Expression analysis of the two ferrochelatase genes in Arabidopsis in different tissues and under stress conditions reveals their different roles in haem biosynthesis.
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.
Singh
Davinder Pal
DP
Department of Plant Sciences, University of Cambridge, UK.
Cornah
Johanna E
JE
Hadingham
Sophie
S
Smith
Alison G
AG
D000085:Acetates / Q000494:pharmacology; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D016718:Arachidonic Acid / Q000494:pharmacology; D003517:Cyclopentanes / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005294:Ferrochelatase / Q000235:genetics* / Q000378:metabolism; D035264:Flowers / Q000201:enzymology / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D006418:Heme / Q000096:biosynthesis*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress; D054883:Oxylipins; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics; D018547:Plant Stems / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000494:pharmacology; D013314:Stress, Mechanical; D013395:Sucrose / Q000494:pharmacology
D000085:Acetates; D003517:Cyclopentanes; D054883:Oxylipins; D011993:Recombinant Fusion Proteins; D016718:Arachidonic Acid; D006418:Heme; D013395:Sucrose; C072239:methyl jasmonate; D006861:Hydrogen Peroxide; D008156:Luciferases; D005966:Glucuronidase; D005294:Ferrochelatase; D020156:Salicylic Acid