Biomedical subjects

J W Todd

Publications and source records attributed to J W Todd.

At least 19 recordsLinked to original sources

PubMed2003

Epidemiology and management of tomato spotted wilt in peanut.

Tomato spotted wilt caused by thrips-vectored tomato spotted wilt virus (TSWV) is a very serious problem in peanut (Arachis hypogaea L.) production. TSWV and the thrips Frankliniella fusca and Frankliniella occidentalis, which vector the virus, present a difficult and complicated challenge from the perspectives of both epidemiology and disease management. Simply controlling the vector typically has not resulted in control of spotted wilt. No single measure can currently provide adequate control of spotted wilt where severe epidemics occur. However, interdisciplinary investigations have resulted in development of integrated management systems that make use of moderately resistant cultivars and chemical and cultural practices, each of which helps to suppress spotted wilt epidemics. Such systems have been successfully deployed in many areas for minimizing losses to this disease. The development of a spotted wilt risk index has aided greatly in relaying information on the importance of using an integrated approach for managing this disease.

Arachis↗

PubMed1996

Factors regulating baculovirus late and very late gene expression in transient-expression assays.

Eighteen genes of Autographa californica nuclear polyhedrosis virus are necessary and sufficient to transactivate expression from the late vp39 promoter in transient-expression assays in SF-21 cells. These 18 genes, known as late expression factor genes (lefs), are also required to transactivate the very late promoter of the polyhedrin gene, polh, but expression from this promoter is relatively weak compared with expression from the vp39 promoter. To further define the factors required for late and very late promoter expression, we first determined that the eighteen lefs were also required for expression from two other major baculovirus promoters: the late basic 6.9-kDa protein gene, p6.9, and the very late 10-kDa protein gene, p10. We next examined the effect of the very late expression factor 1 gene (vlf-1), a gene previously identified by analysis of a temperature-sensitive mutant, in the transient expression assay and found that vlf-1 specifically transactivated the two very late promoters but not the two late promoters. We then surveyed the Autographa californica nuclear polyhedrosis virus genome for additional genes which might specifically regulate very late gene expression; no additional vlf genes were detected, suggesting that VLF-1 is the primary regulator of very late gene expression. Finally, we found that the relative contribution of the antiapoptosis gene p35, which behaves as a lef in these transient-expression assays, depended on the nature of the other viral genes provided in the cotransfection mixtures, suggesting that other viral genes also contribute to the ability of the virus to block apoptosis.

Animals↗

PubMed1995

Eighteen baculovirus genes, including lef-11, p35, 39K, and p47, support late gene expression.

We report the identification of four additional genes of the Autographa californica nuclear polyhedrosis virus involved in expression from a late baculovirus promoter in transient expression assays. Three of these genes, p35, 39K, and p47, have been previously described. The role of the p35 gene product in late gene expression may be related to its ability to block apoptosis, since two other baculovirus genes also known to block apoptosis, Cp-iap and Op-iap, were able to functionally replace p35 in the transient expression assay. The requirement for p47 in this assay confirms its role in late gene expression, a role previously established by characterization of a temperature-sensitive mutant of p47, while the requirement for 39K may be related to its known association with the virogenic stroma. The fourth gene identified as a late expression factor gene, lef-11, was located immediately upstream of 39K and is predicted to encode a 13-kDa polypeptide. When plasmids containing these 4 genes were cotransfected with plasmids containing the 14 genes previously identified as late gene expression factors, the level of expression from the late capsid promoter was similar to that observed for a library of clones representing the entire viral genome. The genes provided by these 18 plasmids thus represent the viral genes necessary and sufficient to support expression from a late viral promoter in this transient expression assay.

Animals↗

PubMed1994

Identification of lef-7: a baculovirus gene affecting late gene expression.

We have examined a 15-kb region of the Autographa californica nuclear polyhedrosis virus (AcMNPV) genome, from 66 to 78 map units, for the presence of genes which transactivate expression from late and very late viral promoters in transient expression assays. One gene in this region activated reporter gene expression approximately six- to eightfold when the reporter gene was under the control of the late promoter of the major capsid protein gene, vp39, or the very late promoter of the polyhedrin gene, polh, but not when the reporter gene was under the control of the early promoter of etl, a homolog of proliferating cell nuclear antigen. The sequence of the predicted polypeptide product of this gene, lef-7, shared no obvious sequence homology to other sequences in available databases. Transcriptional analysis indicated that lef-7 was transcribed early in infection from an initiation site 14 to 16 bp upstream of the putative translational start site and was also transcribed late in infection from an initiation site(s) further upstream. The lef-7 promoter and the promoter of another previously defined late expression factor, lef-3, were both dependent on the multifunctional transregulatory gene, ie-1, for activity in transient expression assays. While sequencing the region of the AcMNPV genome containing lef-7, we also found a 215-codon open reading frame (ORF-215) approximately 1 kb downstream of lef-7 with sequence homology to eIF2 alpha kinases (e.g., rabbit eIF2 alpha and yeast GCN-2 kinase). However, only the six C-terminal conserved domains of protein kinases were present in the predicted ORF-215 product and several of these domains varied from the consensus sequence. ORF-215 did not strongly influence expression from the vp39 promoter-controlled reporter gene in the transient expression assays employed.

Animals↗

PubMed1994

A baculovirus gene involved in late gene expression predicts a large polypeptide with a conserved motif of RNA polymerases.

We have identified and sequenced a novel baculovirus gene, late expression factor eight gene (lef-8), of Autographa californica nuclear polyhedrosis virus that is necessary for efficient expression from late and very late virus gene promoters in a transient expression assay. The predicted gene product, LEF-8, has a molecular mass of 102 kDa and contains a conserved sequence motif, GXKX4HGQ/NKG, found in DNA-directed RNA polymerases throughout the animal, plant, and microbial kingdoms.

Amino Acid Sequence↗

PubMed1987