Single Gene Difference Research Articles

Identification of key genes for atherosclerosis in different arterial beds

Atherosclerosis (AS) is the pathologic basis of various cardiovascular and cerebrovascular events, with a high degree of heterogeneity among different arterial beds. However, mechanistic differences between arterial beds remain unexplored. The aim of this study was to explore key genes and potential mechanistic differences between AS in different arterial beds through bioinformatics analysis. Carotid atherosclerosis (CAS), femoral atherosclerosis (FAS), infrapopliteal atherosclerosis (IPAS), abdominal aortic atherosclerosis (AAS), and AS-specific differentially expressed genes (DEGs) were screened from the GSE100927 and GSE57691 datasets. Immune infiltration analysis was used to identify AS immune cell infiltration differences. Unsupervised cluster analysis of AS samples from different regions based on macrophage polarization gene expression profiles. Weighted gene co-expression network analysis (WGCNA) was performed to identify the most relevant module genes with AS. Hub genes were then screened by LASSO regression, SVM-REF, and single-gene differential analysis, and a nomogram was constructed to predict the risk of AS development. The results showed that differential expression analysis identified 5, 4, 121, and 62 CAS, FAS, IPAS, AAS-specific DEGs, and 42 AS-common DEGs, respectively. Immune infiltration analysis demonstrated that the degree of macrophage and mast cell enrichment differed significantly in different regions of AS. The CAS, FAS, IPAS, and AAS could be distinguished into two different biologically functional and stable molecular clusters based on macrophage polarization gene expression profiles, especially for cardiomyopathy and glycolipid metabolic processes. Hub genes for 6 AS (ADAP2, CSF3R, FABP5, ITGAX, MYOC, and SPP1), 4 IPAS (CLECL1, DIO2, F2RL2, and GUCY1A2), and 3 AAS (RPL21, RPL26, and RPL10A) were obtained based on module gene, gender stratification, machine learning algorithms, and single-gene difference analysis, respectively, and these genes were effective in differentiating between different regions of AS. This study demonstrates that there are similarities and heterogeneities in the pathogenesis of AS between different arterial beds.

Selection and evaluation of stable reference genes for quantitative real-time PCR in the head kidney leukocyte of Oreochromis niloticus

To investigate the antibacterial mechanisms of Nile tilapia, it is necessary to understand the responses of immune-related genes in infected lymphocytes. Usually, quantitative real-time polymerase chain reaction (qRT-PCR) is applied to investigate transcriptional profiling. However, few studies have evaluated stable reference genes for qRT-PCR in Nile tilapia head kidney lymphocytes (HKLs). In this research, we assessed the stability of seven common reference genes, which include 18 S ribosomal RNA (18 s rRNA), beta actin (β-actin), beta-2-microglobulin-like (β-MG), elongation factor 1a (EF1A), Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Tubulin alpha chain-like (TUBA), and Ubiquitin-conjugating enzyme (UBE)，in both resting state and several responding states of Nile tilapia HKLs. Results showed that β-MG was the optimum reference gene in both resting state and LTA stimulation state, while GAPDH was the optimum for LPS stimulation. However, no single candidate gene could be employed as the universal reference under all situations. Next, the geNorm and RefFinder tools was applied to access the adequacy of the union of two reference genes, and the results suggested that the combination of β-MG and GAPDH was the best candidate. Finally, the expression profiles of three typical immune-related genes interleukin-1β (IL-1β), transcription factor p65(P65), and tumor necrosis factor α (TNFα) under LPS/LTA situations in HKLs were evaluated via multiple reference genes and single reference gene difference analysis. The findings revealed that TUBA and UBE were incapable of working as reference genes, and the union of two reference genes was better than any sole reference gene. The single-cell RNA-Seq (scRNA-Seq) data of Nile tilapia HKLs confirmed the above results. In conclusion, our data suggest that the combination of β-MG and GAPDH may be the best criterion for qRT-PCR calculation in tilapia HKLs.

CLEC1B is a Promising Prognostic Biomarker and Correlated with Immune Infiltration in Hepatocellular Carcinoma.

