Single Mendelian Gene Research Articles

The future of research in craniofacial biology and what this will mean for oral health professional education and clinical practice

Today, and looking to the future, scientific discoveries from cellular, developmental and molecular biology inform our understanding of cell, tissue and organ morphogenesis as exemplified in skin, bone, cartilage, dentine, enamel, muscle, nerve and many organs such as salivary glands and teeth. Present day biomedical science yields principles for the biomimetic design and fabrication of cells, tissues and organs. Bioengineering has become a strategy that can 'mimic' biological processes, and inform clinical procedures for tissue and organ replacements. The future of regenerative craniofacial biology holds enormous promise for the diagnosis and treatment of congenital birth defects, traumatic injuries, degenerative chronic diseases as well as for Mendelian single gene and complex multigene diseases and disorders. The past 50 years have heralded the completion of the human genome and the introduction of 'personalized medicine and dentistry', the utilization of stem cell therapy for an array of diseases and disorders, the 'proof of principle' to reverse select inherited diseases such as anhidrotic ectodermal dysplasia (ED), and the fruits from interdisciplinary research drawn from the diverse biomedical sciences. Looking to the future, we can readily anticipate as major goals to emphasize the clinician's role in identifying clinical phenotypes that can lead to differential diagnosis, and rejuvenate missing or damaged tissues by establishing processes for the utilization of gene, cell and/or protein therapies. The future is replete with remarkable opportunities to enhance clinical outcomes for congenital as well as acquired craniofacial malformations. Clinicians play a pivotal role because critical thinking and sound clinical acumen substantially improve diagnostic precision and thereby clinical health outcomes.

Applying Deep DNA Sequencing to Common, Complex Pediatric Traits

* Abbreviations: RDS — : respiratory distress syndrome The specific genetic factors contributing to the causes of complex pediatric diseases are gradually being identified through a combination of technological advances, advanced statistical methods, and large biorepositories with appropriate samples and data. These developments have the capacity to personalize diagnosis and treatment of the common complications faced by preterm infants. The article in this issue of Pediatrics by Wambach et al1 is illustrative of this transformation and was applied to respiratory distress syndrome (RDS), the most common respiratory morbidity associated with prematurity. The authors considered RDS as a complex disease with both genetic and environmental/developmental risk factors. By excluding infants of <34 weeks’ gestation, a sample cohort was studied that was enriched for genetic causes of RDS and depleted of some developmental risk factors. They examined several genes previously associated with Mendelian single-gene (recessive usually) contributors to RDS that may be severe even in the term neonate. They searched for heterozygotes of known mutations or more minor variants that would result in a less-extreme phenotype but still be significant contributors to RDS in the near-term infant. Their finding that ABCA3 mutations are overrepresented in preterm infants with RDS compared with those without … Address correspondence to Jeff Murray, MD, 2182 MedLabs, Department of Pediatrics, University of Iowa, Iowa City, IA 52242. E-mail: jeff-murray{at}uiowa.edu

A new rice &lt;I&gt;dwarf1&lt;/I&gt; mutant caused by a frame-shift mutation

A dwarf mutant C6PS, which has the similar phenotype as the recessive mutant Dwarf1 (d1), was produced from tissue-cultured plants of Zhonghua 11. In its progeny (T2), the ratio of tall to dwarf plants was in agreement with the expected segregation ratio (3:1) of a single Mendelian inheritance gene, which indicated that the variation of plant height is caused by a single gene. To locate the mutation, C6PS was crossed with Zhenshan 97 and Mudanjiang 8 for producing two F2 populations of F2 (CM) and F2 (CZ), respectively. The plant height in each F2 population also showed the same segregation pattern as that in T2 generation. SSR marker RM430 closely linked to Dwarf1 was preferentially used to genotype the F2 (CZ) population because C6PS showed the similar phenotype to d1 mutant. RM430 was significantly associated with plant height, which indicated that the mutant gene might be D1. Comparative sequencing of D1 between C6PS and Zhonghua 11 showed a 6 bp deletion occurred in the splice site of its ninth exon. The marker C6PS-D1L/R designed on the 6 bp deletion was co-segregated with plant height in T2 generation. The results indicated that C6PS was a new mutant of D1. This mutation led to a 26 bp deletion of the transcript and resulted in a frame-shift mutation and a premature stop codon in C6PS, which could not translate the functional Gα protein. C6PS was weakly sensitive to Brassinolide based on the leaf inclination angle test.

