Simulated microgravity and the antagonistic influence of strigolactone on plant nutrient uptake in low nutrient conditions

Abstract

Human-assisted space exploration will require efficient methods of food production. Large-scale farming in presence of an Earth-like atmosphere in space faces two main challenges: plant yield in microgravity and plant nutrition in extraterrestrial soils, which are likely low in nutrients compared to terrestrial farm lands. We propose a plant-fungal symbiosis (i.e. mycorrhiza) as an efficient tool to increase plant biomass production in extraterrestrial environments. We tested the mycorrhization of Solanaceae on the model plant Petunia hybrida using the arbuscular mycorrhizal fungus Rhizophagus irregularis under simulated microgravity (s0-g) conditions obtained through a 3-D random positioning machine. Our results show that s0-g negatively affects mycorrhization and plant phosphate uptake by inhibiting hyphal elongation and secondary branching. However, in low nutrient conditions, the mycorrhiza can still support plant biomass production in s0-g when colonized plants have increased SL root exudation. Alternatively, s0-g in high nutrient conditions boosts tissue-specific cell division and cell expansion and overall plant size in Petunia, which has been reported for other plants species. Finally, we show that the SL mimic molecule rac-GR24 can still induce hyphal branching in vitro under simulated microgravity. Based on these results, we propose that in nutrient limited conditions strigolactone root exudation can challenge the negative microgravity effects on mycorrhization and therefore might play an important role in increasing the efficiency of future space farming.

Strigolactones Play an Important Role in Shaping Exodermal Morphology via a KAI2-Dependent Pathway

“…Increased expression of PDR1 results in higher SL secretion (Sasse et al., 2015) and stronger mycorrhizal colonization (Liu et al., 2018a, Liu et al., 2018b). In contrast, pdr1 ko mutants exude very low amounts of SL and exhibit decreased mycorrhizal colonization rates nearly similar to the SL biosynthetic mutant dad1 (Kretzschmar et al., 2012).…”

The Full-Size ABCG Transporter of Medicago truncatula Is Involved in Strigolactone Secretion, Affecting Arbuscular Mycorrhiza

“…Thus, the PaPDR1 OE strategy appears to be useful for ameliorating mycorrhization rate in Fabaceae. It could improve phosphate acquisition and plant biomass production as it was reported for petunia (Liu et al, 2018a;Liu et al, 2018b). It has been demonstrated that AMF hyphal branching can be initiated by the SL present in the root exudates of legume plants (Akiyama et al, 2005;Steinkellner et al, 2007).…”

Filling the Gap: Functional Clustering of ABC Proteins for the Investigation of Hormonal Transport in planta

“…Last but not least, PDR1 OE plants increased their root and shoot biomass by inducing lateral root development, stem secondary growth and increased plant nutrient uptake (phosphate) on poor soil conditions. These positive effects of PDR1 OE on plant biomass production were also present in simulated-microgravity conditions (Liu et al, 2018a) that could negatively influence the development/branching of mycorrhizal fungi. These several changes in plant development and plant-fungal interactions caused by different expression levels of PhPDR1 show that transport and allocation of SL operated by PhPDR1 play a prominent role in the efficiency of the SL signaling pathway and support the hypothesis that phytohormonal transport is key to regulation of plant development and plant-environment interactions.…”

“…Several SL-driven developmental modules have been shown to be highly conserved in the plant kingdom, like shoot lateral branching, root hair elongation, leaf aging and crosstalk with most phytohormones. The recent development of SL-based strategies seems endless, going from approaches targeted to the improvement of good agricultural practices (Pavan et al, 2016; Cochetel et al, 2018; Liu et al, 2018a; Mohemed et al, 2018) to the amelioration of human health through the recently revealed apoptotic function of SL mimics in different kinds of cancers and diseases (Modi et al, 2017, 2018; Hasan et al, 2018).…”