F1 Hybrids Research Articles

Molecular Diversity and Combining Ability in Newly Developed Maize Inbred Lines under Low-Nitrogen Conditions.

Nitrogen is an essential element for maize growth, but excessive application can lead to various environmental and ecological issues, including water pollution, air pollution, greenhouse gas emissions, and biodiversity loss. Hence, developing maize hybrids resilient to low-N conditions is vital for sustainable agriculture, particularly in nitrogen-deficient soils. Combining ability and genetic relationships among parental lines is crucial for breeding superior hybrids under diverse nitrogen levels. This study aimed to assess the genetic diversity of maize inbred lines using simple sequence repeat (SSR) markers and evaluate their combining ability to identify superior hybrids under low-N and recommended conditions. Local and exotic inbred lines were genotyped using SSR markers, revealing substantial genetic variation with high gene diversity (He = 0.60), moderate polymorphism information content (PIC = 0.54), and an average of 3.64 alleles per locus. Twenty-one F1 hybrids were generated through a diallel mating design using these diverse lines. These hybrids and a high yielding commercial check (SC-131) were field-tested under low-N and recommended N conditions. Significant variations (p < 0.01) were observed among nitrogen levels, hybrids, and their interaction for all recorded traits. Additive genetic variances predominated over non-additive genetic variances for grain yield and most traits. Inbred IL3 emerged as an effective combiner for developing early maturing genotypes with lower ear placement. Additionally, inbreds IL1, IL2, and IL3 showed promise as superior combiners for enhancing grain yield and related traits under both low-N and recommended conditions. Notably, hybrids IL1×IL4, IL2×IL5, IL2×IL6, and IL5×IL7 exhibited specific combining abilities for increasing grain yield and associated traits under low-N stress conditions. Furthermore, strong positive associations were identified between grain yield and specific traits like plant height, ear length, number of rows per ear, and number of kernels per row. Due to their straightforward measurability, these relationships underscore the potential of using these traits as proxies for indirect selection in early breeding generations, particularly under low-N stress. This research contributes to breeding nitrogen-efficient maize hybrids and advances our understanding of the genetic foundations for tolerance to nitrogen limitations.

Image analysis and polyphenol profiling unveil red-flesh apple phenotype complexity.

The genetic basis of colour development in red-flesh apples (Malus domestica Borkh) has been widely characterised; however, current models do not explain the observed variations in red pigmentation intensity and distribution. Available methods to evaluate the red-flesh trait rely on the estimation of an average overall colour using a discrete class notation index. However, colour variations among red-flesh cultivars are continuous while development of red colour is non-homogeneous and genotype-dependent. A robust estimation of red-flesh colour intensity and distribution is essential to fully capture the diversity among genotypes and provide a basis to enable identification of loci influencing the red-flesh trait. In this study, we developed a multivariable approach to evaluate the red-flesh trait in apple. This method was implemented to study the phenotypic diversity in a segregating hybrid F1 family (91 genotypes). We developed a Python pipeline based on image and colour analysis to quantitatively dissect the red-flesh pigmentation from RGB (Red Green Blue) images and compared the efficiency of RGB and CIEL*a*b* colour spaces in discriminating genotypes previously classified with a visual notation. Chemical destructive methods, including targeted-metabolite analysis using ultra-high performance liquid chromatography with ultraviolet detection (UPLC-UV), were performed to quantify major phenolic compounds in fruits' flesh, as well as pH and water contents. Multivariate analyses were performed to study covariations of biochemical factors in relation to colour expression in CIEL*a*b* colour space. Our results indicate that anthocyanin, flavonol and flavanol concentrations, as well as pH, are closely related to flesh pigmentation in apple. Extraction of colour descriptors combined to chemical analyses helped in discriminating genotypes in relation to their flesh colour. These results suggest that the red-flesh trait in apple is a complex trait associated with several biochemical factors.

