A Fluorescent Alternative to the Synthetic Strigolactone GR24

Plant Production, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, Ghent 9000, Belgium.
Molecular Plant (Impact Factor: 6.34). 09/2012; 6(1). DOI: 10.1093/mp/sss110
Source: PubMed


Strigolactones have recently been implicated in both above and below ground developmental pathways in higher plants. To facilitate the molecular and chemical properties of strigolactones in vitro and in vivo, we have developed a fluorescent strigolactone molecule, CISA-1, synthesised via a novel method which was robust, high-yielding and used simple starting materials. We demonstrate that CISA-1 has a broad range of known strigolactone activities and further report on an adventitious rooting assay in Arabidopsis which is a highly sensitive and rapid method for testing biological activity of strigolactone analogues. In this rooting assay and the widely used Orobanche germination assay CISA-1 showed stronger biological activity than the commonly tested GR24. CISA-1 and GR24 were equally effective at inhibiting branching in Arabidopsis inflorescence stems. In both the branching and adventitious rooting assay we also demonstrated that CISA-1 activity is dependent on the max strigolactone signalling pathway. In water methanol solutions, CISA-1 was about 3 fold more stable than GR24, which may contribute to the increased activity observed in the various biological tests.

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    • "As does endogenous SL, GR24 interacts with and is cleaved by the α/β-hydrolase fold protein DAD2/D14 (Hamiaux et al., 2012; Kagiyama et al., 2013; Zhao et al., 2013). Cyano-isoindole-strigolactone-analog-1 (CISA-1) is structurally related to nijmegen-1 (Figure 4A; Nefkens et al., 1997) and has also been shown to act through a MAX2-mediated signaling pathway (Rasmussen et al., 2013). Remarkably, CISA-1 is more active and stable than GR24, and possesses interesting fluorescent properties (Rasmussen et al., 2013, see also the “Labeled molecules: compelling tools to understand the action of signaling molecules” section). "
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    • "Since only caulonema filaments grow in dark, caulonema length and caulonema cell sizes can be easily quantified in dark culture conditions. In addition, the use of the SL-deficient Ppccd8 mutant [6] make it possible to better characterize the effect of exogenous SL added to the growth medium, since this effect is enhanced in comparison with the wild type (WT) which contains endogenous SLs, and as observed in other SAR studies on vascular plants [32], [33], [36], [37]. Here, we show that SLs control filament extension by decreasing the caulonema cell division rate with a slight effect on cell elongation. "
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    ABSTRACT: In vascular plants, strigolactones (SLs) are known for their hormonal role and for their role as signal molecules in the rhizosphere. SLs are also produced by the moss Physcomitrella patens, in which they act as signaling factors for controlling filament extension and possibly interaction with neighboring individuals. To gain a better understanding of SL action at the cellular level, we investigated the effect of exogenously added molecules (SLs or analogs) in moss growth media. We used the previously characterized Ppccd8 mutant that is deficient in SL synthesis and showed that SLs affect moss protonema extension by reducing caulonema cell elongation and mainly cell division rate, both in light and dark conditions. Based on this effect, we set up bioassays to examine chemical structure requirements for SL activity in moss. The results suggest that compounds GR24, GR5, and 5-deoxystrigol are active in moss (as in pea), while other analogs that are highly active in the control of pea branching show little activity in moss. Interestingly, the karrikinolide KAR1, which shares molecular features with SLs, did not have any effect on filament growth, even though the moss genome contains several genes homologous to KAI2 (encoding the KAR1 receptor) and no canonical homologue to D14 (encoding the SL receptor). Further studies should investigate whether SL signaling pathways have been conserved during land plant evolution.
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    • "Induction and measurement of adventitious roots in intact Arabidopsis plants were performed as previously described (Rasmussen et al., 2012, 2013), with minor modifications. Arabidopsis seeds (wild-type Columbia (Col-0) and mutant homozygous seed lines: max2-1, max4-1 were gas sterilized for 4 h and sown on square agar plates containing "
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