Plant Gender Research Articles

Apomixis and the paradox of sex in plants.

The predominance of sex in eukaryotes, despite the high costs of meiosis and mating, is still an evolutionary enigma. Many theories have been proposed, none of them being conclusive on its own, and they are partly not well applicable to land plants. Sexual reproduction is obligate in embryophytes for the great majority of species. This review will compare the main forms of sexual and asexual reproduction in ferns and angiosperms, based on the generation cycling of sporophyte and gametophyte (leaving vegetative propagation aside). The benefits of sexual reproduction for maintenance of genomic integrity compared to asexuality will be discussed in the light of developmental, evolutionary, genetic and phylogenetic studies. Asexual reproduction represents modifications of the sexual pathway, with various forms of facultative sexuality. For sexual land plants, meiosis provides direct DNA repair mechanisms of oxidative damage in reproductive tissues. The ploidy alternations of meiosis-syngamy cycles, and prolonged, multicellular stages in the haploid phase in the gametophytes provide a high efficiency of purifying selection against recessive deleterious mutations. Asexual lineages might buffer effects of such mutations via polyploidy, and can purge the mutational load via facultative sexuality. The role of organelle-nuclear genome compatibility for maintenance of genome integrity is still not well understood. The costs of mating are in plants in general low because of predominant hermaphroditism. Phylogenetic patterns in the Archaeplastid clade suggest that high frequencies of sexuality in land plants are concomitant with a stepwise increase of intrinsic and extrinsic stress factors. Furthermore, expansion of genome size in land plants would increase the potential mutational load. Sexual reproduction appears to be essential for keeping long term genomic integrity, and only rare combinations of extrinsic and intrinsic factors allow for shifts to asexuality.

Genome Assembly and Sex-Determining Region of Male and Female Populus × sibirica.

The genus Populus is presented by dioecious species, and it became a promising object to study the genetics of sex in plants. In this work, genomes of male and female Populus × sibirica individuals were sequenced for the first time. To achieve high-quality genome assemblies, we used Oxford Nanopore Technologies and Illumina platforms. A protocol for the isolation of long and pure DNA from young poplar leaves was developed, which enabled us to obtain 31 Gb (N50 = 21 kb) for the male poplar and 23 Gb (N50 = 24 kb) for the female one using the MinION sequencer. Genome assembly was performed with different tools, and Canu provided the most complete and accurate assemblies with a length of 818 Mb (N50 = 1.5 Mb) for the male poplar and 816 Mb (N50 = 0.5 Mb) for the female one. After polishing with Racon and Medaka (Nanopore reads) and then with POLCA (Illumina reads), assembly completeness was 98.45% (87.48% duplicated) for the male and 98.20% (76.77% duplicated) for the female according to BUSCO (benchmarking universal single-copy orthologs). A high proportion of duplicated BUSCO and the increased genome size (about 300 Mb above the expected) pointed at the separation of haplotypes in a large part of male and female genomes of P. × sibirica. Due to this, we were able to identify two haplotypes of the sex-determining region (SDR) in both assemblies; and one of these four SDR haplotypes, in the male genome, contained partial repeats of the ARR17 gene (Y haplotype), while the rest three did not (X haplotypes). The analysis of the male P. × sibirica SDR suggested that the Y haplotype originated from P. nigra, while the X haplotype is close to P. trichocarpa and P. balsamifera species. Moreover, we revealed a Populus-specific repeat that could be involved in translocation of the ARR17 gene or its part to the SDR of P. × sibirica and other Populus species. The obtained results expand our knowledge on SDR features in the genus Populus and poplar phylogeny.

Determination of sex in humans, animals and plants by a chemical reaction of blood

After many years of research, Manoilov (Vrachebn. Gaz., 1923, No. 15, 21 | 22) managed to establish the 3 most typical reactions. M. especially recommends the third modification, with the help of which he investigated 530 samples of male and female blood and obtained from 86 to 36% of correct answers.