A New Mouse Model for Usher Syndrome Crossing Kunming Mice with CBA/J Mice

BackgroundPreviously, we discovered a strain of Kunming mice, referred to as the KMush/ush strain, that exhibited notably abnormal electroretinogram (ERG) readings and elevated thresholds for auditory brainstem responses (ABRs), which resembled the characteristics of Usher Syndrome (USH). We successfully identified the pathogenic genes, Pde6b and Adgrv1, after KMush/ush crossbred with CBA/CaJ mice, referred to as CBA-1ush/ush, CBA-2ush/ush or CBA-2ush/ush. In this investigation, we crossbred KMush/ush and CBA/J mice to establish novel recombinant inbred lines and analysed their phenotypic and genotypic characteristics. MethodsERG readings, ABR testing, fundus morphology, histological examination of the retina and inner ear, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, western blotting, DNA sequence analysis and behavioural experiments were performed to assess the phenotypes and genotypes of the progeny lines. ResultsNo obvious waveforms in the ERG were detected in F1 hybrid mice while normal ABR results were recorded. The F2 hybrids, which were called J1ush/ush or J2ush/ush, exhibited segregated hearing-loss phenotypes. J1ush/ush mice had a retinitis pigmentosa (RP) phenotype with elevated ABR thresholds, whereas J2ush/ush mice exhibited only the RP phenotype. Interestingly, J1ush/ush mice showed significantly higher ABR thresholds than wild-type mice at 28 days post born (P28), and RT-qPCR and DNA-sequencing analysis showed that Adgrv1 gene expression was significantly altered in J1ush/ush mice, but histological analysis showed no significant structural changes in the organ of Corti or spiral ganglia. Further elevation of ABR-related hearing thresholds by P56 manifested only as a reduced density of spiral ganglion cells, which differed significantly from the previous pattern of cochlear alterations in CBA-2ush/ush mice. ConclusionsWe successfully introduced the hearing-loss phenotype of inbred mice with USH into CBA/J mice, which provides a good animal model for future studies on the important physiological roles of the Adgrv1 gene in inner-ear structure and for therapeutic studies targeting Adgrv1-mutated USH.

Unearthing hybridization opportunities for augmenting biomass yield and harvest index in rajmash (Phaseolus vulgaris L.)

In present study, 21 F1 hybrids derived from crossing between seven female genotypes and three male testers following a line × tester mating design were evaluated for analyzing the component of genetic variation and heterosis of yield contributing traits. The components of variances due to gca and sca revealed the predominance of non-additive gene action for biomass and harvest index. The average better parent heterosis (BPH) and standard heterosis (SH) for Biomass yield (BY) was 43.71 and 114.67, respectively, and the average BPH and SH for the Harvest index (HI) was -13.04 and -20.45, respectively. The higher magnitude of the BPH and SH recorded for BY indicated that the scope for increasing the HI in Rajmash is limited and that further increases in productivity have to come mainly through enhanced BY. The parent RR21-01 and GR 1 were good general combiners for biomass, TRCR 3, TRCR 2, SKAU-R-19 and RKR 1033 for harvest index. Cross combinations IPR-277- 19 × HUR recorded positively significant sca effect for BY and IPR-277-19 × GR, TRCR 3 × GR 1, TRCR 2 × GR 1, IPR-205-19 × HUR, IPR-277-19 × GR 1, SKAU-R-19 ×RKR 1033, RR-21-01 × HUR and RR-21-12 × GR 1 for HI. These results demonstrate that the selection of parents should not only be based on per se performance but also on combining ability and heterosis for achieving genetic improvement in Rajmash,

Whole-genome resequencing identifies candidate genes and allelic variation in the MdNADP-ME promoter that regulate fruit malate and fructose contents in apple

Soluble sugar and organic acids are key determinants of fruit organoleptic quality and directly affect the commodity value and economic returns of fruit crops. We performed whole-genome sequencing of the apple varieties Gala and Xiahongrou, along with their F1 hybrids, to construct a high-density bin map. Our quantitative genetic analysis pinpointed 53 quantitative trait loci (QTLs) related to 11 sugar and acid traits. We identified a candidate gene, MdNADP-ME, responsible for malate degradation, in a stable QTL on linkage group 15. Sequence analysis revealed an A/C SNP in the promoter region (MEp-799) that influences binding of the MdMYB2 transcription factor, thereby affecting MdNADP-ME expression. In our study of various apple genotypes, this SNP has been demonstrated to be linked to malate and fructose levels. We also developed a dCAPS marker associated with fruit fructose content. These results substantiate the role of MdNADP-ME in maintaining the equilibrium between sugar and acid contents in apple fruits.

