Molecular characterization of plastid pyruvate kinase from castor and tobacco

Abstract

Clones encoding two different forms of plastid pyruvate kinase (PKp; EC 2.7.1.40) have been isolated from both castor and tobacco seed cDNA libraries. One form, designated PKpA, from castor was described in a previous report, and the tobacco homologue of PKpA has now been isolated. In addition, a second cDNA, designated PKpG, has been identified and sequenced in both species. Western blot analysis, using antibodies raised against protein overexpressed from these clones, indicates that they encode the two predominant polypeptides of plastid pyruvate kinase from developing castor endosperm. In castor, both PKpA and PKpG are encoded by single genes. In the allotetraploid Nicotiana tabacum, there are two copies of each, one derived from each of the progenitors of this species. The expression of the genes for PKpA and PKpG was examined in various tissues from both castor and tobacco. In castor, both forms are expressed in developing and germinating endosperm and in the root but neither is expressed in the leaf. In tobacco, both forms are expressed in developing seeds but in mature tissues, PKpA is most abundant in roots and PKpG in leaves.

Decreased Expression of Cytosolic Pyruvate Kinase in Potato Tubers Leads to a Decline in Pyruvate Resulting in an in Vivo Repression of the Alternative Oxidase

“…1). As reported previously (Blakeley et al, 1995;Andre et al, 2007), there are two main classes of plastidial PK isozymes (a and b). Our phylogenetic analysis revealed two subgroups of the a and b classes in angiosperms (designated a1, a2, b1, and b2 according to Andre et al, 2007;Fig.…”

A Heteromeric Plastidic Pyruvate Kinase Complex Involved in Seed Oil Biosynthesis inArabidopsis

“…The reconstitution of active PK p s from individually purified inactive subunits in this study and the in vivo co-IP results leave little ambiguity as to the heteromeric structure of the Arabidopsis PK p s. Some studies of recombinant PK p polypeptides from developing R. communis endosperm concluded that the PK p -a and PK p -b homologs are distinct enzymes (Blakeley and Dennis, 1993;Blakeley et al, 1995;Wan et al, 1995), while others have determined that the same proteins are actually subunits of a single heteromeric PK p complex (Plaxton et al, 1990;Plaxton, 1991;Negm et al, 1995). The data presented in this article support the conclusion that PK p is a complex composed of two different subunits.…”

Function of plastidial pyruvate kinases in seeds of Arabidopsis thaliana†

“…In the PK family of A. thaliana , three genes encode isoforms with putative plastid targeting sequences that present a strong homology with previously characterized plant PKps (Figure 1a; Blakeley et al. , 1995; Negm et al.…”

“…The closest homologues of PKp1 and PKp2 have been shown to encode plastidial isoforms of PKs (Figure 1; Blakeley et al. , 1995; Negm et al.…”

“…In both cases, PKp exists as a heterohexamer composed of equal proportions of α‐ and β‐subunit polypeptides. From a molecular point of view, two distinct cDNA clones encoding PKps have been isolated from seeds of R. communis and Nicotiana tabacum , designated as PKpA and PKpG , respectively (Blakeley et al. , 1995).…”