No description available.

To study resistance (R) genes that are expressed when Sophrolaeliacattleya Ginny Champion 'Riverbend' orchid tissue was infected with the tobacco mosaic virus (TMV0), a subtraction library of cDNA clones was previously constructed using mRNA isolated before and after infection (Shuck, unpublished). From 200 clones collected, 5 clones were randomly selected, DNA was isolated, and the cDNA insert was sequenced. These sequences were imported into BLAST to search for homology to other R genes. This search revealed clone 4A to have an 84% homology to a 54 nucleotide region from the Arabidopsis thaliana oligouridylate binding protein which is highly expressed and known to bind RNA Polymerase III transcripts and adenovirus associated RNAs. Further bioinformatics analysis was performed utilizing databases and analysis packages available on the Internet, software such as Vector NTI (Informax, Bethesda, MD), and manual searches. However, no additional domains or motifs indicative of pathogen resistance genes were located in any of the 5 clones. Subsequently, total proteins expressed at various time points following infection were examined on denaturing 5-20% gradient polyacrylamide gels stained with the ProteoSilver Plus TM silver stain kit (Sigma, St. Louis, MO) in order to examine the timing and duration of expression of proteins involved in TMV-O resistance. One protein of-18 kDa was highly expressed at 4 hr after infection that was not seen in the negative control. By 8 hr the band was no longer expressed, it was expressed again from 30 - 48 hr, but was not seen again in later time points. Finally, total mRNA isolated from pooled time points and subjected to in vitro translation indicated a reduction in translation products after infection, providing evidence of posttranscriptional gene silencing (PTGS) following TMV-O infection. / Department of Biology

No description available.

In this study, RAPD (Randomly Amplified Polymorphic DNA) and SCAR (Sequence Amplified Characterized Region) markers found within 5 centiMorgans of known disease resistance loci in L. sativa were tested for their potential use in MAS. Out of thirty RAPD and SCAR markers evaluated, ten were found to be reliable predictors of disease resistance or susceptibility across a wide range of commercial and reference cultivars. Direct sequencing of seven selected markers did not reveal any significant similarity with known sequences. Three SNPs (Single Nucleotide Polymorphism) associated with two markers found in close proximity to corky root (cor) and Lettuce mosaic virus resistance (mo12) genes were identified. This information was used in the development of a non-electrophoresis PCR-based assay called FRET (Fluorescence Resonance Energy Transfer) hybridization probes assay.

Little is known about the mechanism of virus disease resistance in plants. The aim of the work presented here was to answer whether disease resistance is offered within the cell or at the level of intercellular movement of the virus. The protoplast system was used for this purpose. Conditions were optimized to isolate viable protoplasts from the leaves of Lactuca sativa cultivars. Protoplasts and leaves from resistant and susceptible Lactuca sativa cultivars were inoculated separately with turnip mosaic virus (TuMV) and lettuce mosaic virus (LMV), Virus multiplication was examined over time using enzyme-linked immunosorbent assay. Resistant cv. Kordaat did not support TuMV multiplication in protoplasts as well as in leaves. The results indicated that resistance to TuMV is available within the cell. The results ruled out the possibility of involvement of cell to cell movement and resistance to TuMV seems to be constitutive. On the other hand, protoplasts and leaves from both resistant and susceptible lettuce cultivars supported LMV multiplication. This suggested that resistance to LMV may not be offered within the cell. The results also indicated that the resistance to LMV was partly due to a hypersensitive response though virus was still able to spread systemically. To contribute towards mapping of the Tu resistance gene, the genotype of F$ sb2$ individuals was determined by screening an F$ sb3$ population from 71 F$ sb2$ individuals of a cross between cv. Calmar and cv. Kordaat for TuMV-infection. These data were useful for the production of bulks around the Tu locus to facilitate the search for new molecular markers linked to the Tu gene.

No description available.

No description available.

Graduation date: 1994

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Typescript (photocopy). / Digitized by Kansas Correctional Industries