IntroductionChloroplasts are organelles of endosymbiotic origin. During evolution most of the genes from the endosymbiont were transferred to the host nucleus. Today more than 95% of the chloroplast proteome is nuclear encoded. Pre-proteins are synthesized in the cytosol and post translationally imported into the organelle (Chen and Schnell, 1999;Keegstra and Froehlich, 1999;Bauer et al., 2001;Soll, 2002). In most cases pre-proteins are synthesized with an NH2-terminal presequence also called targeting signal. The pre-sequence is both necessary and sufficient for organellar targeting and translocation initiation. Upon import the pre-sequence is proteolytically removed by the stromal processing peptidase (Oblong and Lamppa, 1992) and the protein can attain its native conformation. Chloroplast pre-sequences seem to share little common sequence motifs or secondary structure (v. Heijne and Nishikawa, 1991). The NH2-proximal part is normally devoid of negatively charged amino acids and the central domain is rich in the hydroxylated amino acids serine and threonine. The C-proximal region can form a β-sheet structure, which includes the processing site. The pre-sequence is recognized at the chloroplast surface by receptors, which are integral subunits of the Toc-complex (translocon at the outer envelope of chloroplast) (Hirsch et al., 1994;Kessler et al., 1994;Schnell et al., 1994;. The Toc complex has three distinct core subunits, the GTP-dependent Toc34 receptor (Hirsch et al., 1994;Kessler et al., 1994;, a β-barrel type import channel Toc75 Tranel et al., 1995;Hinnah et al., 1997) and a GTP-dependent receptor and motor protein Toc159 (Hirsch et al., 1994;Kessler et al., 1994;Ma et al., 1996;Schleiff et al., 2003). Binding to and translocation across the Toc-complex is GTP dependent (Schleiff et al., 2003). Import across the inner envelope is facilitated by the Tic-complex and requires ATP in the stroma, most likely for the action of molecular chaperones (Flügge and Hinz, 1986;Schindler et al., 1987;Theg et al., 1989). The Tic complex is composed of several subunits: Tic110 and Tic20, which may form an import channel (Kouranov et al., 1998;Heins et al., 2002); Tic40 as a chaperone coordinating factor on the stromal site of the envelope (Stahl et al., 1999;Chou et al., 2003); Tic22 as an intermembrane space factor (Kouranov, 1998) and finally the redox proteins Tic62 and Tic55 (Caliebe et al., 1997;Küchler et al., 2002). ATP concentrations above 50 µM are generally required to complete import of a standard precursor protein into chloroplasts (Flügge and Hinz, 1986;Schindler et al., 1987;Theg et al., 1989). ATP hydrolysis by molecular chaperones such as HSP93 or HSP70 is thought to provide the driving force for the final membrane passage (Nielsen et al., 1997). Proteins of the outer envelope are generally targeted and inserted into the membrane by internal sequence information and they therefore do not contain a cleavable pre-sequence (Schleiff and Klösgen, 2001). No auxiliary factor or helper protein has been identif...

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Maternal IDA wields a significant influence on maternal and fetal nutritional status. IDA during pregnancy adversely affects both cord blood iron and breast milk mineral status, particularly in moderate to severe anemia and concurrent micronutrient deficiencies occur in maternal IDA. Further investigations including larger population of pregnant women with severe anemia are needed to verify the nutritional interrelation between maternal anemia and breast milk mineral status.

Radiotherapy is a major factor contributing to female infertility by inducing premature ovarian failure (POF). Therefore, the need for an effective radioprotective agent is evident. The present study investigated the mechanism of potential radioprotective effect of sodium selenite on radiation-induced ovarian failure and whether sodium selenite can stimulate in-vivo follicular development in experimental rats. Immature female Sprague-Dawely rats were either exposed to gamma-radiation (3.2 Gy, LD20), once and/or treated with sodium selenite (0.5 mg/kg), once daily for one week before irradiation. Follicular and oocyte development, apoptotic markers, proliferation marker as well as oxidative stress markers were assessed 24-h after irradiation. In addition, fertility assessment was performed after female rats became completely mature at two months of age. Sodium selenite significantly enhanced follicular development as compared to the irradiated group. Sodium selenite significantly reversed the oxidative stress effects of radiation that was evidenced by increasing in lipid peroxide level and decreasing in glutathione level, and glutathione peroxidase (GPx) activity. Assessment of apoptosis and cell proliferation markers revealed that caspase 3 and cytochrome c expressions markedly-increased, whereas, PCNA expression markedly-decreased in the irradiated group; in contrast, sodium selenite treatment prevented these alterations. Histopathological examination further confirmed the radioprotective efficacy of sodium selenite and its in-vivo effect on ovarian follicles’ maturation. In conclusion, sodium selenite showed a radioprotective effect and improved folliculogenesis through increasing ovarian granulosa cells proliferation, estradiol and FSH secretion, and GPx activity, whilst decreasing lipid peroxidation and oxidative stress, leading to inhibition of the apoptosis pathway through decreasing the expressions of caspase 3 and cytochrome c.

Regulated intramembrane proteolysis (RIP) is a fundamental mechanism for controlling a wide range of cellular functions. Cleavage of membrane embedded proteins results in soluble fragments exerting their function, e.g., as transcription factors and thereby regulating gene expression. This process is highly conserved throughout all kingdom of life as are the involved proteases. RIP has been described in eukaryotes, bacteria and archea though until recently not in plant organelles. Here we describe a chloroplastic membrane protease which belongs to the conserved S2P family of membrane metallo proteases. We show that this protease is localized in the inner envelope membrane and is essential for plant development. It could function in a RIP like process regulating the concordant action in the plant cytosol, nucleus and plastids.