ZINC TOLERANCE INDUCED BY IRON 1 reveals the importance of glutathione in the cross-homeostasis between zinc and iron in Arabidopsis thaliana

Zinc is an essential micronutrient for plants, but it is toxic in excess concentrations. In Arabidopsis, additional iron (Fe) can increase Zn tolerance. We isolated a mutant, zinc tolerance induced by iron 1, designated zir1, with a defect in Fe-mediated Zn tolerance. Using map-based cloning and genetic complementation, we identified that zir1 has a mutation of glutamate to lysine at position 385 on γ-glutamylcysteine synthetase (GSH1), the enzyme involved in glutathione biosynthesis. The zir1 mutant contains only 15% of the wild-type glutathione level. Blocking glutathione biosynthesis in wild-type plants by a specific inhibitor of GSH1, buthionine sulfoximine, resulted in loss of Fe-mediated Zn tolerance, which provides further evidence that glutathione plays an essential role in Fe-mediated Zn tolerance. Two glutathione-deficient mutant alleles of GSH1, pad2-1 and cad2-1, which contain 22% and 39%, respectively, of the wild-type glutathione level, revealed that a minimal glutathione level between 22 and 39% of the wild-type level is required for Fe-mediated Zn tolerance. Under excess Zn and Fe, the recovery of shoot Fe contents in pad2-1 and cad2-1 was lower than that of the wild type. However, the phytochelatin-deficient mutant cad1-3 showed normal Fe-mediated Zn tolerance. These results indicate a specific role of glutathione in Fe-mediated Zn tolerance. The induced accumulation of glutathione in response to excess Zn and Fe suggests that glutathione plays a specific role in Fe-mediated Zn tolerance in Arabidopsis. We conclude that glutathione is required for the cross-homeostasis between Zn and Fe in Arabidopsis.     

The Long-Term Health Consequences of Child Physical Abuse,Emotional Abuse,and Neglect: A Systematic Review and Meta-Analysis

Background

Child sexual abuse is considered a modifiable risk factor for mental disorders across the life course. However the long-term consequences of other forms of child maltreatment have not yet been systematically examined. The aim of this study was to summarise the evidence relating to the possible relationship between child physical abuse, emotional abuse, and neglect, and subsequent mental and physical health outcomes.

Methods and Findings

A systematic review was conducted using the Medline, EMBASE, and PsycINFO electronic databases up to 26 June 2012. Published cohort, cross-sectional, and case-control studies that examined non-sexual child maltreatment as a risk factor for loss of health were included. All meta-analyses were based on quality-effects models. Out of 285 articles assessed for eligibility, 124 studies satisfied the pre-determined inclusion criteria for meta-analysis. Statistically significant associations were observed between physical abuse, emotional abuse, and neglect and depressive disorders (physical abuse [odds ratio (OR) = 1.54; 95% CI 1.16–2.04], emotional abuse [OR = 3.06; 95% CI 2.43–3.85], and neglect [OR = 2.11; 95% CI 1.61–2.77]); drug use (physical abuse [OR = 1.92; 95% CI 1.67–2.20], emotional abuse [OR = 1.41; 95% CI 1.11–1.79], and neglect [OR = 1.36; 95% CI 1.21–1.54]); suicide attempts (physical abuse [OR = 3.40; 95% CI 2.17–5.32], emotional abuse [OR = 3.37; 95% CI 2.44–4.67], and neglect [OR = 1.95; 95% CI 1.13–3.37]); and sexually transmitted infections and risky sexual behaviour (physical abuse [OR = 1.78; 95% CI 1.50–2.10], emotional abuse [OR = 1.75; 95% CI 1.49–2.04], and neglect [OR = 1.57; 95% CI 1.39–1.78]). Evidence for causality was assessed using Bradford Hill criteria. While suggestive evidence exists for a relationship between maltreatment and chronic diseases and lifestyle risk factors, more research is required to confirm these relationships.

