Mode Of Reproduction In Plants Research Articles

Limited Mating Ability of a Wasp Strain with Rickettsia-Induced Thelytoky

Abstract Sexual reproduction is the dominant mode of reproduction in plants and animals; however, some species from various taxonomic groups reproduce asexually. Because some of these asexual species lack DNA recombination and so have low genetic variability, these asexual species are more likely to go extinct than sexual species. Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae) is a solitary endoparasitoid in which both arrhenotokous and thelytokous strains occur in sympatry. The thelytokous strain is infected by a parthenogenesis-inducing Rickettsia bacterium. We investigated whether fertilized progeny can be produced between females and antibiotic-induced males of the thelytokous strain. The males produced by antibiotic treatment showed the same courtship behaviors as the arrhenotokous males, but at a lower rate, and did not produce fertilized progeny. The results confirm that the thelytokous strain has been maintained by a functional apomixis mechanism rather than by occasional sex, preserving a degree of heterozygosity.

Methods for grafting Arabidopsis thaliana and Eutrema salsugineum

BackgroundGrafting, an ancient agronomic technique, is an artificial mode of asexual reproduction in plants. Recently, grafting research has gradually shifted from modifying agronomic traits to the study of molecular mechanism. Grafting is an excellent tool to study long-range signaling processes in plants. And the grafting between species will help elucidate the molecular mechanisms underlying contrasting differences between different species. Arabidopsis thaliana is a salt-sensitive model glycophyte and Eutrema salsugineum (previously Thellungiella salsuginea, salt cress) is a salt-tolerant model halophyte. Successful grafting of these two model plants will help further study the physiological and molecular mechanisms underlying salt tolerance in plants. The aim of this study was to demonstrate two sterile micro-grafting methods for Arabidopsis and salt cress.ResultsWe developed the methods for sterile grafting between A. thaliana and E. salsugineum; this is the first report on inter-generic grafting between Arabidopsis and Eutrema. The method involves cut-in grafting under sterile conditions. The grafted plant part was placed in half strength Murashige and Skoog medium with 1% agar and 1% sugar, and then cultured vertically with 22 °C/18 °C short-day/night cycles. The plants were then transferred to half strength Hoagland nutrient solution for hydroponics. The reported method is simple and easy to operate. Self-grafted Arabidopsis–Arabidopsis and Eutrema–Eutrema plants were used as controls, which were obtained with an improved hypocotyl-cutting grafting method. Ion contents in grafted plants were detected by inductively coupled plasma optical emission spectroscopy. The results showed that the ion content in salt cress and Arabidopsis changed to different degrees after grafting.ConclusionsThe inter-species grafting technique described here makes it possible to study hybrid plants between Arabidopsis and Eutrema and will contribute to further understanding of long-distance communications in plants. This technique also provides a reference for improving plant varieties using grafting, such as gardening plants, as well as fruit and vegetable crops.

Causes and consequences of large clonal assemblies in a poplar hybrid zone.

Asexual reproduction is a common and fundamental mode of reproduction in plants. Although persistence in adverse conditions underlies most known cases of clonal dominance, proximal genetic drivers remain unclear, in particular for populations dominated by a few large clones. In this study, we studied a clonal population of the riparian tree Populus alba in the Douro river basin (northwestern Iberian Peninsula) where it hybridizes with Populus tremula, a species that grows in highly contrasted ecological conditions. We used 73 nuclear microsatellites to test whether genomic background (species ancestry) is a relevant cause of clonal success, and to assess the evolutionary consequences of clonal dominance by a few genets. Additional genotyping-by-sequencing data were produced to estimate the age of the largest clones. We found that a few ancient (over a few thousand years old) and widespread genets dominate the population, both in terms of clone size and number of sexual offspring produced. Interestingly, large clones possessed two genomic regions introgressed from P.tremula, which may have favoured their spread under stressful environmental conditions. At the population level, the spread of large genets was accompanied by an overall ancient (>0.1Myr) but soft decline of effective population size. Despite this decrease, and the high clonality and dominance of sexual reproduction by large clones, the Douro hybrid zone still displays considerable genetic diversity and low inbreeding. This suggests that even in extreme cases as in the Douro, asexual and sexual dominance of a few large, geographically extended individuals does not threaten population survival.

