Sympatric genetic divergence between early- and late-season weedy rice populations.

Sympatric genetic divergence is the most appealing and controversial pattern in the theory of ecological speciation. Examples that support sympatric genetic divergence in plant species are extremely rare. Solid evidence of sympatric genetic divergence will provide deep insights for revealing the underlying mechanisms of ecological speciation. We analysed the total genomic DNA sequences of 120 weedy rice (WR; Oryza sativa f. spontanea) plants, representing three WR population pairs separately from three early- and late-season rice fields, in comparison with those of the co-occurring rice cultivars and other rice materials. We detected substantial genetic divergence within the pairs of the sympatric early- and late-season WR populations, although genetic divergence was unevenly distributed across the genomes. Restricted gene flow was determined between the sympatric WR populations, resulting in their distinct genetic structures. We also detected relatively low genetic diversity that was likely to be associated with stronger selection in early-season WR populations. Our findings provide strong evidence for sympatric genetic divergence between the WR populations in the same fields but in different seasons. We conclude that temporal isolation plays an important role in creating genetic divergence between sympatric populations/species in plants.

Reduced weed seed shattering by silencing a cultivated rice gene: strategic mitigation for escaped transgenes.

Transgene flow form a genetically engineered (GE) crop to its wild relatives may result in unwanted environmental consequences. Mitigating transgenes via introducing a gene that is disadvantageous to wild relatives but beneficial to crops, and is tightly-linked with the target transgenes, may provide a promising solution to limit the spread of transgenes in wild/weedy populations. Here we demonstrate a novel system with significantly reduced seed shattering in crop-weed hybrid descendants by partially silenced expression of the seed-shattering gene SH4 in cultivated rice, using artificial microRNA and antisense RNA techniques. Accordingly, fewer seeds were found in the soil of the field plots where transgenic hybrid lineages were grown. However, no differences in productivity-related traits were detected between GE and non-GE cultivated rice. To silence seed-shattering genes provides a useful strategy to reduce the potential environmental impacts caused by transgene flow from commercial GE rice to weedy rice, in addition to the control of weedy rice.

RNAi-directed downregulation of betaine aldehyde dehydrogenase 1 (OsBADH1) results in decreased stress tolerance and increased oxidative markers without affecting glycine betaine biosynthesis in rice (Oryza sativa).

As an important osmoprotectant, glycine betaine (GB) plays an essential role in resistance to abiotic stress in a variety of organisms, including rice (Oryza sativa L.). However, GB content is too low to be detectable in rice, although rice genome possesses several orthologs coding for betaine aldehyde dehydrogenase (BADH) involved in plant GB biosynthesis. Rice BADH1 (OsBADH1) has been shown to be targeted to peroxisome and its overexpression resulted in increased GB biosynthesis and tolerance to abiotic stress. In this study, we demonstrated a pivotal role of OsBADH1 in stress tolerance without altering GB biosynthesis capacity, using the RNA interference (RNAi) technique. OsBADH1 was ubiquitously expressed in different organs, including roots, stems, leaves and flowers. Transgenic rice lines downregulating OsBADH1 exhibited remarkably reduced tolerance to NaCl, drought and cold stresses. The decrease of stress tolerance occurring in the OsBADH1-RNAi repression lines was associated with an elevated level of malondialdehyde content and hydrogen peroxidation. No GB accumulation was detected in transgene-positive and transgene-negative lines derived from heterozygous transgenic T0 plants. Moreover, transgenic OsBADH1-RNAi repression lines showed significantly reduced seed set and yield. In conclusion, the downregulation of OsBADH1, even though not causing any change of GB content, was accounted for the reduction of ability to dehydrogenate the accumulating metabolism-derived aldehydes and subsequently resulted in decreased stress tolerance and crop productivity. These results suggest that OsBADH1 possesses an enzyme activity to catalyze other aldehydes in addition to betaine aldehyde (the precursor of GB) and thus alleviate their toxic effects under abiotic stresses.

A novel 5-enolpyruvoylshikimate-3-phosphate (EPSP) synthase transgene for glyphosate resistance stimulates growth and fecundity in weedy rice (Oryza sativa) without herbicide.

