Untitled

Abstract

The Arabidopsis thaliana genome has two genes (AtFC-I and AtFC-II), encoding ferrochelatase, the terminal enzyme of haem biosynthesis. The roles of the two enzymes in the synthesis of haem for different haemoproteins was investigated using reporter gene analysis. A 1.41 kb fragment from the 5' upstream region of the AtFC-II gene was fused to the luciferase gene, and then introduced into tobacco plants, followed by luciferase activity measurements. AtFC-II-LUCwas expressed in all aerial parts of the plant, and was highest in flowers, but it was not expressed in roots. It was unaffected by viral infection, and considerably reduced by wounding or oxidative stress. Similarly, a 1.76 kb region of the AtFC-I promoter was fused to the uidA gene encoding beta-glucuronidase. AtFC-I-GUS was expressed in all tissues of the plant, but was higher in roots and flowers than in leaves or stems. It was induced by sucrose, wounding and oxidative stress and, most markedly, by plants undergoing the hypersensitive response to TMV infection. Levels of endogenous ferrochelatase activity were increased in pea chloroplasts isolated from wounded leaves, indicating that the induction in promoter activity is likely to result in increased haem biosynthetic potential. Salicylic acid, but not methyl-jasmonate was able to replace the stress treatment in induction of AtFC-I expression, suggesting that the requirement for haem synthesis is part of the defence response. The implications of the results for the different roles of the two ferrochelatases in haem biosynthesis are discussed.

Heme Synthesis by Plastid Ferrochelatase I Regulates Nuclear Gene Expression in Plants

“…FC1 can be induced up to 30-fold by tobacco mosaic virus infection [17], suggesting that FC1 transcript levels in gun6-1D seedlings are well within physiological range. To confirm that overexpression of FC1 caused the gun phenotype in gun6-1D , we constructed stable Arabidopsis transformants constitutively overexpressing FC1 ( FC1-OX ).…”

“…Like FC1, Arabidopsis FC2 (At2g30390, GenBank AAB63095.1) was identified by its ability to complement an Saccharomyces cerevisiae ferrochelatase mutant [25]. Although both proteins are localized to the plastid thylakoid and envelope membranes [26, 27], their sequences and expression profiles suggest functional differences [17, 25, 27]. FC2 contains a regulatory [28] hydrophobic C-terminal LHC motif [29] associated with light harvesting complexes and is coregulated with photosynthetic genes.…”

Photosystem II Assembly in CP47 Mutant of Synechocystis sp. PCC 6803 Is Dependent on the Level of Chlorophyll Precursors Regulated by Ferrochelatase

“…However, there are two different FeCH isozymes in plants (39) and only the FeCH-1 isozyme, ubiquitously expressed throughout the plant, was responsible for the described increase. In contrast, FeCH-2 localized in plastids, was repressed (38). Plant FeCH-2 is a homologue of cyanobacterial FeCH with a putative membrane-spanning region carrying the characteristic Chl-binding motif (40).…”

“…Interestingly, highly increased FeCH activity was found also in a PSI-less mutant, 2 suggesting that FeCH activity is increased in mutants that may have a problem with chlorophyll placement. In higher plants, increase in FeCH activity has been reported as a response to environmental stresses such as wounding, oxidative stress, and viral infection (38). However, there are two different FeCH isozymes in plants (39) and only the FeCH-1 isozyme, ubiquitously expressed throughout the plant, was responsible for the described increase.…”

Towards engineering increased pantothenate (vitamin B5) levels in plants

“…Leaf tissue (50 mg) from young leaf plants was homogenised in 500 ll GUS lysis buffer (GLB) and assayed in a Perkin Elmer LS-50 fluorimeter connected to a microtiter plate reader as described by Singh et al (2002). Activity, calculated by reference to standards, was expressed as pmol (MU) mg -1 protein min -1 .…”