Multitrait genetic parameter estimates in a Tenebrio molitor reference population: high potential for breeding gains.

To address multiple issues impacting the climate imbalance, insects, and in particular Tenebrio molitor, represent now a promising alternative for producing high-quality protein products with low environmental impact. As with any new species farmed on an industrial scale, insect breeding production must be improved through the accumulation of knowledge on rearing techniques and genetic management. Little information on the inheritance of agronomically interesting traits, dedicated to Tenebrio molitor, is available. This study aims to decipher the genetic parameters (heritability and genetic correlations) of reproduction, larval growth and survival, pupation rate and developmental time from a reference population made up of 1 931 sib-groups reared under pedigree, in controlled and stable environments and generated with single pair mating. Considering all sib-groups, 29 599 offspring have been generated and phenotyped over four generations to support this study and provide enough data to estimate, under linear animal models, the additive genetic and common environmental effects. Phenotypic analyses underlined an important variability among sib-groups and individuals, as for the total oviposition during 4 weeks counting (0-680 eggs, min - max, respectively) or larval body mass 63 days posteclosion (36.3-206.8 mg, min - max, respectively). Moderate to important heritability values have been obtained and ranged from 0.17 to 0.54 for reproduction phenotypes, 0.10-0.44 for growth parameters, 0.06-0.22 for developmental time and 0.10-0.17 for larval survival rates. The proportion of phenotypic variance explained by the environmental part varyies from 0.10 to 0.36 for reproductive traits, from 0.17 to 0.38 for growth parameters, from 0.06 to 0.36 for developmental time and 0.17-0.22 for survival rates. Genetic correlations underline relationships among phenotypes such as the trade-off between developmental time from egg to pupae and pupae weight (r2 = 0.48 ± 0.06). These important phenotypic variations coupled with promising heritability values pave the road for future breeding programs in Tenebrio molitor.

Genetic parameter estimation and molecular foundation of chicken egg-laying trait.

The age of first egg (AFE) in chicken can affect early and even life-time egg production performance to some extent, and therefore is an important economic trait that affects production efficiency. To better understand the genetic patterns of AFE and other production traits including body weight at first egg (BWA), first egg weight (FEW), and total egg number from AFE to 58 wk of age (total-EN), we recorded the production performance of 2 widely used layer breeds, white leghorn (WL) and Rhode Island Red (RIR) and estimated genetic parameters based on pedigree and production data. The results showed that the heritability of AFE in both breeds ranged from 0.4 to 0.6, and AFE showed strong positive genetic and phenotypic correlations to BWA as well as FEW, while showing strong negative genetic and phenotypic correlations with total-EN. Furtherly, by genome-wide association analysis study (GWAS), we identified 12 and 26 significant SNPs to be related to AFE in the 2-layer breeds, respectively. A total of 18 genes were identified that could affect AFE based on the significant SNP annotations obtained, but there were no gene overlapped in the 2 breeds indicating the genetic foundation of AFE could differ from breed to breed. Our results provided a deeper understanding of genetic patterns and molecular basement of AFE in different breeds and could help in the selection of egg production traits.

Genome-wide association studies of egg production traits by whole genome sequencing of Laiwu Black chicken.