Introduction to the Maastricht workshop: lessons from the past and new directions in galactosemia

Hereditary galactosemia is an autosomal recessive genetic disorder of carbohydrate metabolism (OMIM 230400; Fridovich-Keil andWalter 2008; Elsas 2010; Berry and Walter 2011). The mutated gene encodes a protein, galactose1-phosphate uridyltransferase (GALT, EC 2.7.7.12), that catalyzes the conversion of galactose-1-phosphate and UDPglucose to UDP-galactose and glucose-1-phosphate (Fig. 1). In the newborn period, a life-threatening disease with multiorgan involvement emerges, particularly in those infants ingesting lactose in breast milk and proprietary baby formulas containing the ingredients of cow’s milk (Berry and Walter 2011). The first observation of this nutritional toxicity state involving the neonate and breast milk was by von Reuss in 1908 (von Reuss 1908). In the next decade, Goppert documented the presence of excess galactose in the urine of a similarly affected infant (Goppert 1917). The first well characterized infant with hypergalactosemia and galactosuria who responded to a lactose-restricted diet was described by Mason and Turner in 1935 (Mason and Turner 1935). This paper, describing an African-American infant with a variant form of galactosemia, served to reveal marked hypergalactosemia as an integral component of GALT deficiency. However, establishment of the abnormal biochemistry awaited the discovery of Schwarz in 1956 (Schwarz et al. 1956) that the substrate, galactose-1-phosphate, was elevated in erythrocytes from galactosemic patients exposed to galactose, and the demonstration later that year in the Kalkar laboratory that GALTenzyme activity was absent (Isselbacher et al. 1956). This rare Mendelian disorder with a world-wide frequency of 1/40,000 to 1/60,000 newborn infants entered the modern era of molecular biology when Reichardt and Berg cloned a GALT cDNA from a human liver library (Reichardt and Berg 1988), and its correct cDNA sequence enabled cloning and delineation of the structure of the GALT gene (Flach et al. 1990; Leslie et al. 1992). Soon thereafter, many causative gene mutations were identified producing a heterogeneous array of impaired pGALT function (Elsas and Lai 1998; Tyfield 2000; Calderon et al. 2007). It was clear in the decades following the landmark Mason and Turner paper that restriction of galactose intake in the affected newborn infant would usually permit survival and allow the following early infantile complications to remit, resolve or disappear: poor growth, poor feeding, emesis, jaundice, liver enlargement and dysfunction that includes hyperbilirubinemia, transaminasemia, hypofibrinoginemia with bleeding diathesis, cataracts, encephalopathy, including lethargy, irritability and hypotonia, hyperchloremic metabolic acidosis, albuminuria, generalized aminoaciduria and anemia. Yet, between 1970 and 1990, there was a growing awareness that there were “clouds over galactosemia” (Anonymous 1982; Holton and Leonard 1994), that patients were not faring as well as physicians had expected (Komrower and Lee 1970; Lee 1972; Fishler et al. 1972, 1980; Komrower 1982; Waisbren et al. 1983; Gitzelmann and Steinmann 1984), especially given the fact that lactose restriction largely eliminates death from E. coli sepsis (Levy et al. 1977). And, this was all the more poignant, as infants Communicated by: Estela Rubio

Four rice QTL controlling number of spikelets per panicle expressed the characteristics of single Mendelian gene in near isogenic backgrounds

