Synthesis of intraspecific somatic hybrids of Solanum tuberosum: assessments of morphological, biochemical and nematode (Globodera pallida) resistance characteristics

In an attempt to produce novel agronomic traits, a number ofintraspecific somatic hybrid plants have been produced followingleaf mesophyll protoplast fusion between S. tuberosum dihaploidclones PDH 40 (possessing good tuber shape and yield) and PDH417 (possessing resistance to potato cyst nematode, G. pallida).PDH 417 protoplast-derived calli failed to regenerate plantsusing the described culture conditions preventing this parentaltype amongst the mass of regenerated fusion products. Initially,somatic hybrid plants were selected based on differential pigmentationin tuber sprouts and where possible on petal colour. Differentialmobility of patatin bands in electrophoresed tuber extractsfurther confinned hybridity. The intraspecific somatic hybridsalso showed different levels of resistance to G. pallida pathotypesPa2 and Pa3 in the somatic hybrid plants examined. Key words: Somatic hybridization, dihaploids, patatin, nematode resistance, Solanum tuberosum, potato     

Plant regeneration via somatic embryogenesis in chickpea (Cicer arietinum L.)

Efficient plant regeneration via somatic embryogenesis has been developed in chickpea cultivar C235. Leaf explants, on MS medium supplemented with 1.25 mg/l 2,4-D and 0.25 mg/l kinetin, yielded somatic embryos with high efficiency during dark incubation. MS medium supplemented with B₅ vitamins, 0.125 mg/l IBA and 2 mg/l BAP was found suitable for embryo maturation. The well formed embryos germinated into plantlets on basal B₅ medium supplemented with 0.25 mg/l BAP. Further development into healthy plantlets was obtained on basal B₅ medium. Hardened plantlets produced normal, fertile plants upon transfer to soil.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - BAP 6-Benzyl-aminopurine - IAA IndoIe-3-acetic acid - IBA Indole-3-butyric acid - NAA 1-Naphthalene acetic acid - Kinetin 6-furfuryl aminopurine - Zeatin 6-(4-hydroxy-3-methylbut-2-enylamino)-purine     

Inhibition of G1 phase cyclin dependent kinases by transforming growth factor β1

Transforming growth factor β1 (TGFβ1) inhibits epithelial cell proliferation late in the G1 phase of the cell cycle. We examined the effect of TGFβ1 on known late G1 cell cycle regulators in an attempt to determine the molecular mechanism of growth inhibition by this physiological inhibitor. The results demonstrate the TGFβ1 inhibits the late G1 and S phase specific histone H1 kinase activity of p33^cdk2. This inhibitiion is not dur to TGFβ1's effect on p33^cdk2 synthesis, but rather due to its negative effect on the late G1 phosphorylation of p33^cdk2. It is also shown that TGFβ1 inhibits both late G1 cyclin A and cyclin E associated histon H1 kinase activities. The inhibitor has no effects on the synthesis of cyclin E but to inhibit the synthesis of cyclin A protein in a cell cycle dependent manner. If TGFβ1 is added to cells which have progressed futher than 8 hours into G1, then it is without inhibitory effect on cyclin A synthesis. These effect on TGFβ1 on late G1 cell cycle regulators correlate well with its inhibitory effects on cellular growth and suggest that these G1 cyclin dependent kinases might serve as targets for TGFβ1-mediated growth arrest.     

Membrane orientation of laminin binding protein.

Earlier we presented several lines of evidence that a 67-kDa laminin binding protein (LBP) in Leishmania donovani, that is different from the putative mammalian 67-kDa laminin receptor, may play an important role in the onset of leishmaniasis, as these parasites invade macrophages in various organs after migrating through the extracellular matrix. Here we describe the membrane orientation of this Leishmania laminin receptor. Flow cytometric analysis using anti-LBP Ig revealed its surface localization, which was further confirmed by enzymatic radiolabeling of Leishmania surface proteins, autoradiography and Western blotting. Efficient incorporation of LBP into artificial lipid bilayer, as well as its presence in the detergent phase after Triton X-114 membrane extraction, suggests that it may be an integral membrane protein. Limited trypsinization of intact parasite and subsequent immunoblotting of trypsin released material using laminin as primary probe revealed that a major part of this protein harbouring the laminin binding site is oriented extracellularly. Carboxypeptidase Y treatment of the whole cell, as well as the membrane preparation, revealed that a small part of the C-terminal is located in the cytosol. A 34-kDa transmembrane part of LBP could be identified using the photoactive probe, 3-(trifluoromethyl)-3-(m-iodophenyl)diazirine (TID). Partial sequence comparison of the intact protein to that with the trypsin-released fragment indicated that N-terminal may be located extracellularly. Together, these results suggest that LBP may be an integral membrane protein, having significant portion of N-terminal end as well as the laminin binding site oriented extracellularly, a membrane spanning domain and a C-terminal cytosolic end.     

TheTy1-copia group retrotransposons inVicia species: copy number,sequence heterogeneity and chromosomal localisation

We present an in-depth study of theTy1-copia group of retrotransposons within the plant genusVicia, which contains species with widely differing genome sizes. We have compared the numbers and sequence heterogeneities of these genetic elements in three diploidVicia species chosen to represent large (V. faba, 1C=13.3 pg), medium (V. melanops, 1C=11.5 pg) and small (V. sativa, 1C=2.3 pg) genomes within the genus. The copy numbers of the retrotransposons are all high but vary greatly, withV. faba containing approximately 10⁶ copies,V. melanops about 1000 copies andV. sativa 5000 copies. The degree of sequence heterogeneity ofTy1-copia group elements correlates with their copy number within each genome, but neither heterogeneity nor copy number are related to the genome size of the host. In situ hybridization to metaphase chromosomes shows that the retrotransposons inV. faba are distributed throughout all chromosomes but are much less abundant in certain heterochromatic regions. These results are discussed in the context of plant retrotransposon evolution.     

The dialectic between globalization and localization: Economic restructuring,women and strategies of cultural reproduction

Dialectical Anthropology -