PurposeC-type lectin domain family 1 member B (CLEC1B) is a protein-coding gene involved in various processes, such as platelet activation, tumor cell metastasis and separation of blood/lymphatic vessels. However, how CLEC1B plays its role in hepatocellular carcinoma (HCC) has not been well studied. The purpose of this study was to investigate the clinical significance and biological function of CLEC1B in HCC.Patients and MethodsBased on (The Cancer Genome Atlas) TCGA database, CLEC1B expression matrix and corresponding clinical information were extracted. ROC curves and Kaplan–Meier method were generated to evaluate the value of CLEC1B as a diagnostic and prognostic biomarker. Moreover, single-gene difference analysis constructed by DESeq2 method and then the related genes were used to predict CLEC1B-related signaling pathways. The ssGSEA algorithm was conducted for studies related to immune infiltration. CLEC1B protein expression was evaluated and immunohistochemistry in HCC tissues through tissue microarray. Finally, the relationship between CLEC1B expression and T cell infiltration was assessed according to tissue microarray.ResultsThe mRNA and protein levels of CLEC1B were significantly down-regulated in HCC compared to paired normal tissues, which were further verified in clinical tissue samples. ROC curves and Kaplan–Meier survival analysis suggested the significant diagnostic and clinical prognostic value of CLEC1B. Meanwhile, downregulation of CLEC1B was significantly associated with clinical parameters such as clinical tumor vascular invasion and distant metastasis. Moreover, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene set enrichment (GSEA) analysis indicated that CLEC1B has significant association with immune function. Finally, immune infiltration analysis indicated that CLEC1B was significantly associated with immune cell subsets and affected the efficacy of immunotherapy in cancer patient.ConclusionCollectively, our findings suggested that CLEC1B could be a promising prognostic biomarker in HCC and its expression was related to immune cell infiltration.

Machine-Learning Single-Stranded DNA Nanoparticles for Bacterial Analysis.

A two-dimensional nanoparticle-single-stranded DNA (ssDNA) array has been assembled for the detection of bacterial species using machine-learning (ML) algorithms. Out of 60 unknowns prepared from bacterial lysates, 54 unknowns were predicted correctly. Furthermore, the nanosensor array, supported by ML algorithms, was able to distinguish wild-type Escherichia coli from its mutant by a single gene difference. In addition, the nanosensor array was able to distinguish untreated wild-type E. coli from those treated with antimicrobial drugs. This work demonstrates the potential of nanoparticle-ssDNA arrays and ML algorithms for the discrimination and identification of complex biological matrixes.

Comparison of the transcriptional profiles of head and body lice

Head and body lice are both blood-feeding parasites of humans although only the body louse is a potent disease vector. In spite of numerous morphological and life history differences, head and body lice have recently been hypothesized to be ecotypes of the same species. We took a comparative genomics approach to measure nucleotide diversity by comparing expressed sequence tag data sets from head and body lice. A total of 10 771 body louse and 10 770 head louse transcripts were predicted from a combined assembly of Roche 454 and Illumina sequenced cDNAs from whole body tissues collected at all life stages and during pesticide exposure and bacterial infection treatments. Illumina reads mapped to the 10 775 draft body louse gene models from the whole genome assembly predicted nine presence/absence differences, but PCR confirmation resulted in a single gene difference. Read per million base pair estimates indicated that 14 genes showed significant differential expression between head and body lice under our treatment conditions. One novel microRNA was predicted in both lice species and 99% of the 544 transcripts from Candidatus riesia indicate that they share the same endosymbiont. Overall, few differences exist, which supports the hypothesis that these two organisms are ecotypes of the same species.

Direct cloning of cell differential expression genes with full-length by a new strategy based on the multiple rounds of ‘long distance’ polymerase chain reaction and magnetic beads mediated subtraction

The paper described a new cDNA subtractive cloning strategy. This strategy was based on the ‘cap-finder’ method, ‘long distance’ polymerase chain reaction (PCR), streptavidin magnetic beads mediated subtraction, and spin column chromatography. When PCR products were resolved on agarose gel after three rounds of subtraction, the ‘single gene difference’ group displayed a predominantly enriched band, but the ‘multiple gene difference’ group did not display any apparent difference. Of 200 clones inserted with 0.7–2 kb fragments from the ‘multiple gene difference’ group, 50% were identified to be new sequences and 35% were known. Of 100 new sequences, 35% contained coding regions and 75% were confirmed by dot-blotting to be differentially expressed by genes of the target cell. The results suggested that this strategy might be very efficient for full-length cloning of differentially expressed genes of the cell.

