Iron and Zinc in the Embryo and Endosperm of Rice (Oryza sativa L.) Seeds in Contrasting 2'-Deoxymugineic Acid/Nicotianamine Scenarios.

Iron and Zn deficiencies are worldwide nutritional disorders that can be alleviated by increasing the metal concentration of rice (Oryza sativa L.) grains via bio-fortification approaches. The overproduction of the metal chelator nicotianamine (NA) is among the most effective ones, but it is still unclear whether this is due to the enrichment in NA itself and/or the concomitant enrichment in the NA derivative 2'-deoxymugineic acid (DMA). The endosperm is the most commonly consumed portion of the rice grain and mediates the transfer of nutrients from vegetative tissues to the metal rich embryo. The impact of contrasting levels of DMA and NA on the metal distribution in the embryo and endosperm of rice seeds has been assessed using wild-type rice and six different transgenic lines overexpressing nicotianamine synthase (OsNAS1) and/or barley nicotianamine amino transferase (HvNAATb). These transgenic lines outlined three different DMA/NA scenarios: (i) in a first scenario, an enhanced NA level (via overexpression of OsNAS1) would not be fully depleted because of a limited capacity to use NA for DMA synthesis (lack of -or low- expression of HvNAATb), and results in consistent enrichments in NA, DMA, Fe and Zn in the endosperm and NA, DMA and Fe in the embryo; (ii) in a second scenario, an enhanced NA level (via overexpression of OsNAS1) would be depleted by an enhanced capacity to use NA for DMA synthesis (via expression of HvNAATb), and results in enrichments only for DMA and Fe, both in the endosperm and embryo, and (iii) in a third scenario, the lack of sufficient NA replenishment would limit DMA synthesis, in spite of the enhanced capacity to use NA for this purpose (via expression of HvNAATb), and results in decreases in NA, variable changes in DMA and moderate decreases in Fe in the embryo and endosperm. Also, quantitative LA-ICP-MS metal map images of the embryo structures show that the first and second scenarios altered local distributions of Fe, and to a lesser extent of Zn. The roles of DMA/NA levels in the transport of Fe and Zn within the embryo are thoroughly discussed.

Arabidopsis nonresponding to oxylipins locus NOXY7 encodes a yeast GCN1 homolog that mediates noncanonical translation regulation and stress adaptation.

Stress adaptation and translational regulation was studied using noxy7 (nonresponding to oxylipins7) from a series of Arabidopsis thaliana mutants. We identified the noxy7 mutation in At1g64790, which encodes a homolog of the yeast translational regulator General Control Nonderepressible1 (GCN1) that activates the GCN2 kinase; GCN2 in turn phosphorylates the α subunit of the translation initiation factor eIF2. This regulatory circuit is conserved in yeast and mammals, in which phosphorylated eIF2α (P-eIF2α) facilitates stress adaptation by inhibiting protein synthesis. In phenotypic and de novo protein synthesis studies with Arabidopsis mutants, we found that NOXY7/GCN1 and GCN2 mediate P-eIF2α formation and adaptation to amino acid deprivation; however, P-eIF2α formation is not linked to general protein synthesis arrest. Additional evidence suggested that NOXY7/GCN1 but not GCN2 regulates adaptation to mitochondrial dysfunction, high boron concentration, and activation of plant immunity to infection by Pseudomonas syringae pv tomato (Pst). In these responses, NOXY7/GCN1 acts with GCN20 to regulate translation in a noncanonical pathway independently of GCN2 and P-eIF2α. These results show the lesser functional relevance of GCN2 and P-eIF2α in plants relative to other eukaryotes and highlight the prominent role of NOXY7/GCN1 and GCN20 in regulation of translation and stress adaptation in plants.

Phytosiderophores determine thresholds for iron and zinc accumulation in biofortified rice endosperm while inhibiting the accumulation of cadmium.

