Characterization of the Arabidopsis thaliana Mutant pcb2 which Accumulates Divinyl Chlorophylls

Abstract

We characterized the pcb2 (pale-green and chlorophyll b reduced 2) mutant. We found through electron microscopic observation that chloroplasts of pcb2 mesophyll cells lacked distinctive grana stacks. High-performance liquid chromatography (HPLC) analysis showed that the pcb2 mutant accumulated divinyl chlorophylls, and the relative amount of divinyl chlorophyll b was remarkably less than that of divinyl chlorophyll a. The responsible gene was mapped in an area of 190 kb length at the upper arm of the 5th chromosome, and comparison of DNA sequences revealed a single nucleotide substitution causing a nonsense mutation in At5g18660. Complementation analysis confirmed that the wild-type of this gene suppressed the phenotypes of the mutation. Antisense transformants of the gene also accumulated divinyl chlorophylls. The genes homologous to At5g18660 are conserved in a broad range of species in the plant kingdom, and have similarity to reductases. Our results suggest that the PCB2 product is divinyl protochlorophyllide 8-vinyl reductase.

slr1923 of Synechocystis sp. PCC6803 Is Essential for Conversion of 3,8-Divinyl(proto)chlorophyll(ide) to 3-Monovinyl(proto)chlorophyll(ide)

“…It is also of note that chl a species were totally replaced by the new chl a species in the mutant. The spectral characteristics and the retention time on HPLC of the modified chlorophyll coincided with those reported by Shedbalkar and Rebeiz (1992), Nagata et al (2005), and Nakanishi et al (2005). They identified the modified chlorophyll molecule as a 3,8-DV-chl a.…”

“…A mutant that accumulates DV-chl was recently reported independently in Arabidopsis by two groups (Nagata et al, 2005;Nakanishi et al, 2005). Their mutants accumulated DV-chl a and DV-chl b.…”

“…2B), indicating a high sensitivity to strong illumination. High sensitivity to strong illumination is reported in an Arabidopsis (Arabidopsis thaliana) mutant (Nagata et al, 2005;Nakanishi et al, 2005) and also in a Synechocystis 6803 mutant (Ito et al, 2008). Although the SD is large, slr1923 M showed a tendency to grow slower than the wild type under low CO 2 (0.03%).…”

“…A mutant that accumulates DV-chl was reported by Bazzaz and Govindjee (1974) and analyzed by Bazzaz (1981) in Zea mays. Nagata et al (2005) and Nakanishi et al (2005) independently identified gene AT5G18660 of Arabidopsis as a divinyl reductase (DVR) that has sequence similarity to isoflavone reductase. By investigation of the mutant created by insertional inactivation, Chew and Bryant (2007) demonstrated that CT1063 (bciA), which is an ortholog of the Arabidopsis gene, encodes a C-8 DVR of Chlorobium tepidum TLS.…”

Characterization of a Plant-like Protochlorophyllide a Divinyl Reductase in Green Sulfur Bacteria

“…In early 2005 two groups independently reported that a protein unrelated to BchJ and encoded by AT5G18660 was responsible for the reduction of the C-8 vinyl group in the biosynthesis of Chl a in Arabidopsis thaliana (14,15). Interestingly, an open reading frame encoding a conserved hypothetical protein (CT1063), which encodes a protein with a very high degree of sequence identity to the AT5G18660 product, is found in the genome of C. tepidum.…”