Conclusions

This overview of the evidence suggests a causal relationship between non-sexual child maltreatment and a range of mental disorders, drug use, suicide attempts, sexually transmitted infections, and risky sexual behaviour. All forms of child maltreatment should be considered important risks to health with a sizeable impact on major contributors to the burden of disease in all parts of the world. The awareness of the serious long-term consequences of child maltreatment should encourage better identification of those at risk and the development of effective interventions to protect children from violence. Please see later in the article for the Editors'' Summary     

A western Eurasian male is found in 2000‐year‐old elite Xiongnu cemetery in Northeast Mongolia

We analyzed mitochondrial DNA (mtDNA), Y‐chromosome single nucleotide polymorphisms (Y‐SNP), and autosomal short tandem repeats (STR) of three skeletons found in a 2,000‐year‐old Xiongnu elite cemetery in Duurlig Nars of Northeast Mongolia. This study is one of the first reports of the detailed genetic analysis of ancient human remains using the three types of genetic markers. The DNA analyses revealed that one subject was an ancient male skeleton with maternal U2e1 and paternal R1a1 haplogroups. This is the first genetic evidence that a male of distinctive Indo‐European lineages (R1a1) was present in the Xiongnu of Mongolia. This might indicate an Indo‐European migration into Northeast Asia 2,000 years ago. Other specimens are a female with mtDNA haplogroup D4 and a male with Y‐SNP haplogroup C3 and mtDNA haplogroup D4. Those haplogroups are common in Northeast Asia. There was no close kinship among them. The genetic evidence of U2e1 and R1a1 may help to clarify the migration patterns of Indo‐Europeans and ancient East‐West contacts of the Xiongnu Empire. Artifacts in the tombs suggested that the Xiongnu had a system of the social stratification. The West Eurasian male might show the racial tolerance of the Xiongnu Empire and some insight into the Xiongnu society. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Iron Is Involved in the Maintenance of Circadian Period Length in Arabidopsis

