Deficiency of Arabidopsis thaliana frataxin alters activity of mitochondrial Fe–S proteins and induces oxidative stress

BUSI, M. V.; MALIANDI, M. V.; VALDEZ, H.; CLEMENTE, M.; EDUARDO ZABALETA; ARAYA, A.; DIEGO FABIAN GOMEZ CASATI

San Pablo, Brasil

Congreso; XXXVII Annual Meeting of SBBq (Brazilian Biochemistry and Molecular Biology Society) and XI PABMB Congress (Pan- American Association for Biochemistry and Molecular Biology); 2008

SBBq Brazilian Biochemistry and Molecular Biology Society

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Arial; mso-fareast-font-family:"Times New Roman"; color:blue; mso-ansi-language:PT; mso-fareast-language:PT-BR;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The deficiency of frataxin was initially described in patients with Friedreich ataxia, an autosomal recessive neuro- and cardiodegenerative disorder. This disease is caused by a GAA triplet expansion or point mutations in the FRDA gene, resulting in reduced expression of frataxin. The deficit of this protein was associated with mitochondrial iron accumulation, increase sensitivity to oxidative stress and deficit of iron–sulphur protein activities. Frataxin, was recently identified in Arabidopsis thaliana. To investigate the role of frataxin in higher plants, we analyze two knock-out and one knock-down T-DNA insertion mutants. The knock-out mutants present an embryo-lethal phenotype, indicating an essential role for frataxin. The knock-down mutant has reduced frataxin mRNA and protein levels. This mutant also presents retarded growth, reduced fresh weight of fruits and reduced number of seeds per fruit. Surprisingly, transcription of aconitase and the Fe–S subunit of succinate dehydrogenase (SDH2-1) are increased in mutant plants; however, the activity of these proteins is reduced, indicating a role for frataxin in Fe–S cluster assembly or insertion of Fe–S clusters into proteins. Mutant plants also have increased CO2 assimilation rates, exhibit increased formation of reactive oxygen species (ROS), have increased levels of iron and increased levels of transcripts for proteins known to be involved in the ROS stress responses. These results indicate that frataxin is an essential protein in plants, required for full activity of mitochondrial Fe–S proteins and playing a protective role against oxidative damage. Keywords: Arabidopsis, frataxin, mitochondria