Structure and expression of Spinacea oleracea L. and Arabidopsis thaliana complementary-DNAs encoding ribulosebisphosphate carboxylase/oxygenase activase

Rubisco activase proteins consist of two immunologically related polypeptides in the range of 40- to 47-kDa in most plant species examined. Rubisco activase precursor polypeptides are synthesized on cytoplasmic ribosomes and post-translationally imported into the chloroplast with cleavage of a chloroplast transit peptide. The rubisco activase mRNA is one of the more abundant poly(A)$\sp+$ mRNAs in the cytoplasm.$\lambda$gt11 cDNA libraries were constructed from Spinacea oleracea L. (spinach), Arabidopsis, and Arabidopsis rca mutant leaf mRNA. Rubisco activase cDNA clones were recovered and sequenced from each library. The primary amino acid sequence derived from the cDNA clones contained two consensus nucleotide binding sites which share homology with other ATP-utilizing enzymes from both animals and bacteria.Rubisco activase polypeptides are not synthesized in the rca mutant of Arabidopsis. In this mutant two rubisco activase mRNAs are synthesized, one larger and the other smaller than the authentic transcript. An error in RNA processing may lead to the absence of rubisco activase polypeptides in this mutant.Normally, the coding region of the rubisco activase RNA is alternatively spliced. This process leads to the production of two related polypeptides in both spinach and Arabidopsis. The two rubisco activase polypeptides differ in that the larger polypeptide has several additional amino acids at the C-terminal end of the protein. Both forms of the enzyme appear to be constitutively expressed in both palisade and mesophyll chloroplasts, and during leaf development.White light induces the rapid accumulation of rubisco activase mRNA in etiolated barley seedlings. Rubisco activase mRNA levels increase after a red light treatment in pea. This effect is abolished by subsequent illumination with far red light, indicating that the expression of rubisco activase mRNA is at least partially regulated by phytochrome.Escherichia coli transformed with a spinach rubisco activase cDNA can be induced to produce rubisco activase. The enzyme purified from E. coli possesses chromatographic and enzymatic properties similar to the chloroplast enzyme.U of I OnlyETDs are only available to UIUC Users without author permissio