Reciprocal Hybrids Research Articles

Comparative transcriptomic reveals the molecular mechanism of maize hybrid Zhengdan538 in response to water deficit.

Heterosis, known as one of the most successful strategies for increasing grain yield and abiotic/biotic stress tolerance, has been widely exploited in maize breeding. However, the underlying molecular processes are still to be elucidated. The maize hybrid "Zhengdan538" shows high tolerance to drought stress. The transcriptomes of the seedling leaves of its parents, "ZhengA88" and "ZhengT22" and their reciprocal F1 hybrid under well-watered and water deficit conditions, were analyzed by RNA sequencing (RNA-Seq). Transcriptome profiling of the reciprocal hybrid revealed 2994-4692 differentially expressed genes (DEGs) under well-watered and water-deficit conditions, which were identified by comparing with their parents. The reciprocal hybrid was more closely related to the parental line "ZhengT22" than to the parental line "ZhengA88" in terms of gene expression patterns under water-deficit condition. Furthermore, genes showed expression level dominance (ELD), especially the high-parental ELD (Class 3 and 5), accounted for the largest proportion of DEGs between the reciprocal F1 hybrid and their parental lines under water deficit. These ELD genes mainly participated in photosynthesis, energy biosynthesis, and metabolism processes. The results indicated that ELD genes played important roles in hybrid tolerance to water deficit. Moreover, a set of important drought-responsive transcription factors were found to be encoded by the identified ELD genes and are thought to function in improving drought tolerance in maize hybrid plants. Our results provide a better understanding of the molecular mechanism of drought tolerance in hybrid maize.

Concurrent improvement of durum and emmer wheat through reciprocal backcrossing and hybridization

AbstractEmmer wheat has not been improved but is a valuable gene source for improving durum (Triticum turgidum ssp. durum). Conversely, durum is less looked upon for emmer (T. turgidum ssp. dicoccum) improvement. This study examined the possibility of concurrently improving the two species by crossing eight durum cultivars with four emmer local varieties in a half‐diallel fashion in two consecutive years. Also, emmer and two durum genotypes were reciprocally backcrossed, and their BC1F1 progeny were field‐evaluated during the wheat cropping season (November–June) at the Isfahan University of Technology research farm (32°32′ N, 51°23′ E). The results showed that durum wheat had a considerable effect on the grain yield (GY), kernel diameter, 1,000‐kernel weight (TKW), and test weight of F1 hybrids, whereas emmer contributed more to increasing the grain protein content (GPC), kernel length, and plant height (PH). A similar pattern was observed for BC1F1 hybrids from the two recurrent durum parents. The GPC was reduced with recurrent durum parents in the backcrosses compared with emmer, but was still higher than in both durum parents. In the backcrosses with the recurrent emmer parent, GY and TKW were higher than those of emmer but only slightly lower than those of the durum parents. The PH was strongly influenced by emmer in all crosses, though the lodging was significantly reduced compared with emmer, possibly through obtaining stronger stems from durum. These findings suggest the possibility of combining desirable genes from the two species and their concurrent improvement in a single breeding program.

Reciprocal effect and heterosis for tomato fruit metabolites revealed by whole transcriptomic analysis of two cultivars and their reciprocal hybrids

External and internal attributes of fleshy fruits can be affected by phenomena like reciprocal effect and heterosis. The aim of this work is to study the genetic and molecular differences between two parental lines and their reciprocal hybrids, as well as the presence of heterosis and reciprocal effects. The tomato cultivars Querubín FCA and Gema FCA were selected as parental genotypes because this cross showed a high presence of heterosis and reciprocal effect. A combined investigation of the gene actions involved in gene expression profile and metabolic content was performed by analysing transcriptomic data and its integration with previously reported metabolic data. The reciprocal hybrids showed the most significant differences at the transcript levels (157 out of 200). Several transcripts which encode transcription factors were found, suggesting that ripe red fruits still have a highly regulated transcriptome. Furthermore, 41 differentially expressed genes connected to 11 metabolites were identified. Afterwards, transcript and metabolite gene actions were calculated. The results showed that the metabolic phenotypes of the parental genotypes are mainly explained by transcripts showing an additive gene action. In contrast, transcripts with non-additive gene actions mainly explained the heterotic metabolic phenotype in the hybrids. This work contributes to a deeper understanding of the molecular basis of reciprocal effect and heterosis in plant crops.

