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

Liu, Guowei; Stirnemann, Marina; Gübeli, Christian; Egloff, S; Courty, Pierre‐Emmanuel; Aubry, Sylvain; Vandenbussche, Michiel; Morel, Patrice; Reinhardt, Didier; Martinoia, Enrico; Borghi, Loris

doi:10.1016/j.isci.2019.06.024

Cited by 26 publications

(26 citation statements)

References 43 publications

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“…By contrast, the endogenous KAI2 ligand(s) still need(s) to be identified. Nevertheless, the widespread phylogenetic distribution of KAI2 from charophyte algae to all land plants, as well as a number of smoke detection-independent kai2 mutant phenotypes described in Arabidopsis, rice, and petunia, indicates that the original function of KAI2 was to perceive a plant hormone (tentatively called "KAI2 ligand"; KL) while, in fire-following plants, KAI2 was secondarily repurposed for smoke detection (5,(8)(9)(10)(11)(12)(13). Duplications of KAI2 occurred during plant diversification, and provided flexibility for additional adaptations.…”

mentioning

confidence: 99%

The karrikin signaling regulator SMAX1 controls Lotus japonicus root and root hair development by suppressing ethylene biosynthesis

Carbonnel

Das

Varshney

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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An evolutionarily ancient plant hormone receptor complex comprising the α/β-fold hydrolase receptor KARRIKIN INSENSITIVE 2 (KAI2) and the F-box protein MORE AXILLARY GROWTH 2 (MAX2) mediates a range of developmental responses to smoke-derived butenolides called karrikins (KARs) and to yet elusive endogenous KAI2 ligands (KLs). Degradation of SUPPRESSOR OF MAX2 1 (SMAX1) after ligand perception is considered to be a key step in KAR/KL signaling. However, molecular events which regulate plant development downstream of SMAX1 removal have not been identified. Here we show that Lotus japonicus SMAX1 is specifically degraded in the presence of KAI2 and MAX2 and plays an important role in regulating root and root hair development. smax1 mutants display very short primary roots and elongated root hairs. Their root transcriptome reveals elevated ethylene responses and expression of ACC Synthase 7 (ACS7), which encodes a rate-limiting enzyme in ethylene biosynthesis. smax1 mutants release increased amounts of ethylene and their root phenotype is rescued by treatment with ethylene biosynthesis and signaling inhibitors. KAR treatment induces ACS7 expression in a KAI2-dependent manner and root developmental responses to KAR treatment depend on ethylene signaling. Furthermore, in Arabidopsis, KAR-induced root hair elongation depends on ACS7. Thus, we reveal a connection between KAR/KL and ethylene signaling in which the KAR/KL signaling module (KAI2–MAX2–SMAX1) regulates the biosynthesis of ethylene to fine-tune root and root hair development, which are important for seedling establishment at the beginning of the plant life cycle.

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mentioning

confidence: 99%

The karrikin signaling regulator SMAX1 controls Lotus japonicus root and root hair development by suppressing ethylene biosynthesis

Carbonnel

Das

Varshney

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…The molecular mechanisms underlying the interaction between plants and AM fungi are not entirely clear. Intriguingly, mutational analysis indicates that the establishment of this symbiosis in Oryza sativa (rice) depends on a KAI2 receptor called D14L (Gutjahr et al ., 2015; Liu et al ., 2019). This suggests that KLs rather than SLs are important in AM fungi–plant symbioses.…”

Section: Strigolactones and Plant–fungal Interactionsmentioning

confidence: 99%

On the outside looking in: roles of endogenous and exogenous strigolactones

2020

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Summary A collection of small molecules called strigolactones (SLs) act as both endogenous hormones to control plant development and as ecological communication cues between organisms. SL signalling overlaps with that of a class of smoke‐derived compounds, karrikins (KARs), which have distinct yet overlapping developmental effects on plants. Although the roles of SLs in shoot and root development, in the promotion of arbuscular mycorrhizal (AM) fungal branching and in parasitic plant germination have been well characterized, recent data have illustrated broader roles for these compounds in the rhizosphere. Here, we review the known roles of SLs in development, growth of AM fungi and germination of parasitic plants to develop a framework for understanding the use of SLs as molecules of communication in the rhizosphere. It appears, for example, that there are many connections between SLs and phosphate utilization. Low phosphate levels regulate SL metabolism and, in turn, SLs sculpt root and shoot architecture to coordinate growth and optimize phosphate uptake from the environment. Plant‐exuded SLs attract fungal symbionts to deliver inorganic phosphate (Pi) to the host. These and other examples suggest the boundary between exogenous and endogenous SL functions can be easily blurred and a more holistic view of these small molecules is likely to be required to fully understand SL biology. Related to this, we summarize and discuss evidence for a primitive role of SLs in moss as a quorum sensing‐like molecule, providing a unifying concept of SLs as endogenous and exogenous signalling molecules.

