Strawberry (Fragaria sp.) stands as an interesting model for studying flowering behaviour and its relationship with asexual plant reproduction in polycarpic perennial plants. Strawberry produces both ...inflorescences and stolons (also called runners), which are lateral stems growing at the soil surface and producing new clone plants. In this study, the flowering and runnering behaviour of two cultivated octoploid strawberry (Fragaria×ananassa Duch., 2n=8×=56) genotypes, a seasonal flowering genotype CF1116 and a perpetual flowering genotype Capitola, were studied along the growing season. The genetic bases of the perpetual flowering and runnering traits were investigated further using a pseudo full-sibling F1 population issued from a cross between these two genotypes. The results showed that a single major quantitative trait locus (QTL) named FaPFRU controlled both traits in the cultivated octoploid strawberry. This locus was not orthologous to the loci affecting perpetual flowering (SFL) and runnering (R) in Fragaria vesca, therefore suggesting different genetic control of perpetual flowering and runnering in the diploid and octoploid Fragaria spp. Furthermore, the FaPFRU QTL displayed opposite effects on flowering (positive effect) and on runnering (negative effect), indicating that both traits share common physiological control. These results suggest that this locus plays a major role in strawberry plant fitness by controlling the balance between sexual and asexual plant reproduction.
Plants differ from animals in their capability to easily regenerate fertile adult individuals from terminally differentiated cells. This unique developmental plasticity is commonly observed in ...nature, where many species can reproduce asexually through the ectopic initiation of organogenic or embryogenic developmental programs. While organ-specific epigenetic marks are not passed on during sexual reproduction, the fate of epigenetic marks during asexual reproduction and the implications for clonal progeny remain unclear. Here we report that organ-specific epigenetic imprints in Arabidopsis thaliana can be partially maintained during asexual propagation from somatic cells in which a zygotic program is artificially induced. The altered marks are inherited even over multiple rounds of sexual reproduction, becoming fixed in hybrids and resulting in heritable molecular and physiological phenotypes that depend on the identity of the founder tissue. Consequently, clonal plants display distinct interactions with beneficial and pathogenic microorganisms. Our results demonstrate how novel phenotypic variation in plants can be unlocked through altered inheritance of epigenetic marks upon asexual propagation.
Root-knot nematodes (genus Meloidogyne) exhibit a diversity of reproductive modes ranging from obligatory sexual to fully asexual reproduction. Intriguingly, the most widespread and devastating ...species to global agriculture are those that reproduce asexually, without meiosis. To disentangle this surprising parasitic success despite the absence of sex and genetic exchanges, we have sequenced and assembled the genomes of three obligatory ameiotic and asexual Meloidogyne. We have compared them to those of relatives able to perform meiosis and sexual reproduction. We show that the genomes of ameiotic asexual Meloidogyne are large, polyploid and made of duplicated regions with a high within-species average nucleotide divergence of ~8%. Phylogenomic analysis of the genes present in these duplicated regions suggests that they originated from multiple hybridization events and are thus homoeologs. We found that up to 22% of homoeologous gene pairs were under positive selection and these genes covered a wide spectrum of predicted functional categories. To biologically assess functional divergence, we compared expression patterns of homoeologous gene pairs across developmental life stages using an RNAseq approach in the most economically important asexually-reproducing nematode. We showed that >60% of homoeologous gene pairs display diverged expression patterns. These results suggest a substantial functional impact of the genome structure. Contrasting with high within-species nuclear genome divergence, mitochondrial genome divergence between the three ameiotic asexuals was very low, signifying that these putative hybrids share a recent common maternal ancestor. Transposable elements (TE) cover a ~1.7 times higher proportion of the genomes of the ameiotic asexual Meloidogyne compared to the sexual relative and might also participate in their plasticity. The intriguing parasitic success of asexually-reproducing Meloidogyne species could be partly explained by their TE-rich composite genomes, resulting from allopolyploidization events, and promoting plasticity and functional divergence between gene copies in the absence of sex and meiosis.