Compared to high-yield commercial laying hens, Chinese indigenous chicken breeds have poor egg laying capacity due to the lack of intensive selection. However, as these breeds have not undergone systematic selection, it is possible that there is a greater abundance of genetic variations related to egg laying traits. In this study, we assessed 5 egg number (EN) traits at different stages of the egg-laying period: EN1 (from the first egg to 23 wk), EN2 (from 23 to 35 wk), EN3 (from 35 to 48 wk), EN4 (from the first egg to 35 wk), and EN5 (from the first egg to 48 wk). To investigate the molecular mechanisms underlying egg number traits in a Chinese local chicken breed, we conducted a genome-wide association study (GWAS) using data from whole-genome sequencing (WGS) of 399 Laiwu Black chickens. We obtained a total of 3.01 Tb of raw data with an average depth of 7.07 × per individual. A total of 86 genome-wide suggestive or significant single-nucleotide polymorphisms (SNP) contained within a set of 45 corresponding candidate genes were identified and found to be associated with stages EN1-EN5. The genes vitellogenin 2 (VTG2), lipase maturation factor 1 (LMF1), calcium voltage-gated channel auxiliary subunit alpha2delta 3 (CACNA2D3), poly(A) binding protein cytoplasmic 1 (PABPC1), programmed cell death 11 (PDCD11) and family with sequence similarity 213 member A (FAM213A) can be considered as the candidate genes associated with egg number traits, due to their reported association with animal reproduction traits. Noteworthy, results suggests that VTG2 and PDCD11 are not only involved in the regulation of EN3, but also in the regulation of EN5, implies that VTG2 and PDCD11 have a significant influence on egg production traits. Our study offers valuable genomic insights into the molecular genetic mechanisms that govern egg number traits in a Chinese indigenous egg-laying chicken breed. These findings have the potential to enhance the egg-laying performance of chickens.

Natural variation in the Caenorhabditis elegans egg-laying circuit modulates an intergenerational fitness trade-off.

Evolutionary transitions from egg laying (oviparity) to live birth (viviparity) are common across various taxa. Many species also exhibit genetic variation in egg-laying mode or display an intermediate mode with laid eggs containing embryos at various stages of development. Understanding the mechanistic basis and fitness consequences of such variation remains experimentally challenging. Here, we report highly variable intra-uterine egg retention across 316 Caenorhabditis elegans wild strains, some exhibiting strong retention, followed by internal hatching. We identify multiple evolutionary origins of such phenotypic extremes and pinpoint underlying candidate loci. Behavioral analysis and genetic manipulation indicates that this variation arises from genetic differences in the neuromodulatory architecture of the egg-laying circuitry. We provide experimental evidence that while strong egg retention can decrease maternal fitness due to in utero hatching, it may enhance offspring protection and confer a competitive advantage. Therefore, natural variation in C. elegans egg-laying behaviour can alter an apparent trade-off between different fitness components across generations. Our findings highlight underappreciated diversity in C. elegans egg-laying behavior and shed light on its fitness consequences. This behavioral variation offers a promising model to elucidate the molecular changes in a simple neural circuit underlying evolutionary shifts between alternative egg-laying modes in invertebrates.

Comparative transcriptomic characterization of the ovary in the spawning process of the mud crab Scylla paramamosain.

Oviposition is induced upon mating in most insects. Spawning is a physiological process that is fundamental for the reproduction of Scylla paramamosain. However, the molecular mechanisms underlying the spawning process in this species are poorly understood. Herein, comprehensive ovary transcriptomic analysis was conducted at the germinal vesicle breakdown stage (GVBD), spawning stage, 0.5 h post-spawning stage, and 24 h post-spawning stage of S. paramamosain for gene discovery. A total of 67,230 unigenes were generated, and 27,975 (41.61%) unigenes were annotated. Meanwhile, the differentially expressed genes (DEGs) between the different groups were identified, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was subsequently conducted. These results suggested that octopamine (OA) and tyramine (TA) could induce oviposition, while dopamine (DA) and serotonin (5-hydroxytryptamine [5-HT]) inhibit oviposition. The 20-hydroxyecdysone (20E) and methyl farnesoate (MF) signal pathways might be positively associated with oviposition. Furthermore, numerous transcripts that encode neuropeptides and their G-protein-coupled receptors (GPCRs), such as CNMamide, RYamide, ecdysis-triggering hormone (ETH), GPA2/GPB5 receptor, and Moody receptor, appear to be differentially expressed during the spawning process. Eleven unigenes were selected for qRT-PCR and the pattern was found to be consistent with the transcriptome expression pattern. Our work is the first spawning-related investigation of S. paramamosain focusing on the ovary at the whole transcriptome level. These findings assist in improving our understanding of spawning regulation in S. paramamosain and provide information for oviposition studies in other crustaceans.

The genetics of resilience and its relationships with egg production traits and antibody traits in chickens.