Understanding evolutionary interactions among crops and weeds can facilitate effective weed management. For example, gene flow from crops to their wild or weedy relatives can lead to rapid evolution in recipient populations. In rice (Oryza sativa), transgenic herbicide resistance is expected to spread to conspecific weedy rice (Oryza sativa f. spontanea) via hybridization. Here, we studied fitness effects of transgenic over-expression of a native 5-enolpyruvoylshikimate-3-phosphate synthase (epsps) gene developed to confer glyphosate resistance in rice. Controlling for genetic background, we examined physiological traits and field performance of crop-weed hybrid lineages that segregated for the presence or absence of this novel epsps transgene. Surprisingly, we found that transgenic F2 crop-weed hybrids produced 48-125% more seeds per plant than nontransgenic controls in monoculture- and mixed-planting designs without glyphosate application. Transgenic plants also had greater EPSPS protein levels, tryptophan concentrations, photosynthetic rates, and per cent seed germination compared with nontransgenic controls. Our findings suggest that over-expression of a native rice epsps gene can lead to fitness advantages, even without exposure to glyphosate. We hypothesize that over-expressed epsps may be useful to breeders and, if deployed, could result in fitness benefits in weedy relatives following transgene introgression.

Biodiversity and Ecosystem Functioning in Naturally and Experimentally Assembled Communities.

Numerous studies have proved that biodiversity and ecosystem functioning (BEF) are closely linked [...].

Reduced Carbon Dioxide by Overexpressing EPSPS Transgene in Arabidopsis and Rice: Implications in Carbon Neutrality through Genetically Engineered Plants.

With the increasing challenges of climate change caused by global warming, the effective reduction of carbon dioxide (CO2) becomes an urgent environmental issue for the sustainable development of human society. Previous reports indicated increased biomass in genetically engineered (GE) Arabidopsis and rice overexpressing the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, suggesting the possibility of consuming more carbon by GE plants. However, whether overexpressing the EPSPS gene in GE plants consumes more CO2 remains a question. To address this question, we measured expression of the EPSPS gene, intercellular CO2 concentration, photosynthetic ratios, and gene expression (RNA-seq and RT-qPCR) in GE (overexpression) and non-GE (normal expression) Arabidopsis and rice plants. Results showed substantially increased EPSPS expression accompanied with CO2 consumption in the GE Arabidopsis and rice plants. Furthermore, overexpressing the EPSPS gene affected carbon-fixation related biological pathways. We also confirmed significant upregulation of four key carbon-fixation associated genes, in addition to increased photosynthetic ratios, in all GE plants. Our finding of significantly enhanced carbon fixation in GE plants overexpressing the EPSPS transgene provides a novel strategy to reduce global CO2 for carbon neutrality by genetic engineering of plant species, in addition to increased plant production by enhanced photosynthesis.

Crop-Weed Introgression Plays Critical Roles in Genetic Differentiation and Diversity of Weedy Rice: A Case Study of Human-Influenced Weed Evolution.

As an important driving force, introgression plays an essential role in shaping the evolution of plant species. However, knowledge concerning how introgression affects plant evolution in agroecosystems with strong human influences is still limited. To generate such knowledge, we used InDel (insertion/deletion) molecular fingerprints to determine the level of introgression from japonica rice cultivars into the indica type of weedy rice. We also analyzed the impact of crop-to-weed introgression on the genetic differentiation and diversity of weedy rice, using InDel (insertion/deletion) and SSR (simple sequence repeat) molecular fingerprints. Results based on the STRUCTURE analysis indicated an evident admixture of some weedy rice samples with indica and japonica components, suggesting different levels of introgression from japonica rice cultivars to the indica type of weedy rice. The principal coordinate analyses indicated indica-japonica genetic differentiation among weedy rice samples, which was positively correlated with the introgression of japonica-specific alleles from the rice cultivars. In addition, increased crop-to-weed introgression formed a parabola pattern of dynamic genetic diversity in weedy rice. Our findings based on this case study provide evidence that human activities, such as the frequent change in crop varieties, can strongly influence weed evolution by altering genetic differentiation and genetic diversity through crop-weed introgression in agroecosystems.

Introgression from cultivated rice influences genetic differentiation of weedy rice populations at a local spatial scale.

