Target sites for chemical regulation of strigolactone signaling

Abstract

Demands for plant growth regulators (PGRs; chemicals that control plant growth) are increasing globally, especially in developing countries. Both positive and negative PGRs are widely used to enhance crop production and to suppress unwanted shoot growth, respectively. Strigolactones (SLs) are multifunctional molecules that function as phytohormones, inhibiting shoot branching and also functioning in the rhizospheric communication with symbiotic fungi and parasitic weeds. Therefore, it is anticipated that chemicals that regulate the functions of SLs will be widely used in agricultural applications. Although the SL biosynthetic pathway is not fully understood, it has been demonstrated that β-carotene isomerases, carotenoid cleavage dioxygenases (CCDs), and a cytochrome P450 monooxygenase are involved in strigolactone biosynthesis. A CCD inhibitor, abamine, which is also an inhibitor of abscisic acid biosynthesis, reduces the levels of SL in several plant species and reduces the germination rate of Orobanche minor seeds grown with tobacco. On the basis of the structure of abamine, several chemicals have been designed to specifically inhibit CCDs during SL synthesis. Cytochrome P450 monooxygenase is another target enzyme in the development of SL biosynthesis inhibitors, and the triazole-derived TIS series of chemicals is known to include SL biosynthesis inhibitors, although their target enzyme has not been identified. Recently, DWARF14 (D14) has been shown to be a receptor for SLs, and the D-ring moiety of SL is essential for its recognition by D14. A variety of SL agonists are currently under development and most agonists commonly contain the D-ring or a D-ring-like moiety. Several research groups have also resolved the crystal structure of D14 in the last two years. It is expected that this information on the D14 structure will be invaluable not only for developing SL agonists with novel structures but also in the design of inhibitors of SL receptors.

Strigolactones are required for nitric oxide to induce root elongation in response to nitrogen and phosphate deficiencies in rice

“…However, no response of seminal root length to SNP application was observed in two d mutants (Figs S5 and 4c). Interestingly, application of an SL inhibitor (Abamine, a CCD inhibitor, Nakamura & Asami ) prevented the LN‐induced, LP‐induced and SNP‐induced seminal root length increase in WT plants (Fig. c).…”

Regulation of biosynthesis, perception, and functions of strigolactones for promoting arbuscular mycorrhizal symbiosis and managing root parasitic weeds

“…CL is the precursor of SLs only, and inhibitors of CCDs have been developed as specific SL biosynthesis inhibitors . Abamine, an ABA biosynthesis inhibitor, also inhibited CCDs and reduced SL production; further modification of its structure may afford more potent SL biosynthesis inhibitors . However, endogenous levels of CL in plants are rather high compared with SLs .…”

“…46 Abamine, an ABA biosynthesis inhibitor, also inhibited CCDs and reduced SL production; further modification of its structure may afford more potent SL biosynthesis inhibitors. 47,48 However, endogenous levels of CL in plants are rather high compared with SLs. 19 Therefore, steps in the biosynthesis of SLs that are downstream of CL appear to be preferable target sites for the regulation of SL biosynthesis, although details of these steps remain elusive.…”

Discovery of Putative Herbicide Resistance Genes and Its Regulatory Network in Chickpea Using Transcriptome Sequencing

“…Della gene has role in regulation of GA signaling by suppressing stress response pathways (Nakamura and Asami, 2014). This gene is associated with growth inhibition of weed (Heuer et al, 2016).…”