Genome-wide identification and expression analysis of SWI1 genes in Boechera species

As a mode of reproduction in plants, apomixis leads to the generation of clones via seeds. Apomictic plants form viable diploid female gametes without meiosis (apomeiosis) and produce embryos without fertilization (parthenogenesis). Apomeiosis, as a major component of apomixis, has recently been reported in some Arabidopsis thaliana mutants; dyad mutants of SWI1 showed developmental processes common to apomeiosis, such as producing functional diploid gametes. However, the orthologs of SWI1 genes in natural apomicts has not been previously reported. To identify the relationship between the SWI1 gene and the apomeiosis process, we isolated and sequenced SWI1 orthologs from Boechera species, including apomictic and sexual species. Boechera species are close relatives of A. thaliana and thus are advantageous model species for apomixis research. The SWI1 cDNAs were obtained by RT-PCR from apomictic and sexual Boechera young flower buds. We sequenced partial SWI1 transcripts that were 650bp for B. holboellii and 684bp for B. stricta. These SWI1-like sequences showed 86% similarity for B. holboellii and 92% for B. stricta to the A. thaliana SWI1 transcript. We also used available genome data and amplified genomic sequences for SWI1 orthologs in B. holboellii and B. stricta. The predicted proteins contain a phospholipase C domain and a nuclear localization signal. Sequence analysis did not show significant mutations related to apomixis, and phylogenetic analysis showed that SWI1-like sequences were common across plant families, regardless of the presence of a sexual or apomictic reproduction system. We also investigated the expression levels of SWI1 mRNA in the B. holboellii and B. stricta young unopened flower buds and found that relatively high levels of expression occurred in apomicts.

Effects of damage and pollination on sexual and asexual reproduction in a flowering clonal plant

The extent to which local biotic factors like herbivory and pollination affect mode of reproduction in plants is not yet fully understood. Mode of reproduction is ecologically important because it can influence the spread and distribution of plant populations through factors like offspring dispersal distance and establishment success. The two experiments described here address the potential effects of damage and pollen receipt on plant growth, sexual reproduction, and asexual reproduction in a clonal flowering plant (Eichhornia crassipes, water hyacinth). These experiments were conducted in greenhouse and outdoor tanks at the Florida State University research facilities in Tallahassee, FL, on plants collected from north Florida populations. Plants received manual damage to leaves (imposing a loss of resources), apical meristems (imposing a loss of leaf and flower production), or axillary meristems (imposing a loss of clone production). Apical meristem damage increased asexual reproduction (clone number). When severe, axillary meristem damage increased plant growth (leaf production). Neither leaf damage nor pollination affected plant growth, clone production, or flower production. Asexual reproductive responses to damage have not been well studied, although sexual reproduction and individual plant growth have been shown to increase following damage. These results have implications for the dispersal and establishment of clonal plants in the presence of herbivory. For a highly invasive species like E. crassipes, these results can further inform the use of insect herbivores to manage invasive populations.

Evolutionary dynamics of mating system shifts in Arabidopsis lyrata

Outcrossing is the prevalent mode of reproduction in plants and animals despite its substantial costs, while selfing and mixed mating occur at much lower frequency. Comparative research on plants has demonstrated the lability of self-incompatibility, but there is little information about the transition on a within-species level from self-incompatibility to predominant selfing. We studied variation in mating system among 18 populations of Arabidopsis lyrata within a phylogenetic context to shed light on the evolution of selfing. Realized and potential mating systems were assessed by genetic analysis with microsatellite markers and hand-self-pollinations on 30 plants from each population. The fraction of self-incompatible plants in a population was highly correlated with the outcrossing rate, showing that the spread of self-compatibility is accompanied by or soon followed by an increase in the rate of selfing. The four predominantly selfing populations (outcrossing rates <0.25) fell into more than one phylogenetic cluster, suggesting that the transition to selfing occurred more than once independently. Hence, A. lyrata offers an opportunity for the comparative analysis of outcrossing as a predominant mode of reproduction in plants and of the causes of the shift to selfing.

