Comprehensive Analysis of DWARF14-LIKE2 (DLK2) Reveals Its Functional Divergence from Strigolactone-Related Paralogs

Végh, Attila Gergely; Incze, Norbert; Fábián, Attila; Huo, Heqiang; Bradford, Kent J.; Balázs, Ervin; Soós, Vilmos

doi:10.3389/fpls.2017.01641

Cited by 44 publications

(51 citation statements)

References 72 publications

(137 reference statements)

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“…Differential scanning fluorimetry (DSF) reports a change in protein thermal stability induced by interacting ligands. DSF has been used to infer the binding of the strigolactone analogue GR24 and other SL‐like compounds to homologues of D14 and KAI2 from several species (Hamiaux et al ., ; Abe et al ., ; Waters et al ., ; Végh et al ., ). These SL‐related ligands reduce the protein‐melting temperature with increasing ligand concentration.…”

Section: Resultsmentioning

confidence: 97%

An allelic series at the KARRIKIN INSENSITIVE 2 locus of Arabidopsis thaliana decouples ligand hydrolysis and receptor degradation from downstream signalling

et al. 2018

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Karrikins are butenolide compounds present in post-fire environments that can stimulate seed germination in many species, including Arabidopsis thaliana. Plants also produce endogenous butenolide compounds that serve as hormones, namely strigolactones (SLs). The receptor for karrikins (KARRIKIN INSENSITIVE 2; KAI2) and the receptor for SLs (DWARF14; D14) are homologous proteins that share many similarities. The mode of action of D14 as a dual enzyme receptor protein is well established, but the nature of KAI2-dependent signalling and its function as a receptor are not fully understood. To expand our knowledge of how KAI2 operates, we screened ethyl methanesulphonate (EMS)-mutagenized populations of A. thaliana for mutants with kai2-like phenotypes and isolated 13 new kai2 alleles. Among these alleles, kai2-10 encoded a D184N protein variant that was stable in planta. Differential scanning fluorimetry assays indicated that the KAI2 D184N protein could interact normally with bioactive ligands. We developed a KAI2-active version of the fluorescent strigolactone analogue Yoshimulactone Green to show that KAI2 D184N exhibits normal rates of ligand hydrolysis. KAI2 D184N degraded in response to treatment with exogenous ligands, suggesting that receptor degradation is a consequence of ligand binding and hydrolysis, but is insufficient for signalling activity. Remarkably, KAI2 D184N degradation was hypersensitive to karrikins, but showed a normal response to strigolactone analogues, implying that these butenolides may interact differently with KAI2. These results demonstrate that the enzymatic and signalling functions of KAI2 can be decoupled, and provide important insights into the mechanistic events that underpin butenolide signalling in plants.

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Section: Resultsmentioning

confidence: 97%

An allelic series at the KARRIKIN INSENSITIVE 2 locus of Arabidopsis thaliana decouples ligand hydrolysis and receptor degradation from downstream signalling

et al. 2018

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“…However, the karrikin signalling pathway that activates DLK2 and KUF1 remains active under osmotic stress, and hypocotyl elongation is inhibited as normal. The function of DLK2 is not clear but it is not important for seed germination or hypocotyl elongation (Végh et al ., ). Therefore the stress‐induced karrikin response might specifically reprogramme the karrikin effect on germination.…”

Section: Discussionmentioning

confidence: 99%

Karrikin‐KAI2 signalling provides Arabidopsis seeds with tolerance to abiotic stress and inhibits germination under conditions unfavourable to seedling establishment

2018

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The control of seed germination in response to environmental conditions is important for plant success. We investigated the role of the karrikin receptor KARRIKIN INSENSITIVE2 (KAI2) in the response of Arabidopsis seeds to osmotic stress, salinity and high temperature. Germination of the kai2 mutant was examined in response to NaCl, mannitol and elevated temperature. The effect of karrikin on germination of wild-type seeds, hypocotyl elongation and the expression of karrikin-responsive genes was also examined in response to such stresses. The kai2 seeds germinated less readily than wild-type seeds and germination was more sensitive to inhibition by abiotic stress. Karrikin-induced KAI2 signalling stimulated germination of wild-type seeds under favourable conditions, but, surprisingly, inhibited germination in the presence of osmolytes or at elevated temperature. By contrast, GA stimulated germination of wild-type seeds and mutants under all conditions. Karrikin induced expression of DLK2 and KUF1 genes and inhibited hypocotyl elongation independently of osmotic stress. Under mild osmotic stress, karrikin enhanced expression of DREB2A, WRKY33 and ERF5 genes, but not ABA signalling genes. Thus, the karrikin-KAI2 signalling system can protect against abiotic stress, first by providing stress tolerance, and second by inhibiting germination under conditions unfavourable to seedling establishment.

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“…8). DSF has been used extensively for inferring the interaction of strigolactone-like compounds with D14-and KAI2-related proteins 29,41,[45][46][47][48] . Racemic GR24 is a widely used synthetic strigolactone analogue that consists of two enantiomers (Supplementary Fig.…”

Section: Btdlk2mentioning

confidence: 99%

Divergent receptor proteins confer responses to different karrikins in two ephemeral weeds

et al. 2020

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Wildfires can encourage the establishment of invasive plants by releasing potent germination stimulants, such as karrikins. Seed germination of Brassica tournefortii, a noxious weed of Mediterranean climates, is strongly stimulated by KAR 1 , the archetypal karrikin produced from burning vegetation. In contrast, the closely-related yet non-fire-associated ephemeral Arabidopsis thaliana is unusual because it responds preferentially to KAR 2. The α/β-hydrolase KARRIKIN INSENSITIVE 2 (KAI2) is the putative karrikin receptor identified in Arabidopsis. Here we show that B. tournefortii expresses three KAI2 homologues, and the most highlyexpressed homologue is sufficient to confer enhanced responses to KAR 1 relative to KAR 2 when expressed in Arabidopsis. We identify two amino acid residues near the KAI2 active site that explain the ligand selectivity, and show that this combination has arisen independently multiple times within dicots. Our results suggest that duplication and diversification of KAI2 proteins could confer differential responses to chemical cues produced by environmental disturbance, including fire.

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Comprehensive Analysis of DWARF14-LIKE2 (DLK2) Reveals Its Functional Divergence from Strigolactone-Related Paralogs

Cited by 44 publications

References 72 publications

An allelic series at the KARRIKIN INSENSITIVE 2 locus of Arabidopsis thaliana decouples ligand hydrolysis and receptor degradation from downstream signalling

An allelic series at the KARRIKIN INSENSITIVE 2 locus of Arabidopsis thaliana decouples ligand hydrolysis and receptor degradation from downstream signalling

Karrikin‐KAI2 signalling provides Arabidopsis seeds with tolerance to abiotic stress and inhibits germination under conditions unfavourable to seedling establishment

Divergent receptor proteins confer responses to different karrikins in two ephemeral weeds

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