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Background and Aims Dipteran insects are known pollinators of many angiosperms, but knowledge on how flies affect floral evolution is relatively scarce. Some plants pollinated by fungus gnats share a unique set of floral characters (dark red display, flat shape and short stamens), which differs from any known pollination syndromes. We tested whether this set of floral characters is a pollination syndrome associated with pollination by fungus gnats, using the genus Euonymus as a model. Methods The pollinator and floral colour, morphology and scent profile were investigated for ten Euonymus species and Tripterygium regelii as an outgroup. The flower colour was evaluated using bee and fly colour vision models. The evolutionary association between fungus gnat pollination and each plant character was tested using a phylogenetically independent contrast. The ancestral state reconstruction was performed on flower colour, which is associated with fungus gnat pollination, to infer the evolution of pollination in the genus Euonymus. Key Results The red-flowered Euonymus species were pollinated predominantly by fungus gnats, whereas the white-flowered species were pollinated by bees, beetles and brachyceran flies. The colour vision analysis suggested that red and white flowers are perceived as different colours by both bees and flies. The floral scents of the fungus gnat-pollinated species were characterized by acetoin, which made up >90 % of the total scent in three species. Phylogenetically independent contrast showed that the evolution of fungus gnat pollination is associated with acquisition of red flowers, short stamens and acetoin emission. Conclusions Our results suggest that the observed combination of floral characters is a pollination syndrome associated with the parallel evolution of pollination by fungus gnats. Although the role of the red floral display and acetoin in pollinator attraction remains to be elucidated, our finding underscores the importance of fungus gnats as potential contributors to floral diversification. [ABSTRACT FROM AUTHOR]

Background  Post-myocardial infarction ventricular septal defects (VSDs) have become rare in the reperfusion era but remain associated with very high morbidity and mortality. As patients defer prompt evaluation and management of acute coronary syndromes during the COVID-19 global pandemic, the incidence of these and other post-infarction mechanical complications is expected to increase. Case summary  A 37-year-old gentleman with multiple coronary artery disease risk factors presented with intermittent chest discomfort and 1 week of heart failure symptoms. An echocardiogram demonstrated a large muscular VSD and coronary angiography confirmed the presence of an anterior wall infarction. He was subsequently referred for transcatheter VSD repair and showed rapid clinical improvement in his symptoms. Discussion  Post-infarction VSDs remain associated with a high degree of morbidity and mortality. Surgical repair of acutely ruptured myocardium can be technically challenging, and transcatheter repair has emerged as a safe and effective alternative. [ABSTRACT FROM AUTHOR]

Cold-adapted hellbender salamanders that inhabit cool mountain streams are expected to fare poorly under warmer projected climate scenarios. This study investigated the physiological consequences of long-term, naturalistic temperature variation on juvenile hellbenders under simulated current and warmer (+1.6 C) climates vs. controlled steady temperatures. Mean temperature and temperature variability were both important predictors of growth as indicated by monthly body mass change (%), stress as indicated by neutrophil:lymphocyte (N:L) ratio and bacteria-killing ability of blood. Cold exposure in hellbenders was associated with weight loss, increased N:L ratios and reduced Escherichia coli killing ability of blood, and these effects were less pronounced under a warmer climate scenario. These observations suggest that cold periods may be more stressful for hellbenders than previously understood. Growth rates peaked in late spring and late fall around 14–17°C. Hellbenders experiencing warmer simulated climates retained body condition better in winter, but this was counter-balanced by a prolonged lack of growth in the 3-month summer period leading up to the fall breeding season where warmer simulated conditions resulted in an average loss of −0.6% body mass/month, compared to a gain +1.5% body mass/month under current climate scenario. Hellbenders can physiologically tolerate projected warmer temperatures and temperature fluctuations, but warmer summers may cause animals to enter the fall breeding season with a caloric deficit that may have population-level consequences. [ABSTRACT FROM AUTHOR]

This article reflects upon the experience of researching and teaching human rights, and related areas, in a number of university settings. It is argued, on the one hand, that interdisciplinarity is necessary, present and considered valuable in academic human rights scholarship. On the other hand, the article argues that disciplinary power is exercised in the academy with the effect of limiting the degree to which interdisciplinary research and teaching can take place in practice. As a consequence, interdisciplinary academics (and students) are punished. Both intellectual horizons and material opportunities are potentially constricted. Reflecting upon this potential, the article considers whether it is practically possible to reduce or avoid the disciplining and punishment of this kind of teaching and research in universities and concludes by making the case for a postdisciplinary reimagining of human rights in the academy. [ABSTRACT FROM AUTHOR]