BACKGROUND: Resilience is the capacity of an animal to be minimally affected by disturbances or to rapidly return to its initial state before exposure to a disturbance. Resilient livestock are desired because of their improved health and increased economic profit. Genetic improvement of resilience may also lead to trade-offs with production traits. Recently, resilience indicators based on longitudinal data have been suggested, but they need further evaluation to determine whether they are indeed predictive of improved resilience, such as disease resilience. This study investigated different resilience indicators based on deviations between expected and observed egg production (EP) by exploring their genetic parameters, their possible trade-offs with production traits, and their relationships with antibody traits in chickens. METHODS: Egg production in a nucleus breeding herd environment based on 1-week-, 2-week-, or 3-week-intervals of two purebred chicken lines, a white egg-laying (33,825 chickens) and a brown egg-laying line (34,397 chickens), were used to determine deviations between observed EP and expected average batch EP, and between observed EP and expected individual EP. These deviations were used to calculate three types of resilience indicators for two life periods of each individual: natural logarithm-transformed variance (ln(variance)), skewness, and lag-one autocorrelation (autocorrelation) of deviations from 25 to 83 weeks of age and from 83 weeks of age to end of life. Then, we estimated their genetic correlations with EP traits and with two antibody traits. RESULTS: The most promising resilience indicators were those based on 1-week-intervals, as they had the highest heritability estimates (0.02-0.12) and high genetic correlations (above 0.60) with the same resilience indicators based on longer intervals. The three types of resilience indicators differed genetically from each other, which indicates that they possibly capture different aspects of resilience. Genetic correlations of the resilience indicator traits based on 1-week-intervals with EP traits were favorable or zero, which means that trade-off effects were marginal. The resilience indicator traits based on 1-week-intervals also showed no genetic correlations with the antibody traits, which suggests that they are not informative for improved immunity or vice versa in the nucleus environment. CONCLUSIONS: This paper gives direction towards the evaluation and implementation of resilience indicators, i.e. to further investigate resilience indicator traits based on 1-week-intervals, in breeding programs for selecting genetically more resilient layer chickens.

Effect of four chitinase genes on the female fecundity in Sogatella furcifera (Horváth).

BACKGROUND: The white-backed planthopper (WPH), Sogatella furcifera (Horváth), is a destructive rice pest with strong reproductive capacity. To gain insights into the roles of chitinases in the reproductive process of this insect species, this study represents the first-ever endeavor to conduct an in-depth exploration into the reproductive functions of four chitinase genes. RESULTS: In this study, it was observed that four chitinase genes were expressed in female adults, with a relatively high expression level in the ovaries. SfCht2 and SfIDGF1 were highly expressed during later ovarian development. while SfENGase increased and then decreased with ovarian development. SfCht2, SfCht6-2 and SfENGase were highly expressed in fat body on the first and second days after eclosion, whereas SfIDGF1 highest on day 7. Compared with control group, Silencing four chitinase genes inhibited ovarian development and significantly shortened the oviposition period of S. furcifera, reducing egg-laying capacity but not affecting egg hatching. The detection demonstrated that the expression levels of SfVg, SfVgR and 70-90% juvenile hormone (JH) signaling pathway-related reproductive genes was significantly down-regulated. Moreover, SfCht6-2 and SfENGase significantly affected the expression levels of Target of Rapamycin (TOR) signaling pathway genes. SfENGase had the ability to impact nutrient signaling pathways and fatty acid metabolism, repressing vitellogenin synthesis and ultimately influencing ovarian development of S. furcifera. CONCLUSIONS: Overall, this study provides insight into the function of chitinases in insect fecundity and is of great significance for enriching the cognition of insect chitinase function. They will become the suitable target genes for controlling the most destructive rice planthoppers. © 2023 Society of Chemical Industry.

Genetic parameters, reciprocal cross differences, and age-related heterosis of egg-laying performance in chickens.

