Reciprocal F1 Hybrids Research Articles

Association analysis of phenotypic and metabolomic changes in Arabidopsis accessions and their F1 hybrids affected by different photoperiod and sucrose supply.

Photoperiod and sucrose (Suc) assimilation play important roles in the regulation of plant growth and development. However, it remains unclear how natural variation of plants could contribute to metabolic changes under various growth conditions. Here, we investigated the developmental and metabolomic responses of two natural accessions of Arabidopsis thaliana, Columbia (Col) and C24, and their reciprocal F1 hybrids grown under four carbon source regimens, i.e., two different photoperiods and the presence or absence of exogenous Suc supply. The effect of exogenous Suc clearly appeared in the growth of Col and the F1 hybrid but not in C24, whereas long-day conditions had significant positive effects on the growth of all lines. Comparative metabolite profiling of Col, C24, and the F1 hybrid revealed that changes in metabolite levels, particularly sugars, were highly dependent on genotype-specific responses rather than growth conditions. The presence of Suc led to over-accumulation of seven metabolites, including four sugars, a polyamine, and two amino acids in C24, whereas no such accumulation was observed in the profiles of Col and the F1 hybrid. Thus, the comparative metabolite profiling revealed that the two parental lines of the hybrid show a distinct difference in sugar metabolism.

Interspecies hybrids of Panax ginseng Meyer new line 0837 and Panax quinquefolius generated superior F1 hybrids with greater biomass and ginsenoside contents

Panax ginseng and Panax quinquefolius are important herbs with similar benefits and medicinal properties. Both possess ginsenosides, the pharmacologically active components, abundantly in their roots. In an attempt to establish ginseng cultivars with improved agronomical characters and higher ginsenoside content, reciprocal interspecific hybrids were generated by artificial pollination of emasculated flowers. Three elite cultivars of P. ginseng, types Jakyung, Chungkyung, and Hwangsook, and two new lines, 0837 and 0702, were used to assess interspecific hybrid potential. Among F1 reciprocal hybrids generated using line 0837 as either the maternal or paternal parent showed excellent agronomical traits and hybrid vigor. They showed strong root phenotypes with many lateral and fine roots resulting in 10 to 20% higher ginsenoside content compared to the parental lines. Among the major ginsenosides, pharmacologically active Re, Rb1, Rb2, and F1 were enriched. They accounted for 70% of the protopanaxadiol ginsenosides in 0837/Pq and Pq/0837 crosses, displaying strong maternal dominance. Thus, based on our results, we conclude that P. ginseng line 0837 is superior compared to already existing lines for performing interspecific hybridization with promising outcomes in root quality and ginsenoside content.

Fitness of reciprocal F1 hybrids between Rhinanthus minor and Rhinanthus major under controlled conditions and in the field.

The performance of first-generation hybrids determines to a large extent the long-term outcome of hybridization in natural populations. F1 hybrids can facilitate further gene flow between the two parental species, especially in animal-pollinated flowering plants. We studied the performance of reciprocal F1 hybrids between Rhinanthus minor and R.major, two hemiparasitic, annual, self-compatible plant species, from seed germination to seed production under controlled conditions and in the field. We sowed seeds with known ancestry outdoors before winter and followed the complete life cycle until plant death in July the following season. Germination under laboratory conditions was much lower for the F1 hybrid formed on R.major compared with the reciprocal hybrid formed on R.minor, and this confirmed previous results from similar experiments. However, this difference was not found under field conditions, which seems to indicate that the experimental conditions used for germination in the laboratory are not representative for the germination behaviour of the hybrids under more natural conditions. The earlier interpretation that F1 hybrid seeds formed on R.major face intrinsic genetic incompatibilities therefore appears to be incorrect. Both F1 hybrids performed at leastas well as andsometimes better than R.minor, which had a higher fitness than R.major in one of the two years in the greenhouse and in the field transplant experiment. The high fitness of the F1 hybrids confirms findings from naturally mixed populations, where F1 hybrids appear in the first year after the two species meet, which leads to extensive advanced-hybrid formation and introgression in subsequent generations.

