Effect of Water Stress on Photochemical Activity of Chloroplasts during Greening of Etiolated Barley Seedlings

Water stress retards accumulation of chlorophyll and chlorophylla/b protein complex during greening of barley seedlings in light.The rate of 2,6-dichlorophenol indophenol (DCPIP) photoreductionin isolated chloroplast which decreases under water stress isenhanced significantly in the presence of electron donors, diphenylcarbazide (DPQ) and Mn²⁺. Under water stress, the decrease ofthe rate of oxygen evolution measured in continuous white lightwas 40–73% and that of oxygen uptake (as a measure ofelectron transport through PS I from reduced DCPIP) was onlyabout 20%. During greening, under water stress, (i) a differentialinhibition of PS II biosynthesis as compared to PS I occurs,(ii) the site of electron donation by DPC seems to be closerto the reaction center ofPS II, (iii) the oxidizing side ofPS II near the oxygen-evolving system is affected maximallyby water stress. (Received March 11, 1980; Accepted November 13, 1980)     

Nitrogen Metabolism of Tamarindus indica: Changes in γ-Methyleneglutamine and its Corresponding Acid γ-Methyleneglutamic Acid During Seedling Growth

Changes in γ-methyleneglulamine, a third non-protein amide, γ-methyleneglutamic acid, its corresponding acid, other free aminoacids and amides, and protein and soluble-nitrogen during the seedling growth of tamarind (Tamarindus indica L.), were studied. The changes in the prolein-N content in different parts of the seedling, during growth parallel closely the growth pattern expressed as changes in fresh weight. γ-Meythyleneglutamine is the principal amide during the early stages of seedling growth, but later on when its content starts declining, asparagini’ takes over its function. Thus, γ-methyleneglutamine seems to spare the utilization of amide asparagine, during the early growth period. During later stages of seedling growth, asparagine content also shows a decline, indicating that during this period, asparagine contributes to the protein synthesis and growth. γ-Methyleneglutamic acid was also recorded in large amounts in various parts of the seedling and its concentration was not found to be less than the amide at any stage of seedling growth. The two peaks observed for some of the key aminoacids including γ-methyleneglulamic acid, γ-methylglulamic acid, α-alanine, glutamic acid, aspartic acid, glycine and serine, are interesting, in that the first corresponds to the active growth period of roots and the hypocotyl in the first eleven days, and the second with the active growth of the epicotyl.     

Steroid metabolism in corpora lutea of the western spotted skunk (Spilogale putorius latifrons)

The present study reports steroid metabolism by corpora lutea (CL) obtained from skunks with diapausing embryos ('delay' CL) and with activated embryos (activated CL). CL from both reproductive periods were incubated with various radioactive precursors. Control incubations without any tissue or with 50 microliter of packed skunk blood cells were also conducted simultaneously. Incubation of skunk CL with [3H]-pregnenolone for 3 h resulted in 36% of the precursor accumulating as progesterone. Metabolism of [3H]dehydroepiandrosterone (DHEA) to androstenedione proceeded with approximately the same amount of product accumulating (34-46%) as was observed in the conversion of pregnenolone to progesterone. These results suggest that delta 5 isomerase, 3 beta-hydroxysteroid dehydrogenase, is the most prominent enzyme in skunk CL. Metabolism of [3H]pregnenolone to 17 alpha-hydroxypregnenolone and [3H]progesterone to 17 alpha-hydroxyprogesterone occurred at low rates (1-7%), suggesting the presence of C21 steroid 17 alpha-hydroxylase in skunk CL. Aromatase activity, as estimated by measuring accumulation of oestradiol-17 beta from [3H]testosterone, was demonstrated in activated CL. These results suggest that skunk CL appear to metabolize steroids in a manner similar to CL of other mustelids such as the ferret and American badger.     

An efficient method for in vitro regeneration from immature inflorescence explants of Canadian wheat cultivars

Fertile, green plants were regenerated from immature inflorescence explants from each of four Canadian wheat cultivars. The cultivars were representative of four classes of Canadian wheat. Explants from immature inflorescences of three size ranges were cultured on two types of media: MSI/MSR, which contains 1650 mg l^-1 NH₄NO₃and sucrose as a carbon source, and BII/BIR, which contains 250 mg l^-1 NH₄NO₃and maltose as a carbon source. Regeneration from all cultivars was significantly better on BII/BIR media than on MSI/MSR media. On BII/BIR media, `AC Karma', `Plenty', and `Fielder' gave the highest number of shoots per 10 explants, where the explants were derived from immature inflorescences 5.1 to 10.0 mm in length. 'Columbus' did not regenerate on MSI/MSR medium, and regenerated poorly on BII/BIR medium. Differences were found between cultivars with regard to the number of regenerant plants produced with the best treatments: `Plenty' produced 16.1 shoots per 10 explants, `AC Karma' 12.4, `Fielder' 6.4, and `Columbus' 2.2.     

