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Key Message: The Ra extreme resistance against potato virus A was mapped to the upper of chromosome 4 in tetraploid potato. Potato virus A (PVA) is one of the major viruses affecting potato worldwide and can cause serious disease symptoms and yield losses. Previously, we determined that potato cultivar Barbara harbors Ry sto (genotype: Ryryryry) and Ra (genotype: Rararara) that each independently confer extreme resistance to PVA. In this study, employing a combination of next-generation sequencing and bulked-segregant analysis, we further located this novel Ra on chromosome 4 using a tetraploid BC 1 potato population derived from a Ry-free progeny (Rararararyryryry) of Barbara (RarararaRyryryry) × F58050 (rararararyryryry). Using 29 insertion-deletion (InDel) markers spanning chromosome 4, Ra was delimited by the InDel markers M8-83 and M10-8 within a genetic interval of 1.46 cM, corresponding to a 1.86-Mb genomic region in the potato DM reference genome. The InDel marker M10-8, which is closely linked with the resistance against PVA in the Ry-free segregating populations, was then used to screen 43 selected Ry sto -free tetraploid potato breeding clones. The phenotype to PVA was significantly correlated with the present/absent of the marker, albeit with a 9.3% false positive rate and a 14.0% false negative rate. These findings are of importance in furthering the cloning of Ra and employing the marker-assisted selection for PVA resistance., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Temperature plays an important role in potato tuberization. The ideal night temperature for tuber formation is ~17 °C while temperature beyond 22 °C drastically reduces the tuber yield. Moreover, high temperature has several undesirable effects on the plant and tubers. Investigation of the genes involved in tuberization under heat stress can be helpful in the generation of heat-tolerant potato varieties. Five genes, including StSSH2 (succinic semialdehyde reductase isoform 2), StWTF (WRKY transcription factor), StUGT (UDP-glucosyltransferase), StBHP (Bel1 homeotic protein), and StFLTP (FLOWERING LOCUS T protein), involved in tuberization and heat stress in potato were investigated. The results of our microarray analysis suggested that these genes regulate and function as transcriptional factors, hormonal signaling, cellular homeostasis, and mobile tuberization signals under elevated temperature in contrasting KS (Kufri Surya) and KCM (Kufri Chandramukhi) potato cultivars. However, no detailed report is available which establishes functions of these genes in tuberization under heat stress. Thus, the present study was designed to validate the functions of these genes in tuber signaling and heat tolerance using virus-induced gene silencing (VIGS). Results indicated that VIGS transformed plants had a consequential reduction in StSSH2, StWTF, StUGT, StBHP, and StFLTP transcripts compared to the control plants. Phenotypic observations suggest an increase in plant senescence, reductions to both number and size of tubers, and a decrease in plant dry matter compared to the control plants. We also establish the potency of VIGS as a high-throughput technique for functional validation of genes.

Key Message: Novel major gene resistance against Potato virus Y in diploid populations of Solanum tuberosum Groups Phureja and Tuberosum was biologically and genetically characterised. Named Ry(o) phu , it mapped to chromosome 9. A new source of genetic resistance derived from Solanum tuberosum Group Phureja against Potato virus Y (PVY) was identified and genetically characterised in three diploid biparental potato populations. Segregation data for two populations (05H1 and 08H1) suggested the presence of a single dominant gene for resistance to PVY which, following DaRT analysis of the 08H1 cross, was mapped to chromosome 9. More detailed genetic analysis of resistance utilised a well-characterised SNP-linkage map for the 06H1 population, together with newly generated marker data. In these plants, which have both S. tuberosum Group Phureja and S. tuberosum Group Tuberosum in their pedigree, the resistance was shown to map to chromosome 9 at a locus not previously associated with PVY resistance, although there is evidence for at least one other genetic factor controlling PVY infection. The resistance factor location on chromosome 9 (named as Ry(o)phu) suggests a potential role of NB-LRR genes in this resistance. Phenotypic analysis using a GUS-tagged virus revealed that a small amount of PVY replication occurred in occasional groups of epidermal cells in inoculated leaves of resistant plants, without inducing any visible hypersensitive response. However, the virus did not enter the vascular system and systemic spread was completely prevented.