Hybridization and introgression can play an important role in genetic differentiation and adaptive evolution of plant species. For example, a conspecific feral species may frequently acquire new alleles from its coexisting crops via introgression. However, little is known about this process. We analyzed 24 weedy rice (Oryza sativa f. spontanea) populations and their coexisting rice cultivars from northern Italy to study their genetic differentiation, outcrossing, and introgression based on microsatellite polymorphisms. A total of 576 maternal plants representing 24 weedy populations were used to estimate their genetic differentiation, and 5,395 progeny (seedlings) derived from 299 families of 15 selected populations were included to measure outcrossing rates. Considerable genetic differentiation (F (st) = 0.26) was detected among weedy rice populations, although the differentiation was not associated with the spatial pattern of the populations. Private alleles (28%) were identified in most populations that exhibited a multiple cluster assignments, indicating stronger genetic affinities of some weedy populations. Outcrossing rates were greatly variable and positively correlated (R (2) = 0.34, P = 0.02) with the private alleles of the corresponding populations. Paternity analysis suggested that ~15% of paternal specific alleles, a considerable portion of which was found to be crop-specific, were acquired from the introgression of the coexisting rice cultivars. Frequent allelic introgression into weedy populations resulting from outcrossing with nearby cultivars determines the private alleles of local feral populations, possibly leading to their genetic differentiation. Introgression from a crop may play an important role in the adaptive evolution of feral populations.

Rice choline monooxygenase (OsCMO) protein functions in enhancing glycine betaine biosynthesis in transgenic tobacco but does not accumulate in rice (Oryza sativa L. ssp. japonica).

UNLABELLED: Glycine betaine (GB) is a compatible quaternary amine that enables plants to tolerate abiotic stresses, including salt, drought and cold. In plants, GB is synthesized through two-step of successive oxidations from choline, catalyzed by choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH), respectively. Rice is considered as a typical non-GB accumulating species, although the entire genome sequencing revealed rice contains orthologs of both CMO and BADH. Several studies unraveled that rice has a functional BADH gene, but whether rice CMO gene (OsCMO) is functional or a pseudogene remains to be elucidated. In the present study, we report the functional characterization of rice CMO gene. The OsCMO gene was isolated from rice cv. Nipponbare (Oryza sativa L. ssp. japonica) using RT-PCR. Northern blot demonstrated the transcription of OsCMO is enhanced by salt stress. Transgenic tobacco plants overexpressing OsCMO results in increased GB content and elevated tolerance to salt stress. Immunoblotting analysis demonstrates that a functional OsCMO protein with correct size was present in transgenic tobacco but rarely accumulated in wild-type rice plants. Surprisingly, a large amount of truncated proteins derived from OsCMO was induced in the rice seedlings in response to salt stresses. This suggests that it is the lack of a functional OsCMO protein that presumably results in non-GB accumulation in the tested rice plant. KEY MESSAGE: Expression and transgenic studies demonstrate OsCMO is transcriptionally induced in response to salt stress and functions in increasing glycinebetaine accumulation and enhancing tolerance to salt stress. Immunoblotting analysis suggests that no accumulation of glycinebetaine in the Japonica rice plant presumably results from lack of a functional OsCMO protein.

Reducing Seed Shattering in Weedy Rice by Editing SH4 and qSH1 Genes: Implications in Environmental Biosafety and Weed Control through Transgene Mitigation.

Mitigating the function of acquired transgenes in crop wild/weedy relatives can provide an ideal strategy to reduce the possible undesired environmental impacts of pollen-mediated transgene flow from genetically engineered (GE) crops. To explore a transgene mitigation system in rice, we edited the seed-shattering genes, SH4 and qSH1, using a weedy rice line ("C9") that originally had strong seed shattering. We also analyzed seed size-related traits, the total genomic transcriptomic data, and RT-qPCR expression of the SH4 or qSH1 gene-edited and SH4/qSH1 gene-edited weedy rice lines. Substantially reduced seed shattering was observed in all gene-edited weedy rice lines. The single gene-edited weedy rice lines, either the SH4 or qSH1 gene, did not show a consistent reduction in their seed size-related traits. In addition, reduced seed shattering was closely linked with the weakness and absence of abscission layers and reduced abscisic acid (ABA). Additionally, the genes closely associated with ABA biosynthesis and signaling transduction, as well as cell-wall hydrolysis, were downregulated in all gene-edited weedy rice lines. These findings facilitate our deep insights into the underlying mechanisms of reduced seed shattering in plants in the rice genus Oryza. In addition, such a mitigating technology also has practical applications for reducing the potential adverse environmental impacts caused by transgene flow and for managing the infestation of weedy rice by acquiring the mitigator from GE rice cultivars through natural gene flow.

