Chloroplast fructose-1,6-bisphosphatase: the product of a mosaic gene

Abstract

We show here that light stimulates the expression of nuclear genes in wheat leaves for chloroplast fructose-1,6-bisphosphatase (FBPase) and describe a sequence of amino acids in this enzyme which may be responsible, via thioredoxin, for the light regulation of its activity. This data results from (a) our isolation and characterization of a cDNA of this enzyme which contains its entire coding sequence, and (b) our use of this cDNA as a probe to detect mRNA levels in wheat plants subjected to different light regimes. The similarity in amino acid sequence of the encoded enzyme from diverse sources suggests that the FBPase genes all had a common origin. However, their control sequences have been adjusted so that they are appropriately expressed and their coding sequences modified so that the enzymic activity of their products are suitably regulated in the particular cellular environment in which they must function. The light-activated regulatory sequences in the gene for the chloroplast protein have probably come together by a shuffling of DNA segments.

Thioredoxins: structure and function in plant cells

“…Fructose-1,6-bisphosphatase is a tetrameric enzyme composed of four identical subunits, each containing c. 350 amino acids with a molecular weight of c. 40 kDa. In eukar\ otic cells, fructose-l,6-bisphosphatase is nuclear-encoded and its transit sequence is cleaved after import into the chloroplast (Raines et al, 1988). Several amino acid sequences have now been determined for the photosynthetic bacterial, cyanobacterial, and plant chloroplastic enzymes, including spinach, pea, Brassica napus, wheat, A. thaliana and soybean (see references in Jacquot et al, 1995).…”

cDNA and gene sequences of wheat chloroplast sedoheptulose‐1,7‐bisphosphatase reveal homology with fructose‐1,6‐bisphosphatases

“…Initially, Sed(l,7)Pzase cDNA clones were isolated from a previously constructed wheat cDNA library (Raines et al, 1988), using the method of Young and Davis (1983). The filters were screened using maize Sed(1 ,7)P2ase polyclonal antibodies (a gift from B.…”

“…Identity and similarity between wheat Sed(l,7)Pzase and a variety of Fru(l,6)Pzase amino acid sequences. Sources of sequences: wheat Sed(1 ,7)P2ase, this work; wheat chloroplast Fru(l,6)P2ase, Raines et al (1988); spinach cytosolic Fru(l,6)P2ase, Ladror et al (1990); pig Fru(l,6)P2ase, Marcus et al (1982); Saccharomyces cerevisiae Fru(l,6)P2ase, Rogers et al (1988); E. coli Fru(l,6)P2ase, Hamilton et al (1988); Rhodobacrer sphoeroides Fru(l,6)P2ase, Gibson et al (1990). The alignments used to generate these values were made using the Wisconsin GAP programme.…”

“…The wheat and spinach chloroplast Fru(1 ,6)P2ases have been shown to have a unique insertion sequence (at position Leu1 53 in the pig sequence), containing two cysteine residues which may be involved in the light regulation of these enzymes (Raines et al, 1988;Marcus et al, 1988). The alignment in Fig.…”

“…Molecular studies have resulted in extensive amino acid sequence information, including that of pig kidney (Marcus et al, 19821, the wheat (Raines et al, 1988) and spinach (Marcus et al, 1988) chloroplast enzymes, and also in the determination of the crystallographic structure of the pig kidney enzyme to a resolution of 0.28 nm (Ke et al, 1989a(Ke et al, , b, 1990(Ke et al, , 1991. In contrast to this, Sed(l,7)P2ase (like ribulose-1,s-bisphosphate carboxylase and phosphoribulokinase) is unique to the photosynthetic carbon-reduction cycle; consequently, much less information on the molecular characteristics of Sed(1 ,7)P2ase is available.…”