CHLOROPHYLL BIOSYNTHETIC-ENZYMES AND PLASTID MEMBRANE STRUCTURES IN MUTANTS OF BARLEY (HORDEUM-VULGARE L)

In barley a number of recessive lethal mutants deficient in chlorophyl l biosynthesis have been identified previously (HENNINGSEN et al. 1993 ). Selected mutants were analysed for activities of four different chl orophyll biosynthetic enzymes, in relation to the development of plast id membrane structures. According to the ultrastructure of membranes i n developing plastids the mutants were divided into three groups. One group (xan-l(35) and -g(45) has normal development of prolamellar body (PLB) and prothylakoids (PTs) resembling the wild type. A second grou p (xan-i(25), -k(42), and -u(21)) has abnormal development of PLB memb ranes and PTs. The third group (xan-n(74) and alb-e(16)) has normal de velopment of PLB but PTs are deficient or, if present, they are highly deranged. In mutants with defective membrane structures, the activiti es of the membrane associated enzymes Mg-chelatase and methyltransfera se were more affected than the activities of the soluble stroma enzyme s ALA-dehydratase and PBG-deaminase. The two mutants xan-n(74) and alb -e(16), which are deficient in PT membranes, had no detectable methylt ransferase activity, indicating that the enzyme methyltransferase is l ocated in association with the PT membranes.