Postmating isolation and evolutionary relationships among Fejervarya species from Lesser Sunda, Indonesia and other Asian countries revealed by crossing experiments and mtDNA Cytb sequence analyses.

To evaluate the degree of postmating isolation and the evolutionary relationships among frog species in the genus Fejervarya from Indonesia (Lesser Sunda), Bangladesh, China, and Japan, crossing experiments and molecular phylogenetic analyses were carried out. Crossing experiments revealed that reciprocal hybrids among F. iskandari, F. verruculosa, and F. sp. large type and between F. multistriata and F. kawamurai are viable through metamorphosis, while those between the F. iskandari group and F. limnocharis group were completely or partially inviable at the tadpole stage and those between Southeast Asian and South Asian Fejervarya groups were completely inviable at the embryonic stage. The mature reciprocal hybrids between F. iskandari and F. verruculosa from Lesser Sunda, Indonesia, showed some degree of abnormality in spermatogenesis. In phylogenetic analyses based on mtDNA Cytb sequences, F. iskandari formed a sister clade with F. verruculosa from Lesser Sunda, Indonesia, with 8.1% sequence divergence. F. multistriata from China formed a clade with populations of F. limnocharis in Thailand, Malaysia, and Indonesia (topotype), and these taxa showed sister relationships to F. kawamurai from Japan with 8.9% sequence divergence. Fejervarya sp. small type from Bangladesh formed a clade with the other South Asian members of the Fejervarya group and formed a sister clade with the Southeast Asian Fejervarya group, with 23.1% sequence divergence in the Cytb gene. These results showed that the degree of postmating isolation reflects molecular phylogenetic relationships and that F. iskandari and F. verruculosa from Indonesia (Lesser Sunda) are reproductively isolated by abnormalities in spermatogenesis and show genetic differentiation.

Developmental evidence for parental conflict in driving Mimulus species barriers.

The endosperm, a tissue that nourishes the embryo in the seeds of flowering plants, is often disrupted in inviable hybrid seeds of closely related species. A key question is whether parental conflict is a major driver of this common form of reproductive isolation. Here, we performed reciprocal crosses between pairs of three monkeyflower species (Mimulus caespitosa, Mimulus tilingii, and Mimulus guttatus). The severity of hybrid seed inviability varies among these crosses, which we inferred to be due to species divergence in effective ploidy. By performing a time series experiment of seed development, we discovered parent-of-origin phenotypes that provide strong evidence for parental conflict in shaping endosperm evolution. We found that the chalazal haustorium, a tissue within the endosperm that is found at the maternal-filial boundary, shows pronounced differences between reciprocal hybrid seeds formed from Mimulus species that differ in effective ploidy. These parent-of-origin effects suggest that the chalazal haustorium might act as a mediator of parental conflict, potentially by controlling sucrose movement from the maternal parent into the endosperm. Our study suggests that parental conflict in the endosperm may function as a driver of speciation by targeting regions and developmental stages critical for resource allocation and thus proper seed development.

Interspecific Hybridization of Transgenic Brassica napus and Brassica rapa-An Overview.

In nature, interspecific hybridization occurs frequently and can contribute to the production of new species or the introgression of beneficial adaptive features between species. It has great potential in agricultural systems to boost the process of targeted crop improvement. In the advent of genetically modified (GM) crops, it has a disadvantage that it involves the transgene escaping to unintended plants, which could result in non-specific weedy crops. Several crop species in the Brassica genus have close kinship: canola (Brassica napus) is an ancestral hybrid of B. rapa and B. oleracea and mustard species such as B. juncea, B. carinata, and B. nigra share common genomes. Hence, intraspecific hybridization among the Brassica species is most common, especially between B. napus and B. rapa. In general, interspecific hybrids cause numerous genetic and phenotypic changes in the parental lines. Consequently, their fitness and reproductive ability are also highly varied. In this review, we discuss the interspecific hybridization and reciprocal hybridization studies of B. napus and B. rapa and their potential in the controlled environment. Further, we address the fate of transgenes (herbicide resistance) and their ability to transfer to their progenies or generations. This could help us to understand the environmental influence of interspecific hybrids and how to effectively manage their transgene escape in the future.

Gut microbiota communities of reciprocal hybrids from koi (Cyprinus carpio) and goldfish (Carassius auratus) are more similar to koi than goldfish.