Nicotianamine (NA) and 2'-deoxymugenic acid (DMA) are metal-chelating ligands that promote the accumulation of metals in rice endosperm, but it is unclear how these phytosiderophores regulate the levels of different metals and limit their accumulation. In this study, transgenic rice plants producing high levels of NA and DMA accumulated up to 4-fold more iron (Fe) and 2-fold more zinc (Zn) in the endosperm compared with wild-type plants. The distribution of Fe and Zn in vegetative tissues suggested that both metals are sequestered as a buffering mechanism to avoid overloading the seeds. The buffering mechanism involves the modulation of genes encoding metal transporters in the roots and aboveground vegetative tissues. As well as accumulating more Fe and Zn, the endosperm of the transgenic plants accumulated less cadmium (Cd), suggesting that higher levels of Fe and Zn competitively inhibit Cd accumulation. Our data show that although there is a strict upper limit for Fe (~22.5 µg g-1 dry weight) and Zn (~84 µg g-1 dry weight) accumulation in the endosperm, the careful selection of strategies to increase endosperm loading with essential minerals can also limit the accumulation of toxic metals such as Cd, thus further increasing the nutritional value of rice.

Metal species involved in long distance metal transport in plants.

The mechanisms plants use to transport metals from roots to shoots are not completely understood. It has long been proposed that organic molecules participate in metal translocation within the plant. However, until recently the identity of the complexes involved in the long-distance transport of metals could only be inferred by using indirect methods, such as analyzing separately the concentrations of metals and putative ligands and then using in silico chemical speciation software to predict metal species. Molecular biology approaches also have provided a breadth of information about putative metal ligands and metal complexes occurring in plant fluids. The new advances in analytical techniques based on mass spectrometry and the increased use of synchrotron X-ray spectroscopy have allowed for the identification of some metal-ligand species in plant fluids such as the xylem and phloem saps. Also, some proteins present in plant fluids can bind metals and a few studies have explored this possibility. This study reviews the analytical challenges researchers have to face to understand long-distance metal transport in plants as well as the recent advances in the identification of the ligand and metal-ligand complexes in plant fluids.

Donor cryopreserved rib allografts for chest wall reconstruction.

Reconstruction after large chest wall resections must ensure not only anatomical coverage but a normal respiratory function, specially in the case of associated ventilatory disturbance. Since prosthetic reconstruction can present some problems such as rejection, excessive rigidity or infection, bone grafts have been proposed as an alternative to synthetic materials, due to their effectiveness and capability of integration with host tissues. Although iliac bone allograft or autologous ribs harvested from the opposite operative side are described for reconstruction, we present here the first reported clinical case of donor cryopreserved rib allografts use after extensive chest wall resection in a patient with severe COPD, showing excellent short-term results in the absence of pulmonary function impairment.

Unilateral dichotomy of nipple (intraareolar polythelia) and areola: report of a case and surgical correction.

An unusual case of intraareolar polythelia with two nipples is presented. The dichotomy affected not only the nipple, but also the areola. No other breast malformation existed. Surgical correction was performed by transposition flaps sutured to one another in the center of the areola. The anatomic and functional results were satisfactory.

Reconstruction of chest wall defects after resection of large neoplasms: ten-year experience.

We review our experience in the treatment of complex large chest-wall defects needing a multidisciplinary approach due to primary or secondary neoplasms. Non-small cell lung cancer with chest-wall invasion cases are excluded. Fifteen patients underwent whole thickness resection of the chest wall due to lesions affecting at least three ribs, sternum, clavicle or thoracic spine and the surrounding soft tissue. Previously operated breast cancer and sarcoma were the most frequent diagnoses. Partial or total sternectomy plus rib resection was performed in 8 patients. Immediate closure of the defects was performed in all cases: 12 with single prosthesis placement and 3 with a rigid one of methylmethacrylate. Coverage was achieved using myocutaneous flaps in most cases and, in one case, using the greater omentum that supported a free split-thickness skin graft. No 30-days mortality was recorded. Three patients had a post-operative complication. Mean hospital stay was 11.7+/-9 days. All cases of primary tumours were alive at the time of review (range: 6-126 months). In conclusion, resection and immediate reconstruction of large chest wall defects can be accomplished without operative mortality and low morbidity whenever close cooperation between plastic and thoracic teams exists.