Phenotypic variation is often used to delineate species and subspecies boundaries. Statistical analysis of phenotypic variation within a species is helpful both for understanding biodiversity and for its conservation. At least three named subspecies of barn swallows (Hirundo rustica) have distributions that span China, yet, to date, no systematic study of phenotypic differentiation has been applied to understand the delineation of these subspecies. In this study, we collected 510 samples of barn swallow from 23 populations in China, including two recognized subspecies, H. r. rustica and H. r. gutturalis , and one potential subspecies, H. r. mandschurica. With these samples, we examined and found morphometric and colour differences among different populations. Western Chinese barn swallows (H. r. rustica) have larger body size and could be clearly differentiated from eastern H. r. gutturalis and H. r. mandschurica , while north-eastern populations (named H. r. mandschurica) have darker, redder ventral plumage than H. r. rustica and H. r. gutturalis. However, we inferred that although there were phenotypic differences between H. r. mandschurica and H. r. gutturalis , they were not sufficiently distinct to assign them to separate subspecies based on the 75% rule for defining subspecies. [ABSTRACT FROM AUTHOR]

Mitotane (o,p'DDD) is established in the adjuvant and advanced-stage treatment of adrenocortical carcinoma and counteracts both tumor growth and tumor-related steroid production. Both the adrenal glands and the gonads are steroidogenically active organs and share a common embryogenic origin. Here, we describe the effects of mitotane in two patients with metastatic Leydig cell tumor (LCT) of the testes and associated severe androgen excess (serum testosterone 93 and 88 nmol/L, respectively; male reference range 7-27 nmol/L). Both men suffered from severe restlessness, insomnia and irritability, which they described as intolerable and disrupting normal life activities. Urinary steroid profiling by gas chromatography-mass spectrometry (GC-MS) confirmed excess androgen production and revealed concurrent overproduction of glucocorticoids and glucocorticoid precursors, which under physiological conditions are produced only by the adrenal glands but not by the gonads. In a palliative approach, they were commenced on mitotane, which achieved swift control of the hormone excess and the debilitating clinical symptoms, restoring normal quality of life. GC-MS demonstrated normalization of steroid production and decreased 5α-reductase activity, resulting in decreased androgen activation, and imaging demonstrated disease stabilization for 4-10 months. In conclusion, mitotane can be highly effective in controlling steroid excess in metastatic LCTs, with anti-tumor activity in some cases. [ABSTRACT FROM AUTHOR]

The maize female gametophyte contains four cell types: two synergids, an egg cell, a central cell, and a variable number of antipodal cells. In maize, these cells are produced after three rounds of free-nuclear divisions followed by cellularization, differentiation, and proliferation of the antipodal cells. Cellularization of the eight-nucleate syncytium produces seven cells with two polar nuclei in the central cell. Nuclear localization is tightly controlled in the embryo sac. This leads to precise allocation of the nuclei into the cells upon cellularization. Nuclear positioning within the syncytium is highly correlated with their identity after cellularization. Two mutants are described with extra polar nuclei, abnormal antipodal cell morphology, and reduced antipodal cell number, as well as frequent loss of antipodal cell marker expression. Mutations in one of these genes, indeterminate gametophyte2 encoding a MICROTUBULE ASSOCIATED PROTEIN65-3 homolog, shows a requirement for MAP65-3 in cellularization of the syncytial embryo sac as well as for normal seed development. The timing of the effects of ig2 suggests that the identity of the nuclei in the syncytial female gametophyte can be changed very late before cellularization. [ABSTRACT FROM AUTHOR]