To investigate the gut microbiota communities of reciprocal hybrids and inbred lines of koi (Cyprinus carpio) and goldfish (Carassius auratus), as well as the genetic effect of intestinal microbiota between hybrids and parents. The reciprocal hybrids and inbred lines derived from the parents, koi and goldfish, were established. Then, the bacterial 16S rRNA gene of intestinal contents was sequenced using Illumina Miseq PE300. Alpha diversity in the two types of hybrids was lower than inbred lines of koi or goldfish and was highest in goldfish, followed by koi. For beta diversity, microbial samples presented clear clusters and the two types of hybrids were more similar to koi than goldfish, indicating the gut microbiota of the reciprocal hybrids was more affected by koi. The dominant phyla were Proteobacteria, Actinobacteria and Firmicutes in koi, and Proteobacteria, Fusobacteria and Actinobacteria in goldfish, and Proteobacteria, Fusobacteria and Firmicutes in the reciprocal hybrids. In the case of Proteobacteria, the dominant classes were Alphaproteobacteria and Gammaproteobacteria in four fish. The dominant genera were norank_f_Rhizobiales_Incertae_Sedis and Plesiomonas in koi, Cetobacterium in goldfish, and Cetobacterium and ZOR0006 in the reciprocal hybrids. PICRUSt1 predictive function analysis showed that the reciprocal hybrids had lower abundance in the most functional categories than koi and goldfish. The gut microbiota of reciprocal hybrids was more affected by koi. Two types of hybrids possessed the same dominated phyla and were different from the inbred lines of koi and goldfish. It enhanced our understanding of gut microbiota of hybrid lines of goldfish and koi and provided a new perspective for the selective breeding of gut microbiota traits.

Multi-omics analysis reveals expression complexity and functional diversity of mouse kinome.

Protein kinases are a crucial component of signaling pathways involved in a wide range of cellular responses, including growth, proliferation, differentiation, and migration. Systematic investigation of protein kinases is critical to better understand phosphorylation-mediated signaling pathways and may provide insights into the development of potential therapeutic drug targets. Here we perform a systems-level analysis of the mouse kinome by analyzing multi-omics data. We used bulk and single-cell transcriptomic data from the C57BL/6J mouse strain to define tissue- and cell-type-specific expression of protein kinases, followed by investigating variations in sequence and expression between C57BL/6J and DBA/2J strains. We then profiled a deep brain phosphoproteome from C57BL/6J and DBA/2J strains as well as their reciprocal hybrids to infer the activity of the mouse kinome. Finally, we performed phenome-wide association analysis using the BXD recombinant inbred (RI) mice (a cross between C57BL/6J and DBA/2J strains) to identify any associations between variants in protein kinases and phenotypes. Collectively, our study provides a comprehensive analysis of the mouse kinome by investigating genetic sequence variation, tissue-specific expression patterns, and associations with downstream phenotypes.

Exogenous paternal mitochondria rescue hybrid incompatibility and the destiny of exogenous mitochondria

The mitochondria of most organisms follow strict maternal inheritance, and the mechanism of elimination of paternal mitochondria is unclear. Our previous studies showed that the paternal mtDNA presented in the embryo of hybrid Megalobrama Amblycephala (BSB,♀) ​× ​Carassius auratus red var(RCC,♂) (BR) and its reciprocal hybrid (RB), but its expression was quiescent. However, the microinjected mitochondria persisted in the embryo and its mtDNA expressed throughout embryonic development. In addition, the chromosome number of RCC (2n ​= ​100) is much larger than that of BSB (2n ​= ​48). All BR embryos were severely abnormal and ultimately died, while the RB embryos could survive and grow up into adult. It implied that the nuclear-cytoplasm incompatibility may be an important cause of BR abnormality. In this study, exogenous parental mitochondria were microinjected into BR embryos, and it was found that paternal mitochondrial DNA persisted and expressed throughout embryonic development. Meanwhile, the study also found that microinjection of isolated paternal (RCC) mitochondria into BR embryos significantly improved the degree of early embryonic abnormality with some fry swimming normally, comparing to the control embryos. However, injection of maternal (BSB) mitochondria did not improve the development of BR embryos. We safely concluded exogenous mitochondria escape the mechanism of elimination and its DNA persist and express throughout embryonic development. In addition, the expression of paternal mitochondrial genes largely reduces the cyto-nuclear conflict, so that the early BR embryos exhibit less degree of abnormality and enhanced activity.

