Color Genes Research Articles

Molecular Mechanisms Underlying Pupal Protective Color Switch in Papilio polytes Butterflies

Mimicry is a survival strategy in which organisms deceive their predators by imitating other organisms or the surrounding environment. One example of this involves pupal color polymorphism, which is widely observed in butterflies and moths. It has been suggested that the pupal colors of Papilio butterflies are selected according to the tactile stimulation experienced before pupation. Specifically, larvae crawling on smooth leaves become green pupae, but those crawling on rough stems become brown pupae. These protective colors fit with the surrounding environment. However, the detailed molecular mechanisms underlying pupal polymorphism have generally remained unknown. To reveal these mechanisms, we first established control over the green and brown pupal coloration in Papilio polytes under laboratory conditions and clarified temporal and spatial changes of pupal pigments under both conditions. We also analyzed the expression of coloration genes during the pre-pupal stage and at pupation in the epidermis under the green and brown conditions, by RNA sequencing and quantitative RT-PCR. These analyses revealed that the brown pupal color is regulated mainly by melanin synthesis genes, tyrosine hydroxylase (TH) and laccase 2. In contrast, the green pupal color was suggested to be formed mainly through the expression of both multiple bilin binding protein (BBP)-related genes responsible for blue pigmentation and multiple juvenile hormone binding protein (JHBP)-related genes responsible for yellow pigmentation. Electroporation-mediated RNAi showed that the knockdown of TH or laccase 2 blocked the brown pupal coloration, and that the knockdown of BBP- or JHBP-related genes caused yellow or blue coloration in the green-conditioned pupae, respectively, supporting the above hypothesis. We here report how genes involved in the pupal coloration of P. polytes are regulated, which sheds light on the evolutionary process of pupal protective colors among Lepidoptera.

Differential divergence in autosomes and sex chromosomes is associated with intra-island diversification at a very small spatial scale in a songbird lineage.

Recently diverged taxa showing marked phenotypic and ecological diversity provide optimal systems to understand the genetic processes underlying speciation. We used genome-wide markers to investigate the diversification of the Reunion grey white-eye (Zosterops borbonicus) on the small volcanic island of Reunion (Mascarene archipelago), where this species complex exhibits four geographical forms that are parapatrically distributed across the island and differ strikingly in plumage colour. One form restricted to the highlands is separated by a steep ecological gradient from three distinct lowland forms which meet at narrow hybrid zones that are not associated with environmental variables. Analyses of genomic variation based on single nucleotide polymorphism data from genotyping-by-sequencing and pooled RAD-seq approaches show that signatures of selection associated with elevation can be found at multiple regions across the genome, whereas most loci associated with the lowland forms are located on the Z sex chromosome. We identified TYRP1, a Z-linked colour gene, as a likely candidate locus underlying colour variation among lowland forms. Tests of demographic models revealed that highland and lowland forms diverged in the presence of gene flow, and divergence has progressed as gene flow was restricted by selection at loci across the genome. This system holds promise for investigating how adaptation and reproductive isolation shape the genomic landscape of divergence at multiple stages of the speciation process.

A genome-wide scan study identifies a single nucleotide substitution in the tyrosinase gene associated with white coat colour in a red deer (Cervus elaphus) population

BackgroundRed deer with very pale coat colour are observed sporadically. In the red deer (Cervus elaphus) population of Reinhardswald in Germany, about 5% of animals have a white coat colour that is not associated with albinism. In order to facilitate the conservation of the animals, it should be determined whether and to what extent brown animals carry the white gene. For this purpose, samples of one white hind and her brown calf were available for whole genome sequencing to identify the single nucleotide polymorphism(s) responsible for the white phenotype. Subsequently, samples from 194 brown and 11 white animals were genotyped.ResultsBased on a list of colour genes of the International Federation of Pigment Cell Societies, a non-synonymous mutation with exchange of a glycine residue at position 291 of the tyrosinase protein by arginine was identified as the cause of dilution of the coat colour. A gene test led to exactly matching genotypes in all examined animals. The study showed that 14% of the brown animals carry the white gene. This provides a simple and reliable way of conservation for the white animals. However, results could not be transferred to another, unrelated red deer population with white animals. Although no brown animals with a white tyrosinase genotype were detected, the cause for the white colouring in this population was different.ConclusionsA gene test for the conservation of white red deer is available for the population of the Reinhardswald. While mutations in the tyrosinase are commonly associated with oculocutaneous albinism type 1, the amino acid exchange at position 291 was found to be associated with coat colour dilution in Cervus elaphus.

