Subategory:

Mutants

Description:

The 72-7JJ nuclear mutant was isolated by screening a collection of acetate-requiring mutants for lack of complementation with a known Rubisco rbcL mutant. 72-7JJ grows on minimal medium at 25 °C, but dies on minimal medium at 35 °C. The mutant was crossed with pf2 mt- to confirm mendelian inheritance, and this mt+ progeny clone was retained for further analysis. 72-7JJ has normal whole-chain electron transport and chlorophyll levels. The 72-7JJ mutation is not in the Rubisco rbcS genes, but it causes a decrease in Rubisco stability and alters Rubisco catalytic properties. When 72-7JJ mt+ was crossed with the very similar 68-11AR mt- mutant, the two genes appeared to be linked (PD=12, NPD=0, T=1), and the 68-11AR/72-7JJ double mutant had a non-temperature-conditional, acetate-requiring phenotype. When 68-11AR/72-7JJ mt+ was crossed with "wild-type" mt- a similar result was observed (PD=21, NPD=0, T=2). Thus, 68-11AR and 72-7JJ are separated by 4 map units. However, some clones of 72-7JJ have been observed to become acetate-requiring at 25 °C after many years of culture. This strain has been maintained with acetate medium in darkness since its isolation.

Species:

Chlamydomonas

Phenotype:

Requires acetate at 35 °C; temperature-conditional