EST analysis of the scaly green flagellate Mesostigma viride (Streptophyta): Implications for the evolution of green plants (Viridiplantae)

Table 8 Regulation of plastidic enzymes by the thioredoxin system. Proteins similar to embryophyte plastidic thioredoxin-regulated proteins were identified in the genomes of Cyanidioschyzon, Chlamydomonas, and the ESTs of Mesostigma using the BLASTP or BLASTX algorithms. A putative thioredoxin-regulated orthologue as revealed by the conserved cysteine residues is indicated with +. An asterisk indicates putative cyanobacterial/plastidic proteins, which do not contain the conserved cysteines required for thioredoxin-regulation. Missing enzymes are indicated with -.

	Cyanobacteria	Rhodophytes Cyanidioschyzon	Chlorophytes Chlamydomonas	Mesostigma	Embryophytes
PRK	+	+	+	+	+
SDPase	*	+	+	+	+
G6PDH	*	+	+	n.d.	+
FBPase	*	*¹⁾	+	+	+
γ-ATPase	*	*	+	+	+
GABDHB	-	-	-	+	+
NADP-MDH	-	-	+²⁾	n.d.	+
Rubisco activase	-³⁾	-	*	*	(+)⁴⁾

n.d. not detected in Mesostigma. ¹⁾ In Galdieria (Cyanidioschyzon) 2 (1) of the 3 conserved cysteines occurring in the Viridiplantae are present [48]. ²⁾ Chlorophyte NADP-malate dehydrogenase possesses a C- and N-terminal extension like the embryophyte enzyme, however only the C-terminal cysteines of the embryophyte enzyme are conserved [49, 50]. ³⁾ A few cyanobacteria contain an unusual rubisco activase. Only the central AAA⁺ domain shows similarity to plant rubisco activases, whereas the N and C terminal domain are very different [51]. ⁴⁾ Many angiosperms contain two forms of rubisco activase. Only the long form is regulated by the thioredoxin system [52].

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