Plants exhibit rapid, systemic signaling systems that allow them to coordinate physiological and developmental responses throughout the plant body, even to highly localized and quickly changing environmental stresses. The propagation of these signals is thought to include processes ranging from electrical and hydraulic networks to waves of reactive oxygen species (ROS) and cytoplasmic Ca2+ traveling throughout the plant. For the Ca2+ wave system, the involvement of the vacuolar ion channel TWO PORE CHANNEL1 (TPC1) has been reported. However, the precise role of this channel and the mechanism of cell-to-cell propagation of the wave have remained largely undefined. Here, we use the fire-diffuse-fire model to analyze the behavior of a Ca2+ wave originating from Ca2+ release involving the TPC1 channel in Arabidopsis (Arabidopsis thaliana). We conclude that a Ca2+ diffusion-dominated calcium-induced calcium-release mechanism is insufficient to explain the observed wave transmission speeds. The addition of a ROS-triggered element, however, is able to quantitatively reproduce the observed transmission characteristics. The treatment of roots with the ROS scavenger ascorbate and the NADPH oxidase inhibitor diphenyliodonium and analysis of Ca2+ wave propagation in the Arabidopsis respiratory burst oxidase homolog D (AtrbohD) knockout background all led to reductions in Ca2+ wave transmission speeds consistent with this model. Furthermore, imaging of extracellular ROS production revealed a systemic spread of ROS release that is dependent on both AtRBOHD and TPC1. These results suggest that, in the root, plant systemic signaling is supported by a ROS-assisted calcium-induced calcium-release mechanism intimately involving ROS production by AtRBOHD and Ca2+ release dependent on the vacuolar channel TPC1. [ABSTRACT FROM AUTHOR]

The mainstream human rights discourse has largely privileged individual rights over collective rights and civil and political rights over economic, social and cultural rights. Furthermore, much scholarship on collective social movements posits a shift in recent decades towards mobilization around identity politics and away from the economic or class-based focus of trade unions. In contrast, this policy and practice note argues against drawing a sharp analytical dichotomy between new identity-based and old class-based social movements. Moreover, it posits that there is value added by considering trade unions as human rights organizations (of a particular kind). Indeed, it is argued that in order to overcome some of the shortcomings of mainstream human rights discourse and practice it is both desirable and necessary to engage with the praxis of trade unions from a human rights perspective. [ABSTRACT FROM AUTHOR]

Whereas a rich literature exists for estimating population genetic divergence, metrics of phenotypic trait divergence are lacking, particularly for comparing multiple traits among three or more populations. Here, we review and analyze via simulation Hedges' g, a widely used parametric estimate of effect size. Our analyses indicate that g is sensitive to a combination of unequal trait variances and unequal sample sizes among populations and to changes in the scale of measurement. We then go on to derive and explain a new, non-parametric distance measure, "Δp", which is calculated based upon a joint cumulative distribution function (CDF) from all populations under study. More precisely, distances are measured in terms of the percentiles in this CDF at which each population's median lies. Δp combines many desirable features of other distance metrics into a single metric; namely, compared to other metrics, p is relatively insensitive to unequal variances and sample sizes among the populations sampled. Furthermore, a key feature of Δp—and our main motivation for developing it—is that it easily accommodates simultaneous comparisons of any number of traits across any number of populations. To exemplify its utility, we employ Δp to address a question related to the role of sexual selection in speciation: are sexual signals more divergent than ecological traits in closely related taxa? Using traits of known function in closely related populations, we show that traits predictive of reproductive performance are, indeed, more divergent and more sexually dimorphic than traits related to ecological adaptation [ABSTRACT FROM AUTHOR]

Speciation processes are largely determined by the relative strength of divergent selection versus the magnitude of gene flow. The barn swallow (Hirundo rustica) has a broad geographic distribution that encompasses substantial geographic variation in morphology and behavior. The European (H. r. rustica) and East-Mediterranean (H. r. transitiva) subspecies are closely related, despite differing in morphological and life-history traits. To explore patterns of genetic differentiation and gene flow, we compared morphological and genetic variation among the nonmigratory breeding population of H. r. transitiva from Israel and the migratory population of H. r. rustica that passes through Israel and compared it with the genetic differentiation between H. r. transitiva from Israel and a breeding population of H. r. rustica from the United Kingdom that uses a different migratory flyway. Mitochondrial haplotype network analysis suggests that the European and East-Mediterranean populations are intermixed, although there was low but significant genetic differentiation between the subspecies based on both mitochondrial (FST = 0.025–0.033) and microsatellite (FST = 0.009–0.014) loci. Coalescent-based analyses suggest recent divergence and substantial gene flow between these populations despite their differences in morphological and behavioral traits. The results suggest that these subspecies are undergoing a differentiation process in the face of gene flow, with selection possibly operating on sexually selected traits. [ABSTRACT FROM PUBLISHER]