Key Message: We have elucidated the Andigena origin of the potato Ry adg gene on chromosome XI of CIP breeding lines and developed two marker assays to facilitate its introgression in potato by marker-assisted selection. Potato virus Y (PVY) is causing yield and quality losses forcing farmers to renew periodically their seeds from clean stocks. Two loci for extreme resistance to PVY, one on chromosome XI and the other on XII, have been identified and used in breeding. The latter corresponds to a well-known source of resistance (Solanum stoloniferum), whereas the one on chromosome XI was reported from S. stoloniferum and S. tuberosum group Andigena as well. To elucidate its taxonomic origin in our breeding lines, we analyzed the nucleotide sequences of tightly linked markers (M45, M6) and screened 251 landraces of S. tuberosum group Andigena for the presence of this gene. Our results indicate that the PVY resistance allele on chromosome XI in our breeding lines originated from S. tuberosum group Andigena. We have developed two marker assays to accelerate the introgression of Ry adg gene into breeding lines by marker-assisted selection (MAS). First, we have multiplexed RYSC3, M6 and M45 DNA markers flanking the Ry adg gene and validated it on potato varieties with known presence/absence of the Ry adg gene and a progeny of 6,521 individuals. Secondly, we developed an allele-dosage assay particularly useful to identify multiplex Ry adg progenitors. The assay based on high-resolution melting analysis at the M6 marker confirmed Ry adg plex level as nulliplex, simplex and duplex progenitors and few triplex progenies. These marker assays have been validated and can be used to facilitate MAS in potato breeding.

Large quantities of potato leafroll virus (PLRV) antigen are difficult to obtain because this virus accumulates in plants at a low titer. To overcome this problem, we constructed a binary vector containing chimeric cDNA, in which the coat protein (CP) gene of the crucifer infecting tobacco mosaic virus (crTMV) was substituted for the coat protein gene of PLRV. The PLRV movement protein (MP) gene, which overlaps completely with the CP gene, was doubly mutated to eliminate priming of the PLRV MP translation from ATG codons with no changes to the amino acid sequence of the CP. The untranslated long intergenic region located upstream of the CP gene was removed from the construct. Transcribed powerful tobamovirus polymerase of the produced vector synthesized PLRV CP gene that was, in turn, translated into the protein. CP PLRV packed RNAs from the helical crTMV in spherical virions. Morphology, size and antigenic specificities of the wild-type and chimeric virus were similar. The yield of isolated chimera was about three orders higher than the yield of native PLRV. The genetic manipulations facilitated the generation of antibodies against the chimeric virus, which recognize the wild-type PLRV.

RNA interference (RNAi) technology has been successfully applied in stacking resistance against viruses in numerous crop plants. During RNAi, the production of small interfering RNAs (siRNAs) from template double-standard RNA (dsRNA) derived from expression constructs provides an on-switch for triggering homology-based targeting of cognate viral transcripts, hence generating a pre-programmed immunity in transgenic plants prior to virus infection. In the current study, transgenic potato lines (Solanum tuberosum cv. Desiree) were generated, expressing fused viral coat protein coding sequences from Potato virus X (PVX), Potato virus Y (PVY), and Potato virus S (PVS) as a 600-bp inverted repeat expressed from a constitutive 35S promoter. The expression cassette (designated Ec1/p5941) was designed to generate dsRNAs having a hairpin loop configuration. The transgene insertions were confirmed by glufosinate resistance, gene-specific PCR, and Southern blotting. Regenerated lines were further assayed for resistance to virus inoculation for up to two consecutive crop seasons. Nearly 100% resistance against PVX, PVY, and PVS infection was observed in transgenic lines when compared with untransformed controls, which developed severe viral disease symptoms. These results establish the efficacy of RNAi using the coat protein gene as a potential target for the successful induction of stable antiviral immunity in potatoes.

Key Message: The method of graphical genotyping is applied to a panel of tetraploid potato cultivars to visualize haplotype sharing. The method allowed to map genes involved in virus and nematode resistance. The physical coordinates of the amount of linkage drag surrounding these genes are easily interpretable. Graphical genotyping is a visually attractive and easily interpretable method to represent genetic marker data. In this paper, the method is extended from diploids to a panel of tetraploid potato cultivars. Application of filters to select a subset of SNPs allows one to visualize haplotype sharing between individuals that also share a specific locus. The method is illustrated with cultivars resistant to Potato virus Y (PVY), while simultaneously selecting for the absence of the SNPs in susceptible clones. SNP data will then merge into an image which displays the coordinates of a distal genomic region on the northern arm of chromosome 11 where a specific haplotype is introgressed from the wild potato species S. stoloniferum (CPC 2093) carrying a gene (Ny (o,n)sto ) conferring resistance to two PVY strains, PVY O and PVY NTN . Graphical genotyping was also successful in showing the haplotypes on chromosome 12 carrying Ry-f sto , another resistance gene derived from S. stoloniferum conferring broad-spectrum resistance to PVY, as well as chromosome 5 haplotypes from S. vernei, with the Gpa5 locus involved in resistance against Globodera pallida cyst nematodes. The image also shows shortening of linkage drag by meiotic recombination of the introgression segment in more recent breeding material. Identity-by-descent was found to be a requirement for using graphical genotyping, which is proposed as a non-statistical alternative method for gene discovery, as compared with genome-wide association studies. The potential and limitations of the method are discussed.