Microplastic exposure is associated with epigenomic effects in the model organism Pimephales promelas (fathead minnow).

Microplastics have evolutionary and ecological impacts across species, affecting organisms' development, reproduction, and behavior along with contributing to genotoxicity and stress. As plastic pollution is increasing and ubiquitous, gaining a better understanding of organismal responses to microplastics is necessary. Epigenetic processes such as DNA methylation are heritable forms of molecular regulation influenced by environmental conditions. Therefore, determining such epigenetic responses to microplastics will reveal potential chronic consequences of this environmental pollutant. We performed an experiment across two generations of fathead minnows (Pimephales promelas) to elucidate transgenerational epigenetic effects of microplastic exposure. We exposed the first generation of fish to four different treatments of microplastics: two concentrations of each of pre-consumer polyethylene (PE) and PE collected from Lake Ontario. We then raised the first filial generation with no microplastic exposure. We used enzymatic methylation sequencing on adult liver tissue and homogenized larvae to evaluate DNA methylation differences among treatments, sexes, and generations. Our findings show the origin of the plastic had a larger effect in female minnows whereas the effect of concentration was stronger in the males. We also observed transgenerational effects, highlighting a mechanism in which parents can pass on the effects of microplastic exposure to their offspring. Many of the genes found within differentially methylated regions in our analyses are known to interact with estrogenic chemicals associated with plastic and are related to metabolism. This study highlights the persistent and potentially serious impacts of microplastic pollution on gene regulation in freshwater systems.

Chromosome stability of synthetic Triticum turgidum–Aegilops umbellulata hybrids

BackgroundUnreduced gamete formation during meiosis plays a critical role in natural polyploidization. However, the unreduced gamete formation mechanisms in Triticum turgidum–Aegilops umbellulata triploid F1 hybrid crosses and the chromsome numbers and compostions in T. turgidum–Ae. umbellulata F2 still not known.ResultsIn this study, 11 T.turgidum–Ae. umbellulata triploid F1 hybrid crosses were produced by distant hybridization. All of the triploid F1 hybrids had 21 chromosomes and two basic pathways of meiotic restitution, namely first-division restitution (FDR) and single-division meiosis (SDM). Only FDR was found in six of the 11 crosses, while both FDR and SDM occurred in the remaining five crosses. The chromosome numbers in the 127 selfed F2 seeds from the triploid F1 hybrid plants of 10 crosses (no F2 seeds for STU 16) varied from 35 to 43, and the proportions of euploid and aneuploid F2 plants were 49.61% and 50.39%, respectively. In the aneuploid F2 plants, the frequency of chromosome loss/gain varied among genomes. The chromosome loss of the U genome was the highest (26.77%) among the three genomes, followed by that of the B (22.83%) and A (11.81%) genomes, and the chromosome gain for the A, B, and U genomes was 3.94%, 3.94%, and 1.57%, respectively. Of the 21 chromosomes, 7U (16.54%), 5 A (3.94%), and 1B (9.45%) had the highest loss frequency among the U, A, and B genomes. In addition to chromosome loss, seven chromosomes, namely 1 A, 3 A, 5 A, 6 A, 1B, 1U, and 6U, were gained in the aneuploids.ConclusionIn the aneuploid F2 plants, the frequency of chromosome loss/gain varied among genomes, chromsomes, and crosses. In addition to variations in chromosome numbers, three types of chromosome translocations including 3UL·2AS, 6UL·1AL, and 4US·6AL were identified in the F2 plants. Furthermore, polymorphic fluorescence in situ hybridization karyotypes for all the U chromosomes were also identified in the F2 plants when compared with the Ae. umbellulata parents. These results provide useful information for our understanding the naturally occurred T. turgidum–Ae. umbellulata amphidiploids.