Heterotic patterns of primary and secondary metabolites in the oilseed crop Brassica juncea.

Heterosis refers to the superior performance of F1 hybrids over their respective parental inbred lines. Although the genetic and expression basis of heterosis have been previously investigated, the metabolic basis for this phenomenon is poorly understood. In a preliminary morphological study in Brassica juncea, we observed significant heterosis at the 50% flowering stage, wherein both the growth and reproduction of F1 reciprocal hybrids were greater than that of their parents. To identify the possible metabolic causes or consequences of this heterosis, we carried out targeted LC-MS analysis of 48 primary (amino acids and sugars) and secondary metabolites (phytohormones, glucosinolates, flavonoids, and phenolic esters) in five developmental tissues at 50% flowering in hybrids and inbred parents. Principal component analysis (PCA) of metabolites clearly separated inbred lines from their hybrids, particularly in the bud tissues. In general, secondary metabolites displayed more negative heterosis values in comparison to primary metabolites. The tested primary and secondary metabolites displayed both additive and non-additive modes of inheritance in F1 hybrids, wherein the number of metabolites showing an additive mode of inheritance were higher in buds and siliques (52.77-97.14%) compared to leaf tissues (47.37-80%). Partial least regression (PLS) analysis further showed that primary metabolites, in general, displayed higher association with morphological parameters in F1 hybrids. Overall, our results are consistent with a resource-cost model for heterosis in B. juncea, where metabolite allocation in hybrids appears to favor growth, at the expense of secondary metabolism.

Transgenerational effects of inter-ploidy cross direction on reproduction and F2 seed development of Arabidopsis thaliana F1 hybrid triploids

Key messageReproduction in triploid plants is important for understanding polyploid population dynamics. We show that genetically identical reciprocal F1 hybrid triploids can display transgenerational epigenetic effects on viable F2 seed development.The success or failure of reproductive outcomes from intra-species crosses between plants of different ploidy levels is an important factor in flowering plant evolution and crop breeding. However, the effects of inter-ploidy cross directions on F1 hybrid offspring fitness are poorly understood. In Arabidopsis thaliana, hybridization between diploid and tetraploid plants can produce viable F1 triploid plants. When selfed, such F1 triploid plants act as aneuploid gamete production “machines” where the vast majority of gametes generated are aneuploid which, following sexual reproduction, can generate aneuploid swarms of F2 progeny (Henry et al. 2009). There is potential for some aneuploids to cause gametophyte abortion and/or F2 seed abortion (Henry et al. 2009). In this study, we analyse the reproductive success of 178 self-fertilized inter-accession F1 hybrid triploids and demonstrate that the proportions of aborted or normally developed F2 seeds from the selfed F1 triploids depend upon a combination of natural variation and cross direction, with strong interaction between these factors. Single-seed ploidy analysis indicates that the embryonic DNA content of phenotypically normal F2 seeds is highly variable and that these DNA content distributions are also affected by genotype and cross direction. Notably, genetically identical reciprocal F1 hybrid triploids display grandparent-of-origin effects on F2 seed set, and hence on the ability to tolerate aneuploidy in F2 seed. There are differences between reciprocal F1 hybrid triploids regarding the proportions of normal and aborted F2 seeds generated, and also for the DNA content averages and distributions of the F2 seeds. To identify genetic variation for tolerance of aneuploidy in F2 seeds, we carried out a GWAS which identified two SNPs, termed MOT and POT, which represent candidate loci for genetic control of the proportion of normal F2 seeds obtained from selfed F1 triploids. Parental and grandparental effects on F2 seeds obtained from selfed F1 triploids can have transgenerational consequences for asymmetric gene flow, emergence of novel genotypes in polyploid populations, and for control of F2 seed set in triploid crops.

