Splicing of precursors to mRNA in higher plants: mechanism, regulation and sub-nuclear organisation of the spliceosomal machinery

Simpson, Gordon G.; Filipowicz, Witold

doi:10.1007/bf00039375

Cited by 252 publications

(124 citation statements)

References 303 publications

(491 reference statements)

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“…More generally, alternative splicing has been associated with developmental patterns, tissue specificity, and cellular targeting, but relatively few examples of alternative splicing have been identified in plants, and in most cases, its biological significance remains unclear (38). In the results presented here, we show that the two isoforms of Rubisco activase have substantially different functions in the regulation of Rubisco.…”

Section: Discussionmentioning

confidence: 58%

Mechanism of light regulation of Rubisco: A specific role for the larger Rubisco activase isoform involving reductive activation by thioredoxin-f

Zhang

Portis

1999

Proc. Natl. Acad. Sci. U.S.A.

295

283

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Rubisco activase is a nuclear-encoded chloroplast protein that is required for the light activation of ribulose 1,5-bisphosphate carboxylase͞oxygenase (Rubisco) in vivo. In most plants examined to date, there are two isoforms of Rubisco activase arising from alternative splicing that differ only at the carboxyl terminus. Here we demonstrate with recombinant proteins that in Arabidopsis the larger isoform has a unique role in the regulation of Rubisco activity. At physiological ratios of ADP͞ATP, the 46-kDa isoform has minimal ATP hydrolysis and Rubisco activation activity in comparison with the 43-kDa isoform. Analysis of a series of carboxyl-terminal deletion and Ala substitution mutants of the 46-kDa isoform revealed that the presence of Cys residues at positions 411 and 392 were essential to preserve a low ATP hydrolysis and Rubisco activation activity in the presence of ADP. Consequently, incubation of the 46-kDa isoform with DTT and thioredoxin-f increased both activities, whereas incubations with DTT alone or with thioredoxin-m were ineffective. Thioredoxin-f and DTT had no effect on the 43-kDa isoform. However, premixing both isoforms before conducting a reduction and oxidation cycle demonstrated that the activity of both isoforms could be regulated. Reduction and oxidation also modulated the activity of native activase proteins isolated from either Arabidopsis or spinach, but not tobacco, which only has the smaller isoform. These findings suggest that in plants containing both isoforms, Rubisco activase regulates the activity of Rubisco in response to light-induced changes in both the ADP͞ATP ratio and the redox potential via thioredoxin-f.

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Section: Discussionmentioning

confidence: 58%

Mechanism of light regulation of Rubisco: A specific role for the larger Rubisco activase isoform involving reductive activation by thioredoxin-f

Zhang

Portis

1999

Proc. Natl. Acad. Sci. U.S.A.

295

283

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“…Introns I, II, III, IV, and V contain 12-28% more A͞U than their adjacent exons, and introns VI and VII contain Ϸ8% more A͞U than their adjacent exons. The average length of introns in the MCT gene is 82 nt, a length that is in the range of the average size of plant introns (12). All exon-intron splicing junction sequences follow the GT-AG rules (13).…”

Section: Resultsmentioning

confidence: 99%

Expression of Batis maritima methyl chloride transferase in Escherichia coli

Hager

1999

Proc. Natl. Acad. Sci. U.S.A.

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Methyl chloride transferase, a novel enzyme found in several fungi, marine algae, and halophytic plants, is a biological catalyst responsible for the production of atmospheric methyl chloride. A previous paper reports the purification of this methylase from Batis maritima and the isolation of a cDNA clone of the gene for this enzyme. In this paper, we describe the isolation of a genomic clone of the methylase gene and the expression of recombinant methyl chloride transferase in Escherichia coli and compare the kinetic behavior of the wild-type and recombinant enzyme. The recombinant enzyme is active and promotes the production of methyl chloride by E. coli under in vivo conditions. The kinetic data indicate that the recombinant and wild-type enzymes have similar halide (Cl ؊ , Br ؊ , and I ؊ )-binding capacities. Both the recombinant and wild-type enzymes were found to function well in high NaCl concentrations. This high salt tolerance resembles the activity of halobacterial enzymes rather than halophytic plant enzymes. These findings support the hypothesis that this enzyme functions in the control and regulation of the internal concentration of chloride ions in halophytic plant cells.It is estimated that methyl chloride, the most abundant halohydrocarbon species in the upper atmosphere, is produced at a level of 5 ϫ 10 6 tons per year (1). The biological production of CH 3 Cl and other volatile halogenated organic compounds in ocean waters has been commonly viewed as one of the major source of chlorinated halohydrocarbons in the upper atmosphere (2). In 1990, Wuosmaa and Hager (3) discovered the presence of methyl chloride transferase (MCT) in fungi, marine algae, and a halophytic plant. MCT catalyzes the conversion of chloride to methyl chloride by using S-adenosyl-L-methionine (AdoMet) as the methyl donor. Wuosmaa and Hager showed that cell-free extracts of Phellinus pomaceus (a white rot fungus), Endocladia muricata (a marine red algae), and Mesembryanthemum crystallium (ice plant, a halophytic plant) contain MCT activity. Wuosmaa (4) also found that 20 of 31 marine algae collected along the Pacific coastal water near Monterey, CA produced methyl chloride. The production of methyl choride by halophytic plants suggests that halophytic plants may be an additional major source of atmospheric methyl chloride (3, 4). Methyl chloride and other halogenated methanes pollute the atmosphere (5) and affect the integrity of the stratospheric ozone layer (6).Previous work led to the isolation of a homogenous MCT preparation and allowed the cDNA cloning of the MCT gene (7). The isolated native enzyme has a M r of 22,434 as determined by matrix-assisted laser-desorption ionization (MALDI) MS, whereas the ORF in the cDNA clone has 230 codons coding for an enzyme having a calculated M r of 25,761. Thus, there is a Ϸ3.3-kDa difference in the molecular masses of the isolated enzyme and the deduced amino acid sequence.It is unclear whether this difference is due to proteolytic cleavage during isolation of the native enz...

