The Response of the Root Proteome to the Synthetic Strigolactone GR24 in Arabidopsis

Abstract

Strigolactones are plant metabolites that act as phytohormones and rhizosphere signals. Whereas most research on unraveling the action mechanisms of strigolactones is focused on plant shoots, we investigated proteome adaptation during strigolactone signaling in the roots of Arabidopsis thaliana. Through large-scale, time-resolved, and quantitative proteomics, the impact of the strigolactone analog rac-GR24 was elucidated on the root proteome of the wild type and the signaling mutant more axillary growth 2 (max2). Our study revealed a clear MAX2-dependent rac-GR24 response: an increase in abundance of enzymes involved in flavonol biosynthesis, which was reduced in the max2-1 mutant. Mass spectrometry-driven metabolite profiling and thin-layer chromatography experiments demonstrated that these changes in protein expression lead to the accumulation of specific flavonols. Moreover, quantitative RT-PCR revealed that the flavonolrelated protein expression profile was caused by rac-GR24-induced changes in transcript levels of the corresponding genes. This induction of flavonol production was shown to be activated by the two pure enantiomers that together make up rac-GR24. Finally, our data provide much needed clues concerning the multiple roles played by MAX2 in the roots and a comprehensive view of the rac-GR24-induced

Physcomitrella patens MAX2 characterization suggests an ancient role for this F‐box protein in photomorphogenesis rather than strigolactone signalling

“…F‐box proteins) may be required. Interestingly, MAX2‐independent SL responses have previously been hypothesized for roots of seed plants (Ruyter‐Spira et al ., ; Shinohara et al ., ; Walton et al ., ) and high doses of (±)‐GR24 (5–10 μM) can induce a response in Arabidopsis max2 mutants (Ruyter‐Spira et al ., ). Furthermore, MAX2‐independent promotion of stromule formation can be induced by (±)‐GR24 (Vismans & van der Meer, ).…”

Strigolactones, karrikins and beyond

“…Indeed, analysis of HTL/KAI2::GUS lines revealed a strong KAI2 expression in the hypocotyl and the root of young Arabidopsis seedlings (Sun & Ni ). Furthermore, flavonol production in Arabidopsis roots was induced mutually by both rac ‐GR24 enantiomers and both through D14 and/or KAI2 signalling (Walton et al ). These results suggest that in roots, a crosstalk between the two receptors exists and further supports the hypothesis that root development can be controlled mutually by strigolactone and karrikin(‐like) molecules.…”

Comparing and Contrasting the Multiple Roles of Butenolide Plant Growth Regulators: Strigolactones and Karrikins in Plant Development and Adaptation to Abiotic Stresses

“…However, studies on SLs and KARs in plant adaptation to environmental stresses are still at the basic stage. The involvement of SLs in regulating the responses to drought, salinity, and nutrient deficiency stress as well as chilling tolerance has been demonstrated [38,[40][41][42][43]47,48,157,193]. KARs are also involved in the regulation of drought tolerance and provide seeds with abiotic stress tolerance in Arabidopsis [8,63].…”

“…SL and KAR signaling pathways may be positively involved in the regulation of flavonoid/anthocyanin syntheses in an MAX2-dependent manner under drought stress [7, 40,193]. This suggests that SL and KAR signaling pathways may link the signaling pathways of reactive oxygen species (ROS) in plant responses to environmental stresses.…”

“…In rice, the d10 and d27 mutants in SL-synthesis and the d3 mutant in SL-signaling decreased seminal root density and increased lateral root density during P or N starvation compared to wild type. In addition, the exogenous application of GR24 restored the reduced response to low-P or low-N conditions in the d10 and d27 mutants, suggesting that SLs promote seminal root development and negatively regulate lateral root development under nutrient stress [157,193]. In Arabidopsis, SL-deficient max4 and SL-response max2 mutants have shorter root hair lengths under low-P conditions compared with wild type.…”