Maternal inheritance of F1 hybrid morphology and colony shape in the coral genus Acropora

BackgroundThe coral genus Acropora contains more than 150 species with very high morphological diversity. This high diversity may have been caused by repeated hybridization via mass spawning. However, we have little information whether hybrids are formed in these corals. Identifying morphological differences between hybrids and their parental species would provide an opportunity to find wild hybrids in the field and to understand how colony shapes of Acropora have become highly diversified throughout evolutionary history. In the two morphologically distinctive coral species Acropora florida and A. intermedia in the Indo-Pacific, their gametes show high rates of bi-directional intercrossing in vitro, and thus these two species are ideal species to investigate the morphological traits of the hybrids.MethodsWe examined morphological characters of F1 hybrids from A. florida to A. intermedia, which were produced from in vitro crossing experiments. To compare morphological differences, we grew juveniles and mature colonies of reciprocal F1 hybrids (FLOint: A. florida eggs × A. intermedia sperm, and INTflo: A. intermedia eggs × A. florida sperm) and of the parental species (purebreds of A. intermedia and A. florida). We analyzed skeletal morphology such as colony size, branch length, and branching number, and compared them with those of a putative F1 hybrid between A. florida and A. intermedia found in the field. We also confirmed the molecular phylogenetic position of F1 hybrids, parental species, and a putative F1 hybrid using the mitochondrial non-coding region.ResultsOur morphological analysis revealed that branching number of the F1 hybrids was intermediate relative to the parental species. Moreover, the FLOint hybrids were morphologically more closely related to the maternal species A. florida, and the INTflo hybrids were to A. intermedia. Molecular data showed that A. florida and A. intermedia were clearly divided into two clades, and that F1 hybrids grouped in the clade based on their maternal parent. A very similar pattern to the INTflo hybrids was obtained for the putative F1 hybrid in nature.DiscussionOur results revealed that F1 hybrids between two Indo-Pacific species A. florida and A. intermedia had intermediate morphology relative to their parent species but reflected the maternal parent more. Similarity to maternal species in hybrids is opposite to the Caribbean Acropora species that had more paternal morphological characters in hybrids. These results further suggest that some genetic factor in eggs is likely to affect determination of colony shape in the Indo-Pacific. At present, we have considered colonies with intermediate morphs between different species to be intra-specific morphological variation, but they may be real F1 hybrids. Indeed, a putative F1 hybrid represented similar morphological and molecular features to the F1 hybrids, and thus it is plausible to be attributed as a “real” F1 hybrid in nature.

Extensive allele-level remodeling of histone methylation modification in reciprocal F1 hybrids of rice subspecies.

Epigenetic mechanisms play a major role in heterosis, partly as a result of the remodeling of epigenetic modifications in F1 hybrids. Based on chromatin immunoprecipitation-sequencing (ChIP-Seq) analyses, we show that at the allele level extensive histone methylation remodeling occurred for a subset of genomic loci in reciprocal F1 hybrids of Oryza sativa (rice) cultivars Nipponbare and 93-11, representing the two subspecies japonica and indica. Globally, the allele modification-altered loci in leaf or root of the reciprocal F1 hybrids involved ˜12-43% or more of the genomic regions carrying either of two typical histone methylation markers, H3K4me3 (>21000 genomic regions) and H3K27me3 (>11000 genomic regions). Nevertheless, at the total modification level, the majority (from ˜43 to >90%) of the modification-altered alleles lay within the range of parental additivity in the hybrids because of concerted alteration in opposite directions, consistent with an overall attenuation of allelic differences in the modifications. Importantly, of the genomic regions that did show non-additivity in total modification level by either marker in the two tissues of hybrids, >80% manifested transgressivity, which involved genes enriched in specific functional categories. Extensive allele-level alteration of H3K4me3 alone was positively correlated with genome-wide changes in allele-level gene expression, whereas at the total level, both H3K4me3 and H3K27me3 remodeling, although affecting just a small number of genes, contributes to the overall non-additive gene expression to variable extents, depending on tissue/marker combinations. Our results emphasize the importance of allele-level analysis in hybrids to assess the remodeling of epigenetic modifications and their relation to changes in gene expression.