Many higher eukaryotes have evolved strategies for the maternal control of growth and development of their offspring. In higher plants this is achieved in part by postmeiotic gene activity controlling the development of the haploid female gametophyte. stunter1 (stt1) is a novel, recessive, maternal effect mutant in maize that displays viable, miniature kernels. Maternal inheritance of stt1 results in seeds with reduced but otherwise normal endosperms and embryos. The stt1 mutation displays reduced transmission through the male and female parents and causes significant changes in the sizes of both male and female gametophytes. stt1 pollen grains are smaller than wild type, have reduced germination efficiency, and reduced pollen tube growth. stt1 embryo sacs have smaller central cells and abnormal antipodal cells that are larger, more vacuolated, and fewer in number than wild type. Embryos and endosperms produced by fertilization of stt1 embryo sacs develop and grow more slowly than wild type. The data suggest that the morphology of mutant embryo sacs influences endosperm development, leading to the production of miniature kernels in stt1. Analysis of seeds carrying a mutant maternal allele of stt1 over a deletion of the paternal allele demonstrates that both parental alleles are active after fertilization in both the endosperm and embryo. This analysis also indicates that embryo development until the globular stage in maize can proceed without endosperm development and is likely supported directly by the diploid mother plant. [ABSTRACT FROM AUTHOR]

Major genes govern the fertilization of teosinte ovules by maize pollen. A pollen–pistil compatibility system different from the previously described systems, Ga1-s and Tcb1-s, was identified among maize lines introgressed with chromosome segments from 2 teosinte populations. The pistil barrier is dominant, and pollen competence is determined by genotype of the individual pollen grain. A major gene governing this incompatibility behaves as a strong allele of ga2, a locus identified previously among maize genetic stocks on the basis of transmission ratio distortion. Additionally, pollen simultaneously carrying both ga2 and Ga2 was functional on Ga2 silks, which have the pistil barrier, indicating that Ga2 conditions acceptance of the pollen grain rather than ga2 conditioning rejection of the pollen grain by Ga2 silks. The strong allele (Ga2-s), a weaker one such as reported among maize genetic stocks (Ga2-w), and an allele having only pollen competence (Ga2-m), or some combination of these, was found in all 13 of the teosinte populations sampled. Sympatric and parapatric maize landraces carried Ga2-m or the presumed null allele ga2, but Ga2-s or Ga2-w was not found. The combination of exclusively Ga2-s teosinte with ga2 maize, which could provide strong reproductive isolation, was not characteristic of the 5, paired populations tested. [ABSTRACT FROM PUBLISHER]

Extrapair mating is known to occur in many animals and potentially has a significant influence on reproductive success. Female extrapair mate choice may explain the occurrence of exaggerated ornaments in socially monogamous species, but the influence of ornamentation on extrapair mating success has rarely been investigated experimentally. Cape sugarbirds (Promerops cafer) are socially monogamous, almost always lay 2 egg clutches and have long-term pair bonds often lasting several seasons. However, they also display sexually dimorphic extravagant ornamentation in the form of a long, graduated tail and have one of the highest rates (65% of young) of extrapair paternity recorded in birds. We provide a test of the hypothesis that the ornamented tail is used in mate choice for extrapair partners by conducting an experiment in which tail length was manipulated after social mating but before copulation. This experiment therefore allowed females to respond to the manipulation of male tail length when making a choice of copulation partner but not social mate. We show that the tail length of male sugarbirds has a significant effect on the success of males in gaining extrapair paternity, with long-tailed males obtaining significantly more extrapair young than short-tailed males. However, males with short tails sire a significantly greater proportion of the nestlings in their own nests than long-tailed individuals. This result suggests that males may adopt alternative strategies dependent on their ornamentation. [ABSTRACT FROM PUBLISHER]