Genetic Analysis and Identification of Amplified Fragment Length Polymorphism Markers Linked to the alm1 Avirulence Gene of Leptosphaeria maculans

ABSTRACT A gene-for-gene interaction was previously suggested by mapping of a single major locus (LEM 1) controlling cotyledon resistance to Leptosphaeria maculans isolate PHW1245 in Brassica napus cv. Major. In this study, we obtained further evidence of a gene-for-gene interaction by studying the inheritance of the corresponding avirulence gene in L. maculans isolate PHW1245. The analysis of segregating F(1) progenies and 14 test crosses suggested that a single major gene is involved in the interaction. This putative avirulence gene was designated alm1 after the resistance locus identified in B. napus. Amplified fragment length polymorphism (AFLP) markers were used to generate a rudimentary genetic linkage map of the L. maculans genome and to locate markers linked to the putative avirulence locus. Two flanking AFLP markers, AC/TCC-1 and AC/CAG-5, were linked to alm1 at 3.1 and 8.1 cM, respectively. Identification of markers linked to the avirulence gene indicated that the differential interaction is controlled by a single gene difference between parental isolates and provides further support for the gene-for-gene relationship in the Leptosphaeria-Brassica system.

Transgenic rats carrying the mouse renin gene--morphological characterization of a low-renin hypertension model.

Transgenic rats [TGR; strain name TGR(mRen2)27] harboring the mouse Ren-2 renin gene have been recently generated as a model for the study of primary hypertension that offers the advantage of a clearly-defined genetic alteration. Expression of the mouse Ren-2 gene causes severe hypertension (200 to 260 mm Hg) which is responsive to converting enzyme inhibitors. Compared to control transgene-negative littermates, plasma renin and angiotensin II values are lowered in TGR, whereas plasma prorenin values are strongly elevated. The adrenal gland in TGR shows marked overexpression of mouse renin messenger RNA; in situ hybridization using a 35S-labelled mouse-renin RNA probe reveals that enhanced renin expression is mainly localized to cells of the zona glomerulosa and outer zona fasciculata. Immunohistochemically, renin protein in the TGR adrenal gland is stored in larger quantities than in controls. Adrenal transgene expression probably accounts for most of the elevated plasma prorenin level in TGR, since bilateral adrenalectomy (ADX) causes a significant decrease in prorenin level (318 +/- 79 ng angiotensin I/ml/hr before ADX to 70 +/- 43 ng 4 days after ADX, P less than 0.0005). In the kidney, renin synthesis is almost completely suppressed in TGR. In situ hybridization demonstrates that few juxtaglomerular afferent arterioles express renin. Immunohistochemically, the TGR kidney shows significantly reduced renin and angiotensin II immunoreactivity at the afferent arteriole. Ultrastructural analysis of the afferent arteriolar wall frequently shows the complete absence of renin secretory granules since the granular cells are mostly converted into smooth muscle cells. Beginning at an age of approximately four to six months, TGR develop hypertension-related alterations and pathological lesions in various tissues. In the kidney, the wall thickness of arterioles and arteries is strongly increased, and glomerular lesions including different stages of sclerosis are observed. The thoracic aorta displays a considerable increase in tunica media thickness due to both myocyte hypertrophy and interstitial fibrosis. Coronary arteries and arterioles of the heart are thickened and perivascular fibrosis is observed. The data show that TGR(mRen2)27 transgenic rats display all typical characteristics of hypertensive pathology, making them an interesting model for therapeutic interventions. The fact that these changes occur in animals with a single gene difference to normotensive rats makes them a particularly suitable model for studies on gene-related hypertensive processes.