BACKGROUND: Egg-laying performance is economically important in poultry breeding programs. Crossbreeding between indigenous and elite commercial lines to exploit heterosis has been an upward trend in traditional layer breeding for niche markets. The objective of this study was to analyse the genetic background and to estimate the heterosis of longitudinal egg-laying traits in reciprocal crosses between an indigenous Beijing-You and an elite commercial White Leghorn layer line. Egg weights were measured for the first three eggs, monthly from 28 to 76 weeks of age, and at 86 and 100 weeks of age. Egg quality traits were measured at 32, 54, 72, 86, and 100 weeks of age. Egg production traits were measured from the start of lay until 43, 72, and 100 weeks of age. Heritabilities and phenotypic and genetic correlations were estimated. Heterosis was estimated as the percentage difference of performance of a crossbred from that of the parental average. Reciprocal cross differences were estimated as the difference between the reciprocal crossbreds as a percentage of the parental average. RESULTS: Estimates of heritability of egg weights ranged from 0.29 to 0.75. Estimates of genetic correlations between egg weights at different ages ranged from 0.72 to 1.00. Estimates of heritability for cumulative egg numbers until 43, 72, and 100 weeks of age were around 0.15. Estimates of heterosis for egg weight and cumulative egg number increased with age, ranging from 1.0 to 9.0% and from 1.4 to 11.6%, respectively. From 72 to 100 weeks of age, crossbreds produced more eggs per week than the superior parent White Leghorn (3.5 eggs for White Leghorn, 3.8 and 3.9 eggs for crossbreds). Heterosis for eggshell thickness ranged from 2.7 to 6.6% when using Beijing-You as the sire breed. No significant difference between reciprocal crosses was observed for the investigated traits, except for eggshell strength at 54 weeks of age. CONCLUSIONS: The heterosis was substantial for egg weight and cumulative egg number, and increased with age, suggesting that non-additive genetic effects are important in crossbreds between the indigenous and elite breeds. Generally, the crossbreds performed similar to or even outperformed the commercial White Leghorns for egg production persistency.

Polymorphism, Genetic Effect, and Association with Egg-Laying Performance of Chahua Chickens Matrix Metalloproteinases 13 Promoter.

Matrix metalloproteinases are a group of proteases involved in the regulation of ovarian follicular development and ovulation. Among the different MMPs, MMP13 is known to play an important role in reproduction. Therefore, this study aimed to screen the molecular genetic markers of the MMP13 gene that affect the egg-laying performance of Chahua chickens. Polymerase chain reaction (PCR) and sequencing were performed in the 5' regulation region of the MMP13 gene to detect loci significantly related to the egg-laying performance of Chahua chickens. A double fluorescence reporting system, quantitative reverse transcription PCR (RT-qPCR), and Western blotting were used to study whether gene expression was regulated by identified sites, providing a theoretical basis to improve egg production in Chahua chickens. The results revealed six single nucleotide polymorphisms (SNPs; A-1887T, T-1889C, A-1890T, T-2252C, T-2329C, and C-2360A) in the promoter region of the MMP13 gene. Further analysis revealed that hens with T-1890-C-1889-T-1887/T-1890-C-1889-T-1887 (mutant type, MT) had an earlier age at first egg (AFE) than hens with A-1890-T-1889-A-1887/A-1890-T-1889-A-1887 (wild type, WT; p < 0.05). RT-qPCR showed that the relative expression level of the MMP13 gene in the ovarian tissues of individuals with the mutation was higher than that of individuals with the wild gene (p < 0.05). Western blot results confirmed higher levels of the MMP13 protein in MT ovaries compared to those in WT ovaries. Thus, this study suggests that mutation sites on the MMP13 promoter may affect gene expression. In conclusion, the MMP13 gene in Chahua chickens may be significant for egg-laying performance, and the polymorphism in its promoter region could be used as a molecular marker to improve egg-laying performance.

Research Note: Genetic parameters for egg production and clutch-related traits in indigenous Beijing-You chickens.