Assessment of Transgressive Segregants for Yield and its Component Traits in French Bean (Phaseolus vulgaris L.)

Background: Extreme phenotypes carried on by transgressive segregation are, moreover, heritably stable in contrast to heterosis. It has been hypothesized that the development of extreme or “transgressive” traits in segregating hybrid populations assists in the adaptive divergence of hybrid taxa. The investigation on French bean was experimented to evaluate transgressive segregants generated in the F2 generation for yield and related traits. Methods: The present study on French bean was conducted during rabi 2019 to 2022 to elicit data on transgressive segregants produced for yield and related traits in F2 generation. Fertile F1 hybrids were developed from three crosses: IC 632961 × Arka Sukomal, IC 632961 × Arka Arjun and Arka Arjun × IC 63296. Heterosis was estimated for yield and related traits in these hybrids. The F2 progeny were evaluated in open field condition. Mean, standard deviation and percentage of transgressive segregants were estimated for quantitative traits under investigation. Result: Transgressive segregants were observed in all three crosses, with the highest number of transgressive segregants for yield traits found in the progeny of the cross IC 632961 × Arka Sukomal. The identification and isolation of such transgressive segregants indicate that the parents possess favourable alleles and genes governing the traits of interest, which can be consolidated into a single or a few genotypes through stringent selection. Superior and desirable transgressive segregants were observed for all sixteen yield and its component traits, except for leaf length, in the two cross combinations Arka Arjun × IC 632961 and IC 632961 × Arka Arjun. The highest percentage of transgressive segregation was observed for the number of inflorescences per plant (79.49%), followed by the number of pods per plant (78.46%) and pod yield per plant (75.61%) in the F2 generation.

Maternal 129S1/SvImJ background attenuates the placental phenotypes induced by chronic paternal alcohol exposure

Paternal alcohol use is emerging as a plausible driver of alcohol-related growth and patterning defects. Studies from our lab using an inbred C57Bl/6 J mouse model suggest that these paternally-inherited phenotypes result from paternally programmed deficits in the formation and function of the placenta. The 129S1/SvImJ genetic background is typically more susceptible to fetoplacental growth defects due to strain-specific differences in placental morphology. We hypothesized that these placental differences would sensitize 129S1/SvImJ-C57Bl/6 J hybrid offspring to paternally-inherited fetoplacental growth phenotypes induced by paternal alcohol exposure. Using a limited access model, we exposed C57Bl/6 J males to alcohol and bred them to naïve 129S1/SvImJ dams. We then assayed F1 hybrid offspring for alterations in fetoplacental growth and used micro-CT imaging to contrast placental histological patterning between the preconception treatments. F1 hybrid placentae exhibit larger placental weights than pure C57Bl/6 J offspring but display a proportionally smaller junctional zone with increased glycogen content. The male F1 hybrid offspring of alcohol-exposed sires exhibit modest placental hyperplasia but, unlike pure C57Bl/6 J offspring, do not display observable changes in placental histology, glycogen content, or measurable impacts on fetal growth. Although F1 hybrid female offspring do not exhibit any measurable alterations in fetoplacental growth, RT-qPCR analysis of placental gene expression reveals increased expression of genes participating in the antioxidant response. The reduced placental junctional zone but increased glycogen stores of 129S1/SvImJ-C57Bl/6 J F1 hybrid placentae ostensibly attenuate the previously observed placental patterning defects and fetal growth restriction induced by paternal alcohol use in the C57Bl/6 J strain.