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“…In rice SL-deficient mutant, the distinct root-cap was reduced, which could be restored by application of SLs [118,119]. SLs also inhibit adventitious root formation in Arabidopsis, tomato, and pea [120][121][122]. Recent research shows that SLs induce the presence of hypodermal passage cells (HPC) in Petunia roots, which may play a role in regulating water and nutrient exchange between the root and the soil.…”

Section: Root System Developmentmentioning

confidence: 99%

“…SLs also inhibit adventitious root formation in different plants, such as Arabidopsis, tomato, and pea [120][121][122], but promote the crown root growth in rice [119]. The effect of auxin on adventitious root formation is opposite to that of SLs, and SLs could partially repress the stimulating effect of auxin on adventitious root formation [120].…”

Section: Sl or Kar Crosstalk With Auxinmentioning

confidence: 99%

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

Tao

Lian

Wang

2019

IJMS

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Strigolactones (SLs) and karrikins (KARs) are both butenolide molecules that play essential roles in plant growth and development. SLs are phytohormones, with SLs having known functions within the plant they are produced in, while KARs are found in smoke emitted from burning plant matter and affect seeds and seedlings in areas of wildfire. It has been suggested that SL and KAR signaling may share similar mechanisms. The α/β hydrolases DWARF14 (D14) and KARRIKIN INSENSITIVE 2 (KAI2), which act as receptors of SL and KAR, respectively, both interact with the F-box protein MORE AXILLARY GROWTH 2 (MAX2) in order to target SUPPRESSOR OF MAX2 1 (SMAX1)-LIKE/D53 family members for degradation via the 26S proteasome. Recent reports suggest that SLs and/or KARs are also involved in regulating plant responses and adaptation to various abiotic stresses, particularly nutrient deficiency, drought, salinity, and chilling. There is also crosstalk with other hormone signaling pathways, including auxin, gibberellic acid (GA), abscisic acid (ABA), cytokinin (CK), and ethylene (ET), under normal and abiotic stress conditions. This review briefly covers the biosynthetic and signaling pathways of SLs and KARs, compares their functions in plant growth and development, and reviews the effects of any crosstalk between SLs or KARs and other plant hormones at various stages of plant development. We also focus on the distinct responses, adaptations, and regulatory mechanisms related to SLs and/or KARs in response to various abiotic stresses. The review closes with discussion on ways to gain additional insights into the SL and KAR pathways and the crosstalk between these related phytohormones.factors through interactions between the phytohormone regulatory networks via the perception and signal transduction originating at various receptors [20][21][22][23].Strigolactones (SLs) were originally isolated from root exudates of cotton and as seed germination stimulants from plants in the Orobanchaceae family that parasitize plant roots (Striga, Phelipanche, and Orobanche spp.) [24][25][26]. SLs normally control seed germination and seedling development [27], shoot branching [28-32], root architecture [33], and leaf senescence [34]. SLs also promote beneficial symbiotic relationships between host plants and mycorrhizal fungi [35,36]. The biosynthesis and signaling of SLs are regulated by various abiotic stress factors [37][38][39][40], including the recently reported SL involvement in responding to nutrient deprivation, drought, chilling and salinity [38,[40][41][42][43][44][45][46][47][48][49][50]. Such studies provide new insights into the novel roles SL signaling plays in the regulation of plant adaptation to adverse environmental conditions [51][52][53][54].Karrikins (KARs) are found in smoke released from the heating or combustion of plant material, after which they can stimulate the germination of dormant seeds [55][56][57][58]. KARs are also involved in the inhibition of hypocotyl elongation and in the promotion of cotyledon expansion and...

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

Cited by 26 publications

References 43 publications

The karrikin signaling regulator SMAX1 controls Lotus japonicus root and root hair development by suppressing ethylene biosynthesis

The karrikin signaling regulator SMAX1 controls Lotus japonicus root and root hair development by suppressing ethylene biosynthesis

On the outside looking in: roles of endogenous and exogenous strigolactones

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

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