Expression Patterns Divergence of Reciprocal F1 Hybrids Between Gossypium hirsutum and Gossypium barbadense Reveals Overdominance Mediating Interspecific Biomass Heterosis.

Hybrid breeding has provided an impetus to the process and achievement of a higher yield and quality of crops. Interspecific hybridization is critical for resolving parental genetic diversity bottleneck problems. The reciprocal interspecific hybrids and their parents (Gossypium hirsutum and Gossypium barbadense) have been applied in this study to elucidate the transcription regulatory mechanism of early biomass heterosis. Phenotypically, the seed biomass, plant height over parent heterosis, leaf area over parent heterosis, and fresh and dry biomass were found to be significantly higher in hybrids than in parents. Analysis of leaf areas revealed that the one-leaf stage exhibits the most significant performance in initial vegetative growth vigor and larger leaves in hybrids, increasing the synthesis of photosynthesis compounds and enhancing photosynthesis compound synthesis. Comparative transcriptome analysis showed that transgressive down-regulation (TDR) is the main gene expression pattern in the hybrids (G. hirsutum × G. barbadense, HB), and it was found that the genes of photosystem I and Adenosine triphosphate (ATP)-binding may promote early growth vigor. Transgressive up-regulation (TUR) is the major primary gene expression pattern in the hybrids (G. barbadense × G. hirsutum, BH), and photosystem II-related genes mediated the performance of early biomass heterosis. The above results demonstrated that overdominance mediates biomass heterosis in interspecific hybrid cotton and the supervisory mechanism divergence of hybrids with different females. Photosynthesis and other metabolic process are jointly involved in controlling early biomass heterosis in interspecific hybrid cotton. The expression pattern data of transcriptome sequencing were supported using the qRT-PCR analysis. Our findings could be useful in theoretical and practical studies of early interspecific biomass heterosis, and the results provide potential resources for the theoretical and applied research on early interspecific biomass heterosis.

Physiological aspects of sex differences and Haldane’s rule in Rumex hastatulus

Haldane’s rule (HR, impairment of fertility and/or viability of interracial hybrids) seems to be one of few generalizations in evolutionary biology. The validity of HR has been confirmed in animals, and more recently in some dioecious plants (Silene and Rumex). Dioecious Rumex hastatulus has two races differing in the sex chromosome system: Texas (T) and North Carolina (NC), and T × NC males showed both reduced pollen fertility and rarity—two classical symptoms of Haldane’s rule (HR). The reduced fertility of these plants has a simple mechanistic explanation, but the reason for their rarity was not elucidated. Here, we measured selected physiological parameters related to the antioxidant defense system in parental races and reciprocal hybrids of R. hastatulus. We showed that the X-autosome configurations, as well as asymmetries associated with Y chromosomes and cytoplasm, could modulate this system in hybrids. The levels and quantitative patterns of the measured parameters distinguish the T × NC hybrid from the other analyzed forms. Our observations suggest that the rarity of T × NC males is caused postzygotically and most likely related to the higher level of oxidative stress induced by the chromosomal incompatibilities. It is the first report on the physiological aspects of HR in plants.

Growth, survival and gonad development of two new types of reciprocal triploid hybrids between Crassostrea gigas and C. angulata

The allotriploid technology has been widely applied to aquaculture worldwide. To overcome the deficiency of low growth, poor taste and high mortality of diploid hybrids between Crassostrea gigas and C. angulata in summer, two new types of triploid hybrids were produced by inhibiting the polar body II using cytochalasin B. The growth, survival and gonad traits of triploid hybrids (TGA – C. gigas ♀ × C. angulata ♂ and TAG – C. angulata ♀ × C. gigas ♂), diploid hybrids (GA – C. gigas ♀ × C. angulata ♂ and AG – C. angulata ♀ × C. gigas ♂) and purebred crosses (GG – C. gigas ♀ × C. gigas ♂ and AA – C. angulata ♀ × C. angulata ♂) were evaluated. A high triploidy induction rate (> 95%) was found by ploidy analysis. The fertilization and hatch rates of triploid hybrids were significantly (P < 0.05) lower than that of diploid crosses. During the larval stage, the triploid advantage (TA) was positive in growth, despite was negative in survival. The triploid hybrids exhibited superior performance during the grow-out stage. Across three culture environments (Rongcheng, Rushan and Huangdao), triploid hybrids performed better than diploid hybrids in growth with an increasing value of TA over time. The incremental survival rates of triploid hybrids, especially that of TGA, were significantly (P < 0.05) higher than that of diploid hybrids at Rushan and Huangdao in summer. The TA in cumulative survival rate ranged from 13.80% to 36.04% among environments. A positive yield advantage for diploid and triploid hybrids was observed at Rongcheng (mid-parent heterosis H: 114.11%; TA: 35.76%), Rushan (H: 148.22%; TA: 48.78%) and Huangdao (H: 138.96%; TA: 60.22%). Additionally, most of the triploid hybrids exhibited high sterility during reproduction phase. These findings demonstrated that triploid hybrids between C. gigas × C. angulata had obvious advantage in growth, survival and yield, which have important application value for commercial oyster cultivation in northern China.