Development of quantitative trait loci (QTL) near isogenic lines is a crucial step to QTL isolation using the strategy of map-based cloning. In this study, a recombinant inbred line (RIL) population derived from two indica rice varieties, Zhenshan 97 and HR5, was employed to map QTL for spikelets per panicle (SPP). One major QTL (qSPP7) and three minor QTL (qSPP1, qSPP2 and qSPP3) were identified on chromosomes 7, 1, 2 and 3, respectively. Four sets of near isogenic lines (NILs) BC(4)F(2) targeted for the four QTL were developed by following a standard procedure of consecutive backcross, respectively. These QTL were not only validated in corresponding NILs, but also explained amounts of phenotypic variation with much larger LOD scores compared with those identified in RILs. SPP in the four QTL-NILs expressed bimodal or discontinuous distributions and followed the expected segregation ratio of single Mendelian factor by progeny test. Finally, qSPP1, qSPP2, qSPP3 and qSPP7 were respectively mapped to a locus, 0.5 cM from MRG2746, 0.6 cM from MRG2762, 0.8 cM from RM49 and 0.7 cM from MRG4436, as co-dominant markers on the basis of progeny tests. These results indicate no matter how small effect minor QTL is, QTL may still express the characteristics of single Mendelian factor in NILs and isolation of minor QTL will be possible using high quality NILs. Pyramiding these QTL into a variety will largely enhance rice grain yield.

An optimal DNA pooling strategy for progressive fine mapping

We present a cost-effective DNA pooling strategy for fine mapping of a single Mendelian gene in controlled crosses. The theoretical argument suggests that it is potentially possible for a single-stage pooling approach to reduce the overall experimental expense considerably by balancing costs for genotyping and sample collection. Further, the genotyping burden can be reduced through multi-stage pooling. Numerical results are provided for practical guidelines. For example, the genotyping effort can be reduced to only a small fraction of that needed for individual genotyping at a small loss of estimation accuracy or at a cost of increasing sample sizes slightly when recombination rates are 0.5% or less. An optimal two-stage pooling scheme can reduce the amount of genotyping to 19.5%, 14.5% and 6.4% of individual genotyping efforts for identifying a gene within 1, 0.5, and 0.1 cM, respectively. Finally, we use a genetic data set for mapping the rice xl(t) gene to demonstrate the feasibility and efficiency of the DNA pooling strategy. Taken together, the results demonstrate that this DNA pooling strategy can greatly reduce the genotyping burden and the overall cost in fine mapping experiments.

38–48 kDa subunits of buckwheat 13S globulins are controlled by a single locus

AbstractThe inheritance of buckwheat (Fagopyrum esculentum Moench) seed storage proteins was investigated by control crosses between accessions containing different SDS‐PAGE protein patterns in the range of 38–48 kDa. Analysis of segregation of individual F1 and F2 seeds obtained by 17 crosses showed segregation of eight electrophoretic bands, from which 12‐banding variants were inferred. Two variants contained one band, nine contained two bands and one variant contained three bands and behaved as a single co‐dominant unit. The segregation of banding variants fits the expected ratios and thus supports the hypothesis of single Mendelian gene inheritance and that alleles are co‐dominant. The results therefore suggest that the genes controlling globulin subunits are tightly linked and inherited as a single locus. The locus was designated Glob‐1 and the twelve segregated protein variants as alleles a‐l. This is the first buckwheat globulin locus identified with multiple alleles, phenotypically expressed as groups of protein bands and thus applicable as a functional marker in buckwheat genomic studies.

38-48 kDa subunits of buckwheat 13S globulins are controlled by a single locus

The inheritance of buckwheat (Fagopyrum esculentum Moench) seed storage proteins was investigated by control crosses between accessions containing different SDS-PAGE protein patterns in the range of 38–48 kDa. Analysis of segregation of individual F1 and F2 seeds obtained by 17 crosses showed segregation of eight electrophoretic bands, from which 12-banding variants were inferred. Two variants contained one band, nine contained two bands and one variant contained three bands and behaved as a single co-dominant unit. The segregation of banding variants fits the expected ratios and thus supports the hypothesis of single Mendelian gene inheritance and that alleles are co-dominant. The results therefore suggest that the genes controlling globulin subunits are tightly linked and inherited as a single locus. The locus was designated Glob-1 and the twelve segregated protein variants as alleles a-l. This is the first buckwheat globulin locus identified with multiple alleles, phenotypically expressed as groups of protein bands and thus applicable as a functional marker in buckwheat genomic studies.