KIF14 and citron kinase act together to promote efficient cytokinesis

Multiple mitotic kinesins and microtubule-associated proteins (MAPs) act in concert to direct cytokinesis (Glotzer, M. 2005. Science. 307:1735-1739). In anaphase cells, many of these proteins associate with an antiparallel array of microtubules termed the central spindle. The MAP and microtubule-bundling protein PRC1 (protein-regulating cytokinesis 1) is one of the key molecules required for the integrity of this structure (Jiang, W., G. Jimenez, N.J. Wells, T.J. Hope, G.M. Wahl, T. Hunter, and R. Fukunaga. 1998. Mol. Cell. 2:877-885; Mollinari, C., J.P. Kleman, W. Jiang, G. Schoehn, T. Hunter, and R.L. Margolis. 2002. J. Cell Biol. 157:1175-1186). In this study, we identify an interaction between endogenous PRC1 and the previously uncharacterized kinesin KIF14 as well as other mitotic kinesins (MKlp1/CHO1, MKlp2, and KIF4) with known functions in cytokinesis (Hill, E., M. Clarke, and F.A. Barr. 2000. EMBO J. 19:5711-5719; Matuliene, J., and R. Kuriyama. 2002. Mol. Biol. Cell. 13:1832-1845; Kurasawa, Y., W.C. Earnshaw, Y. Mochizuki, N. Dohmae, and K. Todokoro. 2004. EMBO J. 23:3237-3248). We find that KIF14 targets to the central spindle via its interaction with PRC1 and has an essential function in cytokinesis. In KIF14-depleted cells, citron kinase but not other components of the central spindle and cleavage furrow fail to localize. Furthermore, the localization of KIF14 and citron kinase to the central spindle and midbody is codependent, and they form a complex depending on the activation state of citron kinase. Contrary to a previous study (Di Cunto, F., S. Imarisio, E. Hirsch, V. Broccoli, A. Bulfone, A. Migheli, C. Atzori, E. Turco, R. Triolo, G.P. Dotto, et al. 2000. Neuron. 28:115-127), we find a general requirement for citron kinase in human cell division. Together, these findings identify a novel pathway required for efficient cytokinesis.     

Splicing of a critical exon of human Survival Motor Neuron is regulated by a unique silencer element located in the last intron

Humans have two nearly identical copies of the Survival Motor Neuron (SMN) gene, SMN1 and SMN2. In spinal muscular atrophy (SMA), SMN2 is not able to compensate for the loss of SMN1 due to exclusion of exon 7. Here we describe a novel inhibitory element located immediately downstream of the 5' splice site in intron 7. We call this element intronic splicing silencer N1 (ISS-N1). Deletion of ISS-N1 promoted exon 7 inclusion in mRNAs derived from the SMN2 minigene. Underlining the dominant role of ISS-N1 in exon 7 skipping, abrogation of a number of positive cis elements was tolerated when ISS-N1 was deleted. Confirming the silencer function of ISS-N1, an antisense oligonucleotide against ISS-N1 restored exon 7 inclusion in mRNAs derived from the SMN2 minigene or from endogenous SMN2. Consistently, this oligonucleotide increased the levels of SMN protein in SMA patient-derived cells that carry only the SMN2 gene. Our findings underscore for the first time the profound impact of an evolutionarily nonconserved intronic element on SMN2 exon 7 splicing. Considering that oligonucleotides annealing to intronic sequences do not interfere with exon-junction complex formation or mRNA transport and translation, ISS-N1 provides a very specific and efficient therapeutic target for antisense oligonucleotide-mediated correction of SMN2 splicing in SMA.     

Evaluation of chemopreventive action of Ginsenoside Rp1

We evaluated the chemopreventive properties of Ginsenoside Rp1 on 7,12-Dimethyl benz (a) anthracene (DMBA) skin papillomagenesis in Swiss albino mice. A significant reduction in values of tumor incidence, tumor burden, and cumulative number of papilloma was observed in mice treated orally with Ginsenoside Rp1 continuously at pre-, peri- and post-initiational stages of papillomagenesis as compared to the control group. Chemopreventive potential of Ginsenoside Rp1 was also observed on the skin metabolizing enzymes in Swiss albino mice. Ginsenoside Rp1 produced a significant elevation in the skin microsomal cytochrome p-450 and cytochrome b5, glutathione S-transferase (GST), reduced glutathione (GSH), glutathione peroxidase (GPX), glutathione reductase (GR), DT-diaphorase, superoxide dismutase (SOD) and catalase levels in the group of mice treated with Ginsenoside Rp1 for seven consecutive days. However, there was significant decrease in lipid peroxidation (LPO) level in Ginsenoside Rp1 treated group.