The homeostasis of iron (Fe) in plants is strictly regulated to maintain an optimal level for plant growth and development but not cause oxidative stress. About 30% of arable land is considered Fe deficient because of calcareous soil that renders Fe unavailable to plants. Under Fe-deficient conditions, Arabidopsis (Arabidopsis thaliana) shows retarded growth, disordered chloroplast development, and delayed flowering time. In this study, we explored the possible connection between Fe availability and the circadian clock in growth and development. Circadian period length in Arabidopsis was longer under Fe-deficient conditions, but the lengthened period was not regulated by the canonical Fe-deficiency signaling pathway involving nitric oxide. However, plants with impaired chloroplast function showed long circadian periods. Fe deficiency and impaired chloroplast function combined did not show additive effects on the circadian period, which suggests that plastid-to-nucleus retrograde signaling is involved in the lengthening of circadian period under Fe deficiency. Expression pattern analyses of the central oscillator genes in mutants defective in CIRCADIAN CLOCK ASSOCIATED1/LATE ELONGATED HYPOCOTYL or GIGANTEA demonstrated their requirement for Fe deficiency-induced long circadian period. In conclusion, Fe is involved in maintaining the period length of circadian rhythm, possibly by acting on specific central oscillators through a retrograde signaling pathway.Metals such as iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), molybdenum, and nickel are essential for the various biological processes that govern plant growth and development (Marschner, 1995). For example, Fe is required for DNA synthesis, photosynthesis, nitrogen fixation, hormone synthesis, and electron transport in the respiratory chain (Briat and Lobreaux, 1997). Similarly, Cu is an important component of electron-transfer reactions mediated by proteins such as superoxide dismutase, cytochrome oxidase, and plastocyanin (Clemens, 2001). Zn is a cofactor for many enzymes, and many proteins contain Zn-binding structural domains (Clarke and Berg, 1998). Although only minimal quantities of these micronutrients are required by plants, their limited availability in soils can significantly hinder crop production and affect nutritional quality (Grotz and Guerinot, 2002). In the case of Fe, about 30% of arable land worldwide is considered calcareous, rendering Fe in these soils unavailable to plants (Mori, 1999). Understanding of the fundamental processes involving metal uptake and sequestration has increased in recent years, but how the availability of particular metals interacts with internal signals to govern the growth and development of plants is largely unknown.The daily biological rhythms of many organisms are regulated by a near 24-h circadian clock that is synchronized by environmental changes such as light and temperature (Harmer, 2009; Imaizumi, 2010). The circadian clock regulates diverse aspects of plant growth and development. The operation of the circadian clock in plants can basically be divided into three main parts, input, central oscillator, and output pathways, and each part has its own complex networks. In Arabidopsis (Arabidopsis thaliana), the central oscillator is composed of a network of multiple feedback loops that can be divided into the morning, central, and evening loops (Harmer, 2009). The central feedback loop is composed of the morning-expressed genes CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) and the evening-expressed gene TIMING OF CAB EXPRESSION1 (TOC1; Schaffer et al., 1998; Wang and Tobin, 1998; Strayer et al., 2000; Alabadí et al., 2001). Although TOC1 is genetically required for the activation of morning genes (Schaffer et al., 1998; Wang and Tobin, 1998; Strayer et al., 2000), it acts as a repressor and directly regulates the expression of CCA1 and LHY (Gendron et al., 2012; Huang et al., 2012; Pokhilko et al., 2012). In the morning loop, CCA1/LHY form another negative feedback loop with the morning genes PSEUDO-RESPONSE REGULATOR7 (PRR7) and PRR9, with PRR9/PRR7 directly repressing the expression of CCA1 and LHY (Farré et al., 2005; Nakamichi et al., 2010). In the evening loop, TOC1 forms a negative feedback loop with GIGANTEA (GI) by repressing its expression, and GI in turn activates the expression of TOC1 through an unknown component, Y (Huq et al., 2000; Mizoguchi et al., 2005). After receiving input signals in the form of environmental cues, the central oscillator of the Arabidopsis circadian clock generates various rhythmic outputs that control various physiological events (Hotta et al., 2007; de Montaigu et al., 2010).The central oscillator controls a range of important physiological output processes such as flowering, stress and hormone responses, and regulation of nutrient acquisition (Haydon et al., 2011). Although the uptake of nutrition in plants is known to be influenced by light and temperature (Lahti et al., 2005; Baligar et al., 2006), the interaction between nutritional status and the circadian clock is less well studied. The homeostasis of Cu is known to influence the regulation of oscillator genes (Andrés-Colás et al., 2010; Peñarrubia et al., 2010). Arabidopsis under excess Cu or overexpressing Cu transporters COPT1 and COPT3 showed increased Cu accumulation and reduced expression of CCA1, LHY, and circadian clock output genes. Defective developmental phenotypes were also observed in these plants. Spatial and temporal control of Cu homeostasis, therefore, may be important for plant environmental fitness (Andrés-Colás et al., 2010). It has also been reported that disordered circadian rhythm affects Fe homeostasis. Tight regulation of Fe homeostasis to maintain an optimal Fe level in plants has been found to be associated with circadian clock regulators such as TIME FOR COFFEE (TIC) that modulates the expression of the ferritin gene AtFer1 (Duc et al., 2009). The expression of AtFer1 was up-regulated with excess Fe. TIC could repress AtFer1 expression under low-Fe conditions in photoperiodic light and dark cycles (Duc et al., 2009). However, whether Fe status feeds back to regulate the circadian clock is uncertain.Although Fe homeostasis in terms of uptake and translocation has been studied for decades, Fe availability is still an agricultural problem worldwide. Revealing the interplay between Fe homeostasis and internal cues such as modulation of the circadian clock can help increase understanding of their contributions to overall plant development. In this work, we investigated the effect of Fe deficiency on the circadian clock and found that it lengthened the circadian period. Our data suggest that the functional status of chloroplasts under Fe deficiency may play a key role in the lengthened circadian period.     