Fine mapping of the region on wheat chromosome 7D controlling grain weight

We report the fine mapping of the previously described quantitative trait loci (QTL) for grain weight QTgw.ipk-7D associated with microsatellite marker Xgwm1002-7D by using introgression lines (ILs) carrying introgressions of the synthetic wheat W-7984 in the genetic background of the German winter wheat variety 'Prinz'. The BC(4)F(3) ILs had a 10% increased thousand grain weight compared to the control group and the recurrent parent 'Prinz', and 84.7% of the phenotypic variance could be explained by the segregation of marker Xgwm1002-7D, suggesting the presence of a gene modulating grain weight, which was preliminarily designated gw1. It was possible to delimit the QTL QTgw.ipk-7D to the interval Xgwm295-Xgwm1002, which is located in the most telomeric bin 7DS4-0.61-1.00 in the physical map of wheat chromosome arm 7DS. Furthermore, our data suggest the presence of a novel plant height-reducing locus Rht on chromosome arm 7DS of 'Prinz'. Larger grain and increased plant height may reflect the pleiotropic action of one gene or may be caused by two linked genes. In general, our data support the concept of using nearly isogenic ILs for validating and dissecting QTLs into single Mendelian genes and open the gateway for map-based cloning of a grain-weight QTL in wheat.

Genome-wide expression profiling of lymphoblastoid cell lines distinguishes different forms of autism and reveals shared pathways †

Autism is a heterogeneous condition that is likely to result from the combined effects of multiple genetic factors interacting with environmental factors. Given its complexity, the study of autism associated with Mendelian single gene disorders or known chromosomal etiologies provides an important perspective. We used microarray analysis to compare the mRNA expression profile in lymphoblastoid cells from males with autism due to a fragile X mutation (FMR1-FM), or a 15q11-q13 duplication (dup(15q)), and non-autistic controls. Gene expression profiles clearly distinguished autism from controls and separated individuals with autism based on their genetic etiology. We identified 68 genes that were dysregulated in common between autism with FMR1-FM and dup(15q). We also identified a potential molecular link between FMR1-FM and dup(15q), the cytoplasmic FMR1 interacting protein 1 (CYFIP1), which was up-regulated in dup(15q) patients. We were able to confirm this link in vitro by showing common regulation of two other dysregulated genes, JAKMIP1 and GPR155, downstream of FMR1 or CYFIP1. We also confirmed the reduction of the Jakmip1 protein in Fmr1 knock-out mice, demonstrating in vivo relevance. Finally, we showed independent confirmation of roles for JAKMIP1 and GPR155 in autism spectrum disorders (ASDs) by showing their differential expression in male sib pairs discordant for idiopathic ASD. These results provide evidence that blood derived lymphoblastoid cells gene expression is likely to be useful for identifying etiological subsets of autism and exploring its pathophysiology.

Isolation, Characterization and Preliminary Genetic Analysis of Laboratory Tricyclazole‐resistant Mutants of the Rice Blast Fungus, Magnaporthe grisea

