Evidence Of Gene Transfer Research Articles

Comparative analysis of chloroplast and mitochondrial genomes of sweet potato provides evidence of gene transfer

The increasing number of plant mitochondrial DNA genomes (mtDNA) sequenced reveals the extent of transfer from both chloroplast DNA genomes (cpDNA) and nuclear DNA genomes (nDNA). This study created a library and assembled the chloroplast and mitochondrial genomes of the leafy sweet potato better to understand the extent of mitochondrial and chloroplast gene transfer. The full-length chloroplast genome of the leafy sweet potato (OM808940) is 161,387 bp, with 132 genes annotated, including 87 protein-coding genes, 8 rRNA genes, and 37 tRNA genes. The mitochondrial genome (OM808941) was 269,578 bp in length and contained 69 functional genes, including 39 protein-coding genes, 6 rRNA genes, and 24 tRNA genes. 68 SSR loci were found in the leafy sweet potato organelle genome, including 54 in the chloroplast genome and 14 in the mitochondria genome. In the sweet potato mitochondrial genome, most genes have RNA editing sites, and the conversion ratio from hydrophilic amino acids to hydrophobic amino acids is the highest, reaching 47.12%. Horizontal transfer occurs in the sweet potato organelle genome and nuclear genome. 40 mitochondrial genome segments share high homology with 14 chloroplast genome segments, 33 of which may be derived from chloroplast genome horizontal transfer. 171 mitochondrial genome sequences come from the horizontal transfer of nuclear genome. The phylogenetic analysis of organelle genes revealed that the leafy sweet potato was closely related to the tetraploid wild species Ipomoea tabascana and the wild diploid species Ipomoea trifida.

Comparative analysis of nuclear, chloroplast, and mitochondrial genomes of watermelon and melon provides evidence of gene transfer

During plant evolution, there is genetic communication between organelle and nuclear genomes. A comparative analysis was performed on the organelle and nuclear genomes of the watermelon and melon. In the watermelon, chloroplast-derived sequences accounted for 7.6% of the total length of the mitochondrial genome. In the melon, chloroplast-derived sequences accounted for approximately 2.73% of the total mitochondrial genome. In watermelon and melon, the chloroplast-derived small-fragment sequences are either a subset of large-fragment sequences or appeared multiple times in the mitochondrial genome, indicating that these fragments may have undergone multiple independent migration integrations or emerged in the mitochondrial genome after migration, replication, and reorganization. There was no evidence of migration from the mitochondria to chloroplast genome. A sequence with a total length of about 73 kb (47%) in the watermelon chloroplast genome was homologous to a sequence of about 313 kb in the nuclear genome. About 33% of sequences in the watermelon mitochondrial genome was homologous with a 260 kb sequence in the nuclear genome. A sequence with a total length of about 38 kb (25%) in the melon chloroplast genome was homologous with 461 sequences in the nuclear genome, with a total length of about 301 kb. A 3.4 Mb sequence in the nuclear genome was homologous with a melon mitochondrial sequence. These results indicate that, during the evolution of watermelon and melon, a large amount of genetic material was exchanged between the nuclear genome and the two organelle genomes in the cytoplasm.

T4 Safety and expression of a single dose of lipid-mediated CFTR gene therapy to the upper and lower airways of patients with Cystic Fibrosis

Introduction and ObjectivesWe undertook a clinical trial of non-viral CFTR gene therapy assessing safety, dose and transgene expression in preparation for a Multi-dose trial (MDT) designed to assess clinical efficacy.MethodsA...

Investigation on gene transfer from genetically modified corn (Zea mays L.) plants to soil bacteria

Knowledge about the prevalence and diversity of antibiotic resistance genes in soil bacteria communities is required to evaluate the possibility and ecological consequences of the transfer of these genes carried by genetically modified (GM) plants to soil bacteria. The neomycin phosphotransferase gene (nptII) conferring resistance to kanamycin and neomycin is one of the antibiotic resistance genes commonly present in GM plants. In this study, we investigated kanamycin-resistant (KmR) and neomycin-resistant (NmR) soil bacterial populations in a 3-year field trial using a commercial GM corn (Zea mays L.) carrying the nptII gene and its near isogenic line. The results showed that a portion (2.3 – 15.6 %) of cultivable soil bacteria was naturally resistant to kanamycin or neomycin. However, no significant difference in the population level of KmR or NmR soil bacteria was observed between the GM and non-GM corn fields. The nptII gene was not detected in any of the total 3000 KmR or NmR isolates screened by PCR. Further, total soil bacterial cells were collected through Nycodenz gradient centrifugation and bacterial community DNA was subjected to PCR. Detection limit was about 500 cells per gram of fresh soil. Our study suggests that the nptII gene was relatively rare in the soil bacterial populations and there was no evidence of gene transfer from a GM corn plant to soil bacteria based on the data from total soil bacterial communities.