Egg products from indigenous chickens have growing market shares as consumers are pursuing differentiation in egg consumption. The genetic improvement in egg production performance of those breeds is crucial for increasing the economic profit. This study aimed to estimate genetic parameters for egg production and clutch-related traits in indigenous Beijing-You chickens for understanding the genetic architecture and exploring proper biological traits for selection. Data on traits including age at first egg (AFE), egg number (EN), average clutch length (ACL), maximum clutch length (MCL), number of clutches (NC) and pauses (NP), and average pause length (APL) were collected from 4 generations of purebred Beijing-You chickens based on the 43-wk and 66-wk of individual egg production record. The heritabilities, genetic and phenotypic correlations were analyzed by the DMU software with the restricted maximum likelihood method in a multivariate animal model. The results showed that the AFE of Beijing-You chickens was 174.45 d of age, and its heritability was as high as 0.62. The heritability was 0.26 for EN43 and 0.18 for EN66. The clutch traits including ACL, MCL, NC, and NP were moderate to high heritable (h2 = 0.15-0.39), but APL was very low heritable (h2 = 0.05). Genetic correlations were high between AFE and EN (rG(AFE, EN43) = -0.79, rG(AFE, EN66) = -0.39), whereas low between AFE and ACL (rG(AFE, ACL43) = -0.08, rG(AFE, ACL66) = 0.01) and MCL (rG(AFE, MCL) = -0.07). EN had higher correlations with ACL (rG(EN43, ACL43) = 0.59, rG(EN66, ACL66) = 0.40) than that with MCL (rG(EN43, MCL43) = 0.56, rG(EN66, MCL66) = 0.32). The heritability for ACL43 (h2 = 0.38) was higher than that for MCL43 (h2 = 0.33). ACL43 had a positive correlation with EN66 (rG(ACL43, EN66) = 0.62). These results indicated that the egg production of whole laying period could be improved by early selection for AFE and ACL at the same time in Beijing-You chickens.

Nest preference and laying duration traits to select against floor eggs in laying hens.

BACKGROUND: Floor eggs, which are defined as eggs that hens lay off-nest, are a major issue in cage-free layer poultry systems. They create additional work for farmers because they must be collected by hand. They are also usually soiled or broken, which results in economic losses. Nonetheless, knowledge about the genetics of nesting behavior is limited. The aim of this study was to estimate genetic parameters for traits related to nest preference for laying and to time spent in the nests used for laying (laying duration). METHODS: Two pure lines of laying hens were studied: 927 Rhode Island Red and 980 White Leghorn. Electronic nests were used to record the nesting behavior of these hens in floor pens from 24 to 64 weeks of age. Nest preference was studied based on the mean distance between nests used for laying and the percentage of nests used for laying. Laying duration was studied based on mean laying duration, mean duration in the nest before laying, and mean duration in the nest after laying. Genetic parameters were estimated for each line using a restricted maximum-likelihood method applied to a pedigree-based multi-trait animal model. RESULTS: Estimates of genetic parameters were similar for the two lines. Estimates of heritability ranged from 0.18 to 0.37 for nest preference traits and from 0.54 to 0.70 for laying duration traits. Estimates of genetic correlations of these traits with clutch number or mean oviposition time were favorable. Positive genetic correlations were estimated between nest preference and laying rate in the nests or nest acceptance for laying (+ 0.06 to + 0.37). CONCLUSIONS: These results show that genetics influences traits related to nest preference and laying duration. Selecting hens that have no preference for particular nests and spend little time laying in the nests could help optimize nest use, reduce their occupation rate, and thus decrease the incidence of floor eggs in cage-free systems. Genetic correlations of these traits with other traits of interest related to hen welfare and egg quality have yet to be estimated.

Oviposition behaviour in Drosophila melanogaster: Genetic and behavioural decoupling between oviposition acceptance and preference for natural fruits.

In phytophagous insects, oviposition behaviour is an important component of habitat selection and, given the multiplicity of genetic and environmental factors affecting its expression, is defined as a complex character resulting from the sum of interdependent traits. Here, we study two components of egg-laying behaviour: oviposition acceptance (OA) and oviposition preference (OP) in Drosophila melanogaster using three natural fruits as resources (grape, tomato and orange) by means of no-choice and two-choice experiments, respectively. This experimental design allowed us to show that the results obtained in two-choice assays (OP) cannot be accounted for by those resulting from no-choice assays (OA). Since the genomes of all lines used are completely sequenced, we perform a genome-wide association study to identify and characterize the genetic underpinnings of these oviposition behaviour traits. The analyses revealed different candidate genes affecting natural genetic variation of both OA and OP traits. Moreover, our results suggest behavioural and genetic decoupling between OA and OP and that egg-laying behaviour is plastic and context-dependent. Such independence in the genetic architectures of OA and OP variation may influence different aspects of oviposition behaviour, including plasticity, canalization, host shift and maintenance of genetic variability, which contributes to the adoption of adaptive strategies during habitat selection.