The Arabidopsis thaliana REVOLUTA (REV) protein is a member of the class III homeodomain-leucine zipper (HD-ZlPIII) proteins. REV is a potent regulator of leaf polarity and vascular development. Here, we report the identification of a gene family that encodes small leucine zipper-containing proteins (LITTLE ZIPPER [ZPR] proteins) where the leucine zipper is similar to that found in REV, PHABULOSA, and PHAVOLUTA proteins. The transcript levels of the ZPR genes increase in response to activation of a steroid-inducible REV protein. We show that the ZPR proteins interact with REV in vitro and that ZPR3 prevents DNA binding by REV in vitro. Overexpression of ZPR proteins in Arabidopsis results in phenotypes similar to those seen when HD-ZlPIII function is reduced. We propose a negative feedback model in which REV promotes transcription of the ZPR genes. The ZPR proteins in turn form heterodimers with the REV protein, preventing it from binding DNA. The HD-ZlPIII/ZPR regulatory module would serve not only to dampen the effect of fluctuations in HD-ZlPIII protein levels but more importantly would provide a potential point of regulation (control over the ratio of inactive heterodimers to active homodimers) that could be influenced by other components of the pathway governing leaf polarity. [ABSTRACT FROM AUTHOR]

Many studies have focused on tail ornamentation in birds, but not all tail shapes have been studied in depth. Graduated and pin tails have received less attention than forked tails, despite being more likely, in terms of aerodynamic theory, to be honest signals. We report morphological variation in live specimens of two sexually dimorphic passerines from the same site with different tail shapes: graduated (Cape sugarbird Promerops cafer) and pin (orange-breasted sunbird Antobaphes violacea). Coefficients of variation (CVs) were calculated for all morphological traits, both non-ornamental (range 1.91–5.72) and ornamental (range 5.83–21.71). Males and females did not differ in CV for any non-ornamental trait. Ornamental traits in males of both species were significantly more variable than all non-ornamental traits. Cape sugarbird ornamental traits were significantly more variable than those of orange-breasted sunbirds. The high levels of variation in graduated tails relative to pintails suggest that these traits have been driven mainly by sexual selection. In contrast, both constraining natural and multiple ornament selection could be responsible for the relatively low levels of variation in pintails. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 437–443. [ABSTRACT FROM AUTHOR]

Angiosperm embryo sac development begins with a phase of free nuclear division followed by cellularization and differentiation of cell types. The indeterminate gametophyte1 (ig1) gene of maize (Zea mays) restricts the proliferative phase of female gametophyte development. ig1 mutant female gametophytes have a prolonged phase of free nuclear divisions leading to a variety of embryo sac abnormalities, including extra egg cells, extra polar nuclei, and extra synergids. Positional cloning of ig1 was performed based on the genome sequence of the orthologous region in rice. ig1 encodes a LATERAL ORGAN BOUNDARIES domain protein with high similarity to ASYMMETRIC LEAVES2 of Arabidopsis thaliana. A second mutant allele of ig1 was identified in a noncomplementation screen using active Mutator transposable element lines. Homozygous ig1 mutants have abnormal leaf morphology as well as abnormal embryo sac development. Affected leaves have disrupted abaxial-adaxial polarity and fail to repress the expression of meristem-specific knotted-like homeobox (knox) genes in leaf primordia, causing a proliferative, stem cell identity to persist in these cells. Despite the superficial similarity of ig1-O leaves and embryo sacs, ectopic knox gene expression cannot be detected in ig1-O embryo sacs. [ABSTRACT FROM AUTHOR]

Vertebrates respond to environmental stressors through the neuro-endocrine stress response, which involves the production of glucocorticoids. We have selected independent, duplicate divergent lines of zebra finches for high, low and control corticosterone responses to a mild stressor. This experiment has shown that over the first four generations, the high lines have demonstrated a significant realized heritability of about 20%. However, the low lines have apparently not changed significantly from controls. This asymmetry in response is potentially because of the fact that all birds appear to be showing increased adaptation to the environment in which they are housed, with significant declines in corticosterone response in control lines as well as low lines. Despite the existence of two- to threefold difference in mean corticosterone titre between high and low lines, there were no observed differences in testosterone titre in adult male birds from the different groups. In addition, there were no consistent, significant differences between the lines in any of the life history variables measured – number of eggs laid per clutch, number of clutches or broods produced per pair, number of fledglings produced per breeding attempt, nor in any of egg, nestling and fledgling mortality. These results highlight the fact that the mechanisms that underlie variation in the avian physiological system can be modified to respond to differences between environments through selection. This adds an additional level of flexibility to the avian physiological system, which will allow it to respond to environmental circumstances. [ABSTRACT FROM AUTHOR]