Functional biogeography as evidence of gene transfer in hypersaline microbial communities.

BackgroundHorizontal gene transfer (HGT) plays a major role in speciation and evolution of bacteria and archaea by controlling gene distribution within an environment. However, information that links HGT to a natural community using relevant population-genetics parameters and spatial considerations is scarce. The Great Salt Lake (Utah, USA) provides an excellent model for studying HGT in the context of biogeography because it is a contiguous system with dispersal limitations due to a strong selective salinity gradient. We hypothesize that in spite of the barrier to phylogenetic dispersal, functional characteristics—in the form of HGT—expand beyond phylogenetic limitations due to selective pressure.Methodology and ResultsTo assay the functional genes and microorganisms throughout the GSL, we used a 16S rRNA oligonucleotide microarray (Phylochip) and a functional gene array (GeoChip) to measure biogeographic patterns of nine microbial communities. We found a significant difference in biogeography based on microarray analyses when comparing Sørensen similarity values for presence/absence of function and phylogeny (Student's t-test; p = 0.005).Conclusion and SignificanceBiogeographic patterns exhibit behavior associated with horizontal gene transfer in that informational genes (16S rRNA) have a lower similarity than functional genes, and functional similarity is positively correlated with lake-wide selective pressure. Specifically, high concentrations of chromium throughout GSL correspond to an average similarity of chromium resistance genes that is 22% higher than taxonomic similarity. This suggests active HGT may be measured at the population level in microbial communities and these biogeographic patterns may serve as a model to study bacteria adaptation and speciation.

Protection of Salmonella by ampicillin-resistant Escherichia coli in the presence of otherwise lethal drug concentrations

Microbial systems have become the preferred testing grounds for experimental work on the evolution of traits that benefit other group members. This work, based on conceptual and theoretical models of frequency-dependent selection within populations, has proven fruitful in terms of understanding the dynamics of group beneficial or 'public goods' traits within species. Here, we expand the scope of microbial work on the evolution of group-beneficial traits to the case of multi-species communities, particularly those that affect human health. We examined whether beta-lactamase-producing Escherichia coli could protect ampicillin-sensitive cohorts of other species, particularly species that could cause human disease. Both beta-lactamase-secreting E. coli and, surprisingly, those engineered to retain it, allowed for survival of a large number of ampicillin-sensitive cohorts of Salmonella enterica serovar Typhimurium, including both laboratory and clinical isolates. The Salmonella survivors, however, remained sensitive to ampicillin when re-plated onto solid medium and there was no evidence of gene transfer. Salmonella survival did not even require direct physical contact with the resistant E. coli. The observed phenomenon appears to involve increased release of beta-lactamase from the E. coli when present with S. enterica. Significantly, these findings imply that resistant E. coli, that are not themselves pathogenic, may be exploited, even when they are normally selfish with respect to other E. coli. Thus, Salmonella can gain protection against antibiotics from E. coli without gene transfer, a phenomenon not previously known. As a consequence, antibiotic-resistant E. coli can play a decisive role in the survival of a species that causes disease and may thereby interfere with successful treatment.

Lateral gene transfer between prokaryotes and multicellular eukaryotes: ongoing and significant?

The expansion of genome sequencing projects has produced accumulating evidence for lateral transfer of genes between prokaryotic and eukaryotic genomes. However, it remains controversial whether these genes are of functional importance in their recipient host. Nikoh and Nakabachi, in a recent paper in BMC Biology, take a first step and show that two genes of bacterial origin are highly expressed in the pea aphid Acyrthosiphon pisum. Active gene expression of transferred genes is supported by three other recent studies. Future studies should reveal whether functional proteins are produced and whether and how these are targeted to the appropriate compartment. We argue that the transfer of genes between host and symbiont may occasionally be of great evolutionary importance, particularly in the evolution of the symbiotic interaction itself.

Are algal genes in nonphotosynthetic protists evidence of historical plastid endosymbioses?