The aim of this study was to evaluate the biological parameters of Chrysoperla externa (Hagen) while feeding on Myzus persicae (Sulzer) acting as a vector of potato leafroll virus (PLRV). In laboratory experiments, three different diets were offered ad libitum to C. externa during the larval period: M. persicae fed on PLRV-infected potato leaves, M. persicae fed on uninfected potato leaves, and eggs of the factitious prey Anagasta kuehniella (Zeller) as the control. The following parameters were studied: the developmental time and survival rate of the larval and pupal stages, the sex ratio, the proportion of fertile females, female fecundity and egg viability, and the survival curve of the first 30 days after adult emergence. PLRV-infected aphids influenced the C. externa larval developmental time and survival compared to PLRV-uninfected aphids and A. kuehniella eggs. The pupal developmental time of C. externa was shorter when fed on aphids compared to A. kuehniella eggs, but no differences were recorded between the PLRV-infected and uninfected aphid diets. Additionally, no differences were observed for pupal survival and reproduction. However, adult survival was affected by the prey type, as 75% of C. externa control adults remained alive at an age of 30 days compared to 51 and 54% for those fed on PLRV-uninfected and infected aphids, respectively.

Virus-like particles (VLPs) are multisubunit self-assembly competent protein structures with identical or highly related overall structure to their corresponding native viruses. To construct a new filamentous VLP carrier, the coat protein (CP) gene from potato virus M (PVM) was amplified from infected potato plants, cloned, and expressed in Escherichia coli cells. As demonstrated by electron microscopy analysis, the PVM CP self-assembles into filamentous PVM-like particles, which are mostly 100-300 nm in length. Adding short Gly-Ser peptide at the C-terminus of the PVM, CP formed short VLPs, whereas peptide and protein A Z-domain fusions at the CP N-terminus retained its ability to form typical PVM VLPs. The PVM-derived VLP carrier accommodates up to 78 amino acid-long foreign sequences on its surface and can be produced in technologically significant amounts. PVM-like particles are stable at physiological conditions and also, apparently do not become disassembled in high salt and high pH solutions as well as in the presence of EDTA or reducing agents. Despite partial proteolytic processing of doubled Z-domain fused to PVM VLPs, the rabbit IgGs specifically bind to the particles, which demonstrates the functional activity and surface location of the Z-domain in the PVM VLP structure. Therefore, PVM VLPs may be recognized as powerful structural blocks for new human-made nanomaterials.

Vector-dependent plant pathogens can alter their hosts such that vector behavior and pathogen spread are affected. For example, Potato leafroll virus (PLRV)-induces changes in volatiles emitted by potato plants (Solanum tuberosum L.) that influence settling behavior by Myzus persicae, a principal vector of the virus. Prior work in this pathosystem has utilized a single potato variety, Russet Burbank, but as is true for other plant responses to biotic stresses, responses may differ among plant genotypes. To examine this, PLRV-induced changes in headspace volatile organic compounds (VOCs) and associated aphid responses to these VOCs were compared among four potato varieties (Chipeta, Desiree, IdaRose, and Russet Burbank). Total headspace VOCs differed among the varieties and were differentially induced by PLRV infection such that the effect of variety, infection, and their interaction was significant; two of the varieties had increased concentrations of headspace VOCs, and two did not. MANOVA for the effect of infection and variety on total VOCs and major VOC classes also was significant. A principal component analysis (PCA) partially separated the VOC profiles from the four varieties. Aphid arrestment differed in response to the VOCs of the four varieties, and was greater on those that were more readily infected by PLRV (Desiree and Russet Burbank) as compared with those that were less readily infected (Chipeta and IdaRose). Aphid responses were not clearly related to specific characteristics of blends, such that total VOCs and composition appear to contribute. The four varieties used in this study have distinct pedigrees representative of different cultivated forms of S. tuberosum. Although cultivated potato varieties have been subjected to genetic manipulation by humans, the differences in PLRV induced changes in VOCs nonetheless indicate the potential for complex effects of PLRV infection on host plant VOC emissions, and vector responses in managed, and natural systems.