Изучение гетерозиса роста у гибридов F1 ячменя

The article presents the results of an analysis of the level of heterosis, and the degree of phenotypic dominance observed in F1 hybrids when plants are crossed between barley germplasms obtained from ICARDA and local varieties of barley. Germplasms PENCO/CHEVRON-BAR/3/ ARUPO/K8755 // MORA CBSS04Y00065S-11Y 1M-0Y-0M-0Y- IBYT-HI, Libya/F6NB_7ICB02-0178-OAP-10TR-OAP-INBYT, MSEL/PFC9214 CBS S01 M00318S-0M-0M-1Y-1 M-OY-IBON-HI, SHENMAI N0.3/MSEL // CANELA/CBSS04Y00367T-A-2Y-2M-0Y-0M-0Y-IBON-HI, TOCTE/3/MJA/BRB2 // QUINA/4/PETUNIA 1 CBSS02Y00362S-0M-0M-2Y-1M-OY-IBON-HI, Barjouj/7/ICNBF8-616/6/Cel/WI2269 // Ore/3/AthsNew/4/Mcu59/Mcul // Moch/5/Rta’S ICB 01-1226-7TR-OTR OAP and local varieties such as Karabakh 7, Karabakh 22, Karabakh 23, Kudretli 48, Baharly, Jalilabad-19. The fertility of flowers in reciprocal hybrid combinations obtained with these parental forms, it was 32.3-57.5%. Most of the analyzed F1 hybrids showed heterosis in plant growth. The degree of phenotypic dominance in combinations varied within +0.5-2.5, and the degree of heterosis - within +1.0-8.6%. The highest heterosis is observed in the following combinations: Karabakh 22 × PENCO/CHEVRON-BAR/3/ ARUPO/K8755 // MORA CBSS04Y00065S-11Y 1M-0Y-0M-0Y (IBYT-HI) (+5.9%), Baharly × Kudretli 48 (+6.4%) and SHENMAI N0.3/MSEL // CANELA CBSS 04Y 00367T-A-2Y-2M-0Y-0M-0Y (IBON-HI) × MSEL/PFC9214 CBS S01 M00318S-0M-0M-1Y-1 M-OY (IBON-HI) (+8.6%). True heterosis was positive in 68.7% of combinations and negative in 25%. In 6.25% of the combinations, heterosis was not observed.

Relative abundance of PGRs in the liquid endosperm of young nuts of Cocos nucifera L. parental cultivars and their reciprocal hybrids

Relative abundance of PGRs in the liquid endosperm of young nuts of Cocos nucifera L. parental cultivars and their reciprocal hybrids

Co-expression network analysis of environmental canalization in the ascidian Ciona

BackgroundCanalization, or buffering, is defined as developmental stability in the face of genetic and/or environmental perturbations. Understanding how canalization works is important in predicting how species survive environmental change, as well as deciphering how development can be altered in the evolutionary process. However, how developmental gene expression is linked to buffering remains unclear. We addressed this by co-expression network analysis, comparing gene expression changes caused by heat stress during development at a whole-embryonic scale in reciprocal hybrid crosses of sibling species of the ascidian Ciona that are adapted to different thermal environments.ResultsSince our previous work showed that developmental buffering in this group is maternally inherited, we first identified maternal developmental buffering genes (MDBGs) in which the expression level in embryos is both correlated to the level of environmental canalization and also differentially expressed depending on the species’ gender roles in hybrid crosses. We found only 15 MDBGs, all of which showed high correlation coefficient values for expression with a large number of other genes, and 14 of these belonged to a single co-expression module. We then calculated correlation coefficients of expression between MDBGs and transcription factors in the central nervous system (CNS) developmental gene network that had previously been identified experimentally. We found that, compared to the correlation coefficients between MDBGs, which had an average of 0.96, the MDBGs are loosely linked to the CNS developmental genes (average correlation coefficient 0.45). Further, we investigated the correlation of each developmental to MDBGs, showing that only four out of 62 CNS developmental genes showed correlation coefficient > 0.9, comparable to the values between MDBGs, and three of these four genes were signaling molecules: BMP2/4, Wnt7, and Delta-like.ConclusionsWe show that the developmental pathway is not centrally located within the buffering network. We found that out of 62 genes in the developmental gene network, only four genes showed correlation coefficients as high as between MDBGs. We propose that loose links to MDBGs stabilize spatiotemporally dynamic development.