Survival of smooth, rough and transposon mutant strains of Brucella abortus in bovine mammary macrophages

Transposon mutants offer a unique way to evaluate the role of lipopolysaccharide (LPS) by producing a theoretical single-gene difference between the original strain and the transposon mutant strain. Comparative survival of Brucella abortus smooth strain 2308, rough RB51, smooth strain 19, and two transposon mutant strains (rough strain 2308::Tn5 Lac Z [m106] and rough strain 19::Tn5 Lac Z [m3], was tested in restrictive bovine mammary macrophages that were able to effectively reduce the percentage of intracellular bacterial survival and permissive bovine mammary macrophages that were unable to control the intracellular replication of B. abortus. The theoretical single-gene difference between strain 19 and strain 19::Tn5 lac Z [m3] and between smooth virulent strain 2308 and rough transposon mutant 2308::Tn5 lacZ [m106] is likely related to differences in LPS content or structure. Significant ( P<0.05) reduction in the survival of rough strain 19::Tn5 Lac Z [m3] with no significant reduction in the rough transposon mutant strain 2308::Tn5 lacZ [m106] indicated that at least one factor other than LPS contributes to the intracellular survival of B. abortus in bovine macrophages.

Expression of airway hyperreactivity to acetylcholine as a simple autosomal recessive trait in mice.

An increased airway response to various bronchoconstricting agents is one of the hallmarks of asthma. An interdependence of heredity and environment appears to determine this nonspecific hyperreactivity of the airways. The present study describes the patterns of inheritance of the airway response to a direct mediator of smooth muscle contraction (acetylcholine) in A/J and C3H/HeJ inbred mice and their offspring. The mean airway response to acetylcholine was greater than sixfold higher in A/J mice as compared with C3H/HeJ mice. Two phenotypes were easily distinguished on the basis of airway responses to acetylcholine in the progeny of A/J and C3H/HeJ mice. These two phenotypes were termed HYPERREACTIVE (after the A/J strain) and HYPOREACTIVE (after the C3H/HeJ strain). The observed frequencies of HYPERREACTIVE and HYPOREACTIVE phenotypes in the (A/J x C3H/HeJ) F1; (C3H/HeJ x A/J) F1 x C3H/HeJ (C3H/HeJ backcross); and the [(A/J x C3H/HeJ) F1 x (C3H/HeJ x A/J) F1] F2 are consistent with a single autosomal recessive gene primarily controlling acetylcholine-mediated airway responses. This single gene difference in airway response is completely inhibited by atropine and therefore mediated entirely by the muscarinic acetylcholine receptor.

Ribonucleic acid efflux from isolated mouse liver nuclei is altered by diet and genotypically determined change in nuclear envelope composition

Differencecs in immunological abnormalities like autoimmunity, abnormal T cell proliferative disorders and accelerated ageing occur between MRL/Mp-Ipr/Ipr(Ipr/Ipr) and MRL/Mp-+/+(+/+) mice as a consequence of one gene. The present study was designed to assess the effect of these differences in genotype and diet on the composition and function of the liver nuclear envelope. Mice of both stains were fed nutritionally adequate diets differing only in fatty acid composition for 4 weeks. Phospholipid fatty acid composition of the liver nuclear envelope was determined and the effect of altering the lipid composition of the nuclear membrane on nucleoside-triphosphatase (NTPase) activity, ribonucleic acid (RNA) efflux and binding of l-triiodothyronine ( l-T 3) was determined. Strain of mouse and level of dietary linoleic acid exhibited significant effects on the phospholipid fatty acid composition of the nuclear envelope. Levels of 18:1(n−9) and 18:2(n−6) were lower and 20:4(n−6) content was higher in nuclear envelope phospholipids of Ipr/Ipr mice compared with mice of the +/+ strain. Mice fed the high linoleic acid diet exhibited higher levels of 18:0, 18:2(n−6) and 20:4(n−6) and lower levels of 16:0 and 18:1(n−9) in liver nuclear envelope phospholipids, compared with mice fed the low linoleic acid diet. These changes in membrane composition were reflected in alteration of NTPase activity and efflux of RNA from isolated mouse liver nuclei. Nucleoside triphosphatase activity and efflux of ribonucleic acid from isolated nuclei were significantly higher in livers of the Ipr/Ipr strain. NTPase activity and RNA efflux from isolated nuclei were higher in the high linoleic acid fed group compared with the low linoleic acid group. A single class of binding sites for l-T 3 was present in liver nuclear envelopes of these mice and K d values were not influenced by strain or dietary linoleic acid levels. Nuclear envelopes prepared from +/+ animals exhibited a significantly higher number of binding sites for l-T 3 compared with the Ipr/Ipr group. These observations indicate that the single gene difference characterizing Ipr/Ipr mice from +/+ mice results in alterations in the composition and function of the nuclear envelope. This genetic differencec also alters the response of this membrane to dietary factors known to modulate characteristics and functions of the nuclear envelope.