Loss-of-Function Mutation of Soybean R2R3 MYB Transcription Factor Dilutes Tawny Pubescence Color.

Pubescence color of soybean is controlled by two genes, T and Td. In the presence of a dominant T allele, dominant and recessive alleles of the Td locus generate tawny and light tawny (or near-gray) pubescence, respectively. Flavones, responsible for pubescence color, are synthesized via two copies of flavone synthase II genes (FNS II-1 and FNS II-2). This study was conducted to map and clone the Td gene. Genetic and linkage analysis using an F2 population and F3 families derived from a cross between a Clark near-isogenic line with light tawny pubescence (genotype: TT tdtd) and a Harosoy near-isogenic line with tawny pubescence (TT TdTd) revealed a single gene for pubescence color around the end of chromosome 3. Genome sequence alignment of plant introductions revealed an association between premature stop codons in Glyma.03G258700 (R2R3 MYB transcription factor) and recessive td allele. Cultivars and lines having near-gray or light tawny pubescence and a gray pubescence cultivar with td allele had premature stop codons in the gene. These results suggest that Glyma.03G258700 corresponds to the Td gene. It was predominantly expressed in pubescence. Compared to a tawny pubescence line, a near-isogenic line with td allele produced extremely small amounts of transcripts of Glyma.03G258700, FNS II-1, and FNS II-2 in pubescence. The promoter of FNS II-1 and FNS II-2 shared cis-acting regulatory elements for binding of MYB proteins. These results suggest that the wild type of Glyma.03G258700 protein may bind to the promoter of FNS II genes and upregulate their expression, resulting in increased flavone content and deeper pubescence color. In contrast, mutated Glyma.03G258700 protein may fail to upregulate the expression of FNS II genes, resulting in decreased flavone content and dilute pubescence color.

Selecting for Coupling Phase Recombination between Potyvirus Resitance and White Endosperm Colour in Maize Preferred by Farmers in Sub-Saharan Africa (SSA)


 
 
 Maize lethal necrosis (MLN) disease caused by a combined infection of Maize chlorotic mottle virus (MCMV) and any cereal infecting potyvirus is a threat to food security in Sub-Saharan Africa (SSA). Resistance to potyvirus has been extensively studied and Mdm1 gene for potyvirus resistance on chromosome 6 of maize is linked to Y1 gene for maize endosperm colour. This study is aimed at se- lecting for coupling-phase recombination of potyvirus resistance and white endosperm colour. White susceptible maize lines CML333 and CML277 were crossed with a yellow resistant line, Pa405, to produce F1 and F2 progenies. Progenies were screened using molecular markers to recover 22 white endosperm recombinants. 22 selections were advanced to F3 recombinant families, and 10 were as- sayed for their responses to Maize dwarf mosaic virus (MDMV) and Sugarcane mosaic virus (SCMV). Four families segregated for SCMV resistance, selection of homozygous recombinants within these families will provide lines appropriate for improving lines with resistance to SCMV and MLN resistance in SSA.
 KEY WORDS: MAIZE LETHAL NECROSIS (MLN), WHITE MAIZE, POTYVIRUS RESISTANCE, GENETIC RECOMBINATION, SUB-SAHARAN AFRICA.
 
 

High resolution genetic mapping and identification of a candidate gene(s) for the purple sheath color and plant height in an interspecific F2 population derived from Oryza nivara Sharma & Shastry × Oryza sativa L. cross

Wild relatives of rice (Oryza sativa L.) represent enormous genetic diversity for many traits. Many domestication related traits found only in wild species that are lost from cultivated species during domestication. In this study, we report high-resolution mapping of two domestications related quantitative trait locus (QTL) controlling purple sheath color and plant height using high-density SNP based linkage map in an interspecific F2 population derived from a cross between O. nivara Sharma & Shastry and O. sativa. The segregation ratio of purple sheath color fit into 3:1 indicated that the presence of a dominant gene. The segregation of plant height trait exhibited a normal distribution in F2 and F2:3 generations. QTL analysis showed the identification of two QTLs controlling purple sheath color (designated as qPsh6.1 and qPsh6.2) on chromosome 6 explaining 27.12% and 14% phenotypic variance, respectively. The only plant height QTL (tentatively designated as qPh1.9) was mapped on chromosome 1 contributing 18.3% phenotypic variance. The qPsh6.1 covers 25.17 Kb region flanked by AX-95928721 and AX-95954573 containing five open reading frames (ORFs) while qPsh6.2 spanned in 118.2 Kb region containing 19 ORFs flanked by markers AX-95956260 and AX-95928295. The qPh1.9 gene controlling plant height was mapped between two SNP markers, AX-95944819 and AX-95964796 co-segregated with the locus LOC_Os01g66690 encoding for ZIP4/SPO22 protein. The detailed genetic study of the location of these genes will be useful for the map-based cloning.