BIOCHEMICAL COMPOSITION OF THE BARK OF ACTINIDIA KOLOMIKTA MALE AND FEMALE PLANTS

The problem of sex recognition in Actinidia Lindl. is associated with the lack of morphological and anatomical markers of sex in juvenile plants and it is impossible to determine the sex of each plant before the first flowering of seedlings. This study is devoted to the search for differences in the physiological and biochemical parameters of male and female plants of the perennial dioecious culture Actinidia kolomikta . The purpose of this study is to find differences in the physiological and biochemical parameters of male and female plants of the perennial dioecious culture A. kolomikta for early diagnosis of the sex of plants. The quantitative content of photosynthetic pigments and the sum of phenolic compounds (using Folin&Ciocalteu’s phenol reagent) were determined by spectrophotometry. It was found that the amount of chlorophyll a and b in the bark of the male plants is 1,1–2 times more than in the female plants during the studied period. The content of chlorophyll a is 1,1–2,9 times greater than chlorophyll b . There are no significant differences in the content of the sum of carotenoids and the sum of phenolic compounds in the bark of male and female actinidia plants. The qualitative and quantitative composition of female and male A. kolomikta bark metabolites was studied using gas chromatography with mass spectrometric detection. There are 52 chemical compounds of various nature were identified in the bark extracts: 18 organic acids, 16 carbohydrates, 5 lactones, 4 phenolic compounds, 3 compounds from the group of organic alcohols, 3 compounds related to fatty acids, as well as individual substances — glycerol, myo-Inositol and aucubin. The bark of the male plant contains 8 more organic acids than the bark of female plant. As a result of the comparative analysis, the presence of common and specific secondary metabolites in the studied samples was established. The differences in the qualitative composition of the metabolomic profiles and the amount of photosynthetic pigments in the bark of annual shoots of male and female plants can be used in the future as biological markers for early diagnosis of sex in A. kolomikta.

Investigating Conflation of Sex and Gender Language in Student Writing About Genetics

Conflation of sex and gender is implicated in the development of essentialist thinking, which has been linked to the justification of systems of prejudice in modern society. This exploratory study presents findings from a person randomized control trial conducted with 460 students in 8th–10th grade that investigated the extent to which students conflate sex and gender in their writing about genetics. Students were randomly assigned to one of three short readings that either (1) explained the genetics of sex in plants; (2) explained the genetics of sex in humans; or (3) refuted neuro-genetic essentialism, offering instead a social explanation for why women receive fewer PhDs in science, technology, mathematics, and engineering than men. While previous findings from the authors suggest links between the condition students were assigned to and psychological indicators related to essentialist thinking, no work was done to investigate how students’ use of language might implicate cognitive conflation as a possible factor in understanding these results. In this study, student responses to a constructed response writing task given after the reading were analyzed to investigate the use of sex and gender language. Students in all three conditions used both sex and gender language. However, students in the refutational text condition tended to use sex and gender language deliberately in order to explain PhD attainment, while students in the traditional genetics conditions used the terms interchangeably, suggesting subconscious conflation. Students in the genetics of human sex condition were more likely to manifest this conflation than students in the genetics of plant sex condition. Implications for instruction are discussed.

Identification of dominant genetic markers relevant to male sex determination in mulberry (Morus alba L.)

Morus alba (white mulberry) is a cultivated species of mulberry that exists as both dioecious and monoecious plants in nature. Although it has been cultivated for years as an essential crop for sericulture, and although various cultivars are readily available, its sex determination mechanisms are not yet clear. In the present study, we aimed to elucidate sex determination mechanisms of mulberry using both genetic and genomic approaches. Female and male cultivars of dioecious M. alba were crossed, and the segregation of sex was analyzed in the F1 plants. In the F1 plants, female and male plants were segregated at an almost equal ratio. By comparing the restriction site associated DNA sequencing analysis data between female- and male-bulked DNA of these F1 plants, the male-bulk-specific RAD tags were predominantly identified. Thus, we presumed that the male M. alba is heterogametic whereas the female M. alba is homogametic. Based on the corresponding sequences of male-bulk-specific RAD tags, putative male-specific markers were developed, and these markers exhibited linkage with the male sex in individual F1 plants. However, genotypes of these markers did not always show an association with sex in the cultivars of M. alba, M. bombycis, and M. lhou. Around half of the analyzed female cultivars showed identical marker genotypes to male, whereas all the analyzed male and monoecious cultivars showed a consistent genotype. According to these results, the DNA markers developed in this study were found to be relevant to male flower determination, and are thus expected to be helpful for elucidating the mechanisms underlying the evolutionary and sex determination systems of mulberry plants.

Female Salix viminalis are more severely infected by Melampsora spp. but neither sex experiences associational effects.

Associational effects of plant genotype or species on plant biotic interactions are common, not least for disease spread, but associational effects of plant sex on interactions have largely been ignored. Sex in dioecious plants can affect biotic interactions with herbivores and pollinators; however, its effects on plant-pathogen interactions are understudied and associational effects are unknown. In a replicated field experiment, we assessed Melampsora spp. leaf rust infection in monosexual and mixed sex plots of dioecious Salix viminalis L. to determine whether plant sex has either direct or associational effects on infection severity. We found no differences in Melampsora spp. infection severity among sexual monocultures and mixtures in our field experiment. However, female plants were overall more severely infected. In addition, we surveyed previous studies of infection in S.viminalis clones and reevaluated the studies after we assigned sex to the clones. We found that females were generally more severely infected, as in our field study. Similarly, in a survey of studies on sex-biased infection in dioecious plants, we found more female-biased infections in plant-pathogen pairs. We conclude that there was no evidence for associational plant sex effects of neighboring conspecifics for either females or males on infection severity. Instead, plant sex effects on infection act at an individual plant level. Our findings also suggest that female plants may in general be more severely affected by fungal pathogens than males.