BackgroundHow photosynthetic organelles, or plastids, were acquired by diverse eukaryotes is among the most hotly debated topics in broad scale eukaryotic evolution. The history of plastid endosymbioses commonly is interpreted under the "chromalveolate" hypothesis, which requires numerous plastid losses from certain heterotrophic groups that now are entirely aplastidic. In this context, discoveries of putatively algal genes in plastid-lacking protists have been cited as evidence of gene transfer from a photosynthetic endosymbiont that subsequently was lost completely. Here we examine this evidence, as it pertains to the chromalveolate hypothesis, through genome-level statistical analyses of similarity scores from queries with two diatoms, Phaeodactylum tricornutum and Thalassiosira pseudonana, and two aplastidic sister taxa, Phytophthora ramorum and P. sojae.ResultsContingency tests of specific predictions of the chromalveolate model find no evidence for an unusual red algal contribution to Phytophthora genomes, nor that putative cyanobacterial sequences that are present entered these genomes through a red algal endosymbiosis. Examination of genes unrelated to plastid function provide extraordinarily significant support for both of these predictions in diatoms, the control group where a red endosymbiosis is known to have occurred, but none of that support is present in genes specifically conserved between diatoms and oomycetes. In addition, we uncovered a strong association between overall sequence similarities among taxa and relative sizes of genomic data sets in numbers of genes.ConclusionSignal from "algal" genes in oomycete genomes is inconsistent with the chromalveolate hypothesis, and better explained by alternative models of sequence and genome evolution. Combined with the numerous sources of intragenomic phylogenetic conflict characterized previously, our results underscore the potential to be mislead by a posteriori interpretations of variable phylogenetic signals contained in complex genome-level data. They argue strongly for explicit testing of the different a priori assumptions inherent in competing evolutionary hypotheses.

Transgene Persistence and Cell Turnover in the Diarthrodial Joint: Implications for Gene Therapy of Chronic Joint Diseases

Local gene therapy for chronic joint diseases requires prolonged transgenic expression, but this has not been reliably achieved in animal models. Using normal and immunocompromised animals, we examined the capacity of various cell types in joint tissues to maintain and express exogenous transgenes after direct intra-articular gene delivery. We found that transgenic expression could persist for the lifetime of the animal but required precise immunological compatibility between the vector, transgene product, and host. It was not dependent on vector integration or promoter origin. We identified two phenotypically distinct sub-populations of genetically modified cells within the joint: (i) transient cells, with a half-life of a few weeks, and (ii) stable cells that reside in the joint tissues indefinitely. Contrary to the prevailing assumption, the transient sub-population was composed almost exclusively of synovial fibroblasts, indicating that the synovium is not an appropriate tissue upon which to base a long-term therapy. Instead, fibroblasts in the ligaments, tendons, and capsule emerged as the primary cell types capable of sustained therapeutic transgene expression. This study sheds new light on the cellular dynamics of articular tissues and suggests that cell turnover and immune reactivity are the key determinants in achieving sustained transgenic expression intra-articularly.

Gene therapy, bioengineered clotting factors and novel technologies for hemophilia treatment.

The World Federation of Hemophilia estimates that of the 400,000 individuals worldwide with hemophilia, 300,000 receive either no, or very sporadic, treatment. Thus, considerable innovation will be required to provide cost-effective therapies/cures for all affected individuals. The high cost of prophylactic regimens hampers their widespread use, which further justifies the search for novel cost-effective therapies and ultimately a cure. Five gene transfer phase I clinical trials have been conducted using either direct in vivo gene delivery with viral vectors or ex vivo plasmid transfections and reimplantation of gene-engineered cells. Although there was evidence of gene transfer and therapeutic effects in some of these trials, stable expression of therapeutic factor VIII or FIX levels has not yet been obtained. Further improvements of the vectors and a better understanding of the immune consequences of gene transfer is warranted, as new trials are being initiated. Bioengineered clotting factors with increased stability and/or activity are being validated further in preclinical studies. Novel clotting factor formulations based on PEGylated liposomes with prolonged activities are being tested in the clinic, and are yielding encouraging results.

