2.1.1.11 physiological function a knockdown mutant of CHLM shows an abscisic acid-insensitive phenotype for stomatal response. In addition, the mutant shows normal abscisic acid-induced expression of the abscisic acid-responsive RAB18 and RD29B genes and abscisic acid-dependent inhibition of seed germination and root growth 734560 2.1.1.11 physiological function Mg protoporphyrin IX methyltransferase is activated and stabilized by interaction with NADPH-dependent thioredoxin reductase NTRC 757980 2.1.1.11 physiological function Mg-protoporphyrin IX methyltransferase activity is the link between methyl cycle and chlorophyll synthesis 700486 2.1.1.11 physiological function mutation yellow-green leaf 18 shows yellow-green leaves, decreased chlorophyll level, and climate-dependent growth differences. Mutant yellow green leaf 18 has lost magnesium protoporphyrin IX methyltransferase activity. Substrate magnesium protoporphyrin IX largely accumulates while the product magnesium protoporphyrin IX monomethylester is reduced in mutant leaves. The retarded growth of mutant plants is caused by the high light intensity 756823