Riboflavin secretion by Hyoscyamus albus hairy roots under Fe deficiency was examined to determine where riboflavin is produced and whether production occurs via an enhancement of riboflavin biosynthesis or a stimulation of flavin mononucleotide (FMN) hydrolysis. Confocal fluorescent microscopy showed that riboflavin was mainly localized in the epidermis and cortex of the root tip and, at the cellular level, in the apoplast. The expressions of three genes involved in the de novo biosynthesis of riboflavin (GTP cyclohydrolase II/3,6, riboflavin synthase) were compared between Fe-starved and Fe-replete roots over a time course of 7 days, using RT-PCR. All three genes were found to be highly expressed over the period 1-7 days in the roots cultured under Fe deficiency. Since riboflavin secretion began to be detected only from 3 days, there was a lag phase observed between the increased transcript accumulations and riboflavin secretion. To determine whether FMN hydrolysis might contribute to the riboflavin secretion in Fe-deficient root cultures, FMN hydrolase activity was determined and was found to be substantially increased after 3 days, when riboflavin secretion became detectable. These results suggested that not only de novo riboflavin synthesis but also the hydrolysis of FMN contributes to riboflavin secretion under conditions of Fe deficiency. Respiration activity was assayed during the time-course, and was also found to be enhanced after 3 days under Fe deficiency, suggesting a possible link with riboflavin secretion. On the other hand, several respiratory inhibitors were found not to affect riboflavin synthase transcript accumulation.Key words: Hyoscyamus albus; hairy roots; iron deficiency; riboflavin secretion; riboflavin biosynthesis; FMN hydrolase; respiration. RibA: GTP cyclohydrolase II · RibB: 3,4-dihydroxy-2-butanone 4-phosphate synthase · RibC: 6,7-dimethyl-8-ribityllumazine synthase · RibD: riboflavin synthase

Hyoscyamus albus is a well-known source of the tropane alkaloids, hyoscyamine and scopolamine, which are biosynthesized in the roots. To assess the major biochemical adaptations that occur in the roots of this plant in response to iron deficiency, we used a small-scale proteomic approach in which 100 mg of root tips were treated with and without Fe, respectively, for 5 days. Two-dimensional mini gels showed that 48 spots were differentially accumulated between the two conditions of Fe availability and a further 36 proteins were identified from these spots using MALDI-QIT-TOF mass spectrometry. The proteins that showed elevated levels in the roots lacking Fe were found to be associated variously with carbohydrate metabolism, cell differentiation, secondary metabolism, and oxidative defense. Most of the proteins involved in carbohydrate metabolism were increased in abundance, but mitochondrial NAD-dependent malate dehydrogenase was decreased, possibly resulting in malate secretion. Otherwise, all the proteins showing diminished levels in the roots were identified as either Fe-containing or ATP-requiring. For example, a significant decrease was observed in the levels of hyoscyamine 6β-hydroxylase (H6H), which requires Fe and is involved in the conversion of hyoscyamine to scopolamine. To investigate the effects of Fe deficiency on alkaloid biosynthesis, gene expression studies were undertaken both for H6H and for another Fe-dependent protein, Cyp80F1, which is involved in the final stage of hyoscyamine biosynthesis. In addition, tropane alkaloid contents were determined. Reduced gene expression was observed in the case of both of these proteins and was accompanied by a decrease in the content of both hyoscyamine and scopolamine. Finally, we have discussed energetic and Fe-conservation strategies that might be adopted by the roots of H. albus to maintain iron homeostasis under Fe-limiting conditions.

This study was conducted to investigate the relationships between arsenic ( As ) levels in human hair and demographic factors on As accumulation in humans. Hair samples of 619 subjects (383 females and 236 males), including 390 confirmed arsenicosis patients, 11 fish and six vegetable samples were analyzed using the Proton Induced X-ray Emission (PIXE) method. The results revealed that As in hair accumulates in different patterns for males and females in accordance with age. Within patient groups, male patients accumulated higher amounts of As than female patients. For all individuals, middle aged females accumulated higher As amounts in hair than children, adolescents and females over 50 years old, while children, adolescents and males over 50 accumulated higher amounts of As than middle aged males in both villages. Surprisingly, high levels of As concentrations were found in hair samples of those living near safe drinking water in both villages, irrespective of age and sex. There were weak positive correlations between hair As levels and groundwater As levels in both villages. Furthermore, toxic levels of As were found in different kinds of food products. Taken together, these findings demonstrate that As accumulation in hair is dependent not only on water contamination, but also on food contamination.

Intake of heavy metals from contaminated agricultural products represents a significant pathway for human exposure. Banglish village in the Comilla district is one of the most devastated arsenic (As) contaminated areas in Bangladesh. This study focus whether As is solely responsible for causing arsenicosis or whether some other heavy metals have a synergistic effect on the toxicity of As . The study sampled various leafy and non-leafy vegetables and groundwaters were analyzed by using the Proton Induced X-ray Emission (PIXE) method. The results revealed that both the vegetables and the groundwater were highly contaminated with As and lead (Pb) , although the contents in the vegetables and the groundwater varied depending on species and tube wells. As and Pb concentrations in the edible part of all tested vegetables and in groundwater exceeded the permissible intake levels of the Food and Agriculture Organization (FAO) and the World Health Organization (WHO). The findings inferred that the inhabitants of the study area are experiencing health risks resulting from the intake of As and Pb , and that Pb might have a synergistic role with As by aggravating the arsenicosis. The potential health risks due to Pb is being reported for the first time in Bangladesh.

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