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“…There are many reports on alternative splicing in higher plants (29), and alternative splicing may occur that would induce synthesis of multiple forms of ceQORH mRNA (with or without an extended N-terminal region coding for a chloroplast transit peptide). In this case, several 5Ј RACE-PCR experiments showing the presence of only one transcript may not be totally conclusive.…”

Section: Fig 3 the Ceqorh Protein Is Bound To The Inner Membrane Ofmentioning

confidence: 99%

Non-canonical Transit Peptide for Import into the Chloroplast

Miras

Salvi

Ferro

et al. 2002

Journal of Biological Chemistry

159

157

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The large majority of plastid proteins are nuclearencoded and, thus, must be imported within these organelles. Unlike most of the outer envelope proteins, targeting of proteins to all other plastid compartments (inner envelope membrane, stroma, and thylakoid) is strictly dependent on the presence of a cleavable transit sequence in the precursor N-terminal region. In this paper, we describe the identification of a new envelope protein component (ceQORH) and demonstrate that its subcellular localization is limited to the inner membrane of the chloroplast envelope. Immunopurification, microsequencing of the natural envelope protein and cloning of the corresponding full-length cDNA demonstrated that this protein is not processed in the N-terminal region during its targeting to the inner envelope membrane. Transient expression experiments in plant cells were performed with truncated forms of the ceQORH protein fused to the green fluorescent protein. These experiments suggest that neither the N-terminal nor the C-terminal are essential for chloroplastic localization of the ceQORH protein. These observations are discussed in the frame of the endosymbiotic theory of chloroplast evolution and suggest that a domain of the ceQORH bacterial ancestor may have evolved so as to exclude the general requirement of an N-terminal plastid transit sequence.Higher plant plastids contain a genome with limited coding capacity. The large majority of plastid proteins are nuclearencoded and thus, must be imported within these organelles. To this purpose, the two envelope membranes that surround chloroplasts contain a protein import apparatus constituted of the TOC and TIC complexes (translocon at the inner or outer membranes of the chloroplast envelope) (for recent reviews, see Refs. 1-4). The major element of this translocation complex is Toc75, which is the most abundant protein in the outer envelope membrane. Moreover, Toc75 seems to form the central pore of the outer envelope translocation channel (5, 6) and interacts specifically with the N-terminal transit peptide of precursor proteins during the import process toward chloroplast (7). This cleavable and N-terminal transit peptide was shown to be necessary and sufficient for transport of precursors (i) across the two envelope membranes (8, 9) and (ii) across the thylakoid membrane if the transit sequence is bipartite (it contains additional targeting information for thylakoid lumen targeting) (9). The cleavage of the transit sequence is performed by two proteases, one in the stroma (10) and one in the thylakoid lumen for the bipartite transit sequences (11). Moreover it is interesting to note that all described inner membrane proteins and intermembrane space proteins possess an N-terminal cleavable transit peptide, while most outer envelope membrane proteins do not have any cleavable transit peptide. In the latter case, the targeting information is contained within the mature protein (12), and after their cytosolic synthesis, proteins are directly incorporated in the lipid bilayer th...

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Splicing of precursors to mRNA in higher plants: mechanism, regulation and sub-nuclear organisation of the spliceosomal machinery

Cited by 252 publications

References 303 publications

Mechanism of light regulation of Rubisco: A specific role for the larger Rubisco activase isoform involving reductive activation by thioredoxin-f

Mechanism of light regulation of Rubisco: A specific role for the larger Rubisco activase isoform involving reductive activation by thioredoxin-f

Expression of Batis maritima methyl chloride transferase in Escherichia coli

Non-canonical Transit Peptide for Import into the Chloroplast

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