Synthesis of Carlactone Derivatives to Develop a Novel Inhibitor of Strigolactone Biosynthesis
Kojiro KawadaTatsuo SaitoSatoshi OnodaTakuma InayamaIkuo TakahashiYoshiya SetoT. NomuraYasuyuki SasakiTadao AsamiShunsuke YajimaShinsaku Ito
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Strigolactones (SLs), phytohormones that inhibit shoot branching in plants, promote the germination of root-parasitic plants, such as Striga spp. and Orobanche spp., which drastically reduces the crop yield. Therefore, reducing SL production via chemical treatment may increase the crop yield. To design specific inhibitors, it is valid to utilize the substrate structure of the target proteins as lead compounds. In this study, we focused on Os900, a rice enzyme that oxidizes the SL precursor carlactone (CL) to 4-deoxyorobanchol (4DO), and synthesized 10 CL derivatives. The effects of the synthesized CL derivatives on SL biosynthesis were evaluated by the Os900 enzyme assay in vitro and by measuring 4DO levels in rice root exudates. We identified some CL derivatives that inhibited SL biosynthesis in vitro and in vivo.Keywords:
Strigolactone
Orobanche
Striga hermonthica
Orobanche
Strigolactone
Orobanchaceae
Stimulant
Sorghum bicolor
Parasitic plant
Striga hermonthica
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The seeds of parasitic plants of the genera Striga and Orobanche will only germinate after induction by a chemical signal exuded from the roots of their host. Up to now, several of these germination stimulants have been isolated and identified in the root exudates of a series of host plants of both Orobanche and Striga spp. In most cases, the compounds were shown to be isoprenoid and belong to one chemical class, collectively called the strigolactones, and suggested by many authors to be sesquiterpene lactones. However, this classification was never proven; hence, the biosynthetic pathways of the germination stimulants are unknown. We have used carotenoid mutants of maize (Zea mays) and inhibitors of isoprenoid pathways on maize, cowpea (Vigna unguiculata), and sorghum (Sorghum bicolor) and assessed the effects on the root exudate-induced germination of Striga hermonthica and Orobanche crenata. Here, we show that for these three host and two parasitic plant species, the strigolactone germination stimulants are derived from the carotenoid pathway. Furthermore, we hypothesize how the germination stimulants are formed. We also discuss this finding as an explanation for some phenomena that have been observed for the host-parasitic plant interaction, such as the effect of mycorrhiza on S. hermonthica infestation.
Striga hermonthica
Orobanche
Strigolactone
Parasitic plant
Orobanchaceae
Exudate
Allelopathy
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Striga hermonthica
Strigolactone
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Several strigol analogues with modifications in the D-ring were synthesized and assayed for germination stimulatory activity of seeds of Striga hermonthica and Orobanche crenata. All of these D-ring analogues are derived from N-phthaloylglycine as the common ABC-fragment. It was concluded that the correct structure of the 2(5H)-furanone D-ring is essential to retain full biological activity. Keywords: Striga; Orobanche; germination; strigol analogue
Orobanche
Striga hermonthica
Parasitic plant
Orobanchaceae
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Striga hermonthica
Strigolactone
Parasitic plant
Orobanche
Obligate parasite
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Citations (64)
Strigolactones are a particular class of plant metabolites with diverse biological functions starting from the stimulation of parasitic seed germination to phytohormonal activity. The expansion of parasitic weeds in the fields of developing countries is threatening the food supply and calls for simple procedures to combat these weeds. Strigolactone analogues represent a promising approach for such control through suicidal germination, i.e., parasitic seed germination without the presence of the host causing parasite death. In the present work, the synthesis of resorcinol-type strigolactone mimics related to debranones is reported. These compounds were highly stable even at alkaline pH levels and able to induce seed germination of parasitic plants Striga hermonthica and Phelipanche ramosa at low concentrations, EC50 ≈ 2 × 10–7 M (Striga) and EC50 ≈ 2 × 10–9 M (Phelipanche). On the other hand, the mimics had no significant effect on root architecture of Arabidopsis plants, suggesting a selective activity for parasitic seed germination, making them a primary target as suicidal germinators.
Striga hermonthica
Strigolactone
Orobanche
Parasitic plant
Haustorium
Orobanchaceae
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Germination signals illuminated The noxious weed Striga can take down an entire crop. Fields in Africa are particularly susceptible to the devastation it can cause. Striga seeds germinate in response to faint traces of the hormone strigolactone released by its targets. Tsuchiya et al. designed a mimic of strigolactone that, when cleaved by the Striga receptor, generates a fluorescent end product. This photogenic mimic lit up Striga seeds upon germination and led to the identification of its strigolactone receptor. Abolishing the activity of this receptor could be an effective defensive strategy. Science , this issue p. 864
Striga hermonthica
Strigolactone
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Strigolactones are a class of plant hormones that inhibit axillary bud outgrowth and are released from plant roots to act as a rhizosphere communication signal. The Orobanchaceae parasitic plant Striga hermonthica perceives strigolactone as its germination signal, indicating host presence. After germination, the Striga plant parasitises the host plant and suppresses host growth by draining photosynthetic products, water and other essential nutrients. Because of this way of life, this parasite threatens crop production in sub-Saharan Africa with infestation in crop fields and crop devastation. Crop protection in such areas is among the most concerning problems to be dealt with as immediately as possible. With respect to crop protection from Striga, many strigolactone agonists have been developed and used in research to reveal Striga biology, and have contributed to development of crop protection methods. However, an effective method has yet to be found. In a previous study, we reported debranones as a group of strigolactone mimics that inhibit axillary buds outgrowth with moderate stimulation activity for Striga germination. Debranones would be accessible because they are simply synthesised from commercially available phenols and bromobutenolide. Taking this advantage of debranones for Striga research, we tried to find the debranones stimulating Striga seed germination. To modulate functional selectivity and to enhance germination inducing activity of debranones, we studied structure–activity relationships. We investigated effects of substituent position and functional group on debranone activity and selectivity as a strigolactone mimic. As a result, we improved stimulation activity of debranones for Striga seed germination by chemical modification, and demonstrated the pharmacophore of debranones for selective modulation of distinct strigolactone responses.
Strigolactone
Striga hermonthica
Parasitic plant
Orobanchaceae
Orobanche
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Citations (34)
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Sorghum bicolor
Root (linguistics)
Stimulant
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The newly designed strigol analogue Nijmegen 1 (rac 7) was prepared in high overall yield starting from N-phthaloylglycine. This relatively simple analogue exhibits high bioactivity in the stimulation of germination of seeds of the parasitic weeds Striga hermonthica and Orobanche crenata. Nijmegen 1 was resolved in its enantiomers 7 and ent 7 by using the homochiral latent D-rings ent 11 and ent 12. The enantiomers 7 and ent 7 show significant differences in germination activity. Keywords: Striga; Orobanche; germination; strigol analogue
Striga hermonthica
Orobanche
Orobanchaceae
Parasitic plant
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Citations (92)