A prediction of handicap and signalling theories is that there should be a positive relationship between ornament size and viability. This prediction was tested in scarlet-tufted malachite sunbirds (Nectarinia johnstoni ). These birds are endemic to the high-altitude zones of East African mountains. They are bright iridescent green with elongated central tail feathers and red pectoral tufts. The elongated tail is believed to be a mate choice cue, and the red tufts play a role in aggressive encounters between males. As adults, they feed almost exclusively on the nectar of Lobelia telekii flowers, which males defend from conspecifics. The long term survival of individually identifiable males colour-marked in 1989 and 1990 was investigated. Territorial adult males had an average annual survival rate of 72%, which is at the top of the range reported for tropical birds. The effects of morphology and territory characteristics on male survival were examined by adding covariates to the survival model. This analysis showed that male N. johnstoni with longer tails had a higher probability of survival than did short-tailed males. There was no apparent relation between tuft size or the number of L. telekii inflorescences on the territory and survival. The results presented here suggest that long-tailed males may be of intrinsically higher quality than are shorter tailed males. If this is true then females may benefit by using this trait as a mate choice cue through increased viability of their offspring. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 125–133. [ABSTRACT FROM AUTHOR]

Presents a study that compared the nesting ecology of barrow's goldeneye and bufflehead in natural cavities in the Cariboo Parklands in British Columbia. Analysis of the physical characteristics of the nest sites; Examination of the clutch sizes of the two birds; Investigation of the sources of predation in the nest sites.

Examines interactions between maternal effect and zygotic effect mutations during maize seed development. Identification of mutations with both sporophytic maternal effects and gametophytic maternal effects; Finding that the maternal effect lethal 1 (mel1) causes the production of defective seed from mutant female gametophytes; Mode of action of mel1; Relationship between mel1 and enhancer of mel1 and enhancer of mel2.

Flowering plants, like placental mammals, have an extensive maternal contribution toward progeny development. Plants are distinguished from animals by a genetically active haploid phase of growth and development between meiosis and fertilization, called the gametophyte. Flowering plants are further distinguished by the process of double fertilization that produces sister progeny, the endosperm and the embryo, of the seed. Because of this, there is substantial gene expression in the female gametophyte that contributes to the regulation of growth and development of the seed. A primary function of the endosperm is to provide growth support to its sister embryo. Several mutations in Zea mays subsp. mays have been identified that affect the contribution of the mother gametophyte to the seed. The majority affect both the endosperm and the embryo, although some embryo-specific effects have been observed. Many alter the pattern of expression of a marker for the basal endosperm transfer layer, a tissue that transports nutrients from the mother plant to the developing seed. Many of them cause abnormal development of the female gametophyte prior to fertilization, revealing potential cellular mechanisms of maternal control of seed development. These effects include reduced central cell size, abnormal architecture of the central cell, abnormal numbers and morphology of the antipodal cells, and abnormal egg cell morphology. These mutants provide insight into the logic of seed development, including necessary features of the gametes and supporting cells prior to fertilization, and set up future studies on the mechanisms regulating maternal contributions to the seed. [ABSTRACT FROM AUTHOR]

Parent-of-origin-effect loci have non-Mendelian inheritance in which phenotypes are determined by either the maternal or paternal allele alone. In angiosperms, parent-of-origin effects can be caused by loci required for gametophyte development or by imprinted genes needed for seed development. Few parent-of-origin-effect loci have been identified in maize (Zea mays) even though there are a large number of imprinted genes known from transcriptomics. We screened rough endosperm (rgh) mutants for parent-oforigin effects using reciprocal crosses with inbred parents. Six maternal rough endosperm (mre) and three paternal rough endosperm (pre) mutants were identified with three mre loci mapped. When inherited from the female parent, mre/+ seeds reduce grain fill with a rough, etched, or pitted endosperm surface. Pollen transmission of pre mutants results in rgh endosperm as well as embryo lethality. Eight of the mutants had significant distortion from the expected one-to-one ratio for parent-of-origin effects. Linked markers for mre1, mre2, and mre3 indicated that the mutant alleles have no bias in transmission. Histological analysis of mre1, mre2, mre3, and pre*-949 showed altered timing of starch grain accumulation and basal endosperm transfer cell layer (BETL) development. The mre1 locus delays BETL and starchy endosperm development, while mre2 and pre*-949 cause ectopic starchy endosperm differentiation. We conclude that many parent-of-origin effects in maize have incomplete penetrance of kernel phenotypes and that there is a large diversity of endosperm developmental roles for parent-of-origin-effect loci. [ABSTRACT FROM AUTHOR]