Two New Species of Balanophora (Balanophoraceae) From South China

Abstract— Populations of Balanophora from southern China are often identified by local botanists as B. laxiflora based on their long cylindric male inflorescence, subsessile male flowers with slender rudimentary bracts, and subdiscoid synandria. In this study, we clarify the identity of seven such populations based on morphological characters and phylogenetic analysis using nuclear 18S and ITS ribosomal DNA sequences. We confirmed the occurrence of dioecious populations of B. yakushimensis and two previously unrecognized species, which we describe here as B. parajaponica and B. appressa. Phylogenetic analyses indicated that B. parajaponica, B. yakushimensis, B. appressa, B. laxiflora, and the agamospermic B. japonica, formed a well resolved clade, viz. the B. laxiflora clade. The four dioecious species, although highly similar in the morphology of male inflorescence and flowers, can be separated by leaf morphology and arrangement, ovary color, and arrangement of female flowers. The species limit of B. laxiflora, however, remains unresolved.

More examples of breakdown the 1:1 partner specificity between figs and fig wasps

Background The obligate mutualism between fig trees (Ficus, Moraceae) and pollinating fig wasps (Agaonidae) is a model system for studying co-evolution due to its perceived extreme specificity, but recent studies have reported a number of examples of trees pollinated by more than one fig wasp or sharing pollinators with other trees. This will make the potential of pollen flow between species and hybridization more likely though only few fig hybrids in nature have been found. We reared pollinator fig wasps from figs of 13 Chinese fig tree species and established their identity using genetic methods in order to investigate the extent to which they were supporting more than one species of pollinator (co-pollinator). Results Our results showed (1) pollinator sharing was frequent among closely-related dioecious species (where pollinator offspring and seeds develop on different trees); (2) that where two pollinator species were developing in figs of one host species there was usually one fig wasp with prominent rate than the other. An exception was F. triloba, where its two pollinators were equally abundant; (3) the extent of co-pollinator within one fig species is related to the dispersal ability of them which is stronger in dioecious figs, especially in small species. Conclusions Our results gave more examples to the breakdown of extreme specificity, which suggest that host expansion events where pollinators reproduce in figs other than those of their usual hosts are not uncommon among fig wasps associated with dioecious hosts. Because closely related trees typically have closely related pollinators that have a very similar appearance, the extent of pollinator-sharing has probably been underestimated. Any pollinators that enter female figs carrying heterospecific pollen could potentially generate hybrid seed, and the extent of hybridization and its significance may also have been underestimated.

Genetic diversity and phylogenetic analysis in Asian and European Asparagus subgenus species

Garden asparagus (Asparagus officinalis L.) is a diploid (2n = 2x = 20), perennial and dioecious species belonging to Asparagus subgenus and worldwide cultivated as a vegetable crop. A narrow genetic base has been pointed out for the current cultivars. Crop wild related species (CWR) could be a valuable genetic resource in this crop but they have been underused up to now. To investigate the phylogenetic relationships between CWR asparagus species from different origin and A. officinalis L., 12 EST-SSR markers were used to assess the genetic variability of 20 accessions. These accessions belong to 10 Asparagus spp. from Asparagus subgenus including wild and naturalized A. officinalis L. (2x, 4x, 8x, 10x) and CWR species with European (A. tenuifolius Lam. (2x), A. pseudoscaber Grec. (6x), A. macrorrhizus Pedrol & al. (12x), A. prostratus Dumort (4x), A. brachyphyllus Turcz. (6x), A. maritimus (L.) Mill. (6x)) and Asian distribution (A. verticillatus L. (2x), A. persicus Baker (2x), A. breslerianus Schult. & Schult. (8x)). A. albus L. (2x) from the Protasparagus subgenus was used as outgroup. As a result, a total of 248 alleles were obtained and specific alleles of accessions were detected among them. After cluster analysis the accessions did not group by their geographical origin. All wild polyploid accessions with European and Asian distributions were grouped together with A. officinalis L. Hence, that cluster could be considered as the ‘officinalis group’ suggesting a monophyletic origin. The diploid accessions of A. verticillatus L. and A. persicus Baker clustered together and were the most genetically distant respect to ‘officinalis group’. The results obtained in this study may provide useful information to design new crosses among accessions aimed to develop new asparagus germplasm or pre-breeding populations.

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.

Distinct neuropeptide-receptor modules regulate a sex-specific behavioral response to a pheromone

Dioecious species are a hallmark of the animal kingdom, with opposing sexes responding differently to identical sensory cues. Here, we study the response of C. elegans to the small-molecule pheromone, ascr#8, which elicits opposing behavioral valences in each sex. We identify a novel neuropeptide-neuropeptide receptor (NP/NPR) module that is active in males, but not in hermaphrodites. Using a novel paradigm of neuropeptide rescue that we established, we leverage bacterial expression of individual peptides to rescue the sex-specific response to ascr#8. Concurrent biochemical studies confirmed individual FLP-3 peptides differentially activate two divergent receptors, NPR-10 and FRPR-16. Interestingly, the two of the peptides that rescued behavior in our feeding paradigm are related through a conserved threonine, suggesting that a specific NP/NPR combination sets a male state, driving the correct behavioral valence of the ascr#8 response. Receptor expression within pre-motor neurons reveals novel coordination of male-specific and core locomotory circuitries.