Hypersensitive resistance (HR) is an efficient defense strategy in plants that restricts pathogen growth and can be activated during host as well as non-host interactions. HR involves programmed cell death and manifests itself in tissue collapse at the site of pathogen attack. A novel hypersensitivity gene, Ny-1, for resistance to Potato virus Y (PVY) was revealed in potato cultivar Rywal. This is the first gene that confers HR in potato plants both to common and necrotic strains of PVY. The locus Ny-1 mapped on the short arm of potato chromosome IX, where various resistance genes are clustered in Solanaceous genomes. Expression of HR was temperature-dependent in cv. Rywal. Strains PVYO and PVYN, including subgroups PVYNW and PVYNTN, were effectively localized when plants were grown at 20 degrees C. At 28 degrees C, plants were systemically infected but no symptoms were observed. In field trials, PVY was restricted to the inoculated leaves and PVY-free tubers were produced. Therefore, the gene Ny-1 can be useful for potato breeding as an alternative donor of PVY resistance, because it is efficacious in practice-like resistance conferred by Ry genes.

The gene encoding the coat protein (CP) of a potato virus Y (PVY) was cloned into expression vector pMPM-A4Omega. PVY CP was expressed in Escherichia coli and the purified recombinant protein was used for raising rabbit polyclonal antibodies. The sera and antibodies were tested for the detection of PVY in the laboratory host Nicotiana tabacum cv. Petit Havana SR1 and in various cultivars of the natural host Solanum tuberosum by ELISA as well as by Western blots. The antibodies can be used for the detection of the whole strain spectrum of PVY by indirect plate trapped antigen ELISA and Western blot, but not by double antigen sandwich ELISA.

The Ns gene confers resistance of potato to Potato virus S (PVS). Sixteen German and Dutch potato cultivars, all registered in Poland, were found to be susceptible to PVS infection. However, scoring of the cultivars for the presence of the Ns-linked SCAR marker SC811(454) revealed additional amplicons with a similar electrophoretic migration rate as that of SC811(454), which resulted in ambiguous determination of the genotype at the Ns locus. MboI or FokI treatment of the PCR products allowed to detect their Ns-unspecificity in PVS-susceptible potato cultivars.

Volatiles from potato plants (Solanum tuberosum L.) infected with Potato leaf roll virus (PLRV) attract and arrest the principal vector of PLRV, the green peach aphid, Myzus persicae (Sulzer), more strongly than volatiles from non-infected plants. The total concentration of volatiles detectable in the headspace of PLRV-infected plants is greater than that in the headspace of non-infected controls, and the relative composition is altered. To determine the basis of the aphid response to PLRV-infection-induced volatiles from potato, behavioral bioassays were conducted. We measured arrestment of aphids by individual components, by synthetic blends of these, and by a naturally occurring blend by using an emigration rate bioassay, and quantified observations of the behavior of individual aphids. The components tested were those elevated at least twofold in response to PLRV infection. Before conducting the behavioral bioassays, electroantennograms confirmed the electrophysiological responses of aphids to the components of the blend. For bioassays, individual compounds or blends were tested by applying them in solution to paper strips at concentrations designed to mimic those present in the headspace of the plants. All bioassays were conducted by placing aphids on fine-mesh screening positioned above treated paper strips. Arrestment was measured by placing groups of 30 aphids directly over the treated strips and counting the number moving away at 10-min intervals for 50 min. Among the individual compounds tested, only beta-pinene was a mild arrestant. The other compounds did not elicit significant changes in arrestment or behavior at a range of physiologically relevant concentrations. In contrast, synthetic blends that mimicked the concentration and composition present in headspace of PLRV-infected potato plants arrested aphids significantly more strongly than blends mimicking volatiles from the headspace of non-infected plants. The naturally occurring blend collected from headspace of PLRV-infected plants also arrested M. persicae more strongly than the blend collected from headspace of non-infected plants. Aphid behavior was quantified by directly observing individual aphids and recording their activities during a 5-min period on screening above strips treated with test materials. Few differences in time budgets were observed among aphids exposed to individual components, but synthetic blends and trapped headspace volatiles from PLRV-infected plants resulted in significantly less time spent walking by aphids than synthetic blends and trapped headspace from non-infected controls. Our results indicate that arrestment of M. persicae by PLRV-infected plants requires the blend of volatile organic compounds released by these plants and is not produced in response to a single compound.

