Iron uptake of etioplasts is independent from photosynthesis but applies the reduction-based strategy

Frontiers in Plant Science

Plant Science

Levente Illés¹  Sándor Lenk¹  Attila Barócsi¹  Katalin Solymosi²  Csaba Hegedűs³  Ádám Solti³  Éva Sárvári³  Máté Sági-Kazár⁴  Barnabás Cseh⁵  Zoltán May⁶ 

[1] Department of Atomic Physics, Budapest University of Technology and Economics, Budapest, Hungary;Department of Plant Anatomy, Institute of Biology, ELTE Eötvös Loránd University, Budapest, Hungary;Department of Plant Physiology and Molecular Plant Biology, Institute of Biology, ELTE Eötvös Loránd University, Budapest, Hungary;Department of Plant Physiology and Molecular Plant Biology, Institute of Biology, ELTE Eötvös Loránd University, Budapest, Hungary;Doctoral School of Biology, Institute of Biology, ELTE Eötvös Loránd University, Budapest, Hungary;Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, Sweden;Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Eötvös Loránd Research Network, Budapest, Hungary;

关键词: chloroplast;    ferric chelate reductase;    Blue Native polyacrylamide gel electrophoresis;    thylakoid;    x-ray fluorescence imaging;   

DOI  :  10.3389/fpls.2023.1227811

 received in 2023-05-23, accepted in 2023-07-21,  发布年份 2023

来源: Frontiers

【 摘 要 】

IntroductionIron (Fe) is one of themost important cofactors in the photosynthetic apparatus, and its uptake by chloroplasts has also been associated with the operation of the photosynthetic electron transport chain during reduction-based plastidial Fe uptake. Therefore, plastidial Fe uptake was considered not to be operational in the absence of the photosynthetic activity. Nevertheless, Fe is also required for enzymatic functions unrelated to photosynthesis, highlighting the importance of Fe acquisition by non-photosynthetic plastids. Yet, it remains unclear how these plastids acquire Fe in the absence of photosynthetic function. Furthermore, plastids of etiolated tissues should already possess the ability to acquire Fe, since the biosynthesis of thylakoid membrane complexes requires a massive amount of readily available Fe. Thus, we aimed to investigate whether the reduction-based plastidial Fe uptake solely relies on the functioning photosynthetic apparatus.MethodsIn our combined structure, iron content and transcript amount analysis studies, we used Savoy cabbage plant as a model, which develops natural etiolation in the inner leaves of the heads due to the shading of the outer leaf layers.ResultsFoliar and plastidial Fe content of Savoy cabbage leaves decreased towards the inner leaf layers. The leaves of the innermost leaf layers proved to be etiolated, containing etioplasts that lacked the photosynthetic machinery and thus were photosynthetically inactive. However, we discovered that these etioplasts contained, and were able to take up, Fe. Although the relative transcript abundance of genes associated with plastidial Fe uptake and homeostasis decreased towards the inner leaf layers, both ferric chelate reductase FRO7 transcripts and activity were detected in the innermost leaf layer. Additionally, a significant NADP(H) pool and NAD(P)H dehydrogenase activity was detected in the etioplasts of the innermost leaf layer, indicating the presence of the reducing capacity that likely supports the reduction-based Fe uptake of etioplasts.DiscussionBased on these findings, the reduction-based plastidial Fe acquisition should not be considered exclusively dependent on the photosynthetic functions.

【 授权许可】

Unknown   
Copyright © 2023 Sági-Kazár, Sárvári, Cseh, Illés, May, Hegedűs, Barócsi, Lenk, Solymosi and Solti