Abstract
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 synthesized from commercially available phenols and bromo butenolide. 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.
Highlights
Global food security is among the most considerable issues in the world, since the increase in population has become a serious problem in the developing countries
In our simulation result, docked 4-bromo debranone (4BD) was anchored near the catalytic residue, and the molecular conformation of docked 4BD considerably overlapped with GR24, whose structure is obtained from co-crystals of OsD14 and GR24 (Figure 1B)
We ran a similar calculation using ShHTL5 of the AtKAI2/HTL ortholog, which is among the candidates for SL receptor in S. hermonthica, as a substitute for OsD14
Summary
Global food security is among the most considerable issues in the world, since the increase in population has become a serious problem in the developing countries. Striga infestation can spread so effectively that Striga-induced crop loss was estimated to be more than $7 billion U.S dollars annually across the African continent (Ejeta, 2007). In this context, it is worth trying to develop a successful method to prevent crops from Striga infection. Striga plants sense small molecules known as strigolactones (SLs) as germination signals, indicating host presence. By exploiting this germination system triggered by SLs, germination control may be an effective method against Striga infestation. A reasonably effective solution has yet to be found
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