Characterization of photosystem II mutants of Chlamydomonas reinhardii lacking the psbA gene

Abstract

We have examined 78 chloroplast mutants of Chlamydomonas reinhardii lacking photosystem II activity. Most of them are unable to synthesize the 32 Kdalton protein. Analysis of 22 of these mutants reveals that they have deleted both copies of the psbA gene (which codes for the 32 Kdalton protein) in their chloroplast genome. Although these mutants are able to synthesize and to integrate the other photosystem II polypeptides in the thylakoid membranes, they are unable to assemble a stable functional photosystem II complex. The 32 Kprotein appears therefore to play an important role not only in photosystem II function, but also in stabilizing this complex.

Cellulose degradation and assimilation by the unicellular phototrophic eukaryote Chlamydomonas reinhardtii

“…Similar results (Fig. 2c, 156±5.85% (s.d./n ¼ 6) with FP versus 100% without cellulose on day 6) were obtained with another photosynthetic mutant cc4147 (FUD7) 33 . In addition to experiments carried out in MM containing a low amount of acetate, cellulose assimilation of photosynthetic mutant FUD16 was also analysed under conditions where cellulose was the sole organic carbon source present in the medium (Fig.…”

“…Liquid cultures of Chlamydomonas reinhardtii wild-type strain cc124 [137c] and Chlorella kessleri (Parachlorella kessleri; SAG 211-11h) were cultivated phototrophically in high-salt MM and mixotrophically in TAP, or by adding different carbon sources to MM under continuous white light (100 mmol photons m À 2 s À 1 ) with or without bubbling (air or carbon dioxideenriched air 5% (v/v)) 30 . The non-phototrophic mutants cc4148 (FUD16) 31 and cc4147 (FUD7) 33 were cultivated in low light (50 mmol photons m À 2 s À 1 ) and air-bubbled MM containing only 10% of the acetate concentration (1.7 mM) used in TAP 30 (17 mM). The following carbon sources were used at a concentration of 0.1% (w/v): CB, CMC (Carl Roth, 3333.1), Avicel (VWR, 1.02331.0500) or Whatman filter paper (Carl Roth, CL64.1).…”

Transcript Levels and Synthesis of Photosystem II Components in Cyanobacterial Mutants with Inactivated Photosystem II Genes.

“…PCC 6803, there is appreciably more effect of various PS II gene inactivations on the transcript level of other PS II genes than has been observed in Chlamydomonas (Erickson et al, 1986;Jensen et al, 1986), even though the reasons for the effects observed in the cyanobacterium are still unclear.…”

“…Upon deletion or interruption of the psbC gene, the level of other PS II core proteins has been drastically decreased (Dzelzkalns and Bogorad, 1988;Vermaas et al, 1988;Rochaix et al, 1989). Thus, generally speaking, in the absence of D1, 02, or CP47, the other large PS II proteins do not accumulate in the thylakoid membrane (Bennoun et al, 1986;Erickson et al, 1986;Jensen et al, 1986;Vermaas et al, 1988Vermaas et al, , 1989, whereas absence of CP43 leads to a decreased amount of other proteins of the PS II core complex in the thylakoid.…”

“…Thylakoids from a Chlamydomonas reinhardtii mutant lacking psbA (Bennoun et al, 1986), as well as those from Chlamydomonas or Synechocystis sp. PCC 6803 mutants impaired in psbD (Erickson et al, 1986;Vermaas et al, 1987bVermaas et al, , 1988, have been shown to be depleted severely in the other PS II core proteins (D2 or D1, CP47, CP43), in addition to lacking the protein (D1 or D2) encoded by the ' To whom correspondence should be addressed. mutated gene.…”