SPARC plays an important role in the oviposition and nymphal development in Nilaparvata lugens Stål.

BACKGROUND: The brown planthopper (Nilaparvata lugens Stål)is a notorious rice pest in many areas of Asia. Study on the molecular mechanisms underlying its development and reproduction will provide scientific basis for effective control. SPARC (Secreted Protein, Acidic and Rich in Cysteine) is one of structural component of the extracellular matrix, which influences a diverse array of biological functions. In this study, the gene for SPARC was identified and functionally analysed from N.lugens. RESULTS: The result showed that the NlSPARC mRNA was highly expressed in fat body, hemolymph and early embryo. The mortality increased significantly when NlSPARC was downregulated after RNA interference (RNAi) in 3 ~ 4th instar nymphs. Downregulation of NlSPARC in adults significantly reduced the number of eggs and offspring, as well as the transcription level of NlSPARC in newly hatched nymphs and survival rate in progeny. The observation with microanatomy on individuals after NlSPARC RNAi showed smaller and less abundant fat body than that in control. No obvious morphological abnormalities in the nymphal development and no differences in development of internal reproductive organ were observed when compared with control. CONCLUSION: NlSPARC is required for oviposition and nymphal development mainly through regulating the tissue of fat body in N.lugens. NlSPARC could be a new candidate target for controlling the rapid propagation of N.lugens population. Our results also demonstrated that the effect of NlSPARC RNAi can transfer to the next generation in N.lugens.

Association analysis and expression level of ACE polymorphisms with egg-laying trait in Taihang chicken.

The number of egg-laying is an important indicator of reproduction performance in poultry breeding. To investigate the relationship between the function of Angiotensin-converting enzyme (ACE) and egg-laying performance of Taihang chicken, the mRNA and protein expression and single nucleotide polymorphism (SNP) of ACE were detected. Analysis of ACE bioinformatics and association analysis of polymorphisms were then performed. The polymorphisms analysis of ACE showed that three SNP loci (g.5066812A>C, g.5080076G>A, and g.5072728A>G) were detected in 800 Taihang chickens with egg-laying records. Association analysis of egg-laying found that ACE g.5066812A>C mutation was significantly associated with the egg-laying performance of Taihang chickens (P < 0.05), and the individuals with the g.5066812A>C mutation showed significantly increasing egg-laying. The mRNA expression was significantly higher in individuals with the AA genotype mutation than those with the AC and CC genotypes (P < 0.01), and the expression of ACE protein levels was consistent with the mRNA expression. Bioinformatics analysis indicated that these mutations affected the secondary and tertiary structure of ACE. This study provides new insights into ACE affecting chicken egg production and some basis for improving the egg production rate of Taihang chickens.

Knockdown of the Halloween Genes spook, shadow and shade Influences Oocyte Development, Egg Shape, Oviposition and Hatching in the Desert Locust.

Ecdysteroids are widely investigated for their role during the molting cascade in insects; however, they are also involved in the development of the female reproductive system. Ecdysteroids are synthesized from cholesterol, which is further converted via a series of enzymatic steps into the main molting hormone, 20-hydoxyecdysone. Most of these biosynthetic conversion steps involve the activity of cytochrome P450 (CYP) hydroxylases, which are encoded by the Halloween genes. Three of these genes, spook (spo), phantom (phm) and shade (shd), were previously characterized in the desert locust, Schistocerca gregaria. Based on recent sequencing data, we have now identified the sequences of disembodied (dib) and shadow (sad), for which we also analyzed spatiotemporal expression profiles using qRT-PCR. Furthermore, we investigated the possible role(s) of five different Halloween genes in the oogenesis process by means of RNA interference mediated knockdown experiments. Our results showed that depleting the expression of SchgrSpo, SchgrSad and SchgrShd had a significant impact on oocyte development, oviposition and hatching of the eggs. Moreover, the shape of the growing oocytes, as well as the deposited eggs, was very drastically altered by the experimental treatments. Consequently, it can be proposed that these three enzymes play an important role in oogenesis.