Genetic Variability of Reproductive Organs of Atlas Pistachio in Tiaret Region, Algeria

Pistacia atlantica Desf., endemic to northern Africa belonging to the family Anacardiceae, is a dioecious species of great ecological and socio-economic importance that exhibits considerable variation between individuals but some cases of monoecis have been discovered within the same family such as Pistacia atlantica Desf., Pistacia therebinthus and Pistacia chinensis. The study was conducted to find for the existence of genetic variability of the Betoum from mid-February to mid-March. The study is made on the morphological parameters of reproductive organs of four sites in the Tiaret region in Algeria. The results showed that this species has a high polymorphism of the morphological, qualitative and quantitative parameters of the reproductive organs. This variation is found in the male and female individuals of the selected stands. Variations in these reproductive organs can in no way be influenced by climatic changes such as leaves and roots and their physiological, biochemical and anatomical parameters. This allowed us to discover the first case of the monoicy in the Rechaiga forest. It is necessary to carry out thorough studies to know all the effects and benefits that this species can bring in our daily life in all the social, ecological and economic medicinal fields with the aim of a better appreciation of the patrimony than presents this species, the maintenance of genetic diversity, its conservation and the prospects for its development.

Sex dimorphism in dioecious Palmer amaranth (Amaranthus palmeri) in response to water stress

Main conclusion Phenological isolation can potentially reduce seed output and may be exploited as a novel tool for ecological management of dioecious weeds. Abstract Dioecious plants may benefit from a maximized outcrossing and optimal sex-specific resource allocation; however, this breeding system may also be exploited for weed management. Seed production in dioecious species is contingent upon the co-occurrence and co-flowering of the two genders and can be further disturbed by flowering asynchrony. We explored dimorphism in secondary sex characters in Amaranthus palmeri, and tested if reproductive synchrony can be affected by water stress. We have used seeds of A. palmeri from California, Kansas and Texas, and studied secondary sex characters under natural conditions and in response to water stress. Seeds of A. palmeri from California (CA) and Kansas (KS) were cordially provided by Dr. Anil Shrestha (California State University, Fresno, California) and Dr. Dallas E. Peterson (Kansas State University, Manhattan, Kansas), respectively. Seeds of a third population were collected from mature plants (about 30 plants) from a set-aside field in College Station, Texas. A. palmeri showed no sexual dimorphism with regard to the timing of emergence, plant height, and relative growth rate. While the initiation of flowering occurred earlier in males than females, females preceded males in timing of anthesis. Water stress delayed anthesis in males to a greater extent than females increasing the anthesis mismatch between the two sexes by seven days. Our data provide the first evidence of environment-controlled flowering asynchrony in A. palmeri. From a practical point of view, phenological isolation can potentially reduce seed output and may be exploited as a novel tool for ecological management of dioecious weeds.

Hybridization potential between Amaranthus tuberculatus and Amaranthus albus

The genus Amaranthus is composed of numerous annual herbs, several of which are primary driver weeds within annual production agricultural systems. In particular, Amaranthus tuberculatus, a dioecious species, is noteworthy for rapid growth rates, high fecundity, and an expanding geographic distribution. Interspecific hybridization within and between the subgenera Amaranthus and Acnidia is reported both in controlled environment and field studies, however a gap in knowledge exists with the subgenus Albersia. Interspecific hybridization may contribute to genetic diversity, and may contribute to the current range expansion of A. tuberculatus. Recently, a herbicide resistance survey of A. tuberculatus across five Midwestern states reported alleles of PPX2 similar to sequences of Amaranthus albus, a monoecious species. Here, we seek to generate empirical data for the hybridization potential of A. albus and A. tuberculatus through replicated, controlled crosses in a greenhouse. Of 65,000 progeny screened from A. albus grown with A. tuberculatus males, three were confirmed as hybrids. Hybrids were dioecious, possessed phenotypic traits of both species, and had limited to no fertility. DNA content analysis of backcross progeny suggested a polyploid state may be required for hybrid formation. Screening of 120 progeny of A. tuberculatus females grown with A. albus identified no hybrids, though a skew to female progeny was observed. The female skew may be due to apomixis or auto-pollination, the spontaneous generation of male flowers on otherwise female plants. Our results indicate that introgression between A. albus and A. tuberculatus will occur less frequently than what has often been reported from hybridization studies with different pairs of Amaranthus species.

Herbivory enhances leaky sex expression in the dioecious herb Mercurialis annua

Plant reproductive traits are widely understood to be responsive to the selective pressures exerted by pollinators, but there is also increasing evidence for an important role of antagonists such as herbivores in shaping these traits. Many dioecious species show leaky sex expression, with males and females occasionally producing flowers of the opposite sex. Here we show that leaky sex expression in both males and females of the wind-pollinated dioecious herb Mercurialis annua (Euphorbiaceae) is enhanced in response to simulated herbivory, increasing the probability and the degree of leakiness in both sexes. We also found that leakiness was greater in larger females but not in larger males. We discuss hypotheses for a possible functional link between herbivory and leaky sex expression, and consider what herbivory-induced leakiness might imply for the evolutionary ecology of plant reproductive systems, especially the breakdown of dioecy and the evolution of hermaphroditism.