Richard A. Jorgensen

Bio: Richard A. Jorgensen is an academic researcher from University of Arizona. The author has contributed to research in topics: Gene & Cosuppression. The author has an hindex of 42, co-authored 77 publications receiving 21733 citations. Previous affiliations of Richard A. Jorgensen include University of Wisconsin-Madison & University of California, Davis.

Conditional Male Fertility in Chalcone Synthase-Deficient Petunia

Abstract: Transgenic petunia plants with suppressed chalcone synthase gene expression produce abnormal anthers devoid of flavonoid pigments Although viable pollen is produced , pollen germination and tube growth are severely reduced both in vivo and in vitro This results in plants that are self-sterile Pollen from the transgenic plants is partially rescued by Inbred V 26 stigmas, resulting in seed set that is approximately 30 % of normal Female fertility in the transgenic petunia is unaffected by the lack of flavonoids We propose the term conditional male fertility (CMF) to describe the state in which viable but flavonoid-deficient pollen does not function in self-crosses and is partially functional on wild-type stigmas Although this condition has attributes of both male sterility and self-incompatibility, it is clearly different This observation in petunia has similarities to the earlier report of Coe et al (1981) that most polli-nations made with chalcone synthase (CHS)-deficient maize pollen were unsuccessful The possibility that normal development of the male gametophyte requires flavonoid synthesis in many or all higher plants is discussed The dominant CHS deficiency and male sterility in petunia, taken together with the recessive CHS deficiency and male sterility in maize, suggest that flavonoid synthesis in the sporophyte rather than the gametophyte is required for fertility. (Jorgensen) We gratefully acknowledge Florigene for providing plant material. We thank Howard Grimes and Vincent Franceschi for their expert advice and assistance with photomicros-co PY through NSF (Dir 9016138) Plant Biology Light icroscope and Image Analysis Facility We acknowledge the helpful suggestions of Thomas Sims Carolyn Failla and Darrell Strenge provided excellent technical S Upport Address reprint requests to I P Taylor at the address above. Ten years ago a maize mutant producing nonfunctional white rather than yellow pollen was isolated and characterized (Coe et al 1981) The white pollen mutant sheds normal amounts of nonpigmented pollen, which germinates on the silk, but no seed is set after most pollinations The condition is sporophytically determined by the expression of stable recessive mutations at the two chalcone synthase (CHS) genes in maize, C 2 and Whp CHS catalyzes the rate-limiting step in flavonoid production, and there is a report, but no published data, that the mutant pollen has no detectable flavonoids (Coe et al 1981) Fla-vonoids are ubiquitous plant natural products that include visible pigments (anthocyanins and chalcones), as well as colorless UV-absorbing compounds (fla-vonols, flavonones, and flavones) The first committed step in …

T-DNA structure and gene expression in petunia plants transformed by Agrobacterium tumefaciens C58 derivatives

Abstract: We have previously described substantial variation in the level of expression of two linked genes which were introduced into transgenic petunia plants using Agrobacterium tumefaciens. These genes were (i) nopaline synthase (nos) and (ii) a chimeric chlorophyll a/b binding protein/octopine synthase (cab/ocs) gene. In this report we analyze the relationship between the level of expression of the introduced genes and T-DNA structure and copy number in 40 transgenic petunia plants derived from 26 transformed calli. Multiple shoots were regenerated from 8 of these calli and in only 6 cases were multiple regenerated shoots from each callus genotypically identical to each other. Many genotypes showed no nos gene expression (22/28). Most of the plants (16/22) which lacked nos gene expression did contain nos-encoding DNA with the expected restriction enzyme map. Similarly, amongst the genotypes showing no cab/ocs gene expression, the majority (11/28) did not show any alterations in restriction fragments corresponding to the expected cab/ocs coding sequences (10/11). Approximately half of the plants carried multiple copies of T-DNA in inverted repeats about the left or right T-DNA boundaries. No positive correlation was observed between the copy number of the introduced DNA and the level of expression of the introduced genes. However, plants with high copy number complex insertions composed of multiple inverted repeats in linear arrays usually showed low levels of expression of the introduced genes.