Isolation of auxotrophic mutants of the hemibiotrophic ascomycete pathogen of brassicas, Pyrenopeziza brassicae

By screening conidia of Pyrenopeziza brassicae which had been irradiated with uv light, mutant strains have been isolated which grow on complete, but not on minimal, medium. A supplement which allows growth of the mutant when added to minimal medium has been identified in the case of eight of the nine initial isolates. All but one of the mutant strains have been crossed to a prototrophic strain which is resistant to the fungicide benomyl. In six of the strains, the auxotrophic phenotype has been shown to segregate in the progeny as if due to a single gene difference, and independently from the fungicide resistance marker. Two of the auxotrophic strains sporulated on host tissue in an in vitro test. Mutants of this kind will be useful in studies of heterokaryon formation, in a proposed molecular genetic analysis of pathogenicity, and as general genetic markers for this species.

Genetic rescue of inviable hybrids between Drosophila melanogaster and its sibling species.

Post-mating mechanisms are central to the establishment of reproductive isolation between different, but closely related, species. Post-mating isolation mechanisms include hybrid breakdown, hybrid sterility and hybrid lethality and may, in some cases, be reinforced by pre-mating mechanisms such as ethological differentiation. In the Drosophila melanogaster species sub-group post-mating reproductive isolation is ensured by both the inviability and the sterility of hybrids. For example when D. melanogaster females are crossed to D. simulans males the hybrid progeny are normally all female; the hybrid males die as third instar larvae. The viable hybrid females are totally sterile. Little is known of the genetic basis for either hybrid sterility or hybrid inviability, although Coyne and others have begun a genetic analysis of the sterility of hybrids within this species sub-group. We have discovered a single gene difference that rescues the otherwise inviable male hybrids from the cross between D. melanogaster females and males of its three closest relatives. The study of this locus may shed light on the genetic control of both speciation and development.

A single gene difference determines relative susceptibility to caffeine-induced lethality in SWR and CBA inbred mice

Inbred mouse strains SWR and CBA differ markedly in their relatively susceptibility to the acute toxic effects of intraperitoneally administered caffeine. At a dose of 187 mg/kg, SWR mice survive a stress-potentiated lethality test apparently related to the generation of tonic seizures; in contrast, CBA mice usually die in less than 30 seconds after this dose. Progeny from several different genetic crosses were characterized to determine the genetic basis underlying this phenotypic difference in caffeine sensitivity. F 1 progeny from reciprocal crosses of the parental strains were uniformly sensitive to caffeine-induced lethality, i.e., caffeine responsiveness behaves like an autosomal dominant trait. Self-crossing of F 1 individuals produced both progeny which were resistant to caffeine-induced lethality (26% of the total) and those which were susceptible (74%). Backcrosses of the F 1 animals to the CBA parent produced no (0/19) resistant progeny. In contrast, backcrosses of F 1 animals to SWR produced 54% resistant progeny. These data indicate that the difference in susceptibility to caffeine-induced lethality between these strains is determined by a single pair of autosomal alleles in which susceptibility (responsiveness) to this methylxanthine is dominant to resistance (nonresponsiveness).

Genetic control of the natural killer cell activity in SJL and other strains of mice.