Feasibility of Retroviral Vector-Mediated in utero Gene Transfer to the Fetal Rabbit

Objectives: Successful treatment or prevention of severe hereditary diseases could conceivably be achieved by genetic intervention early in development. Viral vector-mediated fetal gene transfer is proving a valuable tool to test the above concept in relevant animal models. Although the pregnant rabbit is a well-recognized model for fetal therapy, few preclinical assays have used it to validate fetal gene transfer approaches. In this preliminary study we assessed for the first time the feasibility of retroviral vector-mediated in utero gene transfer in the fetal rabbit. Methods: Different amounts of the vesicular stomatitis virus G pseudotyped MFG(nls)LacZ retroviral vector, expressing a nuclear-localized β-galactosidase reporter protein were injected intraperitoneally and -hepatically into 20- to 22-day-old fetuses. At 8–9 days post-treatment, the pups were sacrificed and the tissues harvested for analysis. Evidence of gene transfer was obtained by PCR amplification of proviral sequences within genomic DNA isolated from the treated samples. Transgenic β-galactosidase expression was assessed by X-gal histochemical staining. Results: By intraperitoneal injection 43% of the viable fetuses treated (3/7) showed evidence of successful LacZ gene transfer and low-level β-galactosidase expression into liver and heart, whereas by intrahepatic injection roughly 38% (3/8) of the livers were positive for LacZ gene transfer and expression. The success rate for the viable fetuses rose to 67% positive livers (4/6) when a near double amount of recombinant virus was injected using a 10-fold concentrated virus stock. In terms of short-term safety, fetal and maternal survival rates approached 80% of treated fetuses, and 100% of treated does. Conclusions: The pregnant rabbit is a useful and reliable model allowing the design of further studies to optimize the conditions for effective, safer, and persistent retroviral vector-mediated fetal gene transfer.

Fetal Gene Transfer Using Lentiviral Vectors and the Potential for Germ Cell Transduction in Rhesus Monkeys (Macaca mulatta)

Genetic modification of germ cells in somatic gene therapy protocols is a concern, particularly with fetal approaches. This study focused on the potential for germ cell gene transfer post-fetal gene delivery using a human immunodeficiency virus type 1 (HIV-1)-derived lentiviral vector pseudotyped with the vesicular stomatitis virus-glycoprotein (VSV-G). Rhesus monkey fetuses (n = 47) were administered vector supernatant (10(7) infectious particles per fetus) via the intraperitoneal (IP), intrapulmonary (Ipu), or intracardiac routes (Ica) under ultrasound guidance. Tissue harvests were performed near term or 3 months postnatal age, and genomic DNA obtained to analyze for vector sequences from collected sections of gonads and gonadal cells obtained by laser capture microdissection (germ cells, stroma, epithelium). Results indicated no evidence of germ cell gene transfer in fetuses or infants with Ipu or Ica routes of administration. However, evidence of the transgene (1.33 +/- 0.78 enhanced green fluorescent protein [EGFP] copies per copy epsilon-globin) was found in females, but not males, when using the IP administration approach (p < 0.05). The highest EGFP copies were detected on the surface epithelium (p < 0.05). The results of these studies suggest that the HIV-1-derived lentiviral vector pseudotyped with VSV-G may transduce a subpopulation of gonadal cells in female fetuses with IP administration, whereas no evidence of gene transfer was shown to occur in males or with organ-targeting approaches.

984. Fetal Administration of Lentiviral Vectors and the Potential for Germ Cell Transduction in Rhesus Monkeys (Macaca mulatta)