Insertion of short L1 sequences generates inter-strain histone acetylation differences in the mouse

BackgroundGene expression divergence between populations and between individuals can emerge from genetic variations within the genes and/or in the cis regulatory elements. Since epigenetic modifications regulate gene expression, it is conceivable that epigenetic variations in cis regulatory elements can also be a source of gene expression divergence.ResultsIn this study, we compared histone acetylation (namely, H3K9ac) profiles in two mouse strains of different subspecies origin, C57BL/6 J (B6) and MSM/Ms (MSM), as well as their F1 hybrids. This identified 319 regions of strain-specific acetylation, about half of which were observed between the alleles of F1 hybrids. While the allele-specific presence of the interferon regulatory factor 3 (IRF3) binding sequence was associated with allele-specific histone acetylation, we also revealed that B6-specific insertions of a short 3′ fragment of LINE-1 (L1) retrotransposon occur within or proximal to MSM-specific acetylated regions. Furthermore, even in hyperacetylated domains, flanking regions of non-polymorphic 3′ L1 fragments were hypoacetylated, suggesting a general activity of the 3′ L1 fragment to induce hypoacetylation. Indeed, we confirmed the binding of the 3′ region of L1 by three Krüppel-associated box domain-containing zinc finger proteins (KZFPs), which interact with histone deacetylases. These results suggest that even a short insertion of L1 would be excluded from gene- and acetylation-rich regions by natural selection. Finally, mRNA-seq analysis for F1 hybrids was carried out, which disclosed a link between allele-specific promoter/enhancer acetylation and gene expression.ConclusionsThis study disclosed a number of genetic changes that have changed the histone acetylation levels during the evolution of mouse subspecies, a part of which is associated with gene expression changes. Insertions of even a very short L1 fragment can decrease the acetylation level in their neighboring regions and thereby have been counter-selected in gene-rich regions, which may explain a long-standing mystery of discrete genomic distribution of LINEs and SINEs.

Phytochemical studies in some varieties of soybean [Glycine max (L.) Merr.] and their hybrids

In the present investigation, an attempt has been made to congregate the phytochemical studies done on intervarietal F1 hybrids of soybean (Glycine max L.) along with their parents. The eleven F1 hybrids were obtained by intervarietal crossing done using five varieties of soybean viz Bragg(BG), NRC7(NR), Punjab1(PN), PUSA98-14(PU) and JS9560(JS).Estimation of phenols was done by FCR Method using Gallic acid as standard. The total phenolic content was found highest in the cross JSXNR and lowest in BGXNR. Total tannin content was determined using FCR method. Total tannin content was highest in NRXJS and least in BGXPN. In addition, total flavonoids were determined using Alcl3 reagent and antioxidant activity by DPPH method. Total flavonoids was found maximum in PNXNR and least in PUXPN respectively. Highest Antioxidant Activity was 50.31% in JSXPN and lowest was 39.08% in NRXJS. The results suggested that besides protein and oil contents, the phenolic contents should also be considered as an important characteristic feature of soybean seeds, and as a potential selection criterion for antioxidant activity in soybean.

Combining Ability Analysis of Yield and Quality Traits in Pumpkin [Cucurbita moschataduch. Ex Poir

The present analysis was carried out with aims to estimate the general and specific combining ability of pumpkin involving six parents namely, Arka Chandan (P1), Ambili (P2), Arka Suryamukhi(P3), Pusa Vishwas (P4), CO 2 (P5) and CO 1 (P6) and 30 F1 hybrids obtained through full diallel analysis in randomized block design with three replication. The observation were recorded for eighteen traits viz., vine length, node number at which first male flower anthesis, node number at which first female flower anthesis, number of primary branches vine-1, days to first male flower anthesis, days to first female flower anthesis, number of male flowers vine-1, number of female flowers vine-1, sex ratio, number of fruits vine-1, fruit weight, polar diameter of fruit, equatorial diameter of fruit, flesh thickness, 100 seed weight, carotene content, total soluble solids and yield vine-1.. The analysis of variance for combining ability among various traits in pumpkin revealed that there were significant differences for all the traits. Among the parents, Ambili was the best general combiner for number of fruits vine-1, yield vine-1 and yield contributing traits. The highest desirable SCA were obtained from a cross of Ambili x Arka Suryamukhi for yield and attributing traits, which was the best and promising hybrid.