Reciprocal compatibility within the genus Pisum L. as studied in F1 hybrids: 2. Crosses involving P. fulvum Sibth. et Smith

Pisum fulvum Sibth. et Smith. (accession WL2140) was crossed, in both directions, with seven accessions representing other pea taxa: P. abyssinicum A. Br. (1 accession), P. sativum L. subsp. elatius (Bieb.) Schmalh. s.l. (5 accessions) and the cultivated pea, P. sativum L. subsp. sativum (1 accession). Efficiency of crosses (the average number of hybrid seeds per cross), pollen and seed fertility and general quantitative traits of reciprocal F1 hybrids were evaluated in a greenhouse experiment. Crossability with P. fulvum as the seed parent was very poor but at least some viable seeds were obtained in all crosses. F1 hybrids with accessions VIR320, 721 and CE1 (P. s. elatius) were very weak and produced 0–3 seeds; those with WL1238 (P. s. sativum) were variable in vigour and fertility; both reciprocal hybrids with JI1794 were small plants. Other hybrids were tall, vigorously branching but poorly fertile plants. In all F1 hybrids, pollen fertility did not exceed or scarcely exceeded 50% without differences between reciprocal hybrids except for the pair P. fulvum × P. s. sativum. Pollen of all hybrids contained micro-grains formed around chromosomes retarded in anaphase I. Seed fertility was low, with significant differences between reciprocal hybrids found only in the pair P. fulvum—JI1794. F1 hybrids between P. fulvum and peas of the evolutionary ‘lineage AC’ showed higher pollen and seed fertility than those with peas of the ‘lineage B’. The sum of evidence available suggests that P. fulvum does not differ from P. sativum by reciprocal translocations.

Reciprocal F1 Hybrids of Two Inbred Mouse Strains Reveal Parent-of-Origin and Perinatal Diet Effects on Behavior and Expression.

Parent-of-origin effects (POE) in mammals typically arise from maternal effects or imprinting. In some instances, such POE have been associated with psychiatric disorders, as well as with changes in a handful of animal behaviors. However, POE on complex traits such as behavior remain largely uncharacterized. Moreover, although both behavior and epigenetic effects are known to be modified by perinatal environmental exposures such as nutrient deficiency, the architecture of such environment-by-POE is mostly unexplored. To study POE and environment-by-POE, we employ a relatively neglected but especially powerful experimental system for POE-detection: reciprocal F1 hybrids (RF1s). We exposed female NOD/ShiLtJC57Bl/6J and C57Bl/6J×NOD/ShiLtJ mice, perinatally, to one of four different diets, then after weaning recorded a set of behaviors that model psychiatric disease. Whole-brain microarray expression data revealed an imprinting-enriched set of 15 genes subject to POE. The most-significant expression POE, on the non-imprinted gene Carmil1 (a.k.a. Lrrc16a), was validated using qPCR in the same and in a new set of mice. Several behaviors, especially locomotor behaviors, also showed POE. Bayesian mediation analysis suggested Carmil1 expression suppresses behavioral POE, and that the imprinted gene Airn suppresses POE on Carmil1 expression. A suggestive diet-by-POE was observed on percent center time in the open field test, and a significant diet-by-POE was observed on one imprinted gene, Mir341, and on 16 non-imprinted genes. The relatively small, tractable set of POE and diet-by-POE detected on behavior and expression here motivates further studies examining such effects across RF1s on multiple genetic backgrounds.

