved in increasing root system branching. SCOPE: This review discusses the possible causes of increased branching in AM plants. The differential root responses to Pi, sugars and hormones of potential AM host species are also highlighted and discussed in comparison with those of the non-host Arabidopsis thaliana. CONCLUSIONS: Fungal exudates are probably the main compounds regulating AM root morphogenesis during the first colonization steps, while a complex network of interactions governs root development in established AMs. Colonization and high Pi act synergistically to increase root branching, and sugar transport towards the arbusculated cells may contribute to LR formation. In addition, AM colonization and high Pi generally increase auxin and cytokinin and decrease ethylene and strigolactone levels. With the exception of cytokinins, which seem to regulate mainly the root:shoot biomass ratio, these hormones play a leading role in governing root morphogenesis, with strigolactones and ethylene blocking LR formation in the non-colonized, Pi-starved plants, and auxin inducing them in colonized plants, or in plants grown under high Pi conditions.
BACKGROUND: Arbuscular mycorrhizae (AMs) form a widespread root-fungus symbiosis that improves plant phosphate (Pi) acquisition and modifies the physiology and development of host plants. Increased branching is recognized as a general feature of AM roots, and has been interpreted as a means of increasing suitable sites for colonization. Fungal exudates, which are involved in the dialogue between AM fungi and their host during the pre-colonization phase, play a well-documented role in lateral root (LR) formation. In addition, the increased Pi content of AM plants, in relation to Pi-starved controls, as well as changes in the delivery of carbohydrates to the roots and modulation of phytohormone concentration, transport and sensitivity, are probably involved in increasing root system branching. SCOPE: This review discusses the possible causes of increased branching in AM plants. The differential root responses to Pi, sugars and hormones of potential AM host species are also highlighted and discussed in comparison with those of the non-host Arabidopsis thaliana. CONCLUSIONS: Fungal exudates are probably the main compounds regulating AM root morphogenesis during the first colonization steps, while a complex network of interactions governs root development in established AMs. Colonization and high Pi act synergistically to increase root branching, and sugar transport towards the arbusculated cells may contribute to LR formation. In addition, AM colonization and high Pi generally increase auxin and cytokinin and decrease ethylene and strigolactone levels. With the exception of cytokinins, which seem to regulate mainly the root:shoot biomass ratio, these hormones play a leading role in governing root morphogenesis, with strigolactones and ethylene blocking LR formation in the non-colonized, Pi-starved plants, and auxin inducing them in colonized plants, or in plants grown under high Pi conditions.
Authors: G Berta; A Trotta; A Fusconi; J E Hooker; M Munro; D Atkinson; M Giovannetti; S Morini; P Fortuna; B Tisserant; V Gianinazzi-Pearson; S Gianinazzi Journal: Tree Physiol Date: 1995-05 Impact factor: 4.196
Authors: Kevin R Cope; Adeline Bascaules; Thomas B Irving; Muthusubramanian Venkateshwaran; Junko Maeda; Kevin Garcia; Tomás A Rush; Cathleen Ma; Jessy Labbé; Sara Jawdy; Edward Steigerwald; Jonathan Setzke; Emmeline Fung; Kimberly G Schnell; Yunqian Wang; Nathaniel Schlief; Heike Bücking; Steven H Strauss; Fabienne Maillet; Patricia Jargeat; Guillaume Bécard; Virginie Puech-Pagès; Jean-Michel Ané Journal: Plant Cell Date: 2019-08-15 Impact factor: 11.277
Authors: Lisa Adolfsson; Katalin Solymosi; Mats X Andersson; Áron Keresztes; Johan Uddling; Benoît Schoefs; Cornelia Spetea Journal: PLoS One Date: 2015-01-23 Impact factor: 3.240