Rapid evolutionary divergence and ecotypic diversification of germination behavior in weedy rice populations.

Feral plants have evolved from well-studied crops, providing good systems for elucidation of how weediness evolves. As yet, they have been largely neglected for this purpose. The evolution of weediness can occur by simple back mutations in domestication genes (domestication in reverse). Whether the evolutionary steps to weediness always occur in reverse remains largely unknown. We examined seed germination behavior in recently evolved weedy rice (Oryza sativa f. spontanea) populations and their coexisting cultivars in eastern and north-eastern China to address whether 'dedomestication' is the simple reverse of domestication. We found that these weedy populations did not diverge from their progenitors by reverting to the pre-domestication trait of seed dormancy. Instead, they have evolved a novel mechanism to avoid growing in inappropriate environments via changes in critical temperature cues for seed germination. Furthermore, we found evidence for subsequent ecotypic divergence of these populations such that the critical temperature for germination correlates with the local habitat temperature at latitudinal gradients. The origins of problematic plant species, weeds and invasives, have already been studied in detail. These plants can thus be used as systems for studying rapid evolution. To determine whether and how that evolution is adaptive, experiments such as those described here can be performed.

Enhanced yield performance of Bt rice under target-insect attacks: implications for field insect management.

The rapid development of transgenic biotechnology has greatly promoted the breeding of genetically engineered (GE) rice in China, and many GE rice lines are in the pipeline for commercialization. To understand field performances of GE rice, key agronomic traits of two insect-resistant Bt rice lines that have been granted biosafety certificates for commercial production in China were evaluated together with their nontransgenic counterparts under environmental conditions with significant differences in insect pressure. Results from the experiments showed enhanced field performances of the Bt GE rice lines compared with the non-GE counterparts for yield-related traits such as number of panicles and filled seeds per plant, under environmental conditions with no insecticide application. No detectable underlying cost of the Bt transgene was observed in the two insect-resistant GE rice lines, particularly in the GE hybrid rice line. Results further indicated significantly greater yield performances of the two insect-resistant GE rice lines under environmental conditions with non-target insect control compared with no insect control. It is concluded from this study that insect-resistant Bt GE rice, particularly the hybrid line, has great potential to maintain its high yield when ambient insect pressure is high. In addition, proper application of insecticides to control non-target insects will guarantee optimal performance of insect-resistant Bt GE rice.

Increased Longevity and Dormancy of Soil-Buried Seeds from Advanced Crop-Wild Rice Hybrids Overexpressing the EPSPS Transgene.

Estimating the fitness effect conferred by a transgene introgressed into populations of wild relative species from a genetically engineered (GE) crop plays an important role in assessing the potential environmental risks caused by transgene flow. Such estimation has essentially focused on the survival and fecundity-related characteristics measured above the ground, but with little attention to the fate of GE seeds shattered in the soil seed banks after maturation. To explore the survival and longevity of GE seeds in soil, we examined the germination behaviors of crop-wild hybrid seeds (F4-F6) from the lineages of a GE herbicide-tolerant rice (Oryzasativa) line that contains an endogenous EPSPS transgene hybridized with two wild O. rufipogon populations after the seeds were buried in soil. The results showed significantly increased germination of the GE crop-wild hybrid seeds after soil burial, compared with that of the non-GE hybrid seeds. Additionally, the proportion of dormant seeds and the content of the growth hormone auxin (indole-3-acetic acid, IAA) in the GE crop-wild hybrid seeds significantly increased. Evidently, the EPSPS transgene enhances the survival and longevity of GE crop-wild rice seeds in the soil seed banks. The enhanced survival and longevity of the GE hybrid seeds is likely associated with the increases in seed dormancy and auxin (IAA) by overexpressing the rice endogenous EPSPS transgene. Thus, the fate of GE seeds in the soil seed banks should be earnestly considered when assessing the environmental risks caused by transgene flow.

Key Roles of De-Domestication and Novel Mutation in Origin and Diversification of Global Weedy Rice.

