Em. Chekunova et al., REGULATION OF BIOSYNTHESIS OF CHLOROPHYLL PRECURSORS IN MUTANTS OF THE GREEN-ALGA CHLAMYDOMONAS-REINHARDTII, Biochemistry, 58(9), 1993, pp. 1040-1045
The chlorophyll-deficient nuclear gene chl1 mutant of the green alga C
hlamydomonas reinhardtii accumulates protoporphyrin IX (PP), which giv
es a brown-yellow color to the colony. In chl1-mutant cells, protochlo
rophyllide (Pchlde) accumulation is decreased, while delta-aminolevuli
nic acid (ALA)-synthesizing activity is increased A double mutant chl1
mod-u-25 was isolated whose cells accumulate 20 times more PP than th
ose of the parent strain and form dark-brown colonies. The regulatory
mutation mod-u-25 increases two-fold the ALA-synthesizing activity and
results also in an enhancement of the Pchlde and chlorophyllide conte
nt in comparison with the wild strain. The ALA-synthesizing enzymes fr
om the single (chil1) and double (chl1 mod-u-25) mutants as well as fr
om the wild strain are equally sensitive to heme inhibition. In the do
uble mutant protoheme synthesis is unimpaired Some peculiarities of ch
lorophyll biosynthesis regulation in the chl1 mod-u-25 double mutant o
f C. reinhardtii are discussed