Benefits and Costs of Vegetative and Sexual Reproduction in Perennial Plants: A Review of Literature

ABSTRACT A number of perennial plant species can have different modes of reproduction, depending on environmental conditions. The objective of this paper is to review previously published literature regarding the benefits and costs of asexual (vegetative) and sexual reproduction in perennial plants, and to address which environmental conditions tend to favor each mode of reproduction in plants exhibiting both vegetative and sexual reproduction. Benefits of vegetative reproduction, through physiological integration among intraclonal ramets, may prolong the life in clones of individuals by spreading the risk of mortality over space. Costs of long-term integration may involve maintenance of connections and support of numerous daughter ramets at the expense of the parental clone. The depletion of genotypic variability within clonal populations through time makes them more susceptible to diseases, pathogens, and environmental stochasticity. However, benefits of sexual reproduction include genetic diversity, pr...

Automictic Reproduction in Interspecific Hybrids of Poeciliid Fish

Automixis, the process whereby the fusion of meiotic products restores the diploid state of the egg, is a common mode of reproduction in plants but has also been described in invertebrate animals. In vertebrates, however, automixis has so far only been discussed as one of several explanations for isolated cases of facultative parthenogenesis. Analyzing oocyte formation in F1 hybrids derived from Poecilia mexicana limantouri and P. latipinna crosses (the cross that led to the formation of the gynogenetic Poecilia formosa), we found molecular evidence for automictic oocyte production. The mechanism involves the random fusion of meiotic products after the second meiotic division. The fertilization of diploid oocytes gives rise to fully viable triploid offspring. Although the automictic production of diploid oocytes as seen in these F1 hybrids clearly represents a preadaptation to parthenogenetic reproduction, it is also a powerful intrinsic postzygotic isolation mechanism because the resulting next generation triploids were always sterile. The mechanism described here can explain facultative parthenogenesis, as well as varying ploidy levels reported in different animal groups. Most importantly, at least some of the reported cases of triploidy in humans can now be traced back to automixis.

Identification of differentially expressed cDNA sequences in ovaries of sexual and apomictic plants of Brachiaria brizantha.

The isolation of genes associated with apomixis would improve understanding of the molecular mechanism of this mode of reproduction in plants as well as open the possibility of transfer of apomixis to sexual plants, enabling cloning of crops through seeds. Brachiaria brizantha is a highly apomictic grass species with 274 tetraploid apomicts accessions and only one diploid sexual. In this study we have compared gene expression in ovaries at megasporogenesis and megagametogenesis of sexual and apomictic accessions of B. brizantha by differential display (DD-PCR), with 60 primer combinations. Specificity of 65 cloned fragments, checked by reverse northern blot analysis, showed that 11 clones were differentially expressed, 6 in apomictic ovaries, 2 in sexual and 3 in apomictic and sexual, but at different stages. Of the 6 sequences isolated that were preferentially expressed in the apomictic accession: one sequence was from ovaries at megasporogenesis stage; three were from megagametogenesis stage; two were from both stages. Of the two sequences isolated from the sexual accessions, one showed expression in ovaries at megagametogenesis, while the other sequence was shown to be specific to both stages. Three sequences were from megasporogenesis stage in apomicts but were also detected at megagametogenesis in sexual plants. Sequence analysis showed that 5 of the 11 clones had no apparent homologues in the protein database. Some of the clones identified as apomictic-specific shared homology with known genes enabling their functional annotation. The relationships of these functions to the generation of the apomictic trait are discussed.

Variability of Chloroplast Number in Populations of Stomata Guard Cells in Sugar Beet Beta vulgaris L.

Diploid sugar beet plants demonstrate a broad variability of the number of chloroplasts in stomata guard cells, which is related to mixoploidy of cell populations in leaf apical meristems (epigenomic variability). In addition to random organelle segregation between daughter cells, this variability is affected by factors disrupting the mitotic cycle: (1) plant treatment with a mitotic poison, such as colchicine; (2) duration of the life cycle of a plant; the variability in second-year plants is greater than in first-year ones; (3) the mode of plant reproduction; the variability in inbred plants is greater than in the initial population. Treatment of germinating seeds with a diluted colchicine solution increases the number of organelles in cells in the myxoploid generation (generation C0) and the variance of the distributions in the first vegetation year. The variability in the organelle number in stomata cells correlates with that in maternal meristem cells. It is concluded that the epidermal cell monolayer (including stomata guard cells) keeps record of the epigenomic and epiplastome variability in meristem cells. The variability of the number of chloroplasts in stomata guard cells is approximated by binomials with negative powers.