Genome-wide association analysis reveals QTL and candidate mutations involved in white spotting in cattle

BackgroundWhite spotting of the coat is a characteristic trait of various domestic species including cattle and other mammals. It is a hallmark of Holstein–Friesian cattle, and several previous studies have detected genetic loci with major effects for white spotting in animals with Holstein–Friesian ancestry. Here, our aim was to better understand the underlying genetic and molecular mechanisms of white spotting, by conducting the largest mapping study for this trait in cattle, to date.ResultsUsing imputed whole-genome sequence data, we conducted a genome-wide association analysis in 2973 mixed-breed cows and bulls. Highly significant quantitative trait loci (QTL) were found on chromosomes 6 and 22, highlighting the well-established coat color genes KIT and MITF as likely responsible for these effects. These results are in broad agreement with previous studies, although we also report a third significant QTL on chromosome 2 that appears to be novel. This signal maps immediately adjacent to the PAX3 gene, which encodes a known transcription factor that controls MITF expression and is the causal locus for white spotting in horses. More detailed examination of these loci revealed a candidate causal mutation in PAX3 (p.Thr424Met), and another candidate mutation (rs209784468) within a conserved element in intron 2 of MITF transcripts expressed in the skin. These analyses also revealed a mechanistic ambiguity at the chromosome 6 locus, where highly dispersed association signals suggested multiple or multiallelic QTL involving KIT and/or other genes in this region.ConclusionsOur findings extend those of previous studies that reported KIT as a likely causal gene for white spotting, and report novel associations between candidate causal mutations in both the MITF and PAX3 genes. The sizes of the effects of these QTL are substantial, and could be used to select animals with darker, or conversely whiter, coats depending on the desired characteristics.

Mapping Quantitative Trait Loci for Carotenoid Concentration in Three F2 Populations of Chickpea.

Quantitative trait locus (QTL) analyses for carotenoids in chickpea were completed for three F2 populations. A moderate number of QTLs and candidate genes associated with carotenoid concentration in chickpea seeds were identified. Green cotyledon color is positively associated with provitamin A carotenoids. Three F2 populations derived from crosses between cultivars with green and yellow cotyledon colors were used to identify quantitative trait loci (QTLs) associated with carotenoid components in chickpea (Cicer arietinum L.) seeds developed by the Crop Development Centre (CDC). Carotenoids including violaxanthin, lutein, zeaxanthin, β-cryptoxanthin, and β-carotene were assessed in the F2:3 seeds via high-performance liquid chromatography (HPLC). In the 'CDC Jade' × 'CDC Frontier' population, 1068 bin markers derived from the 50K Axiom CicerSNP array were mapped onto eight linkage groups (LGs). Eight QTLs, including two each for β-carotene and zeaxanthin and one each for total carotenoids, β-cryptoxanthin, β-carotene, and violaxanthin were identified in this population. In the 'CDC Cory' × 'CDC Jade' population, 694 bin markers were mapped onto eight LGs and one partial LG. Quantitative trait loci for β-cryptoxanthin, β-carotene, violaxanthin, lutein, and total carotenoids were identified on LG8. A map with eight LGs was developed from 581 bin markers in the third population derived from the 'ICC4475' × 'CDC Jade' cross. One QTL for β-carotene and four QTLs, one each for β-cryptoxanthin, β-carotene, lutein, and total carotenoids, were identified in this population. The highest phenotypic variation explained by the QTLs was for β-carotene, which ranged from 58 to 70% in all three populations. A major gene for cotyledon color was mapped on LG8 in each population. A significant positive correlation between cotyledon color and carotenoid concentration was observed. Potential candidate genes associated with carotenoid components were obtained and their locations on the chickpea genome are presented.