Rapid and pervasive development- and tissue-specific homeolog expression partitioning in newly formed inter-subspecific rice segmental allotetraploids

BackgroundIn diverse plant taxa, whole-genome duplication (WGD) events are major sources of phenotypic novelty. Studies of gene expression in synthetic polyploids have shown immediate expression and functional partitioning of duplicated genes among different tissues. Many studies of the tissue-specific homeolog expression partitioning have focused on allopolyploids that have very different parental genomes, while few studies have focused on autopolyploids or allopolyploids that have similar parental genomes.ResultsIn this study, we used a set of reciprocal F1 hybrids and synthetic tetraploids constructed from subspecies (japonica and indica) of Asian rice (Oryza sativa L.) as a model to gain insights into the expression partitioning of homeologs among tissues in a developmental context. We assayed the tissue-specific silencing (TSS) of the parental homeologs of 30 key genes in the hybrids and tetraploids relative to the in vitro “hybrids” (parental mixes) using Sequenom MassARRAY. We found that the parental mix and synthetic tetraploids had higher frequencies of homeolog TSS than the F1, revealing an instantaneous role of WGD on homeolog expression partitioning.ConclusionsOur observations contradicted those of previous studies in which newly formed allopolyploids had a low TSS frequency, similar to that of F1 hybrids, suggesting that the impact of WGD on homeolog expression requires a longer time to manifest. In addition, we found that the TSS frequency in the tetraploids varied at different growth stages and that roots had a much higher frequency of TSS than leaves, which indicated that developmental and metabolic traits may influence the expression states of duplicated genes in newly formed plant polyploids.

Pleiotropic effects of propargite on life-table parameters of susceptible and resistant strains and reciprocal F1 hybrids of Tetranychus urticae Koch, 1836 and their implications for population growth

Demografik toksikolojik calismalar ya da yasam tablosu tepki denemeleri, tarlada insektisit etkisini ongormek icin daha guvenilir bir yaklasim olarak onerilmektedir. Tetranychus urticae Koch, 1836 (Prostigmata: Tetranychidae)'nin hassas, propargite karsi direncli ve karsilikli F1 capraz melezlerinin yasam tablosu parametreleri, Lincoln Universitesi (Yeni Zelanda)’de hassas irkin LC 50 ve LC 99 'unda propargite kalintilarinin varliginda ve yoklugunda calisilmistir. Tum bireylerin yasam tablosu verileri, yas-evre, iki cinsiyetli yasam tablosu kullanilarak analiz edilmistir. Duyarli irkin LC 50 degerleri, herhangi bir irkta gelisim zamanini etkilememistir. Bununla birlikte, hassas irkin LC 99 'u, propargite direncli irkin gelisim suresini yaklasik iki gun uzatmistir. Duyarli irkin LC 50 degerleri, propargite direncli irkin ve S ♂ × R ♀ hibridinin kalitsal ureme yetenegi ( r m ), R o ve toplam dol verimi, hassas irk ve R ♂ × S ♂ hibritine kiyasla daha yuksek bulunmustur. Populasyon tahminleri, T. urticae 'nin irklari / melezlerinin yasam tablosu parametrelerindeki nispeten kucuk farkliliklarin etkilerini incelemek icin kullanilmistir. Uygulama yapilmayan kontrol gruplari icin hassas irk 10 dolden sonra en yuksek populasyon tahminini vermistir. Duyarli irkin LC 50 degeri uygulanan gruplarda, tahmin edilen populasyon buyuklugu, propargite direncli irkin ergin disi sayisinin, hassas irkin yerine gectigini gostermistir. Hibrid S ♂ × R ♀ , hassas irkin LC 50 'si ile uygulamadan en fazla artmistir. Bu yuzden, farkli irklarin kademeli basarisi, bir bolgede yetistirme sezonu boyunca direnc sikligini degistirebilir.

