Tadao Asami
Guest Professor, Kihara Biological Institute, Yokohama City University (YCU);
Specifically Appointed Researcher, Graduate School of Agricultural and Life Sciences, The University of Tokyo (UTokyo)

Lecture Title

Chemical Strategies for Suppressing Root Parasitic Weeds

Abstract

Strigolactones (SLs) are germination stimulants for root parasitic weeds that cause devastating damage to crop production in regions such as Africa and the Mediterranean. As shown in Figure 1, the seeds of root parasitic plants remain dormant in the soil, but during the rainy season, the seeds near the roots begin to germinate when they receive stimulation from SLs exuded by the host plant in addition to warm and humid environmental conditions. Subsequently, these parasitic plants start to invade crops, causing serious damage. We have investigated methods to chemically inhibit SL biosynthesis in crops to suppress the parasitism of root parasitic weeds, which will be introduced below.

SL Biosynthesis Inhibitors: These inhibitors target the cytochrome P450 present in the SL biosynthesis pathway, inducing an SL-deficiency in crops to suppress root parasitic weed infestation[1]. This compound induces an SL-deficiency in plants to suppress root parasitic weed infestation, but unlike SL-deficient mutants, it does not induce excessive branching. Finally we revealed that this is due to the selectivity of TIS108 towards the biosynthetic pathway enzymes. The effectiveness of knockout lines for this target was confirmed.

GA Agonists: Based on the discovery that gibberellin (GA) suppresses SL biosynthesis in rice and significantly reduces SL levels[2], GA agonists were discovered and developed[3,4]. Through co-crystallization of these chemicals with the rice gibberellin receptor GID1, the mechanism by which these compounds express gibberellin activity was elucidated.

Reference

  1. Shinsaku Ito et al. Canonical strigolactones are not the major determinant of tillering but important rhizospheric signals in rice. Science Advances 8, eadd1278 (2022). DOI: 10.1126/sciadv.add1278.
  2. Shinsaku Ito et al. Regulation of Strigolactone Biosynthesis by Gibberellin Signaling. Plant Physiology 174:1250–1259 (2017). DOI: 10.1104/pp.17.00301
  3. Kai Jiang et al. Substituted Phthalimide AC94377 Is a Selective Agonist of the Gibberellin Receptor GID1. Plant Physiology 173:825-835 (2017). DOI: 10.1104/pp.16.00937
  4. Kai Jiang et al. Chemical screening and development of novel gibberellin mimics. Bioorganic & Medicinal Chemistry Letters 27: 3678-3682 (2017). DOI: 10.1016/j.bmcl.2017.07.012