scholarly journals A Secondary Processing Site in the Precursor of the Small Subunit of Ribulose Bisphosphate Carboxylase of Chlamydomonas reinhardtii y-1

1986 ◽  
Vol 81 (2) ◽  
pp. 702-704 ◽  
Author(s):  
Dawn B. Marks ◽  
Barbara J. Keller ◽  
J. Kenneth Hoober

2002 ◽  
Vol 366 (3) ◽  
pp. 989-998 ◽  
Author(s):  
Cédric INVERNIZZI ◽  
Jonathan IMHOF ◽  
Gabriela BURKARD ◽  
Katharina SCHMID ◽  
Arminio BOSCHETTI

The role of the two processing sites in the precursor of the small subunit (SS) of ribulose-1,5-bisphosphate carboxylase/oxygenase (pSS) of Chlamydomonas reinhardtii was studied by introducing mutations at the cleavage sites for the stromal processing peptidases SPP-1 and SPP-2, which hydrolyse wild-type pSS (20.6kDa) to an intermediate-sized product iSS (18.3kDa) and to the mature SS (16.3kDa), respectively. The mutations introduced into cDNA resulted in exchange of (a) two amino acids flanking processing site 1, or (b) one or (c) both amino acids flanking processing site 2. Mutation (a) prevented pSS from being processed at site 1 but not from cleavage at site 2. Mutation (c) abolished the action of SPP-2 but not SPP-1. When pSS with mutation (c) was imported into isolated chloroplasts, iSS accumulated while SS formation was abolished. However, mature SS was produced even in the absence of iSS synthesis (mutation a). Import of pSS bearing mutation (b), which only partially inhibited processing at the SPP-2 site, slowed the rate of SS formation down whereas iSS and some slightly smaller derivatives accumulated. These experiments suggested that in Chlamydomonas processing of pSS can occur in two steps, whereby the first step is facultative. The same three mutations were studied in vivo after transformation of SS-deficient C. reinhardtii T60-3 with mutated genomic DNA. Growth and photosynthesis was as in control transformants, except for the slower-growing transformants (mutation c) where no mature SS was immuno-detected. However, pSS fragments with molecular masses between those of iSS and SS were present even in the ribulose-1,5-bisphosphate carboxylase/oxygenase holoenzyme.



1994 ◽  
Vol 14 (6) ◽  
pp. 4011-4019
Author(s):  
J A Nelson ◽  
P B Savereide ◽  
P A Lefebvre

We have cloned and sequenced the CRY1 gene, encoding ribosomal protein S14 in Chlamydomonas reinhardtii, and found that it is highly similar to S14/rp59 proteins from other organisms, including mammals, Drosophila melanogaster, and Saccharomyces cerevisiae. We isolated a mutant strain resistant to the eukaryotic translational inhibitors cryptopleurine and emetine in which the resistance was due to a missense mutation (CRY1-1) in the CRY1 gene; resistance was dominant in heterozygous stable diploids. Cotransformation experiments using the CRY1-1 gene and the gene for nitrate reductase (NIT1) produced a low level of resistance to cryptopleurine and emetine. Resistance levels were increased when the CRY1-1 gene was placed under the control of a constitutive promoter from the ribulose bisphosphate carboxylase/oxygenase small subunit 2 (RBCS2) gene. We also found that the 5' untranslated region of the CRY1 gene was required for expression of the CRY1-1 transgene. Direct selection of emetine-resistant transformants was possible when transformed cells were first induced to differentiate into gametes by nitrogen starvation and then allowed to dedifferentiate back to vegetative cells before emetine selection was applied. With this transformation protocol, the RBCS2/CRY1-1 dominant selectable marker gene is a powerful tool for many molecular genetic applications in C. reinhardtii.



1986 ◽  
Vol 34 (2) ◽  
pp. 187 ◽  
Author(s):  
PG Martin ◽  
JM Dowd ◽  
C Morris ◽  
DE Symon

The N-terminal 40 amino acid sequences of the small subunit of ribulose bisphosphate carboxylase have been determined for 13 species of Solanum, one other species of Solanaceae and two of Convolvulaceae. From these, and previously published sequences from Solanaceae, a minimal phylogenetic tree is derived. This agrees well with current taxonomy; the first dichotomy in the Solanaceae tree is between the two subfamilies Solanoideae and Cestroideae; within Solanum the subgenera Solanum and Leptostemonum separate dichotomously; within subgenus Leptostemonum the African and Asian species diverge from the Australian. Within the Australian species of subgenus Leptostemonum two most unusual substitutions have been noted. The implications for the hypotheses of a 'molecular evolutionary clock' and of biogeographical dispersal by continental drift are discussed.



1984 ◽  
Vol 32 (3) ◽  
pp. 301 ◽  
Author(s):  
PG Martin ◽  
JM Dowd

N-terminal, 40 amino acid sequences of ribulose bisphosphate carboxylase small subunit are given for three species of Polygonaceae, three of Magnoliaceae and for Metasequoia. Making use of three plastocyanin and one cytochrome c sequences from the literature, these families are added to a previously published phylogenetic tree. Fagaceae and Proteaceae are also added. Uncertainties in the 14-family tree are pointed out. The root of the tree is identified using gymnosperm sequences. The concept of primitiveness as it is relevant to this research is discussed. From the phylogenetic tree there is no evidence for primitiveness of Magnoliaceae, though it is not precluded. Polygonaceae and Chenopodiaceae form a branch that diverges from the main tree near the presumptive dicotyledonous origin.





Development ◽  
1984 ◽  
Vol 83 (Supplement) ◽  
pp. 163-178
Author(s):  
R. John Ellis ◽  
Thomas F. Gallagher ◽  
Gareth I. Jenkins ◽  
C. Ruth Lennox

Chloroplast development in higher plants is light dependent, and is accompanied by the synthesis of chlorophyll and the accumulation of many chloroplast polypeptides. There is a 100-fold greater content of the photosynthetic enzyme, ribulose-1,5-bisphosphate carboxylase-oxygenase, in light-grown seedlings of Pisum sativum than in dark-grown seedlings. Following the illumination of dark-grown seedlings, there is a parallel increase in the content of both the mRNA and the polypeptide of the small subunit of the carboxylase; this subunit is a product of the nuclear genome. The increases in the mRNA and the polypeptide of the large subunit, which is a product of the chloroplast genome, show less synchronicity. Studies with isolated leaf nuclei show that the increase in small subunit mRNA is mediated primarily at the level of transcription. Three distinct effects of light on transcription of small subunit genes have been found; a rapid (∼1 h) burst, followed by a decline, when etiolated plants are first exposed to light; a slow (∼36h) development of the competence to transcribe rapidly after the initial burst; rapid (∼20 min) switches in both directions when fully greened plants are exposed to light—dark transitions.



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