Inheritance of the duration of fertility in chickens and its correlation with laying performance.

BACKGROUND: Duration of fertility (DF) is an important economic trait in poultry production because it has a strong effect on chick output. Various criteria or traits to assess DF on individual hens have been reported but they are affected by many nongenetic factors. Thus, a reliable definition and associated genetic parameters are needed. Because egg production is also vital in chicken breeding, knowledge of the relationship between DF and laying performance is needed for designing selection programs. METHODS: We used five traits that consider both fertility and embryonic livability to delineate DF. Phenotypic and genetic analyses were completed for 2094 hens, with measurements of DF at 35 and 60 weeks of age and hatching egg production at 400 days of age (HEP400). The selection differentials for DF and HEP400 were evaluated. RESULTS: DF is largely independent of the number of oviposited eggs in the peak laying period but both egg production and DF naturally decline with age. The heritability of the five DF traits ranged from 0.11 to 0.13 at 35 weeks of age and increased slightly in the later laying period, ranging from 0.14 to 0.17 (except for efficient duration, time between insemination and the first unhatched egg). Estimates of the genetic correlation for a given trait measured at the two ages were moderate (0.37-0.44), except for efficient duration. However, number of viable embryos depends strongly on egg production. Estimates of genetic correlations of fertility duration day (FDD) at both ages with HEP were weak. Selection for FDD improved DF but without a significant change in laying performance. Selection for increased HEP400 did not contribute to DF improvement. CONCLUSIONS: Although estimates of heritability of the five traits related to DF were low, selection to improve DF based on any one of them is possible. Among these, FDD is an effective selection criterion when the eggs are collected for approximately two weeks after insemination. The best selection procedure for DF improvement would involve multiple measurements at various ages. FDD is independent of laying performance and can be incorporated into a breeding program with egg production to improve reproductive efficiency.

Ovarian Transcriptomic Analysis of Ninghai Indigenous Chickens at Different Egg-Laying Periods.

Egg production is an essential indicator of poultry fertility. The ovary is a crucial organ involved in egg production; however, little is known about the key genes and signaling pathways involved in the whole egg-laying cycle of hens. In order to explore the mechanism of egg production at different stages of the egg-laying process, ovarian tissues from four chickens were randomly selected for transcriptome analysis at each of the three ages (145 d, 204 d, and 300 d in the early, peak, and late stages of egg laying). A total of 12 gene libraries were constructed, and a total of 8433 differential genes were identified from NH145d vs. NH204d, NH145d vs. NH300d and NH300d vs. NH204d (Ninghai 145-day-old, Ninghai 204-day-old, and Ninghai 300-day-old), with 1176, 1653 and 1868 up-regulated genes, and 621, 1955 and 1160 down-regulated genes, respectively. In each of the two comparison groups, 73, 1004, and 1030 differentially expressed genes were found to be co-expressed. We analyzed the differentially expressed genes and predicted nine genes involved in egg production regulation, including LRP8, BMP6, ZP4, COL4A1, VCAN, INHBA, LOX, PTX3, and IHH, as well as several essential egg production pathways, such as regulation adhesion molecules (CAMs), calcium signaling pathways, neuroactive ligand-receptor interaction, and cytokine-cytokine receptor interaction. Transcriptional analysis of the chicken ovary during different phases of egg-lay will provide a useful molecular basis for study of the development of the egg-laying ovary.

Screening for odorant receptor genes expressed in Aedes aegypti involved in host-seeking, blood-feeding and oviposition behaviors.