Histological evidence that diploid hybrids of Cobitis taenia and C. elongatoides (Teleostei, Cobitidae) develop into fertile females and sterile males

In Europe, two bisexual fish species, Cobitis taenia (TT) and Cobitis elongatoides (EE), hybridized, producing diploid and polyploid clonal lineages. This study compared, for the first time, embryonic development, hatching success, sex ratio, body size and as well as reproductive ability based on the gonad histology of F1 reciprocal diploid hybrids (TE, ET) of both species. Hybrid F1 progeny showed the same proper pattern of embryonic and larval development. Among TE and ET offspring, slightly more females and males, respectively, occurred, but sex parity among 18-month-old hybrids was observed. Two- and three-year-old F1 hybrid females were mature, possessing all stages of oogenesis in their ovaries. Females (TE) back-crossed with C. taenia males had properly developing progeny. In testes of two- and three-year-old F1 hybrids, only early stages of spermatogenesis and pyknotic cells indicating the degeneration process were observed, but they exhibited an external feature (lamina circularis) of maturation. The results were confirmed by the structure of gonads that two sexual species, C. taenia and C. elongatoides, hybridize, producing F1 progeny of sterile males and fertile females. Hybrid females may participate in subsequent steps of speciation via hybridization and polyploidy or, on the contrary, represent an element of new species isolation.

Assessment of genetic effects on important breeding traits in reciprocal DH populations of winter oilseed rape (Brassica napus L.)

Here we present a study on the genetic effects of agronomic and seed quality traits in double haploid (DH) populations, which were developed by microspore culture from reciprocal F1 hybrids produced between cultivar Californium and DH W-15. Each of the populations consisted of 25 DH lines. The field experiments were conducted in a randomized complete block design with three replications during three growing seasons. Field observations were recorded on seed yield and its structure: the number of branches and pods per plant, the number of seeds per pod, the 1000-seed weight, the content of fat in the seeds, and three unsaturated fatty acids (oleic, linoleic, linolenic) in the seed oil. In order to investigate the influence of cross direction on the studied traits, parental effects were evaluated on the basis of differences between reciprocal DH populations. The maternal effect was revealed on the number of seeds per pod and the effect of the paternal form on linolenic acid content. The occurrence of transgression effects also depended on the direction of crossing and this was particularly noticeable in terms of the number of seeds per pod. The use of multivariate statistical methods allowed for the simultaneous characterization and grouping of tested lines in terms of several traits. Graphic images of the distribution of DH lines in the space of the two first canonical variates showed a great variation between the two reciprocal populations, both in terms of yield and its components, as well as fat and those unsaturated fatty acids.

Perinatal nutrition interacts with genetic background to alter behavior in a parent-of-origin-dependent manner in adult Collaborative Cross mice.

Previous studies in animal models and humans have shown that exposure to nutritional deficiencies in the perinatal period increases the risk of psychiatric disease. Less well understood is how such effects are modulated by the combination of genetic background and parent-of-origin (PO). To explore this, we exposed female mice from 20 Collaborative Cross (CC) strains to protein deficient, vitamin D deficient, methyl donor enriched or standard diet during the perinatal period. These CC females were then crossed to a male from a different CC strain to produce reciprocal F1 hybrid females comprising 10 distinct genetic backgrounds. The adult F1 females were then tested in the open field, light/dark, stress-induced hyperthermia, forced swim and restraint stress assays. Our experimental design allowed us to estimate effects of genetic background, perinatal diet, PO and their interactions on behavior. Genetic background significantly affected all assessed phenotypes. Perinatal diet exposure interacted with genetic background to affect body weight, basal body temperature, anxiety-like behavior and stress response. In 8 of 9 genetic backgrounds, PO effects were observed on multiple phenotypes. Additionally, we identified a small number of diet-by-PO effects on body weight, stress response, anxiety- and depressive-like behavior. Our data show that rodent behaviors that model psychiatric disorders are affected by genetic background, PO and perinatal diet, as well as interactions among these factors.

Parental-genome dosage effects on the transcriptome of F1 hybrid triploid embryos of Arabidopsis thaliana.