Murine natural killer (NK) cell activity against lymphoma targets can be classified into three major functional phenotypes, i.e., low, inducible, and high, according to the levels of endogeneous activity and the extent of augmentation by interferon (IFN) or IFN inducers, as previously described. The prototype strains identifying these three phenotypes are SJL, A.SW, and B10.S, respectively, all bearing the H-2s haplotype. In the present study, the genetic basis of the low phenotype of SJL mice was examined further. F1 hybrid offspring of crosses between SJL and a strain with the high NK phenotype (B10.S, B10.D2, B10, C3H/HeN, or D1.LP) invariably expressed the high NK phenotype, indicating recessiveness of the low phenotype. Crosses between SJL and another low NK strain, such as A/J, A/HeN, or I/St, resulted in offspring of either the inducible or the high NK phenotype. Such genetic complementation between the low NK pairs indicates that the low phenotype of SJL and that of the other strains have different genetic bases. F1 hybrid mice between SJL and an inducible strain, A/WySn, were inducible, but those between SJL and the second inducible strain, A.SW, had the high NK phenotype. Thus, the congenic A/WySn and A.SW have distinct genotypes resulting in the same inducible phenotype. According to analyses of the segregating offspring from backcrosses of (SJL X B10.S)F1 mice to SJL, a single gene difference is responsible for the low endogenous level of NK activity in SJL as opposed to the high endogenous level in B10.S, and that the difference in three genes accounts for the poor responsiveness of NK cells to IFN in SJL mice. Studies of the two congenic lines of SJL, i.e., SJL-Igha and SJL-nu, indicated that the Igh locus is irrelevant for the low NK phenotype of SJL, but the nu locus clearly is relevant; SJL mice homozygous for the nu allele were phenotypically inducible in contrast to the nu/+ or +/+ mice which are low. The nu gene homozygosity rendered SJL mice responsive to IFN, not only in NK activity against lymphomas but also in ADCC activity against antibody-coated lymphoma cells.

Genetic considerations in the effects of ethanol in mice. II. A trans-acting inducibility regulator(s) affecting alcohol dehydrogenase (ADH) activity.

The inducibility of alcohol dehydrogenase (ADH) has been recognized in different systems including maize, Drosophila, and mice. Our earlier results showed strain-specific ADH responses to chronic ethanol administration relative to matched littermate controls in mice. For this study we used two strains which showed "induction" (BALB/c and S.W.) and two strains which showed "repression" (C57BL/6J and 129/ReJ) to produce three sets of F1 hybrids and their reciprocals and one set (BALB/c X C57BL/6J) of recombinant inbred (RI) lines. The ADH properties of the resulting genotypes were again evaluated following 15% ethanol treatment in drinking water (2 weeks) in relation to their littermate matched controls in replicated trials. Our F1 results suggest complete dominance for induction over repression at the phenotypic level, and the two repressed strains showed complementation. No significant differences were observed in the reciprocal F1's and all pairs of a given genotype-treatment combination yielded consistent results. The 1:1 segregation of RI lines suggests a single gene difference for ADH inducibility between BALB/c and C57BL/6J. These findings suggest the presence of a trans-acting inducibility regulator(s) for ADH which may or may not represent a single locus. Variability for such regulatory elements may provide an explanation for the commonly observed individual differences in natural populations for response to alcohol including alcohol metabolism.

GENETIC STUDIES ON KERNEL HARDNESS IN WHEAT USING GRINDING TIME AND NEAR INFRARED REFLECTANCE SPECTROSCOPY

Kernel hardness was measured in 600 random lines from five crosses and in seven control cultivars of spring wheat grown in 2 yr, using grinding time and near infrared reflectance spectroscopy. Both methods clearly differentiated soft from hard cultivars. Grinding time was the more accurate method because it gave lower coefficients of variation and higher correlations between years but it required five times more grain. The parents of the five crosses represented a range in hardness and were themselves from the cross Opal (hard) × Pitic 62 (soft). A hard × hard cross gave only hard lines; a medium × soft cross gave mostly soft; three soft or medium × hard crosses gave a wide range of hardness types that in two crosses suggested a single gene difference between hard and soft. Heritability of grinding time in standard units ranged from 55 to 92% per progeny and on average was 10% greater for soft lines than for hard.Key words: Wheat, kernel hardness, grinding time, Technicon InfraAlyzer, genetics

Inheritance of Male Sterility in Flax Involving Nuclear‐Cytoplasmic Interaction, Including Methods of Testing for Cytoplasmic Restoration1