AbstractThe minimum inhibitory concentration of tricyclazole for hyphal melanization (MIC‐H) was adopted to detect the sensitivity of 129 Magnaporthe grisea isolates collected in China in 2000. Results showed that the mean MIC‐H was 0.2 μg/ml and no isolate with a MIC‐H ≥1 μg/ml was detected. Therefore, 1 μg/ml was chosen as a discriminatory dose to identify resistant mutants generated by ultraviolet (UV) radiation. Only three low‐level resistant (R) mutants derived from the sensitive (S) isolate TH16 were obtained. In addition, fitness decrease was observed for all mutants, with lower sporulation ability and pathogenicity to rice than that of the wild strain TH16. Four crosses between S × R and S × S were tested to determine the inheritance mode of resistance during the process of sexual recombination by analysing the sensitivity of hybrid F1 progeny to tricyclazole. Progeny of crosses between a tricyclazole‐sensitive strain and tricyclazole‐resistant mutants segregated in a 1 : 1 (R : S) ratio and no segregation was found in the cross of S × S, indicating that each mutant contained a single gene for resistance. No nucleotide differences leading to amino acid changes in the coding sequences for 1,3,6,8‐tetrahydroxynaphthalene reductase (4HNR) and 1,3,8‐trihydroxynaphthalene reductase (3HNR) were found between resistant mutants and sensitive strains. Therefore, it is preliminarily concluded that tricyclazole resistance in M. grisea was conferred by a one‐locus mutation in a single Mendelian gene other than those encoding for 4HNR or 3HNR.

Abnormal ascospore morphology in the bud mutant of Neurospora tetrasperma

A recessive ascospore mutant of Neurospora tetrasperma, named bud, was isolated from a wild-collected heterokaryotic strain with four different nuclear components. bud segregates as a single mendelian gene. When bud is homozygous, meiosis is apparently normal but postmeiotic events are not. Abnormal orientation of spindles at the postmeiotic mitosis often results in failed pair-wise association of nuclei and their irregular distribution along the length of the ascus prior to spore delimitation. Consequently, many asci cut out more than four ascospores; some contain no nuclei while others contain more than two. The most dramatic effect of bud is on ascospore delimitation itself. Many ascospores are irregularly shaped and are often interconnected, because of incomplete spore delimitation. Ascospores also show one or two lobes or bud-like extensions of varying sizes. Over 75% of ascospores from bud × bud remain white or tan and are inviable. The interaction of bud with a dominant Eight-spore mutant ( E) was examined in both heterozygous and homozygous crosses. When both bud and E are heterozygous, bud has no effect on ascospore delimitation or on the phenotype of E because bud is recessive; many asci produce 5–8 ascospores just as in E × E +. And when bud is homozygous and E is heterozygous, ascospore delimitation is less affected than when E is absent. Moreover, when both bud and E are homozygous, the effect on ascospore development is less extreme than when E is homozygous singly. Index Descriptors: Ascus development; Abnormal ascospore delimitation; Ascospore mutant; Ascospore lobes; Budded ascospores; Neurospora tetrasperma.

Renal epithelial proliferation and its clinical expression in Brown Norway (BN) rats.

Renal epithelial proliferation has previously been found to be a common condition in a colony of Lewis x Brown Norway (BN) F2 hybrid rats. The aim of this study was to investigate the prevalence and clinical consequences of this condition in pure inbred BN and Lewis rats. Renal epithelial proliferation was found in 29 of 49 BN rats (59%) examined and in four of 50 Lewis rats (8%) examined. Serum creatinine and serum corticosterone was not influenced by the condition. Haematuria was more common in BN rats with (74%) than without renal papillary proliferation (35%, P < 0.05), but it may not be used to diagnose renal epithelial proliferation, as we found rats having renal epithelial proliferation without showing haematuria and rats showing haematuria without having renal epithelial proliferation. Haematuria was also common in Lewis rats (16-56% dependent of age and gender), in which renal epithelial proliferation were found in only 8%. Fluctuating asymmetry, which was used as a measure of developmental instability, was found to be increased in rats with renal epithelial proliferation (P < 0.05). Haematuria was also found to be related to the degree of fluctuating asymmetry (P < 0.01). Although the prevalence of renal epithelial proliferation is clearly higher in BN rats than in Lewis rats (P < 0.01), and although in previous reports the condition was found in F2 BN x Lewis hybrids and not in F1 BN x Lewis hybrids it cannot clearly be defined as having been caused by a single Mendelian gene, as we found it in both inbred strains. Futhermore, we found that morphologically the proliferations could be placed on the papillary as well as the medullary wall of the renal pelvis, while previously it has only been described on the papillary wall.