Assembling seed dormancy genes into a system identified their effects on seedbank longevity in weedy rice.

Seed dormancy (SD) and longevity (SL) may share developmental and genetic mechanisms, as both traits are developed in the same maternal environment and evolved to coordinate the timing of germination and the life span of seedbanks. To test the hypothesis, allelic variants at the SD1-2, 7-1, 7-2, and 12 loci from weedy and cultivated rice (Oryza sativa) were assembled into the same genetic background, and 16 homozygous lines selected as a tetragenic system. These lines were evaluated for SD measured by germination at 7, 21, 35, and 150 days of after-ripening (DAR), and for SL measured by the seed decay rate and survivability in the soil of a rice field for 7 months. Pyramiding the alleles from weedy rice lengthened the dormancy duration, and seeds survived in the soil remained dormant at the excavation. Germination levels at 7 to 150 DAR were correlated positively with the seed decay rate (r = 0.41-0.53) and negatively with the survivability (r = -0.45 to -0.28) in the tetragenic system. All four loci contributed to genotypic variation for each of the SD and SL measurements through main and/or epistatic (two- to four-order interactions) effects. SD7-1 (identical to the pericarp color gene Rc) played a major role in regulating seedbank longevity when interacted with the other SD gene(s). This research provided evidence that natural genes controlling SD are involved in regulation of soil seedbank longevity. Thus, accumulation of SD genes in a population could result in persistence of wild plants and weeds in conventional tillage systems.

Fine mapping and candidate gene analysis of the yellow petal gene ckpc in Chinese kale (Brassica oleracea L. var. alboglabra Bailey) by whole-genome resequencing

Chinese kale is a characteristic vegetable crop originating from China and being suggested to be a possible ancestor of various cultivated B. oleracea vegetables. It has both white and yellow petals and is therefore a desirable plant for use in research on petal color formation. In our study, the Chinese kale landrace YCK-1 (yellow petals) was crossed with the Chinese kale inbred line Lb07M (white petals) to construct mapping populations for genetic analysis and fine mapping of the petal color gene. The results indicated that yellow petal color is controlled by a single recessive gene named ckpc, which was preliminarily located in a 2.06-Mb candidate region of chromosome C03 using whole-genome resequencing combined with bulked segregant analysis (BSA). Fine mapping with traditional molecular marker technology was used to narrow down the ckpc gene in a 69.0-kb interval flanked by the markers M916 and SNP4 at genetic distances of 0.07 cM and 0.04 cM, respectively. Gene annotation revealed 5 genes in that region, and Bo3g158650 was annotated as a carotenoid cleavage dioxygenase 4 (CCD4) gene, which is known to function in flower and flesh color formation. Sequence analysis revealed that the Bo3g158650 gene in the white-petaled parent, Lb07M, had an identical sequence to that in the ‘TO1000’ reference genome, while a 7.61-kb CACTA-like transposable element 1 (TE1) insertion was found in this gene in the yellow-petaled parent, YCK-1. These results increase the understanding of the mechanism underlying petal color formation in Brassica.

Chromosomal Localization of Candidate Genes for Fiber Growth and Color in Alpaca (Vicugna pacos).

The alpaca (Vicugna pacos) is an economically important and cultural signature species in Peru. Thus, molecular genomic information about the genes underlying the traits of interest, such as fiber properties and color, is critical for improved breeding and management schemes. Current knowledge about the alpaca genome, particularly the chromosomal location of such genes of interest is limited and lags far behind other livestock species. The main objective of this work was to localize alpaca candidate genes for fiber growth and color using fluorescence in situ hybridization (FISH). We report the mapping of candidate genes for fiber growth COL1A1, CTNNB1, DAB2IP, KRT15, KRTAP13-1, and TNFSF12 to chromosomes 16, 17, 4, 16, 1, and 16, respectively. Likewise, we report the mapping of candidate genes for fiber color ALX3, NCOA6, SOX9, ZIC1, and ZIC5 to chromosomes 9, 19, 16, 1, and 14, respectively. In addition, since KRT15 clusters with five other keratin genes (KRT31, KRT13, KRT9, KRT14, and KRT16) in scaffold 450 (Vic.Pac 2.0.2), the entire gene cluster was assigned to chromosome 16. Similarly, mapping NCOA6 to chromosome 19, anchored scaffold 34 with 8 genes, viz., RALY, EIF2S2, XPOTP1, ASIP, AHCY, ITCH, PIGU, and GGT7 to chromosome 19. These results are concordant with known conserved synteny blocks between camelids and humans, cattle and pigs.