Identification of novel conserved peptide uORF homology groups in Arabidopsis and rice reveals ancient eukaryotic origin of select groups and preferential association with transcription factor-encoding genes

Abstract: Upstream open reading frames (uORFs) can mediate translational control over the largest, or major ORF (mORF) in response to starvation, polyamine concentrations, and sucrose concentrations. One plant uORF with conserved peptide sequences has been shown to exert this control in an amino acid sequence-dependent manner but generally it is not clear what kinds of genes are regulated, or how extensively this mechanism is invoked in a given genome. By comparing full-length cDNA sequences from Arabidopsis and rice we identified 26 distinct homology groups of conserved peptide uORFs, only three of which have been reported previously. Pairwise K a /K s analysis showed that purifying selection had acted on nearly all conserved peptide uORFs and their associated mORFs. Functions of predicted mORF proteins could be inferred for 16 homology groups and many of these proteins appear to have a regulatory function, including 6 transcription factors, 5 signal transduction factors, 3 developmental signal molecules, a homolog of translation initiation factor eIF5, and a RING finger protein. Transcription factors are clearly overrepresented in this data set when compared to the frequency calculated for the entire genome (p = 1.2 × 10-7). Duplicate gene pairs arising from a whole genome duplication (ohnologs) with a conserved uORF are much more likely to have been retained in Arabidopsis (Arabidopsis thaliana) than are ohnologs of other genes (39% vs 14% of ancestral genes, p = 5 × 10-3). Two uORF groups were found in animals, indicating an ancient origin of these putative regulatory elements. Conservation of uORF amino acid sequence, association with homologous mORFs over long evolutionary time periods, preferential retention after whole genome duplications, and preferential association with mORFs coding for transcription factors suggest that the conserved peptide uORFs identified in this study are strong candidates for translational controllers of regulatory genes.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

A broad host range mobilization system for in vivo genetic engineering: transposon mutagenesis in Gram negative bacteria

Abstract: We have developed a new vector strategy for the insertion of foreign genes into the genomes of gram negative bacteria not closely related to Escherichia coli. The system consists of two components: special E. coli donor strains and derivatives of E. coli vector plasmids. The donor strains (called mobilizing strains) carry the transfer genes of the broad host range IncP–type plasmid RP4 integrated in their chromosomes. They can utilize any gram negative bacterium as a recipient for conjugative DNA transfer. The vector plasmids contain the P–type specific recognition site for mobilization (Mob site) and can be mobilized with high frequency from the donor strains. The mobilizable vectors are derived from the commonly used E. coli vectors pACYC184, pACYC177, and pBR325, and are unable to replicate in strains outside the enteric bacterial group. Therefore, they are widely applicable as transposon carrier replicons for random transposon insertion mutagenesis in any strain into which they can be mobilized but not stably maintained. The vectors are especially useful for site–directed transposon mutagenesis and for site–specific gene transfer in a wide variety of gram negative organisms.

The Carbohydrate-Active EnZymes database (CAZy): an expert resource for Glycogenomics

Abstract: The Carbohydrate-Active Enzyme (CAZy) database is a knowledge-based resource specialized in the enzymes that build and breakdown complex carbohydrates and glycoconjugates. As of September 2008, the database describes the present knowledge on 113 glycoside hydrolase, 91 glycosyltransferase, 19 polysaccharide lyase, 15 carbohydrate esterase and 52 carbohydrate-binding module families. These families are created based on experimentally characterized proteins and are populated by sequences from public databases with significant similarity. Protein biochemical information is continuously curated based on the available literature and structural information. Over 6400 proteins have assigned EC numbers and 700 proteins have a PDB structure. The classification (i) reflects the structural features of these enzymes better than their sole substrate specificity, (ii) helps to reveal the evolutionary relationships between these enzymes and (iii) provides a convenient framework to understand mechanistic properties. This resource has been available for over 10 years to the scientific community, contributing to information dissemination and providing a transversal nomenclature to glycobiologists. More recently, this resource has been used to improve the quality of functional predictions of a number genome projects by providing expert annotation. The CAZy resource resides at URL: http://www.cazy.org/.