Linkage mapping of genes controlling resistance to white rust (Albugo candida) in Brassica rapa (syn. campestris) and comparative mapping to Brassica napus and Arabidopsis thaliana.

Genes for resistance to white rust (Albugo candida) in oilseed Brassica rapa were mapped using a recombinant inbred (RI) population and a genetic linkage map consisting of 144 restriction fragment length polymorphism (RFLP) markers and 3 phenotypic markers. Young seedlings were evaluated by inoculating cotyledons with A. candida race 2 (AC2) and race 7 (AC7) and scoring the interaction phenotype (IP) on a 0-9 scale. The IP of each line was nearly identical for the two races and the population showed bimodal distributions, suggesting that a single major gene (or tightly linked genes) controlled resistance to the two races. The IP scores were converted to categorical resistant and susceptible scores, and these data were used to map a single Mendelian gene controlling resistance to both races on linkage group 4 where resistance to race 2 had been mapped previously. A quantitative trait loci (QTL) mapping approach using the IP scores detected the same major resistance locus for both races, plus a second minor QTL effect for AC2 on linkage group 2. These results indicate that either a dominant allele at a single locus (Acal) or two tightly linked loci control seedling resistance to both races of white rust in the biennial turnip rape cultivar Per. The map positions of white rust resistance genes in B. rapa and Brassica napus were compared and the results indicate where additional loci that have not been mapped may be located. Alignment of these maps to the physical map of the Arabidopsis genome identified regions to target for comparative fine mapping using this model organism.

Klippel-Feil anomaly with Sprengel anomaly, omovertebral bone, thumb abnormalities, and flexion-crease changes: Novel association or syndrome?

We report on a family with Klippel-Feil anomaly (KF), Sprengel anomaly, omovertebral bone, thumb abnormalities, and flexion-crease abnormalities. This combination of abnormalities does not fit into Holt-Oram syndrome, Wildervanck syndrome, oculo-auriculo-vertebral (Goldenhar) anomaly, or the VATER complex. Clinical aspects of a KF classification are discussed. The state of molecular research on KF is briefly reported. We conclude that this set of anomalies is a novel combination, probably representing pleiotropy of a single Mendelian gene.

The Control of Meiosis Progression in the Fungus Coprinus cinereus by Light/Dark Cycles

Meiosis progression in Coprinus cinereus is controlled by light/dark cycles. Light is essential to propel basidia into karyogamy and light intensity determines the timing of meiotic events. The higher the light intensities, the faster the fruiting bodies enter karyogamy. The critical period when light has this influence is between 16 and 6 h before karyogamy. The control is highly stage specific. A 3-h dark period is essential for a Java dikaryon and the Japanese AmutBmut homokaryon to enter meiotic metaphase; without it the fruit body is permanently arrested at diffused diplotene. This arrest is light intensity-dependent (>20 hlx) and temperature-dependent (e.g., 27°C). The placement of the dark period is very stage specific; it has no effect when placed before karyogamy stage. A dikaryon of London origin is light blind and able to complete meiosis under continuous high light regime. Fruiting bodies arrested under a continuous high light can be rescued by a 3-h dark treatment, but there is always an 8-h lag time to enter meiotic metaphase. It is possible that the dark effect signals cellular processes leading to division events. Cytological studies of arrested fruiting bodies showed that chromosomes are normal in meiotic prophase through pachytene and diplotene, but are unable to undergo chromosome condensation. Genetic crosses between a monokaryon of Java stock J6;5.4 and a monokaryon BL55 or H5 of London stock showed that light-blindness is dominant, and is controlled by a single Mendelian gene.

