Hybridization between wild and cultivated potato species in the Peruvian Andes and biosafety implications for deployment of GM potatoes

The nature and extent of past and current hybridization between cultivated potato and wild relatives in nature is of interest to crop evolutionists, taxonomists, breeders and recently to molecular biologists because of the possibilities of inverse gene flow in the deployment of genetically-modified (GM) crops. This research proves that natural hybridization occurs in areas of potato diversity in the Andes, the possibilities for survival of these new hybrids, and shows a possible way forward in case of GM potatoes should prove advantageous in such areas

Identification and functional analysis of pistil self-incompatibility factor HT-B of Petunia

Gametophytic self-incompatibility (GSI) in Solanaceae, Rosaceae, and Plantaginaceae is controlled by a multiallelic S-locus. The specificities of pistil and pollen are controlled by separate S-locus genes, S-RNase and SLF/SFB, respectively. Although the S-specificity is determined by the S-locus genes, factors located outside the S-locus are also required for expression of GSI. HT-B is one of the pistil non-S-factors identified in Nicotiana and Solanum, and encodes a small asparagine/aspartate-rich extracellular protein with unknown biochemical function. Here, HT-B was cloned from Petunia and characterized. The structural features and expression pattern of Petunia HT-B were very similar to those of Nicotiana and Solanum. Unlike other solanaceous species, expression of HT-B was also observed in self-compatible Petunia species. RNA interference (RNAi)-mediated suppression of Petunia HT-B resulted in partial breakdown of GSI. Quantitative analysis of the HT-B mRNA accumulation in the transgenics showed that a 100-fold reduction is not sufficient and a >1000-fold reduction is required to achieve partial breakdown of GSI

CR1 — a dispersed repeated element associated with the Cab-1 locus in tomato

Cab-1 is a complex genetic locus in tomato consisting of four clustered genes encoding chlorophyll a/b-binding polypeptide. Southern blot analysis of total tomato DNA with genomic clones corresponding to the Cab-1 locus has revealed the presence of a repetitive element in the 3 kb spacer regions between two of these genes. This repetitive element, named CR1, has been characterized via sequencing, genetic mapping and hybridization to related solanaceous species. Results indicate that there are as many as 30 copies of this element in the tomato genome and that most, if not all, are found at independent loci. Sites corresponding to 12 of the repeats have been located on different regions of chromosomes 2, 4, 5, 7, 10 and 11. A 1.6 kb Pst I- Eco RI fragment from the Cab-1 locus containing the element was sequenced and found to be 75% AT-rich. No open reading frames larger than 150 bp were detected. Several imperfect inverted repeats flanked by direct repeats could be found at the ends of the element. This arrangement is reminiscent of known transposons. Southern hybridization analysis indicates that multiple copies of CR1 exist in all species of the genus Lycopersicon as well as in Solanum lycopersicoides and S. tuberosum (potato), but not in eggplant, pepper, petunia, Datura or tobacco. Melt-off experiments indicate that members of the CR1 family in the tomato genome are more closely related to one another than to homologous members in the genomes of S. lycopersicoides or S. tuberosum , suggesting some type of concerted evolution.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43418/1/11103_2004_Article_BF00014948.pd

Molecular characterization and genetic mapping of DNA sequences encoding the Type I chlorophyll a/b-binding polypeptide of photosystem I in Lycopersicon esculentum (tomato)

We report the isolation and characterization of a tomato nuclear gene encoding a chlorophyll a/b-binding (CAB) protein of photosystem I (PSI). The coding nucleotide sequence of the gene, designated Cab -6B, is different at eight positions from that of a previously isolated cDNA clone derived from the Cab -6A gene, but the two genes encode identical proteins. Sequence comparison with the cDNA clone revealed the presence of three short introns in Cab -6B. Genetic mapping experiments demonstrate that Cab -6A and Cab -6B are tightly linked and reside on chromosome 5, but the physical distance between the two genes is at least 7 kilobases. Cab -6A and Cab -6B have been designated Type I PSI CAB genes. They are the only two genes of this branch of the CAB gene family in the tomato genome, and they show substantial divergence to the genes encoding CAB polypeptides of photosystem II. The Type I PSI CAB genes, like the genes encoding PSII CAB proteins, are highly expressed in illuminated leaf tissue and to a lesser extent in other green organs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43459/1/11103_2004_Article_BF00166457.pd

Exploring Late Bronze Age systems of bronzework production in Switzerland through Network Science