Molecular cloning of the phospholipase D gene from <Emphasis Type="Italic">Streptomyces</Emphasis> sp. YU100 and its expression in <Emphasis Type="Italic">Escherichia coli</Emphasis>

The gene for phospholipase D (PLD) of Streptomyces sp. YU100 was cloned from λ phage library and hetero-logously expressed in Escherichia coli. Using an amplified gene fragment based on the consensus sequences of streptomycetes PLDs, λ phage library of Streptomyces sp. YU100 chromosomal DNA was screened. The sequencing result of BamHI-digested 3.8 kb fragment in a positive phage clone revealed the presence of an open reading frame of a full sequence of PLD gene encoding a 540-amino acid protein including 33-amino acid signal peptide. The deduced amino acid sequence showed a high homology with other Streptomyces PLDs, having the highly conserved ‘HKD’ motifs. The PLD gene excluding signal peptide sequence was amplified and subcloned into a pET-32b(+) expression vector in E. coli BL21(DE3). The recombinant PLD was purified by nickel affinity chromatography and compared the enzyme activity with wild-type PLD. The results imply that the recombinant PLD produced by E. coli had the nearly same enzyme activity as PLD from Streptomyces sp. YU100.     

On the stratigraphy of the reference section of the Upper Mesozoic deposits of Undur-Bogd in southern Mongolia

All successive Cretaceous reference horizons (except the uppermost one) are described in one section, the most complete in Mongolia.     

Glutathione plays an essential role in nitric oxide‐mediated iron‐deficiency signaling and iron‐deficiency tolerance in Arabidopsis

Iron (Fe) deficiency is a common agricultural problem that affects both the productivity and nutritional quality of plants. Thus, identifying the key factors involved in the tolerance of Fe deficiency is important. In the present study, the zir1 mutant, which is glutathione deficient, was found to be more sensitive to Fe deficiency than the wild type, and grew poorly in alkaline soil. Other glutathione‐deficient mutants also showed various degrees of sensitivity to Fe‐limited conditions. Interestingly, we found that the glutathione level was increased under Fe deficiency in the wild type. By contrast, blocking glutathione biosynthesis led to increased physiological sensitivity to Fe deficiency. On the other hand, overexpressing glutathione enhanced the tolerance to Fe deficiency. Under Fe‐limited conditions, glutathione‐deficient mutants, zir1, pad2 and cad2 accumulated lower levels of Fe than the wild type. The key genes involved in Fe uptake, including IRT1, FRO2 and FIT, are expressed at low levels in zir1; however, a split‐root experiment suggested that the systemic signals that govern the expression of Fe uptake‐related genes are still active in zir1. Furthermore, we found that zir1 had a lower accumulation of nitric oxide (NO) and NO reservoir S‐nitrosoglutathione (GSNO). Although NO is a signaling molecule involved in the induction of Fe uptake‐related genes during Fe deficiency, the NO‐mediated induction of Fe‐uptake genes is dependent on glutathione supply in the zir1 mutant. These results provide direct evidence that glutathione plays an essential role in Fe‐deficiency tolerance and NO‐mediated Fe‐deficiency signaling in Arabidopsis.     

A sensitive LC-ESI-Q-TOF-MS method reveals novel phytosiderophores and phytosiderophore-iron complexes in barley

? The direct analysis of phytosiderophores (PSs) and their metal complexes in plants is critical to understanding the biological functions of different PSs. Here we report on a rapid and highly sensitive liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry (LC-ESI-Q-TOF-MS) method for the direct and simultaneous determination of free PSs and their ferric complexes in plants. ? In addition to previously reported PSs - deoxymugineic acid (DMA), mugineic acid (MA) and epihydroxymugineic acid (epi-HMA) - two more PSs, avenic acid (AVA) and hydroxyavenic acid (HAVA), were identified by this method in roots of Hordeum vulgare cv Himalaya and in root exudates under iron (Fe) deficiency. ? The two identified PSs could be responsible for Fe acquisition under Fe deficiency because of their relative abundance and ability to form ferric complexes in secreted root exudates. ? This LC-ESI-Q-TOF-MS method greatly facilitates the identification of free PSs and PS-Fe complexes in one plant sample.