Heterosis and Differential DNA Methylation in Soybean Hybrids and Their Parental Lines.

Heterosis is an important biological phenomenon and is widely applied to increase agricultural productivity. However, the underlying molecular mechanisms of heterosis are still unclear. Here we constructed three combinations of reciprocal hybrids of soybean, and subsequently used MethylRAD-seq to detect CCGG and CCWGG (W = A or T) methylation in the whole genome of these hybrids and their parents at the middle development period of contemporary seed. We were able to prove that changes in DNA methylation patterns occurred in immature hybrid seeds and the parental variation was to some degree responsible for differential expression between the reciprocal hybrids. Non-additive differential methylation sites (DMSs) were also identified in large numbers in hybrids. Interestingly, most of these DMSs were hyper-methylated and were more concentrated in gene regions than the natural distribution of the methylated sites. Further analysis of the non-additive DMSs located in gene regions exhibited their participation in various biological processes, especially those related to transcriptional regulation and hormonal function. These results revealed DNA methylation reprogramming pattern in the hybrid soybean, which is associated with phenotypic variation and heterosis initiation.

Experimental sympatry suggests geographic isolation as an essential reproductive barrier between two sister species ofPedicularis

AbstractAlthough mechanical isolation mediated by shared pollinators has been considered as a classic model of pollinator‐mediated floral isolation inPedicularis, a superdiverse genus in Hengduan Mountains, southwest China, there has been no empirical study of interspecific pollen flow between closely related species. We examined reproductive barriers at six different stages betweenPedicularis cranolophaandPedicularis tricolor, two sister species. The two sister species were geographically isolated from each other based on our field survey and the records of herbarium specimens. Translocation experiments showed that flowering phenology partly overlapped and bumblebee pollinators did not discriminate between flowers of the two species. Bumblebee interspecific moves could mediate interspecific pollination as traced using fluorescent powder, in which pollen analogs placed on one species were transferred to the stigmas of the other species in experimental plots containing both species. Heterospecific pollen tubes grew in the style as well as conspecific pollen in hand‐pollination experiments. Reciprocal hybridization between the two species could produce (partially) viable seeds, suggesting weak post‐pollination barriers. Our results showed that geographic isolation was an important barrier of two species, and the total reproductive isolation between two species was incomplete when without geographical isolation. The formation of Big Snow Mountains could introduce an important pre‐zygotic reproductive barrier between the two sister species ofPedicularis; such geographical isolation could be responsible for allopatric speciation, giving a clue to understanding the rapid radiation on mountain areas.

DNA demethylation affects imprinted gene expression in maize endosperm

BackgroundDNA demethylation occurs in many species and is involved in diverse biological processes. However, the occurrence and role of DNA demethylation in maize remain unknown.ResultsWe analyze loss-of-function mutants of two major genes encoding DNA demethylases. No significant change in DNA methylation has been detected in these mutants. However, we detect increased DNA methylation levels in the mutants around genes and some transposons. The increase in DNA methylation is accompanied by alteration in gene expression, with a tendency to show downregulation, especially for the genes that are preferentially expressed in endosperm. Imprinted expression of both maternally and paternally expressed genes changes in F1 hybrid with the mutant as female and the wild-type as male parental line, but not in the reciprocal hybrid. This alteration in gene expression is accompanied by allele-specific DNA methylation differences, suggesting that removal of DNA methylation of the maternal allele is required for the proper expression of these imprinted genes. Finally, we demonstrate that hypermethylation in the double mutant is associated with reduced binding of transcription factor to its target, and altered gene expression.ConclusionsOur results suggest that active removal of DNA methylation is important for transcription factor binding and proper gene expression in maize endosperm.