YesMany hundreds of Bronze Age bronze artefacts are known from excavations in Switzerland, yet the interpretation of production networks from the object find locations remain problematic. It is proposed that the decorative elements used on items, such as ring-jewellery, can be used as elements to assist in the identification of artisanal traditions and ‘schools’, and also regional or community preference and selection of specific designs. Combining the analysis of over 1700 items of ring-jewellery from Switzerland with approaches from network science has facilitated the identification of regional clustering of design elements, comparable with cultural typologies in the area. It is also possible to identify potential instances of cultural differentiation through decoration within the broader regional cultural traditions. The study highlights important facets of bronzework production in the region of Switzerland, while also demonstrating future potential directions which could build upon the European wide dataset of prehistoric bronzework.Primary research conducted under previous funding at University of Basel, Switzerland – SNF gran

Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

The tomato Cab -4 and Cab -5 genes encode a second type of CAB polypeptides localized in Photosystem II

The photosynthetic apparatus of plant chloroplasts contains two photosystems, termed Photosystem I (PSI) and Photosystem II (PSII). Both PSI and PSII contain several types of chlorophyll a/b-binding (CAB) polypeptides, at least some of which are structurally related. It has been previously shown that multiple genes encoding one type of PSII CAB polypeptides exist in the genome of many higher plants. In tomato, there are at least eight such genes, distributed in three independent loci. Genes encoding a second type of CAB polypeptides have been isolated from several plant species, but the precise location of the gene products has not been determined. Here we show that tomato has two unlinked genes encoding this second type and that this type of CAB polypeptide is also localized in PSII.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43458/1/11103_2004_Article_BF00015643.pd

Grafting versus seed propagated apricot populations: two main gene pools in Tunisia evidenced by SSR markers and model-based Bayesian clustering

Apricot was introduced into the Mediterranean Basin from China and Asian mountains through the Middle-East and the Central Europe. Traditionally present in Tunisia, we were interested in accessing the origin of apricot species in the country, and in particular in the number and the location of its introductions. A set of 82 representative apricot accessions including 49 grafted cultivars and 33 seed propagated ‘Bargougs’ were genotyped using 24 microsatellite loci revealing a total of 135 alleles. The model-based Bayesian clustering analysis using both Structure and InStruct programs as well as the multivariate method revealed five distinct genetic clusters. The genetic differentiation among clusters showed that cluster 1, with only four cultivars, was the most differentiated from the four remaining genetic clusters, which constituted the largest part of the studied germplasm. According to their geographic origin, the five identified groups (north, centre, south, Gafsa oasis and other oases groups) enclosed a similar variation within group, with a low level of differentiation. Overall results highlighted the distinction of two apricot gene pools in Tunisia related to the different mode of propagation of the cultivars: grafted and seed propagated apricot, which enclosed a narrow genetic basis. Our findings support the assumption that grafting and seed propagated apricots shared the same origin

A new member of the CAB gene family: structure, expression and chromosomal location of Cab -8, the tomato gene encoding the Type III chlorophyll a/b-binding polypeptide of photosystem I

We have previously reported the isolation and characterization of tomato nuclear genes encoding two types of chlorophyll a/b-binding (CAB) polypeptides localized in photosystem (PS) I and two types of CAB polypeptides localized in PSII. Sequence comparisons shows that all these genes are related to each other and thus belong to a single gene family. Here we report the isolation and characterization of an additional member of the tomato CAB gene family, the single tomato nuclear gene, designated Cab -8, which encodes a third type of CAB polypeptide localized in PSI. The protein encoded by Cab -8 is 65% and 60% divergent from the PSI Type I and Type II CAB polypeptides, respectively. The latter two are 65% divergent from each other. Only some short regions of the polypeptides are strongly conserved. The Cab -8 locus maps to chromosome 10, 9 map units from Cab -7, the gene encoding the Type II PSI CAB polypeptide. The Cab -8 gene contains two introns; the first intron matches in position the single intron in the Type II PSII CAB genes and the second intron matches in position the second intron in the Type II PSI CAB gene. Like other CAB genes, Cab -8 is light-regulated and is highly expressed in the leaf and to a lesser extent in other green organs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43422/1/11103_2004_Article_BF00043203.pd

Restriction fragment length polymorphisms distinguish among accessions of Ceratopteris thalictroides and C. richardii ( Parkeriaceae )

We have used cDNA clones as probes on Southern blots to detect restriction fragment length polymorphisms among seven Ceratopteris thalictroides accessions, three C. richardii accessions, and one putative interspecific hybrid. We found that the stringency of post-hybridization washes was a critical parameter affecting the quality of our blots; even with homologous cDNA sequences low stringency conditions resulted in a smear of signal, but high stringency washes gave blots with distinct bands. Most probes showed hybridization with four or more genomic fragments. Similarities in the number and size of fragments between and within species indicated that (i) C. richardii shows limited polymorphism among accessions tested, (ii) C. thalictroides is highly polymorphic, and (iii) Hawaiian accessions of C. thalictroides are divergent relative to their continental cohorts and among themselves. The putative interspecific hybrid did not group closely with either of these species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41637/1/606_2004_Article_BF00939725.pd