Our prior studies have shown that the HIV-1-derived lentiviral vector can efficiently deliver transgenes into cells of multiple organ systems in rhesus monkey fetuses (Macaca mulatta) when delivered using systemic and organ-targeting approaches. In this study, we have focused on the potential for germ-line transduction post-fetal gene delivery when using the HIV-1-derived lentiviral vector expressing the enhanced green fluorescent protein (EGFP) under the control of the cytomegalovirus (CMV) promoter (HIV/VSV-G/CMV/EGFP; 107 infectious particles/fetus). Rhesus monkey fetuses (N=21) were administered lentiviral vector supernatant intraperitoneal (IP) at 50 days gestation, or using an intrapulmonary (N=24; 55-90 days gestation), intramyocardial (N=6; 60 days gestation), or yolk sac route (N=6; 25 days gestation) (term 165±10 days). Tissue harvests were performed near term or 3 months postnatal age. Genomic DNA obtained from collected sections of gonads was analyzed for vector sequences. Results indicated that higher EGFP copies per 50,000 cells were detected in fetal (4,464.9±1,485.7) or infant (43,442.7±31,833.8) ovaries compared to fetal (56.7±27.4) or infant (947.6±599.1) testes with IP administration. Germ cells, surrounding stromal cells, and the surface epithelium were then individually isolated from formalin-fixed tissue sections using laser capture microdissection, and re-analyzed for vector sequences. Vector sequences were detected in female fetal (2.5±1.7 EGFP copies/copy e-globin) or infant (0.5±0.5 EGFP copies/copy e-globin) germ cells, whereas no vector sequences were detected in male germ cells. For the ovarian surface epithelium, 0.7±0.4 to 2.2±1.7 EGFP copies/copy e-globin were detected in both age groups, whereas no or 0.8±0.8 EGFP copies/copy -globin were observed in males. Limited copies (<0.02 EGFP copies/copy e-globin) were detected in surrounding stromal cells of females, whereas no vector sequences were detected in males. There was no evidence of gene transfer to germ cells using any of the other routes of administration. The results of these studies suggest that the HIV-1-derived lentiviral vector may have a higher likelihood of transducing germ cells in vivo in female fetuses when administered IP at a defined period in gestation and when compared to male fetuses. These findings contrast results with direct organ-targeting gene transfer approaches (e.g., intrapulmonary, intramyocardial, intra-yolk sac), where no evidence of germ cell gene transfer was shown to occur.

The challenge of gene therapy and DNA delivery.

It is 10 years since the first gene therapeutic was administered to patients. Since that time approximately 3500 patients have been treated and although some evidence of gene transfer has been seen it has generally been inadequate for a meaningful clinical response. The major challenges have been delivery of DNA to the target cells and duration of expression. A variety of gene transfer systems have been evaluated and these are summarized with their advantages and disadvantages. Encouraging data have been obtained recently by a number of workers and there is some optimism that the enormous potential of gene therapy will be realized in the second decade of its development.

Evidence for Gene Transfer and Expression of Factor IX in Haemophilia B Patients Treated with an AAV Vector

Evidence for Gene Transfer and Expression of Factor IX in Haemophilia B Patients Treated with an AAV Vector

Hemophilia gene therapy: better than we hoped for?

The initial results of the first clinical trial of gene therapy in patients with hemophilia B have been reported 1 Kay M.A. et al. Evidence for gene transfer and expression of factor IX in hemophilia B patients treated with an AAV vector. Nat. Genet. 2000; 24: 257-261 Crossref PubMed Scopus (859) Google Scholar . This on-going trial is assessing the intra-muscular injection of an adeno-associated viral (AAV) vector expressing factor IX (F.IX) and, like most of the Phase I trials of gene therapy, the primary goal of the trial is safety.

Effect of host modification and age on airway epithelial gene transfer mediated by a murine leukemia virus-derived vector.

To study retroviral gene transfer to airway epithelia, we used a transient transfection technique to generate high titers (approximately 10(9) infectious units/ml after concentration) of murine leukemia virus (MuLV)-derived vectors pseudotyped with the vesicular stomatitis virus envelope glycoprotein (VSV-G). Transformed (CFT1) and primary airway epithelial cells were efficiently transduced by a VSV-G-pseudotyped lacZ vector (HIT-LZ) in vitro. CFT1 cells and primary cystic fibrosis (CF) airway cell monolayers infected with a vector (HIT-LCFSN) containing human CF transmembrane conductance regulator (CFTR) in the absence of selection expressed CFTR, as assessed by Western blot analysis, and exhibited functional correction of CFTR-mediated Cl- secretion. In vitro studies of persistence suggested that pseudotransduction was not a significant problem with our vector preparations. In a sulfur dioxide (SO2) inhalational injury model, bromodeoxyuridine (BrdU) incorporation rates were measured and found to exceed 50% in SO2-injured murine tracheal epithelium. HIT-LZ vector (multiplicity of infection of approximately 10) instilled into the SO2-injured tracheas of anesthetized mice transduced 6.1% +/- 1.3% of superficial airway cells in tracheas of weanling mice (3 to 4 weeks old; n = 10), compared to 1.4 +/- 0.9% in mice 5 weeks of age (n = 4) and 0.2% in mice older than 6 weeks (n = 15). No evidence for gene transfer following delivery of HIT-LZ to tracheas of either weanling or older mice not injured with SO2 was detected. Because only a small fraction of BrdU-labeled airway cells were transduced, we examined the stability of the vector. No significant loss of vector infectivity over intervals (2 h) paralleling those of in vivo protocols was detected in in vitro assays using CFT1 cells. In summary, high-titer vectors permitted complementation of defective CFTR-mediated Cl- transport in CF airway cells in vitro without selection and demonstrated that the age of the animal appeared to be a major factor affecting in vivo retroviral transduction efficiency.

