Summary: Only graminaceous monocots possess the Strategy II iron (Fe)‐uptake system in which Fe is absorbed by roots as an Fe³⁺‐phytosiderophore. In spite of being a Strategy II plant, however, rice (Oryza sativa) contains the previously identified Fe²⁺ transporter OsIRT1. In this study, we isolated the OsIRT2 gene from rice, which is highly homologous to OsIRT1. Real‐time PCR analysis revealed that OsIRT1 and OsIRT2 are expressed predominantly in roots, and these transporters are induced by low‐Fe conditions. When expressed in yeast (Saccharomyces cerevisiae) cells, OsIRT2 cDNA reversed the growth defects of a yeast Fe‐uptake mutant. This was similar to the effect of OsIRT1 cDNA. OsIRT1– and OsIRT2–green fluorescent protein fusion proteins localized to the plasma membrane when transiently expressed in onion (Allium cepa L.) epidermal cells. OsIRT1 promoter–GUS analysis revealed that OsIRT1 is expressed in the epidermis and exodermis of the elongating zone and in the inner layer of the cortex of the mature zone of Fe‐deficient roots. OsIRT1 expression was also detected in the ccompanion cells. Analysis using the positron‐emitting tracer imaging system showed that rice plants are able to take up both an Fe³⁺‐phytosiderophore and Fe²⁺. This result indicates that, in addition to absorbing an Fe³⁺‐phytosiderophore, rice possesses a novel Fe‐uptake system that directly absorbs the Fe²⁺, a strategy that is advantageous for growth in submerged conditions.

Serum albumin is the most abundant circulating protein in mammals including humans. It has three isoforms according to the redox state of the free cysteine residue at position 34, named as mercaptalbumin (reduced albumin), non-mercaptalbumin-1 and -2 (oxidized albumin), respectively. The serum albumin redox state has long been viewed as a biomarker of systemic oxidative stress, as the redox state shifts to a more oxidized state in response to the severity of the pathological condition in various diseases such as liver diseases and renal failures. However, recent ex vivo studies revealed oxidized albumin per se could aggravate the pathological conditions. Furthermore, the possibility of the serum albumin redox state as a sensitive protein nutrition biomarker has also been demonstrated in a series of animal studies. A paradigm shift is thus ongoing in the research field of the serum albumin. This article provides an updated overview of analytical techniques for serum albumin redox state and its association with human health, focusing on recent findings.

Pasteurized donor human milk (HM) serves as the best alternative for breast-feeding when availability of mother’s milk is limited. Pasteurization is also applied to mother’s own milk for very low birth weight infants, who are vulnerable to microbial infection. Whether pasteurization affects protein digestibility and therefore modulates the profile of bioactive peptides released from HM proteins by gastrointestinal digestion, has not been examined to date. HM with and without pasteurization (62.5 °C for 30 min) were subjected to in vitro gastrointestinal digestion, followed by peptidomic analysis to compare the formation of bioactive peptides. Some of the bioactive peptides, such as caseinophosphopeptide homologues, a possible opioid peptide (or propeptide), and an antibacterial peptide, were present in undigested HM and showed resistance to in vitro digestion, suggesting that these peptides are likely to exert their bioactivities in the gastrointestinal lumen, or be stably transported to target organs. In vitro digestion of HM released a large variety of bioactive peptides such as angiotensin I-converting enzyme-inhibitory, antioxidative, and immunomodulatory peptides. Bioactive peptides were released largely in the same manner with and without pasteurization. Provision of pasteurized HM may be as beneficial as breast-feeding in terms of milk protein-derived bioactive peptides.

Albumin is the major protein in the serum of mammals. It is synthesized exclusively in the liver, before being secreted into the circulation. Similar to skeletal muscle protein, albumin synthesis is stimulated by dietary amino acids and proteins as well as exercise. Albumin has three isoforms based on the redox states of the free cysteine residue at position 34. The redox state of serum albumin has long been extensively investigated in terms of oxidative stress-related chronic diseases, with the redox state of serum albumin having been regarded as a marker of systemic oxidative stress. However, according to recent animal studies, the redox state of serum albumin is modulated by albumin turnover and may also reflect amino acid/protein nutritional status. Furthermore, as the redox state of serum albumin is modulated by exercise training, measuring the pre- and post-exercise redox states of serum albumin in athletes may be useful in assessing amino acid/protein nutritional status and exercise-induced oxidative stress, which are closely associated with skeletal muscle adaptive responses. This article extensively reviews serum albumin and the redox state of albumin in the context of amino acid/protein nutritional status and exercise training.