Chlorophyll synthesis and protochlorophyllide reduction in the barley mutant albina-f17

Abstract

Plastids isolated from dark-grown leaves of the barley chlorophyll mutant alb-f 17 contain only 40% of the protochlorophyllide reductase enzyme present in the wild-type. The low level of enzyme is functionally linked to the similarly low level of protochlorophyllide in whole leaves. The chlorophyllide in illuminated leaves fails to undergo the Shibata shift. However, when dark-grown shoots are fed δ-aminolaevulinate, resulting in accumulation of non-photoconvertible protochlorophyllide, the newly-formed chlorophyllide undergoes a Shibata shift (18). The rate of the Shibata shift is proportional to the amount of accumulated non-photoconvertible protochlorophyllide.It has been suggested that alb-f 17 is blocked in the synthesis of esterified protochlorophyll and chlorophyll. It is shown that prolonged incubation of illuminated mutant leaves, whether or not fed with δ-aminolaevulinate, results in a significant accumulation of chlorophyll. The data support the view that the primary lesion is in the control of δ-aminolaevulinate synthesis.