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dr and spr/sr mutations of Chlamydomonas reinhardtii affecting D1 protein function and synthesis define two independent steps leading to chronic photoinhibition and confer differential fitness
Author(s) -
HEIFETZ P. B.,
LERS A.,
TURPIN D. H.,
GILLHAM N. W.,
BOYNTON J. E.,
OSMOND C. B.
Publication year - 1997
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1997.d01-143.x
Subject(s) - chlamydomonas reinhardtii , photoinhibition , photosynthesis , biology , chlamydomonas , mutant , wild type , chloroplast , botany , protein biosynthesis , biophysics , biochemistry , photosystem ii , gene
The effects of introduced chloroplast gene mutations affecting D1 synthesis, turnover and function on photosynthesis, growth and competitive ability were examined in autotrophic cultures of Chlamydomonas reinhardtii (Chlorophyta) adapted to low or high irradiance. Few discernible effects were evident when the mutants were grown in low light (LL, 70 μmol m −2 s −1 ). The herbicide‐resistant psbA mutation Ser 264 → Ala ( dr ) slowed electron transfer and accelerated D1 degradation in cells grown under high light (HL, 600 μmol m −2 s −1 ). The maximum rate of light‐and CO 2 ‐saturated photosynthesis, cell growth rate and competitive ability in the dr mutant were reduced compared to wild type under HL. However, the wild‐type rate of D1 synthesis in dr was adequate to compensate for accelerated D1 degradation. 16S rRNA mutations conferring resistance to streptomycin and spectinomycin ( spr/sr ) that altered chloroplast ribosome structure and assembly were used to inhibit chloroplast protein synthesis. In spr/sr cells grown under HL, D1 synthesis was reduced by 40–60% compared to wild type and D1 degradation was accelerated, leading to a 4‐fold reduction in D1 pool size. The reduced D1 levels were accompanied by an elevation of F o and a decline in F v / F m , quantum yield and maximum rate of CO 2 ‐saturated photosynthesis. Chemostat experiments showed that the growth rate and competitive ability of spr/sr were reduced against both wild type and dr.