Transcriptome analysis of shell color-related genes in the hard clam Mercenaria mercenaria

The shell color of marine bivalves shows great diversity and is considered as an economic trait. In China, the hard clam, Mercenaria mercenaria, commonly has three shell colors in the wild: red, white, and mottled. The genetic mechanisms controlling color segregation are not fully understood. In this study, RNA-seq was performed to exploit the related shell color genes and determine the genetic basis of the different shell colors. Nine sequence libraries with those three shell colors of hard clam were constructed; 406,377 transcripts and 248,251 unigenes were obtained with N50 values of 1365 and 1682 base pairs, respectively. Cluster analysis identified 363, 392, and 220 genes exclusively highly expressed in red, white, and mottled clams, respectively. We further classified differentially expressed genes (DEGs), the genes involved in lipid binding and transport, signal transduction, ATP synthesis, and other processes in the red vs white comparison were found, which may participate in red shell formation. DEGs related to signal transduction, particularly G protein-coupled receptor activity, were found in the red vs mottled comparison, suggesting that these genes might be important in mottled shell formation. In the white vs mottled comparison, DEGs involved in zinc ion binding were found. Our results provide new insights into shell color formation mechanisms in molluscs. This information could be used in selective breeding and marker-assisted breeding of this economically important clam species.

Evolutionary Perspective in Rickets and Vitamin D.

Modern lifestyle limits our exposure to sunlight, which photosynthesizes vitamin D in the skin, and the incidence of nutritional rickets has been resurging. Vitamin D is one of the first hormones; it is photosynthesized in all organism from the phytoplankton to mammals. A selective sweep of the promoter of the vitamin D receptor (VDR) happened as soon as Homo sapiens migrated out of Africa; it co-adapted with skin color genes to provide adaptation to latitudes and the levels of exposure to ultraviolet (UV)B radiation along the route out of Africa. Exposure to UVB radiation balances the need for vitamin D photosynthesis and degradation of folic acid by UVB radiation. Skin color follows a latitude distribution: the darkest populations dwell in the tropical belt; and the fair-skinned populations inhabit the northern countries. Due to their greater need for calcium during their reproductive life, the skin color of women is lighter- than that of men. Vitamin D is essential for mineral homeostasis and has a wide variety of non-skeletal functions, of which the most important for natural selection is a regulatory function in the innate immune system. In the human fossil record, vitamin D deficiency coincided with bone tuberculosis. About 6,000 years ago, a diet which included cow's milk provided Neolithic humans with twice as much calcium and was more alkaline than that of its Paleolithic predecessors. Adiposity is negatively associated with the vitamin D status and obese individuals require 2–3 times more vitamin D than non-obese individuals to normalize circulating 25OHD levels. In an era of an obesity epidemic, we need more research to determine whether adiposity should be considered when determining the dietary requirements for vitamin D and calcium and the optimal serum 25OHD levels.

Molecular-genetic bases of plumage coloring in chicken

The color of plumage in birds is an important feature, often determining descent to a particular species or breed. It serves as a key factor in the interaction of birds with each other due to their well-developed visual perception of the surrounding world. In poultry including chickens, the color of the plumage can be treated as a genetic marker, useful for identifying breeds, populations and breeding groups with their specific traits. The origin of diverse color plumage is the result of two interrelated physical processes, chemical and optical, due to which pigment and structural colors in the color are formed. The pigment melanin, which is presented in two forms, eumelanin and pheomelanin, is widely spread in birds. The basis for the formation of melanin is the aromatic amino acid tyrosine. The process of melano-genesis involves many loci, part of the complex expression of plumage color genes. In birds, the solid black color locus encodes the melanocortin 1 receptor (MC1R), mutations in which lead to a change in receptor activation and form different variants of the E locus. Using the GWAS analysis, possible genes affecting the formation of color in chickens were detected. The biosynthesis and types of melanin are affected by the activity of the enzyme tyrosine, and mutations in the tyrosinase gene (TYR) cause albinism in different species. The formation mechanism of brown, silver, gold, lavender and a number of other shades is determined by the influence on the work of the MC1R genes and TYR specific modifier genes. Thus, locus I currently associated with the PMEL17 gene inhibits the expression of eumelanin, and the MLPH gene affects tyrosinase function. Research on the mechanisms of formation of the secondary coloring of plumage in chickens is being actively conducted nowadays. The formation of a marble feather pattern is associated with the mutation of the endothelin B2 receptor (EDNRB2), in the coding part of the gene of which a polymorphism is found associated with the mo locus. The molecular base that causes the feather banding (locus B and autosomal recessive banding) is identified. Today, only some genes that determine the color of the plumage of chickens are studied and described. Different genes can produce similar plumage patterns, and different phenotypes can be determined by the polymorphism of a single gene. Using molecular methods, you can more accurately identify these differences. This overview shows the nature of melanin coloration in birds using the example of chickens of various breeds and also attempts to systematize knowledge about the molecular-genetic mechanisms of the appearance of various types of coloration.