CORRELATION, REGRESSION COEFFICIENTS AND HERITABILITY BETWEEN MAIN SELECTION TRAITS OF SHEEP

The article presents information on improvement of selection traits of lambs born from "inbred" breeding of F2 crossbred sheep using selection-genetic indicators. Studies show that selection of lambs born from inbreeding of F2 hybrid sheep based on positive correlation coefficients between selection traits is important for creating high-yielding breeding flocks in the future. At the same time, the regression coefficients of crossbred lambs in group II were higher than the regression coefficients of pure jaidari lambs in group I, and especially it was found that the regression coefficients of crossbred rams in group II achieved the highest result. According to the heredity of the sheep, it was found that the live weight of the sheep, the height of the withers, the oblique length of the body, the width of the chest, the depth of the chest, the circumference of the udder, and the circumference of the calf, that is, the coefficients of heredity are moderate.

Morphological variation of tail bone among two chicken breeds and their F1 progeny.

Fancy breeds of Japanese indigenous chicken display extensive morphological diversity, particularly in tail feathers. Although marked differences in tail and bone traits have been reported between Tosa-jidori (wild type) and Minohikichabo (rich type) breeds, little is known about the pattern of genetic inheritance in cross experiments. Therefore, this study aimed to investigate the strain and sex effects, and inheritance patterns, in the morphometric variation of pygostyle bones among Tosa-jidori, Minohikichabo, and their F1 hybrids. Five morphological traits, angle of the apex of the pygostyle, pygostyle length, margo cranialis length, tail feather number, and body weight, were evaluated at the adult stage. A significant strain difference was detected in all traits, whereas significant sex differences were observed in only three traits, but not in the angle of the apex of the pygostyle and tail feather number. In F1 hybrids, the angle of the apex of the pygostyle was significantly different to that of Tosa-jidori but not that of Minohikichabo, whereas the pygostyle length and tail number of F1 hybrids were significantly different from those of Minohikichabo but not those of Tosa-jidori. A significant heterosis effect was found in the margo cranialis length and body weight. All five traits showed nonadditive inheritance patterns but varied in each trait between partial dominance (angle of the apex of pygostyle), full dominance (pygostyle length and tail feather number), and over-dominance (margo cranialis length and body weight). Interestingly, different patterns of genetic inheritance in the F1 hybrid were observed at different locations, even within the same pygostyle bone. Using the Japanese indigenous chicken model, these results provide a substantial step toward understanding the genetic architecture of morphology in chickens.

The effect of mitochondrial genome heterogeneity on voluntary wheel running activity in aged rats