Major gene inheritance of resistance to Potato leafroll virus (PLRV) was demonstrated in a parthenogenic population derived from the highly resistant tetraploid andigena landrace, LOP-868. This major gene or chromosome region seems to control a single mechanism for resistance to infection and virus accumulation in this source. About 149 dihaploid lines segregated in a ratio of 107 resistant to 32 susceptible, fitting the expected ratio for inheritance of a duplex gene under random chromatid segregation. A tetraploid AFLP map was constructed using as reference the ultra high density (UHD) map. All AFLP markers associated with PLRV resistance mapped to the same linkage group. Map position was confirmed by analysis of previously-mapped SSR markers. Rl (adg) is located on the upper arm of chromosome V, at 1 cM from its most closely linked AFLP marker, E35M48.192. This marker will be used to develop allele-specific primers or a pair of flanking PCR-based markers for their use in marker assisted selection.

In this work, Potato virus Y (PVY) resistant potatoes were generated using an environmentally safe construct. For this purpose, a 'shooter' mutant Agrobacterium-based transformation system was used. The isopentenyl transferase gene (ipt) present on the Ti plasmid of 'shooter' strains enhances shoot regeneration and can be used as a phenotypic selection marker. The introduced marker-free binary vector carried a hairpin construct derived from the coat protein gene of PVY-NTN strain in order to induce gene silencing. Transformation resulted in high regeneration rates (1.4-5.7 shoots per explant). With pre-selection for the ipt (+) phenotype the transformation frequency was 24-53%, while without selection 12-28% of the shoots were PCR positive. The presence of the transgene was verified by Southern hybridization. In 16 of 31 challenged transformant lines PVY could be detected neither by RT-PCR nor by back inoculation. A 62.5% of these resistant lines proved to be also ipt-free. This transformation system was reproducible in four potato cultivars, suggesting that it could easily be adapted for other species.

The nucleotide sequence was determined for Czech potato mop-top virus (PMTV) isolate Korneta-Nemilkov, found in the potato field situated in South Bohemia. The nucleotide and amino acid sequences were compared with other PMTV isolates available in databases. The sequence identity was always >99% when Czech isolate RNA 2 and RNA 3 sequences were compared with each of the 3 Danish isolates and with Sw isolate, and slightly lower when compared to Scottish isolates. Similarity of deduced proteins was 100% for 5 out of 6 proteins used in comparison of Czech isolate with Danish isolate 54-15. The only difference between 2 isolates was found in coat protein (CP) gene. Interestingly, the CP of the Czech isolate seems to be 100% identical to the one of Sw, while many changes were found in the region encoding TGBp2, TGBp3 and cysteine-rich protein (CRP) for these 2 isolates. The lowest similarity scores were found when comparing the Czech isolate CRP with CRP of Scottish isolates.

A synthetic gene encoding a single chain Fv fragment of an antibody directed against the nuclear inclusion a (NIa) protein of potato virus Y (PVY) was used to transform two commercial potato cultivars (Claustar and BF15). The NIa protease forms the nuclear inclusion body A and acts as the major protease in the cleavage of the viral polyprotein into functional proteins. Immunoblot analysis showed that most of the resulting transgenic plants accumulate high levels of the transgenic protein. Furthermore, a majority of the selected transgenic lines showed an efficient and complete protection against the challenge virus after mechanical inoculation with PVYO strain. Two transgenic lines showed an incomplete resistance with delayed appearance of symptoms accompanied by low virus titers, whereas one line developed symptoms during the first days after inoculation but recovered rapidly, leading to a low virus accumulation rate. These results confirm that expression of scFv antibody is able to inhibit a crucial step in the virus multiplication, such as polyprotein cleavage is a powerful strategy for engineered virus resistance. It can lead to a complete resistance that was not obtained previously by expression of scFv directed against the viral coat protein.

Two new loci for resistance to potato virus M (PVM), Gm and Rm, have been mapped in potato. The gene Gm was derived from Solanum gourlayi, whereas, Solanum megistacrolobum is the source of the gene Rm. Gm confers resistance to PVM infection after mechanical inoculation. Rm induces a hypersensitive response in potato plants. Two diploid populations segregating for Gm and Rm, bulked segregant analysis (BSA) using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR), and available potato molecular maps were instrumental for mapping the resistance loci. The novel locus Gm was mapped to a central region on potato chromosome IX. The locus Rm was placed on the short arm of chromosome XI, close to the marker loci GP250 and GP283, where a hotspot for monogenic and polygenic resistance to diverse pathogens is located in the potato and tomato genome.

