Chloroplasts preferentially take up ferric–citrate over iron–nicotianamine complexes in Brassica napus
Fe uptake machinery of chloroplasts prefers to utilise Fe(III)–citrate over Fe–nicotianamine complexes.
Iron uptake in chloroplasts is a process of prime importance. Although a few members of their iron transport machinery were identified, the substrate preference of the system is still unknown. Intact chloroplasts of oilseed rape (Brassica napus) were purified and subjected to iron uptake studies using natural and artificial iron complexes. Fe–nicotianamine (NA) complexes were characterised by 5 K, 5 T Mössbauer spectrometry. Expression of components of the chloroplast Fe uptake machinery was also studied. Fe(III)–NA contained a minor paramagnetic Fe(II) component (ca. 9%), a paramagnetic Fe(III) component exhibiting dimeric or oligomeric structure (ca. 20%), and a Fe(III) complex, likely being a monomeric structure, which undergoes slow electronic relaxation at 5 K (ca. 61%). Fe(II)–NA contained more than one similar chemical Fe(II) environment with no sign of Fe(III) components. Chloroplasts preferred Fe(III)–citrate compared to Fe(III)–NA and Fe(II)–NA, but also to Fe(III)–EDTA and Fe(III)–o,o′EDDHA, and the Km value was lower for Fe(III)-citrate than for the Fe–NA complexes. Only the uptake of Fe(III)–citrate was light-dependent. Regarding the components of the chloroplast Fe uptake system, only genes of the reduction-based Fe uptake system showed high expression. Chloroplasts more effectively utilize Fe(III)–citrate, but hardly Fe–NA complexes in Fe uptake.
KeywordsBathophenanthroline disulfonate Ferric chelate reductase Gene expression Mössbauer spectroscopy Oilseed rape
Multiple antibiotic resistance 1
Permease in chloroplast 1
This work was supported by the grants financed by the National Research, Development and Innovation Office, Hungary (NKFIH PD-112047, PD-111979 and K-124159), VEKOP-2.3.3-15-2016-00008 and the Spanish Ministry of Economy and Competitiveness (MINECO; project AGL2016-75226-R, co-financed with FEDER). Á.S. was also supported by the Bolyai János Research Scholarship of the Hungarian Academy of Sciences (BO/00207/15/4). The authors (JP, LM, and RZ) gratefully acknowledge the financial support provided by the project LO1305 of the Ministry of Education, Youth and Sports of the Czech Republic.
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Conflict of interest
The authors declare no conflict of interest in relation with the submitted manuscript.
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