BACKGROUND: Aedes aegypti is one of the most important vectors of zoonotic diseases worldwide, and its survival and reproductive processes depend heavily on its olfactory system. In this study, the expression levels of all odorant receptor (OR) genes of Ae. aegypti were explored during different physiological periods to identify olfactory genes that may be associated with mosquito blood-feeding and the search for oviposition sites. METHODS: Four experimental groups, consisting of Ae. aegypti males, pre-blood-feeding females, post-blood-feeding females and post-oviposition females, were established. A total of 114 pairs of primers targeting all messenger RNA encoded by OR genes were designed based on the whole genome of Ae. aegypti. The expression of OR genes was evaluated by real-time fluorescence quantitative PCR for relative quantification and the comparison of differences between groups. RESULTS: A total of 53 differentially expressed OR genes were identified between males and females in Ae. aegypti antennae. Also, eight, eight and 13 differentially expressed OR genes were identified in pre- versus post-blood-feeding females, in pre- versus post-oviposition females and in post-blood-feeding versus post-oviposition females, respectively. In addition, 16 OR genes were significantly differentially expressed in multiple physiological periods of the mosquitoes. CONCLUSIONS: A large number of ORs with significant intergroup differences and high expression levels were screened in this study. Some of these genes are reported for the first time, providing possible targets for the development of mosquito control pathways based on the olfactory system.

Genetics and breeding of a black-bone and blue eggshell chicken line. 2. Laying patterns and egg production in two consecutive generations.

The BG line was originated from the cross between 2 Chinese indigenous breeds, Dongxiang blue eggshell, and Jiangshan black-bone, and has been bred to combine dark heavy black-bone body and high production of blue-shell eggs, into single dual-purpose line. Full-pedigree hens from 2 generations, G4 (n = 441) and G5 (n = 464), were reared in the same single-cage laying facility in 2019-2020 and 2020-2021, respectively. Starting from the first egg of each hen, its daily egg production was recorded until 300 days-of-age. Up to 7 "no-egg" days were considered normal laying breaks between clutches, whereas laying cessation of 8 or more days was considered Pause, and the laying pattern of each hen was assigned either with Pause or No-Pause. The other traits included PsDays: number of Pause days; AFE: age at first egg; EN300: eggs laid until 300 d; %L300: total laying rate (EN300/[300-AFE]); %Lnet: net laying rate (EN300/[300-AFE-PsDays]); ClLng: average clutch length; EW200 and EW300: average egg weight around 200 d and 300 d. Estimates of heritability (h2) of each trait, and phenotypic and genetic correlation between traits, were calculated in each generation using the animal model. Heritability estimates were calculated also by regressing the means of full-sib G5 hens on their G4 parents' means. Mean overall laying rate of all G4 hens was low (%L300 = 57%) because 53% of them had Pause in their laying pattern. In G5, incidence of Pause was higher (75%) due to a 3-wk cold stress, with mean %L300 = 54%. However, significant estimates of heritability and genetic correlations suggest that selection for low PsDays will reduce the incidence of Pause in BG hens and elevate the line's mean laying rate towards %L300 = 70%, as the No-Pause hens in G5. PsDays-free laying rate (%Lnet) was found to be highly correlated with the significantly heritable (h2≈0.4) clutch length (ClLng). Selection index combining the genetically independent low PsDays and high ClLng is expected to maximize egg production improvement in the BG line, and in similar populations derived from indigenous breeds.

Orcokinin neuropeptides regulate reproduction in the fruit fly, Drosophila melanogaster.

In animals, neuropeptidergic signaling is essential for the regulation of survival and reproduction. In insects, Orcokinins are poorly studied, despite their high level of conservation among different orders. In particular, there are currently no reports on the role of Orcokinins in the experimental insect model, the fruit fly, Drosophila melanogaster. In the present work, we made use of the genetic tools available in this species to investigate the role of Orcokinins in the regulation of different innate behaviors including ecdysis, sleep, locomotor activity, oviposition, and courtship. We found that RNAi-mediated knockdown of the orcokinin gene caused a disinhibition of male courtship behavior, including the occurrence of male to male courtship, which is rarely seen in wildtype flies. In addition, orcokinin gene silencing caused a reduction in egg production. Orcokinin is emerging as an important neuropeptide family in the regulation of the physiology of insects from different orders. In the case of the fruit fly, our results suggest an important role in reproductive success.