A gene encoding the outer capsid glycoprotein (VP7) of simian rotavirus SA11, was genetically linked to the amino terminus of the ricin toxin B subunit (RTB) isolated from castor-oil plant (Ricinus communis) seeds. To assess fusion protein expression in plant cells, the VP7::RTB fusion gene was transferred into potato (Solanum tuberosum) cells by Agrobacterium tumefaciens-mediated transformation methods and transformed plants regenerated. The fusion gene was detected in transformed potato genomic DNA by polymerase chain reaction DNA amplification methods. Immunoblot analysis with anti-SA11 antiserum as the primary antibody verified the presence of VP7::RTB fusion protein in transformed potato tuber tissues. The plant-synthesized fusion protein bound RTB membrane receptors as measured by asialofetuin-enzyme-linked immunosorbent assay (ELISA). The ELISA results indicated that the VP7::RTB fusion protein was biologically active and made up approx 0.03% of total soluble transformed tuber protein. The biosynthesis of receptor binding VP7::RTB fusion protein in potato tissues demonstrates the feasibility of producing monomeric ricin toxin B subunit adjuvant-virus antigen fusion proteins in crop plants for enhanced immunity.

The inheritance of extreme resistance to PVY (Ry (sto)) by a single dominant locus was confirmed by obtaining a 1:1 segregation ratio in a virus inoculation test with 28 resistant (Ryry) to 29 susceptible (ryry) anther culture-derived dihaploid lines (2n=2x=24) from cv. "Assia" (2n=4x=48) having extreme resistance derived from Solanum stoloniferum in simplex constitution (Ryryryry). Twelve Ry (sto) markers selected in AFLP assays using bulked segregant analysis were applied to 106 tested potato cultivars from Germany, The Netherlands and Poland and 19 potato cultivars were identified by these markers as extremely resistant to PVY in alignment with phenotypic data. The locus for extreme resistance (Ry (sto)) to PVY was mapped on chromosome XII co-segregating with the SSR marker STM 0003. The utility of anther-culture derived dihaploid potatoes for genetic marker development was demonstrated. Marker transferability from diploids to tetraploids provides an optimistic potential for marker-assisted selection in potato breeding programs.

A DNA fragment encoding a 12-amino acid (aa) HIV-1 Tat transduction peptide fused to a 90-aa murine rotavirus NSP4 enterotoxin protein (Tat-NSP4(90)) was transferred to Solanum tuberosum by Agrobacterium tumefaciens-mediated transformation. The fusion gene was detected in the genomic DNA of transformed plant leaf tissues by PCR DNA amplification. The Tat-NSP4(90 )fusion protein was identified in transformed tuber extracts by immunoblot analysis using anti-NSP4(90) and anti-Tat as the primary antibodies. Enzyme-linked immunosorbent assay results showed that the Tat-NSP4(90) fusion protein made up to 0.0015% of the total soluble tuber protein. The synthesis of Tat-NSP4(90) fusion protein in transformed potato tuber tissues demonstrates the feasibility of plant cell delivery of the HIV-1 Tat transduction domain as a carrier for non-specific targeting of fused antigens to the mucosal immune system.

Nine resistance gene homologues (RGHs) were identified in two diploid potato clones (SH and RH), with a specific primer pair based on conserved motifs in the LRR domain of the potato cyst nematode resistance gene Gpa2 and the potato virus X resistance gene Rx1. A modified AFLP method was used to facilitate the genetic mapping of the RGHs in the four haplotypes under investigation. All nine RGHs appeared to be located in the Gpa2/ Rx1 cluster on chromosome XII. Construction of a physical map using bacterial artificial chromosome (BAC) clones for both the Solanum tuberosum ssp. tuberosum and the S. tuberosum ssp. andigena haplotype of SH showed that the RGHs are located within a stretch of less than 200 kb. Sequence analysis of the RGHs revealed that they are highly similar (93 to 95%) to Gpa2 and Rx1. The sequence identities among all RGHs range from 85 to 100%. Two pairs of RGHs are identical, or nearly so (100 and 99.9%), with each member located in a different genotype. Southern-blot analysis on genomic DNA revealed no evidence for additional homologues outside the Gpa2/ Rx1 cluster on chromosome XII.