Genomic imprinting in the seed endosperm could be due to unequal parental-genome contribution effects in triploid endosperm tissue that trigger parent-of-origin specific activation and/or silencing of loci prone to genomic imprinting. To determine whether genomic imprinting is triggered by unequal parental-genome contribution effects, we generated a whole-genome transcriptome dataset of F1 hybrid triploid embryos (as mimics of F1 hybrid triploid endosperm). For the vast majority of genes, the parental contributions to their expression levels in the F1 triploid hybrid embryos follow a biallelic and linear expression pattern. While allele-specific expression (ASE) bias was detected, such effects were predominantly parent-of-origin independent. We demonstrate that genomic imprinting is largely absent from F1 triploid embryos, strongly suggesting that neither triploidy nor unequal parental-genome contribution are key triggers of genomic imprinting in plants. However, extensive parental-genome dosage effects on gene expression were observed between the reciprocal F1 hybrid embryos, particularly for genes involved in defence response and nutrient reservoir activity, potentially leading to the seed size differences between reciprocal triploids. We further determined that unequal parental-genome contribution in F1 triploids can lead to overexpression effects that are parent-of-origin dependent, and which are not observed in diploid or tetraploid embryos in which the parental-genome dosage is balanced. Overall, our study demonstrates that neither triploidy nor unequal parental-genome contribution is sufficient to trigger imprinting in plant tissues, suggesting that genomic imprinting is an intrinsic and unique feature of the triploid seed endosperm.

Inheritance of Monocrotophos Resistance in Egg Parasitoid Trichogramma Chilonis (Ishii) (Hymenoptera:Trichogrammatidae)

Inheritance of monocrotophos resistance was studied in the laboratory population of T. chilonis. After 10 cycles of selection pressure under laboratory condition, the resistant strain acquired LC50 value of 0.346mL compared toLC50 value of 0.114 mL in the susceptible strain. Evidence from bioassay of F1 reciprocal hybrid crosses backcrossed with respective resistant 'R' and susceptible 'S'parentalstrains of T. chilonis, aimed to determine mode of inheritance of insecticide tolerance indicated that F1 crosses exhibited a complete dominant response to monocrotophos, with degree of dominance value (D) of 1.62. The resistance factor (Rf) of resistant strain was 3.04 folds and of F1 crosses were 3.675 folds over susceptible strain. Result of this study suggests resistance to the insecticide was probably controlled by a single gene. These results provide the basic information for designing successful management programmes for the control of Lepidopteran pests using resistant strain as a component of IPM.

Imprinted gene expression in maize starchy endosperm and aleurone tissues of reciprocal F1 hybrids at a defined developmental stage.

Imprinted gene expression in flowering plants predominantly occurs in the triploid endosperm of developing seed. However, endosperm is composed of distinct tissue types. For example, the maize (Zea mays) endosperm is constituted by two major tissues, starchy endosperm and aleurone. Previous studies in imprinted gene expression have generally assumed that the different tissues constituting endosperm would behavior the same, and hence have not examined them separately. Here, to examine parental-specific expression of imprinted genes in different parts of the seed, eight previously reported maize protein-coding imprinted genes were selected, and analyzed by cleaved amplified polymorphic sequence (CAPS) coupled with Sanger sequencing for transcripts from the various seed tissues collected at 18 days after pollination (DAP). The studied tissues included seed coat, embryo, starchy endosperm and aleurone, which were collected from a pair of reciprocal F1 hybrids produced by crossing inbred lines B73 and Mo17. Six of these eight analyzed imprinted genes showed the same imprinted expression pattern between the starchy endosperm and aleurone, but two showed imprinted expression only in the starchy endosperm. Comparison of the expression pattern of 20 selected imprinted genes in multiple seed tissues and vegetative tissues indicated that the majority (~ 75%) of these imprinted genes exhibited seed-specific or endosperm-specific expression. Our results also uncovered that imprinted genes have a high propensity to be alternatively spliced via intron retention in the developing embryo compared with the other tissues.