Evaluation of heterosis through reciprocal crosses of inbred cucumber lines (Cucumis sativus L.)

The purpose of the study. The aim of the study was to determine the effect of heterosis in short-fruited parthenocarpic F1 cucumber hybrids by the main economically valuable characteristics, when grown using low-volume technology in industrial greenhouses of the Moscow region.Materials and methods. The object of the study is short-fruited parthenocarpic reciprocal hybrids of cucumber Druzhny (F1 I73514 x I74011), F1 I74011 x I73514 and their parent inbred lines I73514 and I74011 of selection by N.N. Timofeev Breeding Station LLC. F1 SV4097CV of foreign selection of Semenis company (Netherlands) was used as a control. The study was conducted in 2020-2021 in industrial greenhouses of the "V. I. Edelstein Vegetable Experimental Station" of the K.A. Timiryazev Russian State Agrarian University-Moscow Agricultural Academy in Moscow on low-volume hydroponics in peat bags. Parental lines and hybrid combinations were evaluated by earliness, early yield, yield, number of fruits per plant, average fruit weight and marketability.Results. According to the results of the study, F1 Druzhny (F1 I73514 x I74011) and the reverse hybrid I73514 x I74011 demonstrated high positive effects of heterosis in yield (MPH=19.4...22%; HPH=13.4...15.9%; CH=9.6...12%) and the number of fruits per plant (MPH=22.5...26.4%; HPH=12.5...15.8%; CH=11.7...15%). Negative indicators of the heterosis effect were noted for earliness from germination to flowering (MPH=-3.4...-1.1%; HPH=-6.5...-4.4%; CH=-4.4...-2.2%) and average fruit weight (MPH=-2.2...-1.3%; HPH=-5.3...-4.3%; CH=-3.4...-2.4%). The value of the degree of dominance indicates the presence of positive overdominance in the inheritance of such traits as yield (hp=2.7...3.2), the number of fruits from the plant (hp=1.5...1.9) and marketability (hp=1.6...2.3). Negative overdomination was observed in earliness from germination to flowering (hp= -2...-1.3) and average fruit weight (hp=-1.7...-1.2). According to the signs of earliness from germination to fruiting (hp =0) and early yield (hp=-0.1...0.5), intermediate inheritance was revealed. The Druzhny hybrid significantly exceeded the control hybrid SV4097CV in early yield, yield and number of fruits from the plant, and the reverse hybrid F1 I74011 x I73514 was at the control level, which indicates the prospects of growing these hybrids in the conditions of spring-summer turnover on low-volume hydroponics.

Melanization plasticity of Drosophila kikkawai, Drosophila leontia and reciprocal hybrids under different temperatures

• Drosophila kikkawai and Drosophila leontia produces hybrids. • No plasticity for melanization in D. kikkawai and D. leontia but hybrids show plasticity. • Generations proceed in the direction of female. Drosophila (Sophophora) kikkawai , Burla, 1954 and Drosophila (Sophophora) leontia , Tsacas & David 1978 are closely related sibling species, the former being cosmopolitan and the latter is restricted to tropical localities. We investigated the influence of introgressive hybridization on phenotypic diversity of the two sibling species in the present study. How hybridization supports the relative abundance of pure species according to latitudinal cline is the aim of this study because hybrids show a tendency to acquire geographical location of their parent species in equal or greater abundance. How hybridization supports the plasticity for melanization of hybrids is not explored yet. The two species can cross and generate hybrids. For this, we crossed true breeding strains of both species to obtain the hybrids i.e. dark female (♀) of D. kikkawai ( D. k ) with males (♂) of D. leontia ( D. l ) in cross I and light ♀ of D. k with ♂ of D. l in cross II along with their reciprocal crosses. Finally, we studied the plasticity of both species and their hybrids at 6 growth temperatures (14, 17, 21, 25, 28 and 31 °C). We found that there is no plasticity for melanization in true breeding darker and lighter strain of D. kikkawai as well as D. leontia whereas hybrids of both species showed high phenotypic plasticity. Significant differences in slope values across temperatures in parental and hybrid lines suggest plastic effects. Phenotypic variation in abdominal melanization in hybrids can be interpreted as a result of gene introgression with D. kikkawai . We conclude that introgressive hybridization might be an important, although underestimated, mechanism shaping species distribution and adaptation.