An interaction between cytoplasm and nuclear genes affecting the inheritance of male sterility in flax (Linum usitatissimum L.) was reported first by workers in England in the 1920s in crosses between procumbent and tall plants and later by a worker in Poland using Linum floccosum. Previously unpublished data are reported on a similar case involving a large‐seeded flax from Crete. The interaction was discovered in all cases by noting that crosses using procumbent, L. floccosum, and Crete as female parents with most other stocks as male parents had fertile and male‐sterile plants in F2; whereas the reciprocal crosses had only fertile plants.For certain crosses using Crete as the female parent, the F2 segregation ratios were for a single gene difference. Other crosses may have involved two genes complementary either for restoration of pollen fertility in F1 or for incomplete restoration. Either of two hypotheses will explain the difference in behavior between reciprocal crosses. One hypothesis is that procumbent, L. floccosum, and Crete have a dominant fertility allele, Ms, and a non‐restorer [N] cytoplasm. Most other stocks have the recessive male‐sterile, ms ms, nuclear genotype but a cytoplasm [c R] that restores fertility. The cross of male steriles [N] ms ms with maintainer [c R] ms ms stocks would produce all male‐sterile progeny. Crossing these male steriles with Ms Ms would produce hybrid seed.The second hypothesis that may explain the difference in behavior between reciprocal crosses assumes that procumbent, L. floccosum, and Crete have cytoplasmic male sterility [cms] together with a nuclear gene for restoration of pollen fertility (Rf). Most other flax stocks would have a normal non‐male‐sterile cytoplasm [N] and the non‐restorer gene, rf. Male‐sterile plants would be [cms] rf rf and maintainer stocks would be [N] rf rf.Tests using genetic male sterility to identify lines with cytoplasmic restoration of fertility are discussed, together with methods of distinguishing the possible nuclear genotypes.For any species in which most stocks have the nonrestorer [N] type of cytoplasm and the restorer type [c R] is rare, an advantage of this system for producing hybrid seed is the ability to produce large quantities of seed that will give only male‐sterile plants yet not transmit a unique cytoplasm to the hybrid seed offered to farmers. Development and maintenance of the parental stocks can be accomplished by conventional breeding techniques.

ALTERNATIVE PHENOTYPIC STATES IN GENOMICALLY IDENTICAL CELLS: INTERSTOCK GENETICS OF A TRICHOCYST PHENOTYPE IN PARAMECIUM TETRAURELIA

The trichocysts of most wild stocks of Paramecium tetraurelia discharge en masse in response to picric acid. In most nonresponding wild stocks, the defective phenotype is simply determined by a single recessive gene difference from the standard wild type, stock 51. However, two wild stocks, 146 and 148, which are completely homozygous at all loci, express either a nondischarge, ND, or discharge, DI, phenotype. In stock 146, both ND and DI sublines generally reproduce true to type, but observed changes are highly biased. Changes from ND to DI occur more than ten times as often as changes from DI to ND. After conjugation between ND and DI cells, genomically identical exconjugant lines from the ND parent may be either ND or DI, while those from the DI parent invariably remain DI.-Interstock crosses between stocks 146 and 51 indicate that stock 146 possesses a recessive gene, nd146, which, when homozygous in stock 51 background, produces a distinct nondischarge phenotype, KO. Crosses between stock 146 and KO phenotype nd146 homozygotes in stock 51 background demonstrate that stock 146 possesses a dominant gene, M-nd146, which modifies the defect of nd146 homozygotes, resulting in either the ND or DI phenotype. The two loci, M-nd146 and nd146, are linked and estimated to be 5.3 centiMorgans apart. Stock 148 has the same alleles as stock 146 at these loci.-Presumably M-nd146 is involved in the dual phenotypic states in stock 146, but M-nd146 nd146 homozygotes backcrossed into stock 51 are invariably discharging. The possibility that the original ND state is independent of these genes is discussed and is regarded as unlikely. The phenotypic and genetic relationship discovered in these stocks should remind population biologists that phenotypic and genotypic variability do not always have a simple relationship. The nature and frequency of epistasis in the highly inbreeding P. tetraurelia are reviewed.

Fruit-setting inSophora microphyllaAit.

Abstract Observation of fruit-set in Sophora microphylla Ait. suggests that differences in both natural populations and ornamental plantings depend on the extent of self-pollination which can occur. This appears to be regulated by the time of style elongation which, if it occurs before anthesis, effectively prevents selling. A single gene difference could account for the observed variation.