The assembly of Fe cofactors in plants

Lead Research Organisation: John Innes Centre
Department Name: Contracts Office

Abstract

Janneke Balk leads a research group studying the biogenesis of iron-sulfur (Fe-S) proteins in plants, algae and fungi. She has previously characterized several proteins involved in the assembly of iron-sulfur cofactors, however key questions such as the source of iron, and the chemical nature of the mitochondrial-cytoplasmic link remain to be answered.

Objectives
1. Characterize new genes required for Fe-S protein biogenesis in (crop) plants. Candidate genes from our previous work will be investigated for their in-planta and in-vitro functions. The model organism will be Arabidopsis, but legumes (Lotus, Medicago) will also be studied.
2. Determine the substrate of the mitochondrial ATP-binding cassette transporters (ATMs). The ATM3 transporter in Arabidopsis was shown to have a similar function as the yeast Atm1p and human ABCB7, in that they are required for the assembly of Fe-S clusters in the cytosol. Using a combination of in-vitro and in-vivo studies, we will focus on sulfur compounds as the putative substrate of the “ATMs” to unravel in what form they are transported (BBSRC BB/H0028X/1).
3. Iron storage and mobilization in seeds. Iron is stored in seeds in either the vacuole or the protein complex ferritin, and is rapidly mobilized upon germination for the benefit of the germinating seedling. Our aim is to obtain a better understanding of both Fe storage and mobilization for incorporation into iron cofactors, and how these processes are regulated. Model species are Arabidopsis, wheat and pulses. Iron will be visualized in situ using 3D spectroscopy or microscopy techniques, and the dominant Fe proteins will be identified using proteomics. The knowledge is important for improving germination in the field, iron fertilization of soils, and for seeds as a source of minerals for human nutrition.

Publications

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Balk J (2014) Iron cofactor assembly in plants. in Annual review of plant biology

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Bernard DG (2013) Requirements of the cytosolic iron-sulfur cluster assembly pathway in Arabidopsis. in Philosophical transactions of the Royal Society of London. Series B, Biological sciences

 
Description We have discovered two genes involved in storing iron in a sub-cellular compartment, the vacuole. We have used one the two genes to develop wheat with 2-fold increased iron in the endosperm, the part of the grain that is milled to white flour. We also showed that the iron in white flour of these lines is more bioavailable to human gut cells in vitro (Connorton et al 2017 Plant Physiol). In a separate project, we have characterized the gene for the first step of molybdenum cofactor assembly in plants, named CNX2, which encoded an iron-sulphur binding protein (Kruse et al 2018 Biochem J). Through collaborations we have also elucidated the biological role of Erv1 (Ozer et al 2015 J Biol Chem) and Grxs17 (Knuesting et al 2015 Plant Physiol).
Exploitation Route High iron wheat can be milled and used in the baking industry, or for breakfast cereals. Currently, chemical forms of iron are added during the milling process and to breakfast cereals, but this won't be necessary if wheat contains more iron.
Sectors Agriculture, Food and Drink

 
Description Our research on iron in peas facilitated the award of a NIBB business voucher to work with a company interested in developing pea flour for the "free from" market. I also gave a 10 minute invited presentation at an APPG meeting on bio-fortification of crops at the Houses of Parliament (February 2015).
First Year Of Impact 2015
Sector Agriculture, Food and Drink
Impact Types Economic

 
Description APPG attendance
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a advisory committee
Impact The policy brief to improve the nutritional quality of staple foods through biofortification is starting to have a huge impact globally. Asia and Africa are the main benefactors, although the impact differs from country to country. An important policy change is that biofortification could include genetic engineering, and not just breeding.
 
Description Yeast glutathione 
Organisation University of South Carolina
Country United States 
Sector Academic/University 
PI Contribution My research team provided data on sulfite reductase activity and isopropyl malate isomerase. I was also involved in writing the manuscript.
Collaborator Contribution The partner provided the initial results for the manuscript and was senior author.
Impact Manuscript, PMID: 26396185
Start Year 2012
 
Title NUBPL mutations 
Description We have shown that a yeast model, Yarrowia lipolytica, can be used to test pathogenicity of mutations in the human NUBPL gene. 
Type Diagnostic Tool - Non-Imaging
Current Stage Of Development Refinement. Non-clinical
Year Development Stage Completed 2018
Development Status Actively seeking support
Impact The most notable impact is that when patients with likely pathogenic mutations in NUBPL are identified through whole genome sequencing, the pathogenicity of certain mutants, esp. non-synonymous mutations, can be confirmed in a yeast model. This is important because filtering of SNPs may lead to the wrong conclusion. 
URL https://www.ncbi.nlm.nih.gov/pubmed/23828044
 
Description NUBPL fundraising event 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Patients, carers and/or patient groups
Results and Impact Presentation on progress in research on the NUBPL gene, for a patient group and clinicians. The main outcome is fundraising by the patient group for this research (to labs in the US, not my own lab).
Year(s) Of Engagement Activity 2017