Variation in pigmentation gene expression is associated with distinct aposematic color morphs in the poison frog Dendrobates auratus

BackgroundColor and pattern phenotypes have clear implications for survival and reproduction in many species. However, the mechanisms that produce this coloration are still poorly characterized, especially at the genomic level. Here we have taken a transcriptomics-based approach to elucidate the underlying genetic mechanisms affecting color and pattern in a highly polytypic poison frog. We sequenced RNA from the skin from four different color morphs during the final stage of metamorphosis and assembled a de novo transcriptome. We then investigated differential gene expression, with an emphasis on examining candidate color genes from other taxa.ResultsOverall, we found differential expression of a suite of genes that control melanogenesis, melanocyte differentiation, and melanocyte proliferation (e.g., tyrp1, lef1, leo1, and mitf) as well as several differentially expressed genes involved in purine synthesis and iridophore development (e.g., arfgap1, arfgap2, airc, and gart).ConclusionsOur results provide evidence that several gene networks known to affect color and pattern in vertebrates play a role in color and pattern variation in this species of poison frog.

Inheritance of different coat colours in Newfoundland dogs in Poland

The aim of the study was to present the manner in which coat colour genes are inherited in the Newfoundland dog breed and to estimate the number of dogs with various coat colours in the Polish Newfoundland dog population in 2017. This population numbered 656 dogs, including 248 males and 408 females. The estimated number of dogs of this breed also included all registered puppies, broken down by gender and coat colour. The genes determining coat colour are described, including more precisely the genes responsible for the coat colour of the Newfoundland breed. According to FCI regulations, the coat colours for Newfoundland dogs are black, brown and black-and-white. Other colours, such as brown-and-white or blue, are not recognized for breeding purposes in Europe. The study found that the dominant black coat was predominant in the Polish Newfoundland dog population in 2017. These dogs could be heterozygous at some other loci and have undesirable alleles. The second most common coat colour was chocolate, while the fewest dogs had spotted coats. The group with spotted coats contained more males than females, in contrast to the other two colour variants. There were also individuals with the blue coat colour, which is not accepted for breeding, as the result of mating of parents with proper coat colours. An understanding of how dog coat colours are inherited and the need for tests to determine coat colour genotypes would make it possible to foresee the occurrence of incorrect colours in subsequent generations, which is crucial for Newfoundland dog breeders, whose goal is to obtain dogs whose coat colour is in line with the FCI standard.

Exaggerated heterochiasmy in a fish with sex-linked male coloration polymorphisms

It is often stated that polymorphisms for mutations affecting fitness of males and females in opposite directions [sexually antagonistic (SA) polymorphisms] are the main selective force for the evolution of recombination suppression between sex chromosomes. However, empirical evidence to discriminate between different hypotheses is difficult to obtain. We report genetic mapping results in laboratory-raised families of the guppy (Poecilia reticulata), a sexually dimorphic fish with SA polymorphisms for male coloration genes, mostly on the sex chromosomes. Comparison of the genetic and physical maps shows that crossovers are distributed very differently in the two sexes (heterochiasmy); in male meiosis, they are restricted to the termini of all four chromosomes studied, including chromosome 12, which carries the sex-determining locus. Genome resequencing of male and female guppies from a population also indicates sex linkage of variants across almost the entire chromosome 12. More than 90% of the chromosome carrying the male-determining locus is therefore transmitted largely through the male lineage. A lack of heterochiasmy in a related fish species suggests that it originated recently in the lineage leading to the guppy. Our findings do not support the hypothesis that suppressed recombination evolved in response to the presence of SA polymorphisms. Instead, a low frequency of recombination on a chromosome that carries a male-determining locus and has not undergone genetic degeneration has probably facilitated the establishment of male-beneficial coloration polymorphisms.