Introduction: Variation in the response to exercise training is a widely accepted concept. A large portion of exercise response variability is attributable to genetic heritability, potentially due to inherited maternal mitochondrial characteristics. Importantly, humans exhibit a heterogenous mitochondrial genome. Unfortunately, many preclinical models used to investigate molecular transducers of exercise training are inbred rodent models that lack mitochondrial diversity, which has poor translatability to humans. Recently, a rat model has been generated to reflect human mitochondrial genome heterogeneity. Hence, we propose using this rat model to investigate the impact of mitochondrial genome heterogeneity on voluntary wheel running (VWR) activity. Objective: To investigate the effect of mitochondrial genome heterogeneity on VWR activity in aged rats. Hypothesis: VWR activity will differ between two rat strains with divergent mitochondrial genomes. Methodology: Male and female OKC-HETB and OKC-HETW rats were obtained from the Oklahoma City VA Medical Center. Briefly, the OKC-HETB and OKC-HETW rat strains were generated by a four-way cross strategy using four inbred strains (Brown Norway [BN], Fischer 344, Lewis, and Wistar Kyto [WKY]). Subsequent reciprocal crosses between males and females from the two F1 hybrids were made to generate genetically heterogeneous rats with mitochondrial genomes from either the BN (OKC-HETB) or WKY (OKC-HETW) parental strains. As a result, OKC-HETB and OKC-HETW rats have equal numbers of alleles yet divergent mitochondrial genomes. Endurance capacity and neuromuscular function in 18-to 20-month-old rats were assessed by treadmill running and rotarod protocols before and after 8 weeks of VWR. After post-testing, animals are euthanized at 21-24 months old, and tissues are collected. The mitochondrial function of obtained tissues will be analyzed via high-resolution respirometry, and protein levels will be quantified using immunohistochemistry and Western blotting. Results: Current baseline data shows female rats weighed less than males, which was not affected by strain. Although no strain effect on treadmill performance was observed, females ran longer than males during the treadmill test. However, this sex effect was lost within strain comparisons. There was no strain effect on rotarod performance as latency to fall times were similar between strains. However, OKCHetW rats showed some improved latency to falls over time. Female OKC-HETB rats had a longer latency to falls at baseline than their male counterparts, which became similar between the sexes over time. Conversely, female OKC-HETW rats developed longer latency to falls compared to their male counterparts over time. Currently, 2 weeks of VWR activity was highly variable among rats in the W stain but similar among rats in the B strain. Conclusions: Our preliminary findings suggest that mitochondrial genome heterogeneity does not impact baseline physical function outcomes such as endurance capacity and neuromuscular function in exercise naïve 18-20 months old rats. However, biological sex appears to have a greater influence. Currently, strain and sex did not affect 2-weeks of VWR activity. However, this study is currently ongoing using an 8-week VWR intervention. Importantly, this study will evaluate the impact of mitochondrial genome heterogeneity on VWR adaptations in young and aged rats. Wake Forest University School of Medicine Start-up Funds to Ahn. R21 AG072137 to Richardson, Stout, and Austad. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Enhancement of the Clastogenic Effects of Topotecan In Vivo by Tyrosyl-DNA Phosphodiesterase 1 Inhibitors.

Topotecan administered intraperitoneally at single doses of 0.25, 0.5, and 1 mg/kg induced chromosomal aberrations in bone marrow cells of F1(CBA×C57BL/6) hybrid mice in a dose-dependent manner. A tyrosyl-DNA phosphodiesterase 1 (TDP1) inhibitor, an usnic acid derivative OL9-116 was inactive in a dose range of 20-240 mg/kg, but enhanced the cytogenetic effect of topotecan (0.25 mg/kg) at a dose of 40 mg/kg (per os). The TDP1 inhibitor, a coumarin derivative TX-2552 (at doses of 20, 40, 80, and 160 mg/kg per os), increased the level of aberrant metaphases induced by topotecan (0.25 mg/kg) by 2.1-2.6 times, but was inactive at a dose of 10 mg/kg. The results indicate that TDP1 inhibitors enhance the clastogenic activity of topotecan in mouse bone marrow cells in vivo and are characterized by different dose profiles of the co-mutagenic effects.

Naturally occurring polymorphisms reveal the cis-regulatory sites and transcription factors controlling follicular and marginal zone B cells

Abstract The splenic B cell compartment consists of follicular (FoB) and marginal zone (MZB) B cells. In contrast to FoB, MZB exist in a poised state and rapidly respond to blood-borne pathogens in the absence of T cell help, predominately generating a rapid wave of short-lived plasma cells. These differences in responses are driven by differential genetic and epigenetic priming of each subset. MZB epigenetic programming are enriched for bHLH, POU, Rel and RUNT motifs, whereas FoB are enriched for IRF and KLF motifs. MZB also exhibit increased expression of genes associated with Notch signaling, Myc, and mTORC1 pathways. However, it is unclear how sequence specific transcription factors directly and indirectly regulate distinct states in MZB and FoB that underpin B cell activation, differentiation, and acquisition of effector functions. To address this, we generated an F1 hybrid model which utilizes naturally occurring polymorphism present in the wild-derived mouse line Spret/EiJ compared to the reference strain C57BL/6. The monoallelic polymorphisms present in this F1 generation allows us to use the allelic imbalance to dissect how alterations in genetic features impact TF binding, epigenetic architecture, and ultimately resulting gene expression programs. MZB and FoB were sorted from naive (Spret x B6) F1’s and subject to RNA and ATAC-seq. This study aims to define the cis-regulatory mechanisms responsible for the epigenetic and transcriptional differences of FoB and MZB cells.

