ストリゴラクトンの受容とシグナル伝達

抄録

Analyses of strigolactone-insensitive mutants have enabled the identification of important factors for strigolactone perception and signaling; D14, an α/β hydrolase, D3/MAX2, an F-box protein and D53/SMXLs.　It is postulated that strigolactone is received by D14 and then D14 interacts with D3/MAX2.　This interaction stimulates the degradation of repressors of strigolactone signaling, including D53/SMXL proteins.　D14 cleaves strigolactone and form a covalent bond between D14 and a cleaved D-ring fragment of strigolactone.　This evokes dramatic change in the lid domain of D14 and the exposed surfaces in the changed lid domain interact with D3/MAX2.　Karrikins are another class of butenolide molecules found in smoke.　Strigolactones and karrikins are recognized through highly similar signaling mechanisms.　Karrikin receptor, KAI2/HTL, is a paralog of D14 and involved in karrikin-regulated seed germination and photomorphogenesis.　Parasitic plants have divergent KAI2 homologs, KAI2c, KAI2i and KAI2d.　Recent papers have demonstrated that strigolactones are received by ShKAI2d to induce seed germination in Striga hermonthica.　Crystal structural studies of ShKAI2d revealed that ShKAI2d has larger binding pocket than that of Arabidopsis KAI2 and some amino acid residues in its binding pocket are changed to increase an affinity to strigolactones.　These data will help us to develop novel chemical regulators of strigolactone functions for agricultural applications.