Macroalgal cultures are currently of great interest worldwide. Although along the Romanian Black Sea coast, there is no tradition in this sense, currently, a major interest in developing this ...direction exists, taking into consideration that the overexploitation of wild seaweed resources involves the disturbance of the marine environment, with implications that can sometimes be irreversible. Porphyra and Pyropia species (also known as nori algae) are considered the world’s most valuable mariculture algal products due to their high nutritional value and multiple active principles, considered unique representatives of marine algae. Considering these aspects, attention was focused on the only nori species from the Romanian Black Sea coast, namely, Pyropia leucosticta. The species was cultivated in controlled laboratory conditions for 5.5 months by manipulating its reproductive elements. The aim was to establish a simple, low-cost method by avoiding the complicated conchocelis phase of the species; therefore, reproduction and further species development were achieved by collecting the released neutral spores and isolating them in culture vessels, ensuring, at the same time, proper nutrient conditions, using sterile enriched seawater and mimicking ambient conditions. At the end of the experiment, specimens of almost 80−90 mm were obtained, making this method suitable for obtaining ex situ P. leucosticta blades on the Romanian Black Sea shore.
Abstract
Standing genetic variation is a major driver of fitness and resilience and therefore of fundamental importance for threatened species such as stony corals. We analyzed RNA-seq data generated ...from 132 Montipora capitata and 119 Pocillopora acuta coral colonies collected from Kāneʻohe Bay, Oʻahu, Hawaiʻi. Our goals were to determine the extent of colony genetic variation and to study reproductive strategies in these two sympatric species. Surprisingly, we found that 63% of the P. acuta colonies were triploid, with putative independent origins of the different triploid clades. These corals have spread primarily via asexual reproduction and are descended from a small number of genotypes, whose diploid ancestor invaded the bay. In contrast, all M. capitata colonies are diploid and outbreeding, with almost all colonies genetically distinct. Only two cases of asexual reproduction, likely via fragmentation, were identified in this species. We report two distinct strategies in sympatric coral species that inhabit the largest sheltered body of water in the main Hawaiian Islands. These data highlight divergence in reproductive behavior and genome biology, both of which contribute to coral resilience and persistence.
Abstract Centrioles are the core constituent of centrosomes, microtubule-organizing centers involved in directing mitotic spindle assembly and chromosome segregation in animal cells. In sexually ...reproducing species, centrioles degenerate during oogenesis and female meiosis is usually acentrosomal. Centrioles are retained during male meiosis and, in most species, are reintroduced with the sperm during fertilization, restoring centriole numbers in embryos. In contrast, the presence, origin, and function of centrioles in parthenogenetic species is unknown. We found that centrioles are maternally inherited in two species of asexual parthenogenetic nematodes and identified two different strategies for maternal inheritance evolved in the two species. In Rhabditophanes diutinus , centrioles organize the poles of the meiotic spindle and are inherited by both the polar body and embryo. In Disploscapter pachys , the two pairs of centrioles remain close together and are inherited by the embryo only. Our results suggest that maternally-inherited centrioles organize the embryonic spindle poles and act as a symmetry-breaking cue to induce embryo polarization. Thus, in these parthenogenetic nematodes, centrioles are maternally-inherited and functionally replace their sperm-inherited counterparts in sexually reproducing species.
Is Biomass a Reliable Estimate of Plant Fitness? Younginger, Brett S; Sirová, Dagmara; Cruzan, Mitchell B ...
Applications in plant sciences,
2017-February, February 2017, 2017-Feb, 2017-02-00, 20170201, Volume:
5, Issue:
2
Journal Article
Peer reviewed
Open access
The measurement of fitness is critical to biological research. Although the determination of fitness for some organisms may be relatively straightforward under controlled conditions, it is often a ...difficult or nearly impossible task in nature. Plants are no exception. The potential for long-distance pollen dispersal, likelihood of multiple reproductive events per inflorescence, varying degrees of reproductive growth in perennials, and asexual reproduction all confound accurate fitness measurements. For these reasons, biomass is frequently used as a proxy for plant fitness. However, the suitability of indirect fitness measurements such as plant size is rarely evaluated. This review outlines the important associations between plant performance, fecundity, and fitness. We make a case for the reliability of biomass as an estimate of fitness when comparing conspecifics of the same age class. We reviewed 170 studies on plant fitness and discuss the metrics commonly employed for fitness estimations. We find that biomass or growth rate are frequently used and often positively associated with fecundity, which in turn suggests greater overall fitness. Our results support the utility of biomass as an appropriate surrogate for fitness under many circumstances, and suggest that additional fitness measures should be reported along with biomass or growth rate whenever possible.
