Soybean Ferritin Expression in Saccharomyces cerevisiae Modulates Iron Accumulation and Resistance to Elevated Iron Concentrations

Abstract

Fungi, including the yeast Saccharomyces cerevisiae, lack ferritin and use vacuoles as iron storage organelles. This work explored how plant ferritin expression influenced baker's yeast iron metabolism. Soybean seed ferritin H1 (SFerH1) and SFerH2 genes were cloned and expressed in yeast cells. Both soybean ferritins assembled as multimeric complexes, which bound yeast intracellular iron in vivo and, consequently, induced the activation of the genes expressed during iron scarcity. Soybean ferritin protected yeast cells that lacked the Ccc1 vacuolar iron detoxification transporter from toxic iron levels by reducing cellular oxidation, thus allowing growth at high iron concentrations. Interestingly, when simultaneously expressed in ccc1⌬ cells, SFerH1 and SFerH2 assembled as heteropolymers, which further increased iron resistance and reduced the oxidative stress produced by excess iron compared to ferritin homopolymer complexes. Finally, soybean ferritin expression led to increased iron accumulation in both wild-type and ccc1⌬ yeast cells at certain environmental iron concentrations. IMPORTANCEIron deficiency is a worldwide nutritional disorder to which women and children are especially vulnerable. A common strategy to combat iron deficiency consists of dietary supplementation with inorganic iron salts, whose bioavailability is very low. Ironenriched yeasts and cereals are alternative strategies to diminish iron deficiency. Animals and plants possess large ferritin complexes that accumulate, detoxify, or buffer excess cellular iron. However, the yeast Saccharomyces cerevisiae lacks ferritin and uses vacuoles as iron storage organelles. Here, we explored how soybean ferritin expression influenced yeast iron metabolism, confirming that yeasts that express soybean seed ferritin could be explored as a novel strategy to increase dietary iron absorption. Iron is an essential micronutrient for most living organisms because it participates as a redox cofactor in many metabolic pathways, including respiration, lipid biosynthesis, translation, DNA replication, and photosynthesis. Despite its abundance, iron bioavailability is very low because Fe 3ϩ forms ferric hydroxides that tend to precipitate at a physiological pH. In humans, iron deficiency anemia (IDA) is the most extended and common nutritional disorder worldwide. The World Health Organization estimates that IDA affects approximately one-fourth of the world's population, especially women and children. Consequences of IDA include diminished learning ability in infants, fatigue and reduced physical capacity and work productivity in adults, and poor pregnancy outcomes (reviewed in references 1 and 2). Iron supplementation with ferrous salts is one of the most widely applied strategies to combat IDA. However, such treatment can cause gastric problems like vomiting, faintness, constipation, or diarrhea. Furthermore, inorganic iron induces oxidative changes, and its absorption in the intestine is vastly altered by diet composition. Many studies have demonstrated th...

Fungal–Metal Interactions: A Review of Toxicity and Homeostasis

“…Ferritin is an iron storage protein found in many other eukaryotes, but is not native to fungi [ 122 , 123 , 124 ]. Its effects on increased iron resistance and storage capacity in yeast has been investigated and results indicate that the expression of human, soybean, and tadpole ferritin genes ( HuFH , SFerH1/SFerH2, and TFH , respectively) resulted in the increased ability of yeast to store and carry higher concentration of iron [ 122 , 123 , 124 ]. Llanos et al showed the ability of soybean ferritin genes, SFerH1 and SFerH2, to increase iron resistance in ccc1 Δ mutants [ 122 ].…”

“…Its effects on increased iron resistance and storage capacity in yeast has been investigated and results indicate that the expression of human, soybean, and tadpole ferritin genes ( HuFH , SFerH1/SFerH2, and TFH , respectively) resulted in the increased ability of yeast to store and carry higher concentration of iron [ 122 , 123 , 124 ]. Llanos et al showed the ability of soybean ferritin genes, SFerH1 and SFerH2, to increase iron resistance in ccc1 Δ mutants [ 122 ]. This is significant because, even without the natural vacuolar detoxification system, yeast cells with soybean ferritin were still able to store increased concentrations of iron and evade toxicity.…”

Foliar application of 3‐hydroxy‐4‐pyridinone Fe‐chelate [Fe(mpp) 3 ] induces responses at the root level amending iron deficiency chlorosis in soybean

“…We have shown, under hydroponic conditions, that [Fe(mpp) 3 ] supplementation is associated with increased FERRITIN expression (Santos, Carvalho, et al, 2016; Santos, Leite, et al, 2020) and here, under calcareous standard soil conditions, we observed that this pattern was maintained (Figure 5). The overexpression of FERRITIN in yeast cells upregulated the iron uptake machinery and iron accumulation (de Llanos et al, 2016). In wheat plants, its overexpression enhanced the tolerance to oxidative and iron stresses, ultimately leading to increased leaf Fe content (Zang et al, 2017).…”

Differential accumulation of proteins in oil palms affected by fatal yellowing disease

“…The increase in ferritin expression also occurs in response to oxidative stress, since the excess of Fe generates reactive oxygen species through the Haber-Weiss reaction [ 42 , 43 ]. Increased levels of free Fe in cell is toxic, and the ferritin acts as a detoxification protein [ 36 , 38 , 44 ]. In this study, iron concentrations in the plants were not verified.…”