THE EFFECT OF DIFFERENT IRRIGATION REGIMES ON THE YIELD OF MAIZE HYBRIDS

In this article, information is given on the date, number and norm of irrigation of Uzbekistan-601 ECB, NS-6010 F1 hybrids of maize, which were carried out by furrow and drip irrigation in the conditions of weakly salted meadow alluvial soils of Bukhara province, and yield data obtained from options conducted in different irrigation regimes.

Investigation of heat stress responses and adaptation mechanisms by integrative metabolome and transcriptome analysis in tea plants (Camellia sinensis).

Extreme high temperature has deleterious impact on the yield and quality of tea production, which has aroused the attention of growers and breeders. However, the mechanisms by which tea plant varieties respond to extreme environmental heat is not clear. In this study, we analyzed physiological indices, metabolites and transcriptome differences in three different heat-tolerant tea plant F1 hybrid progenies. Results showed that the antioxidant enzyme activity, proline, and malondialdehyde were significantly decreased in heat-sensitive 'FWS' variety, and the accumulation of reactive oxygen molecules such as H2O2 and O2- was remarkably increased during heat stress. Metabolomic analysis was used to investigate the metabolite accumulation pattern of different varieties in response to heat stress. The result showed that a total of 810 metabolites were identified and more than 300 metabolites were differentially accumulated. Transcriptional profiling of three tea varieties found that such genes encoding proteins with chaperon domains were preferentially expressed in heat-tolerant varieties under heat stress, including universal stress protein (USP32, USP-like), chaperonin-like protein 2 (CLP2), small heat shock protein (HSP18.1), and late embryogenesis abundant protein (LEA5). Combining metabolomic with transcriptomic analyses discovered that the flavonoids biosynthesis pathway was affected by heat stress and most flavonols were up-regulated in heat-tolerant varieties, which owe to the preferential expression of key FLS genes controlling flavonol biosynthesis. Take together, molecular chaperons, or chaperon-like proteins, flavonols accumulation collaboratively contributed to the heat stress adaptation in tea plant. The present study elucidated the differences in metabolite accumulation and gene expression patterns among three different heat-tolerant tea varieties under extreme ambient high temperatures, which helps to reveal the regulatory mechanisms of tea plant adaptation to heat stress, and provides a reference for the breeding of heat-tolerant tea plant varieties.

Development of near homozygous lines for diploid hybrid TPS breeding in potatoes

Diploid inbred-based F1 hybrid True Potato Seed (DHTPS) breeding is a novel technique to transform potato breeding and cultivation across the globe. Significant efforts are being made to identify elite diploids, dihaploids and develop diploid inbred lines for heterosis exploitation in potatoes. Self-incompatibility is the first obstacle for developing inbred lines in diploid potatoes, which necessitates the introgression of a dominant S locus inhibitor gene (Sli) for switching self-incompatibility to self-compatibility. We evaluated a set of 357 diploid clones in different selfing generations for self-compatibility and degree of homozygosity using Kompetitive Allele Specific PCR (KASP) Single Nucleotide Polymorphism (SNP) markers. A subset of 10 KASP markers of the Sli candidate region on chromosome 12 showed an association with the phenotype for self-compatibility. The results revealed that the selected 10 KASP markers for the Sli gene genotype could be deployed for high throughput rapid screening of self-compatibility in diploid populations and to identify new sources of self-compatibility. The homozygosity assessed through 99 KASP markers distributed across all the chromosomes of the potato genome was 20–78 % in founder diploid clones, while different selfing generations, i.e., S0, S1, S2 and S3 observed 36.1–80.4, 56.9–82.8, 59.5–85.4 and 73.7–87.8 % average homozygosity, respectively. The diploid plants with ∼80 % homozygosity were also observed in the first selfing generation, which inferred that homozygosity assessment in the early generations itself could identify the best plants with high homozygosity to speed up the generation of diploid inbred lines.