Single-cell transcriptome analysis reveals widespread monoallelic gene expression in individual rice mesophyll cells

Monoallelic gene expression refers to the phenomenon that all transcripts of a gene in a cell are expressed from only one of the two alleles in a diploid organism. Although monoallelic gene expression has been occasionally reported with bulk transcriptome analysis in plants, how prevalent it is in individual plant cells remains unknown. Here, we developed a single-cell RNA-seq protocol in rice and investigated allelic expression patterns in mesophyll cells of indica (93-11) and japonica (Nipponbare) inbred lines, as well as their F1 reciprocal hybrids. We observed pervasive monoallelic gene expression in individual mesophyll cells, which could be largely explained by stochastic and independent transcription of two alleles. By contrast, two mechanisms that were proposed previously based on bulk transcriptome analyses, parent-of-origin effects and allelic repression, were not well supported by our data. Furthermore, monoallelically expressed genes exhibited a number of characteristics, such as lower expression levels, narrower H3K4me3/H3K9ac/H3K27me3 peaks, and larger expression divergences between 93-11 and Nipponbare. Taken together, the development of a single-cell RNA-seq protocol in this study offers us an excellent opportunity to investigate the origins and prevalence of monoallelic gene expression in plant cells.

Segmental allotetraploidy generates extensive homoeologous expression rewiring and phenotypic diversity at the population level in rice.

Allopolyploidization, that is, concomitant merging and doubling of two or more divergent genomes in a common nucleus/cytoplasm, is known to instantly alter genomewide transcriptome dynamics, a phenomenon referred to as "transcriptomic shock." However, the immediate effects of transcriptomic alteration in generating phenotypic diversity at the population level remain underinvestigated. Here, we employed the MassARRAY-based Sequenom platform to assess and compare orthologous, allelic and homoeologous gene expression status in two tissues (leaf and root) of a set of randomly chosen individuals from populations of parental rice subspecies (indica and japonica), invitro "hybrids" (parental mixes), reciprocal F1 hybrids and reciprocal tetraploids at the 5th-selfed generation (S5). We show that hybridization and whole genome duplication (WGD) have opposing effects on allelic and homoeologous expression in the F1 hybrids and tetraploids, respectively. Whereas hybridization exerts strong attenuating effects on allelic expression differences in diploid hybrids, WGD augments the intrinsic parental differences and generates extensive and variable homoeolog content which triggers diversification in expression patterning among the tetraploid plants. Coupled with the vast phenotypic diversity observed among the tetraploid individuals, our results provide experimental evidence in support of the notion that allopolyploidy catalyses rapid phenotypic diversification in higher plants. Our data further suggest that largely stochastic homoeolog content reshuffling rather than alteration in total expression level may be an important feature of evolution in young segmental allopolyploids, which underlies rapid expression diversity at the population level.

Lasting effects of early life stress in mice: interaction of maternal environment and infant genes.

In the mouse, a powerful paradigm of early life stress, infant maternal separation (IMS), can trigger emotional and cognitive dysfunctions in adulthood similar to those found in humans with a history of childhood adversity. The magnitude of IMS effects differs among diverse inbred strains suggesting an interaction between the genetic background of pups and the maternal care they received. Here, we investigated this interaction with studies on reciprocal F1 hybrid mice of the stress-susceptible Balb/c and the resilient C57Bl/6 strains that were either raised by Balb/c mothers (low maternal care) or by C57Bl/6 mothers (higher maternal care) with or without IMS exposure. The ultrasonic vocalization response to isolation was recorded from infant F1 pups, and their emotional, executive cognitive and epigenetic phenotypes were assessed in adulthood. These studies showed that, regardless of the maternal care received, the emotional phenotype of F1 hybrids was not significantly affected by IMS exposure. However, F1 pups raised by Balb/c (but not C57Bl/6) mothers during IMS exposure exhibit deficits in working memory and attention-set-shifting in adulthood. They also exhibit reduced histone deacetylase 1 levels at promotors of brain-derived neurotrophic factor and early growth response 2 genes, and abnormally high induction of expression of these genes during cognitive testing. As one of affected genes was previously shown to associate with the Balb/c and the other with the C57Bl/6 genetic background, these findings indicate that both parental alleles interact with the maternal environment to modulate the cognitive and epigenetic phenotypes of F1 mice exposed to the IMS.