Half the Genetic Variance in Vitamin D Concentration is Shared with Skin Colour and Sun Exposure Genes.

This study assessed the heritability of 25 hydroxyvitamin D3 (25(OH)D3) in a large twin cohort and the shared effect of sun exposure and skin colour on 25(OH)D3 variance. Study participants included 1604 twin pairs and their siblings (n = 4020). Twin correlations for 25(OH)D3 concentration were rMZ=0.79 (584 pairs) and rDZ = 0.52 (1020 pairs) consistent with an average h2 = 0.50 throughout the year. Significant phenotypic and genetic seasonal fluctuation was observed in 25(OH)D3 concentrations with heritability decreasing during the winter (h2 = 0.37) compared to summer (h2 = 0.62). Skin colour (measured both ordinally and quantitatively) and self-reported sun exposure were found to significantly affect 25(OH)D3 concentration. Twins with olive/dark skin had significantly lower 25(OH)D3 concentrations than those with fair/pale skin and multivariate genetic analysis showed that approximately half of the total additive genetic variation in 25(OH)D3 results from genes whose primary influence is on skin colour and sun exposure. Additionally, 37% of the total variance was attributed to shared environmental effects on vitamin D, skin colour and sun exposure measures. These results support a moderate estimate of vitamin D heritability and suggest significant influence of season, skin colour and sun exposure on the genetic variance.

Selecting for Coupling-Phase Recombination Between Potyvirus Resistance and White Endosperm Colour in Maize Preferred by Farmers in Sub-Saharan Africa (SSA)

Maize lethal necrosis (MLN) disease caused by a combined infection of Maize chlorotic mottle virus (MCMV) and any cereal infecting potyvirus is a threat to food security in Sub-Saharan Africa (SSA). Resistance to potyvirus has been extensively studied and Mdm1 gene for potyvirus resistance on chromosome 6 of maize is linked to Y1 gene for maize endosperm colour. This study is aimed at selecting for coupling-phase recombination of potyvirus resistance and white endosperm colour. White susceptible maize lines CML333 and CML277 were crossed with a yellow resistant line, Pa405, to produce F1 and F2 progenies. Progenies were screened using molecular markers to recover 22 white endosperm recombinants. 22 selections were advanced to F3 recombinant families, and 10 were assayed for their responses to Maize dwarf mosaic virus (MDMV) and Sugarcane mosaic virus (SCMV). Four families segregated for SCMV resistance, selection of homozygous recombinants within these families will provide lines appropriate for improving lines with resistance to SCMV and MLN resistance in SSA.

Sampling for DUS Test of Flower Colors of Ranunculus asiaticus L. in View of Spatial and Temporal Changes of Flower Colorations, Anthocyanin Contents, and Gene Expression Levels.

Sampling for DUS test of flower colors should be fixed at the stages and sites that petals are fully colored, and besides, flower colorations are uniform among individuals and stable for a period of time to allow testers to get consistent results. It remains a problem since spatial and temporal flower colorations are reported a lot but their change traits are little discussed. In this study, expression state, uniformity and stability of color phenotypes, anthocyanin contents, and gene expression levels were taken into account based on measurements at 12 development stages and three layers (inner, middle, and outer petals) of two varieties of Ranunculus asiaticus L. to get their best sampling. Our results showed that, outer petals of L9–L10 (stage 9–stage 10 of variety ‘Jiaoyan zhuanhong’) and C5–C6 (stage 5–stage 6 of variety ‘Jiaoyan yanghong’) were the best sampling, respectively. For DUS test, it is suggested to track flower colorations continuously to get the best sampling as well as representative colors since different cultivars had different change traits, and moreover, full expression of color phenotypes came later and lasted for a shorter duration than those of anthocyanin contents and gene expressions. Our innovation exists in following two points. Firstly, a model of change dynamic was introduced to illustrate the change traits of flower colorations, anthocyanin contents, and gene expressions. Secondly, genes used for expression analysis were screened on account of tentative anthocyanins, which were identified based on comparison between liquid chromatography–mass spectrometry (LC–MS) results and molecular mass and mass fragment pattern (M2) of each putative anthocyanin and their fragments deduced in our previous study. Gene screening in this regard may also be interest for other non-model plant genera with little molecular background.