Ecological relevance of strigolactones in nutrient uptake and other abiotic stresses, and in plant-microbe interactions below-ground

Abstract

Background Plants are exposed to ever changing and often unfavourable environmental conditions, which cause both abiotic and biotic stresses. They have evolved sophisticated mechanisms to flexibly adapt themselves to these stress conditions. To achieve such adaptation, they need to control and coordinate physiological, developmental and defence responses. These responses are regulated through a complex network of interconnected signalling pathways, in which plant hormones play a key role. Strigolactones (SLs) are multifunctional molecules recently classified as a new class of phytohormones, playing a key role as modulators of the coordinated plant development in response to nutrient deficient conditions, especially phosphorus shortage. Belowground, besides regulating root architecture, they also act as molecular cues that help plants to communicate with their environment. Scope This review discusses current knowledge on the different roles of SLs below-ground, paying special attention to their involvement in phosphorus uptake by the plant by regulating root architecture and the establishment of mutualistic symbiosis with arbuscular mycorrhizal fungi. Their involvement in plant responses to other abiotic stresses such as drought and salinity, as well as in other plant-(micro)organisms interactions such as nodulation and root parasitic plants are also highlighted. Finally, the agronomical implications of SLs below-ground and their potential use in sustainable agriculture are addressed. Conclusions Experimental evidence illustrates the biological and ecological importance of SLs in the rhizosphere. Their multifunctional nature opens up a wide range of possibilities for potential applications in agriculture. However, a more in-depth understanding on the SL functioning/signalling mechanisms is required to allow us to exploit their full potential.

Arbuscular mycorrhizal symbiosis induces strigolactone biosynthesis under drought and improves drought tolerance in lettuce and tomato

“…As mentioned previously, AM symbiosis establishment requires a finely regulated molecular dialogue between the two partners, in which SLs have arisen as essential cues (Bucher et al , , Gutjahr & Parniske, , López‐Ráez et al , ). It is well known that SL production is promoted by nutrient deficiency, mainly phosphorus starvation (López‐Ráez et al , , Yoneyama et al , ) to promote AM fungal development and symbiosis establishment (Andreo‐Jiménez et al , , Kapulnik & Koltai, ). In addition to nutritional stress, an increased SL production in the presence of R. irregularis under salt stress was proposed in lettuce (Aroca et al , ).…”

“…Arbuscular mycorrhizal symbiosis establishment and functioning requires a high degree of coordination between the two partners, which implies a signal exchange that leads to mutual recognition (Andreo-Jiménez et al, 2015, Bucher et al, 2014, Gutjahr & Parniske, 2013. The molecular dialoguethe so-called pre-symbiotic stagestarts with the production and exudation into the rhizosphere of strigolactones (SLs) by the host plant.…”

Expression of molecular markers associated to defense signaling pathways and strigolactone biosynthesis during the early interaction tomato-Phelipanche ramosa

“…SLs are multifunctional molecules classified as a new class of plant hormones having a crucial role in the pre-infection phase of the host-root parasitic weed interaction [6,23,26]. Surprisingly, very little or nothing is known beyond its function as germination stimulants in this parasitic association.…”

“…In addition, they also act as host detection cues for symbiotic arbuscular mycorrhizal (AM) fungi, favoring symbiosis establishment [6,22]. Accordingly to their role as molecular cues in the rhizosphere, SLs are mainly produced in the roots and they have been detected in the root extracts and root exudates of monocot and dicot plants [14,23]. Since 2008, SLs are classified as a new class of plant hormones controlling several different processes within the plants [14,23e25].…”

Strigolactones in plant adaptation to abiotic stresses: An emerging avenue of plant research

“…SLs are produced and exuded at extremely low quantities, being active at pico‐ to nanomolar concentrations, and have been reported in a variety of plant species (Andreo‐Jimenez et al, ; Delaux et al, ; Xie, ). A single plant species can produce various types of SLs, and even different varieties of the same plant species appear to synthesize a blend of SL molecules in different quantities (Ruyter‐Spira, Al‐Babili, van der Krol, & Bouwmeester, ; Xie, Yoneyama, & Yoneyama, ).…”