Parthenogenesis is asexual reproduction without any required participation from males and, as such, is a null model for sexual reproduction. In a comparative context, we can expand our understanding ...of the evolution and ecology of sex by investigating the consequences of parthenogenesis. In this review, we examine the theoretical predictions of and empirical results on the evolution of asexual reproduction in vertebrates, focusing on recent studies addressing the origins and geographic spread of parthenogenetic lineages and the genomic consequences of an asexual life history. With advances in computational methods and genome technologies, researchers are poised to make rapid and significant progress in studying the origin and evolution of parthenogenesis in vertebrates, thus providing an important perspective on understanding biodiversity patterns of both asexual and sexual populations.
To evaluate the growth and feeding responses of the polyp stage of the moon jellyfish Aurelia coerulea to natural microzooplankton assemblages, bud production among A. coerulea polyps was monitored ...in field bottle incubation experiments using fractionated field seawater (<200-µm fraction) in summer. During this incubation period, feeding rates were measured twice by examining changes in the abundance of various microzooplankton taxa over two days. The number of buds increased with incubation period, reaching a mean of 5.8–9.3 buds per polyp after 16 days, at which point the carbon content of the new buds and the mother polyp was estimated to be 1.3–2.5 times higher than the carbon content of the initial polyp. Using these carbon content estimates, I calculated specific growth rates of 0.1–0.2 d−1 during the first 10 days. The results of the present feeding experiments suggest that polyps utilize diverse groups of microzooplankton and achieve relatively high carbon ingestion rates from ciliates, dinoflagellates, molluscs, and copepod nauplii. Total microzooplankton ingestion rates were estimated to be 4.05 and 3.27 µgC polyp−1 d−1 in the two experiments, respectively. These findings show that natural microzooplankton assemblages play a role as prey of polyps and can promote asexual reproduction of polyps under natural summer conditions.
Many eukaryotic microbes have complex life cycles that include both sexual and asexual phases with strict species specificity. Whereas the asexual cycle of the protistan parasite Toxoplasma gondii ...can occur in any warm-blooded mammal, the sexual cycle is restricted to the feline intestine. The molecular determinants that identify cats as the definitive host for T. gondii are unknown. Here, we defined the mechanism of species specificity for T. gondii sexual development and break the species barrier to allow the sexual cycle to occur in mice. We determined that T. gondii sexual development occurs when cultured feline intestinal epithelial cells are supplemented with linoleic acid. Felines are the only mammals that lack delta-6-desaturase activity in their intestines, which is required for linoleic acid metabolism, resulting in systemic excess of linoleic acid. We found that inhibition of murine delta-6-desaturase and supplementation of their diet with linoleic acid allowed T. gondii sexual development in mice. This mechanism of species specificity is the first defined for a parasite sexual cycle. This work highlights how host diet and metabolism shape coevolution with microbes. The key to unlocking the species boundaries for other eukaryotic microbes may also rely on the lipid composition of their environments as we see increasing evidence for the importance of host lipid metabolism during parasitic lifecycles. Pregnant women are advised against handling cat litter, as maternal infection with T. gondii can be transmitted to the fetus with potentially lethal outcomes. Knowing the molecular components that create a conducive environment for T. gondii sexual reproduction will allow for development of therapeutics that prevent shedding of T. gondii parasites. Finally, given the current reliance on companion animals to study T. gondii sexual development, this work will allow the T. gondii field to use of alternative models in future studies.
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