Safe sex in plants

Safe sex in plants

Does the speciation clock tick more slowly in the absence of heteromorphic sex chromosomes?

Squamates may be an attractive group in which to study the influence of sex chromosomes on speciation rates because of the repeated evolution of heterogamety (both XY and ZW), as well as an apparently large number of taxa with environmental sex-determination.

Genetic Identification of FemaleCannabis sativaPlants at Early Developmental Stage

Sequence-characterized amplified region (SCAR) markers were used to identify female plants at an early developmental stage in four different varieties of Cannabis sativa. Using the cetyl trimethylammonium bromide (CTAB) method, DNA was isolated from two-week-old plants of three drug-type varieties (Terbag W1, Terbag K2, and Terbag MX) and one fiber-type variety (Terbag Fedora A7) of C. sativa grown under controlled environmental conditions through seeds. Attempts to use MADC2 (male-associated DNA from Cannabis sativa) primers as a marker to identify the sex of Cannabis sativa plants were successful. Amplification of genomic DNA using MADC2-F and MADC2-R primers produced two distinct fragments, one with a size of approximately 450 bp for female plants and one for male plants with a size of approximately 300 bp. After harvesting the tissues for DNA extraction, plants were subjected to a flowering photoperiod (i.e., 12-h light cycle), and the appearance of flowers was compared with the DNA analysis. The results of the molecular analysis were found to be concordant with the appearance of male or female flowers. The results of this study represent a quick and reliable technique for the identification of sex in Cannabis plants using SCAR markers at a very early developmental stage.

Death without sex—the ‘problem of the small’ and selection for reproductive economy in flowering plants

Most of the resident plants within vegetation fail to leave descendants because of death without sex—i.e. sexual reproduction fails (zero fecundity), primarily because of relatively small plant size. I propose that this ‘problem of the small’ represents one of the principal driving forces of evolution by natural selection, and that the main product of this selection is ‘reproductive economy’, manifested by several plant traits that are widely distributed among angiosperms: sexual maturity at a relatively young age and small size, relatively small seed size, selfing (including through mixed mating), and of particular interest here, clonality. In non-clonal species, an offspring develops from a zygote into a single ‘rooted unit’, i.e. a distinct vascular transition point between live shoot and root tissue. Clonal species can produce an indeterminate number of these rooted unit offspring asexually, all as products of a single zygote. Clonality is a common strategy in angiosperms because it confers a potential two-fold fitness benefit—especially in relatively small species—by promoting longevity of the zygote product, while at the same time providing a fecundity supplement (through asexual multiplication of rooted units), thereby allowing offspring production economically, i.e. without requiring large adult size, and without even requiring the fertilization of ovules. The primary fitness benefit from clonality, therefore, is that the somatic product of a zygote can effectively avoid an intrinsic limitation predicted for all non-clonal plants: the trade-off between longevity and the potential rate of offspring/descendant production. These major fitness benefits of clonality are explored in considering why clonality is less common in larger species, why the largest species (trees) generally do not have the longest-lived zygote product, and in re-assessing traditional and recent views concerning the loss of sex in clonal plants, the predicted trade-off between the size and number of clonal offspring, and the predicted trade-off between sexual and asexual reproduction.

Identification of DNA Regions Specific to the X and Y Chromosomes in Sphaerocarpos texanus

Abstract The majority of dioecious plants are not sexually dimorphic until the onset of reproductive maturation. The inability to identify sex in pre-reproductive plants limits sex-related studies in plant populations. Molecular techniques to identify sex in seed plants have had increasing success. However, sex-specific markers in bryophytes have not yet been found. Bryophytes can be effective model systems in understanding the reproductive biology of plant species with unisexual individuals, as well as the molecular biology of sex chromosomes and sex determination. This study was specifically designed to find sex-specific markers in Sphaerocarpos texanus. The study relied on the Polymerase Chain Reaction procedure to amplify arbitrary regions of genomic DNA to locate sex-specific markers. Bulk segregant analysis using 238 decamer primers, and involving a single full-sibling pedigree was used to identify sex-specific markers. Inheritance of specific markers by male or female individuals was tested in prog...