Fetoscopic gene therapy for congenital lung disease

Fetal gene therapy offers the promise of cure for certain genetic diseases, like cystic fibrosis and surfactant protein B deficiency. The authors hypothesized that a fetoscopic approach could attain a high level of organ-specific gene transfer to the fetal lung late in gestation. To test this hypothesis the authors examined the efficacy, specificity, and toxicity of recombinant adenovirus-mediated transfer of the β-galactosidase marker gene to the lung of late gestation fetal sheep using a fetoscopic technique. Twelve fetal sheep of 125 to 135 days' gestation (term, 145 days) underwent fetoscopic bronchoscopy and intratracheal administration of a replication-deficient adenoviral vector that transduces the β-galactosidase marker gene. Escape of administered virus was prevented by the fetoscopic deployment of a detachable silicone balloon in the fetal trachea. All fetuses survived until being killed at 2 days after vector delivery for the histopathologic assessment of vector efficacy and specificity. Optimal β-galactosidase transgene expression was observed at a viral titer of 2 × 10 12 particles per milliliter of administered volume. Expression was greatest in the distal pulmonary parenchyma, particularly in type II pneumocytes, and extended out to the pleura. There was no evidence of gene transfer in either the large conducting airways or in any other fetal organ. The autoors have developed a minimally invasive technique for the specific pulmonary delivery of gene therapy vectors to the fetus with no associated acute toxicity. Gene transfer to the late gestation fetus for the treatment of congenital pulmonary disease may be feasible through fetoscopy.

Kidney-targeted liposome-mediated gene transfer in mice.

To develop gene therapy targeted to the kidney, we compared three different routes of liposome-mediated gene delivery to the kidney in mice, ie intra-renal-pelvic, intra-renal-arterial, and intra-renal-parenchymal injections. A plasmid construct, pCMV beta gal, containing a cytomegalovirus (CMV) immediate-early gene promoter and a beta-galactosidase reporter gene was mixed with a 1:1 liposome mixture of N[1-(2,3-dioleoyloxy)propyl]-N,N,trimethylammonium chloride (DOTMA)/dioleoyl phosphatidyl ethanolamine (DOPE). The pCMV beta gal-liposome complex was injected into the left kidney via three different routes. The efficacy of gene transfer was assessed using 5-bromo-4-chloro-3-indolyl beta-D-galactopyranoside (X-gal) staining on frozen kidney sections 3 to 42 days after injections. Cells with beta-galactosidase activity were detected in the cortex and outer medulla in both intra-renal-pelvic and intra-renal-arterial groups, but not in the intra-renal-parenchymal group or in the contralateral noninjected kidney. Evidence of gene transfer was observed only in tubular epithelial cells, but not in glomerular, vascular, or interstitial compartments. The levels of beta-galactosidase expression started to decrease 3 weeks after injection. The gene transfer in the kidney was not associated with nephrotoxicity as assessed by blood urea nitrogen levels and renal histology. We conclude that both intra-renal-pelvic and intra-renal-arterial injections provide a transient gene transfer to the renal tubular cells and are suitable routes for kidney-targeted gene therapy.

Pollen irradiation and possible gene transfer in Nicotiana species

Progeny from crosses of Nicotiana langsdorffii with gamma irradiated pollen of Nicotiana alata 'Crimson Bedder' showed skewed segregation in the F2 favoring the maternal parent. This is probably not gene transfer in a strict sense, rather just an extreme case of reduced transmission of irradiated chromosomes, leading to massive overrepresentation of maternal genes. Gene transfer or mutational loss may explain some anomalous F1 plants. Segregation in the F2 progeny showed the presence of several genes from the irradiated pollen. Crosses of Nicotiana sylvestris, N. plumbaginifolia N. paniculata, and Petunia parodii with irradiated pollen from N. alata and Petunia hybrida showed no evidence of gene transfer, nor did experiments with irradiated mentor pollen. This indicates that gene transfer with irradiated pollen between non-crossing species or between species giving sterile hybrids is probably a rare phenomenon.