摘要
Derived from burnt vegetation, karrikins （KAR） are butenolide chemicals that stimulate seed germination and enhance seedling responses to light. Genetic and biochemical studies have identified KARRIKIN INSENSITIVE2 （KAI2） as a putative karrikin receptor protein （reviewed by Waters et al., 2014）. KAI2 is an od J3-fold hydrolase and a paralog of DWARF14 （D14; AtD14 in Arabidopsis）, and both possess the conserved catalytic triad of Ser, His, and Asp residues typical of this class of hydrolytic enzymes. D14 proteins are likely receptors for strigolactones （SL）, a group of butenolide plant hormones involved in the regulation of shoot architecture, and an intact catalytic triad is essential for D14-mediated SL responses （Hamiaux et al., 2012）. It has been proposed that the catalytic serine of KAI2 and AtD14 initiates nucleophilic attack on the butenolide moiety of KAR and SLs, respectively （Scaffidi et al., 2012; Zhao et al., 2013）, and that these proteins have both enzyme-like and receptor-like qualities （Waters et al., 2014）.
Derived from burnt vegetation, karrikins （KAR） are butenolide chemicals that stimulate seed germination and enhance seedling responses to light. Genetic and biochemical studies have identified KARRIKIN INSENSITIVE2 （KAI2） as a putative karrikin receptor protein （reviewed by Waters et al., 2014）. KAI2 is an od J3-fold hydrolase and a paralog of DWARF14 （D14; AtD14 in Arabidopsis）, and both possess the conserved catalytic triad of Ser, His, and Asp residues typical of this class of hydrolytic enzymes. D14 proteins are likely receptors for strigolactones （SL）, a group of butenolide plant hormones involved in the regulation of shoot architecture, and an intact catalytic triad is essential for D14-mediated SL responses （Hamiaux et al., 2012）. It has been proposed that the catalytic serine of KAI2 and AtD14 initiates nucleophilic attack on the butenolide moiety of KAR and SLs, respectively （Scaffidi et al., 2012; Zhao et al., 2013）, and that these proteins have both enzyme-like and receptor-like qualities （Waters et al., 2014）.