The loss of sex in clonal plants

The loss of sex in clonal plants

Mendelian inheritance in Germany between 1900 and 1910. The case of Carl Correns (1864–1933)

Carl Correns (1864-1933) came to recognize Mendel’s rules between 1894 and 1900 while trying to find out the mechanism of xenia, that is, the direct influcence of the fertilizing pollen on the mother plant in maize and peas among other species. In this paper, I am concerned with the ten years of Correns’ work after the annus mirabilis of 1900 until 1910, when the main outlines of the new science of genetics had been established. It is generally assumed that after 1900 Correns quickly began probing the limits of Mendelian inheritance, both as far as the explanatory force of formal transmission genetics and the generality of Mendel’s laws are concerned. A careful examination of his papers however shows that he was much more interested in the scope of Mendelian inheritance than in its limits. Even his work with variegated Mirabilis plants, which historiographical folklore still presents as a result of Correns’ growing interest in cytoplasmic inheritance, can be shown to have been conducted to corroborate just the opposite, namley, the validity of the nuclear paradigm. The paper will show that Correns’research results in those years (among them the Mendelian inheritance of sex in higher plants) were the outcome of a complex experimental program which involved breeding experiments with dozens of different species.

Foliar Herbivory Affects Floral Characters and Plant Attractiveness to Pollinators: Implications for Male and Female Plant Fitness

Foliar Herbivory Affects Floral Characters and Plant Attractiveness to Pollinators: Implications for Male and Female Plant Fitness

Pathogens and sex in plants

Extant theories that attribute the evolution of sex to pathogen attack depend on the assumption that pathogens are narrowly specialized, so that high fitness on one host genotype results in poor fitness on hosts with other allele combinations. This assumption is necessary in order for frequency-dependent selection to produce sustained cycling of gametic disequilibrium across the host's disease resistance loci, which makes recombination advantageous. However, a review of numerous genetic studies on plant disease resistance failed to uncover a single example consistent with this assumption. Instead, the empirical results provide strong support for a different pattern of pathogen specificity, in which adaptation by pathogens to one resistance allele does not preclude high fitness on alternate host genotypes lacking that allele. Modification of traditional models for pathogen-mediated evolution of sex showed that for conditions close to the empirical pattern of genotypic specificity, sex is almost never favoured. For plants, these results cast doubt on current theories arguing that pathogens are the primary selective agent responsible for sexual reproduction.

Parasite loads in parthenogenetic and sexual lizards (Heteronotia binoei) : support for the Red Queen hypothesis

One version of the Red Queen hypothesis suggests that sexual reproduction is maintained in populations because of the need to continually create genotypes that confer resistance against rapidly evolving pathogens and parasites. Here, we report that parthenogenetic individuals of the Heteronotia binoei species complex are much more prone to infection by mites than are their sexual relatives. This accords with a central prediction of the Red Queen hypothesis. The greater susceptibility of the parthenogens is consistent across localities with different combinations of parthenogenetic genotypes and sexual chromosome races and occurs despite the unusually high genetic diversity of the parthenogenetic form. These observations support the contention that clonal reproduction increases the susceptibility of hosts to infection by parasites.

Introduction to the Workshop

Abstract The potentials of interspecific hybridization have been explored since the discovery of sex in plants. The rationale for interspecific hybridization ranges from curiosity concerning the evolution of species to the transfer of a single trait into a cultivar. Breeders of ornamental plants have utilized interspecific hybridization to produce novel plant and flower forms so vital to the trade.

Botanist's Corner : Flowers, Sex, and Hybridization in Carnivorous Plants

Botanist's Corner : Flowers, Sex, and Hybridization in Carnivorous Plants

CHEMICAL COMPOSITION OF ROOTS AND TOPS OF DIOECIOUS LYCHNIS IN VEGETATIVE AND FLOWERING PHASES OF GROWTH

In view of the current interest in problems of nutritional ontogeny and the evident influence of reproductive processes thereon, experimental data on the composition of the dioecious species, Lychnis dioica L., are presented. Dioecious forms appear to have the advantage in studies of this type in permitting recognition of compositional and metabolic differences associated with sex expression. By virtue of their perennial habit, individual plants of Lychnis can be studied throughout their growth cycle, thus permitting repeated comparison of the nutritional trend in each of the two sexes in the vegetative and reproductive stages of a single plant. The fact that inception of the reproductive processes appears to exert a marked metabolic effect upon the entire parent sporophyte, made it seem advisable to include a study of the root systems of the two sexes in order to determine compositional alterations and top-root interrelationships distinguishing vegetative and reproductive plants. Observations and analyses thus include both roots and tops of plants in the vegetative (rosette or pre-blooming) as well as the early flowering stage. The former is of particular interest since few studies exist in which initial tests on roots of dioecious plants in the vegetative stage have been interpreted in the light of ultimate sex expression. In earlier publications (17,18) the writer has summarized certain quantitative determinations and their relation to sex in dioecious plants and has presented analytical data relative to the physico-chemical aspects of sexual expression in Lychnis dioica L. Subsequent to this report, the cogent work by Loehwing (15) has given the most comprehensive integration of data relative to the physiological aspects of sex in angiosperms to be found in the literature. Since that time additional investigations have been reported (6,8,9,10,11,12,13,16,21). Methods