Inheritance and fine mapping of a major barley seed dormancy QTL

A major barley seed dormancy locus, SD1, was previously identified along with three others by quantitative trait locus (QTL) analysis in a Steptoe×Morex mapping population. Located in the centromere region of barley chromosome 7 (5H), SD1 shows the largest and most consistent effect on dormancy. Steptoe contributes the dormancy allele at SD1. The objective of this study was to determine the inheritance of and a more precise map location for SD1. A segregating population was designed and generated by marker assisted mating in which only SD1 segregated. The segregation ratio suggested a single Mendelian gene in which the dormancy allele is dominant to the non-dormancy allele at SD1. In addition, near isogenic lines (NIL) for the SD1 chromosome region were generated by molecular marker assisted backcrossing. Statistical analysis of germination percentages of these NIL revealed that there may be a gene cluster of at least three genes in the SD1 locus region. The dormancy locus, presumably SD1 or a part of the SD1 complex, was resolved into a ≈4.4 cM region.

Genetic control of blood infection levels in human malaria: evidence for a complex genetic model.

There is now accumulating evidence for the involvement of genetic factors in the control of immune response against malaria. These arguments come from numerous animal models, from population studies showing associations of red blood cell genetic defects as well as HLA antigens with severe malaria, and from familial studies including a recent segregation analysis, which led to detection of a major gene effect predisposing to high infection levels. The heterogeneity and complexity of this genetic control is one of the main findings of these previous studies, and probably a major cause of the difficulty in developing an effective malaria vaccine. A segregation analysis of blood infection levels is performed here in 44 pedigrees living in the tropical rain forest of southern Cameroon and exposed to high vectorial transmission intensity. The results confirm the existence of complex genetic factors controlling blood infection levels in human malaria but are not consistent with the parent-offspring transmission of a single Mendelian gene. This study also shows the dramatic effect of age on infection levels and its interaction with a putative major gene suggesting that genetic related differences are much more important in children than in adults. Further genetic studies focused on children may help to identify the nature of the genetic factors involved in the expression of human malaria, by means of linkage analyses using both familial information and genetic markers.

Isozyme inheritance and variation in Actindia

Isozyme inheritance and variation in Actinidia was investigated using 23 enzyme systems. Ten isozyme loci from six enzyme systems, Acp-2, Est, Prx-1, Prx-2, Prx-3, Prx-4, Prx-5, Pgi-2, Pgm-2 and Tpi, were found to be inherited as single Mendelian genes in families of two interspecific crosses. Disomic inheritance detected at 10 loci in progenies of a cross between the hexaploid A. deliciosa and the diploid A chinensis (Jingkui × Moshan no. 4) provided convincing evidence that A. deliciosa is an allohexaploid. Allelic segregation for tetrasomic inheritance at the 10 isozyme loci was demonstrated in the progenies of a cross between the tetraploid A. chinensis and the diploid A. eriantha, a result suggesting autoploid origin of the tetraploid A. chinensis, which apparently originated from its diploid ancestor A. chinensis. A high level of isozyme variation and heterozygosity was observed in the 22 cultivars and 56 plants from 28 Actinidia taxa. Allozyme phenotype can be used effectively for cultivar identification. The application of isozyme markers in the study of phylogeny could still be difficult in polyploids of natural populations in which estimations of gene frequencies are a prerequisite.

Sinapic Acid Ester Metabolism in Wild Type and a Sinapoylglucose-Accumulating Mutant of Arabidopsis

Sinapoylmalate is one of the major phenylpropanoid metabolites that is accumulated in the vegetative tissue of Arabidopsis thaliana. A thin-layer chromatography-based mutant screen identified two allelic mutant lines that accumulated sinapoylglucose in their leaves in place of sinapoylmalate. Both mutations were found to be recessive and segregated as single Mendelian genes. These mutants define a new locus called SNG1 for sinapoylglucose accumulator. Plants that are homozygous for the sng1 mutation accumulate normal levels of malate in their leaves but lack detectable levels of the final enzyme in sinapate ester biosynthesis, sinapoylglucose:malate sinapoyltransferase. A study of wild-type and sng1 seedlings found that sinapic acid ester biosynthesis in Arabidopsis is developmentally regulated and that the accumulation of sinapate esters is delayed in sng1 mutant seedlings.