Agricultural weeds pose great challenges to sustainable crop production, owing to their complex origins and abundant genetic diversity. Weedy rice (WD) infests rice fields worldwide causing tremendous losses of rice yield/quality. To explore WD origins and evolution, we analyzed DNA sequence polymorphisms of the seed shattering genes (sh4 and qsh1) in weedy, wild, and cultivated rice from a worldwide distribution. We also used microsatellite and insertion/deletion molecular fingerprinting to determine their genetic relationship and structure. Results indicate multiple origins of WD with most samples having evolved from their cultivated progenitors and a few samples from wild rice. WD that evolved from de-domestication showed distinct genetic structures associated with indica and japonica rice differentiation. In addition, the weed-unique haplotypes that were only identified in the WD samples suggest their novel mutations. Findings in this study demonstrate the key role of de-domestication in WD origins, in which indica and japonica cultivars stimulated further evolution and divergence of WD in various agroecosystems. Furthermore, novel mutations promote continued evolution and genetic diversity of WD adapting to different environments. Knowledge generated from this study provides deep insights into the origin and evolution of conspecific weeds, in addition to the design of effective measures to control these weeds.

Increases in Genetic Diversity of Weedy Rice Associated with Ambient Temperatures and Limited Gene Flow.

Hypotheses regarding the association of increased species or genetic diversity with gradually warmer regions as a global pattern have been proposed, but no direct and solid experimental data are available to approve the association between plant genetic diversity and ambient temperatures. To test the diversity-temperature hypothesis, we studied genetic diversity and genetic differentiation of weedy rice (Oryza sativa f. spontanea) populations occurring naturally in early- and late-season rice fields that share nearly the same ecological conditions but with slightly different temperatures. Data collected from 10-year historical climatic records indicated a ~2 ℃ higher average air temperature in the late rice-cultivation seasons than in the early seasons. Results based on molecular fingerprints of 27 SSR (simple sequence repeat) loci showed a higher level of genetic diversity in the late-season weedy rice populations than in the early-season populations. In addition, a positive correlation was detected between the increased proportion of genetic diversity (ΔHe ) and genetic differentiation among the weedy rice populations, suggesting limited gene flow. Therefore, we conclude from this study that increased genetic diversity in the late-season weedy rice populations is probably caused by the higher ambient temperatures. This finding provides evidence for the possible association between genetic diversity and ambient temperatures.

The New Is Old: Novel Germination Strategy Evolved From Standing Genetic Variation in Weedy Rice.

Feralization of crop plants has aroused an increasing interest in recent years, not only for the reduced yield and quality of crop production caused by feral plants but also for the rapid evolution of novel traits that facilitate the evolution and persistence of weedy forms. Weedy rice (Oryza sativa f. spontanea) is a conspecific weed of cultivated rice, with separate and independent origins. The weedy rice distributed in eastern and northeastern China did not diverge from their cultivated ancestors by reverting to the pre-domestication trait of seed dormancy during feralization. Instead, they developed a temperature-sensing mechanism to control the timing of seed germination. Subsequent divergence in the minimum critical temperature for germination has been detected between northeastern and eastern populations. An integrative analysis was conducted using combinations of phenotypic, genomic and transcriptomic data to investigate the genetic mechanism underlying local adaptation and feralization. A dozen genes were identified, which showed extreme allele frequency differences between eastern and northeastern populations, and high correlations between allele-specific gene expression and feral phenotypes. Trancing the origin of potential adaptive alleles based on genomic sequences revealed the presence of most selected alleles in wild and cultivated rice genomes, indicating that weedy rice drew upon pre-existing, "conditionally neutral" alleles to respond to the feral selection regimes. The cryptic phenotype was exposed by activating formerly silent alleles to facilitate the transition from cultivation to wild existence, promoting the evolution and persistence of weedy forms.

Duplication and independent selection of cell-wall invertase genes GIF1 and OsCIN1 during rice evolution and domestication.

BACKGROUND: Various evolutionary models have been proposed to interpret the fate of paralogous duplicates, which provides substrates on which evolution selection could act. In particular, domestication, as a special selection, has played important role in crop cultivation with divergence of many genes controlling important agronomic traits. Recent studies have indicated that a pair of duplicate genes was often sub-functionalized from their ancestral functions held by the parental genes. We previously demonstrated that the rice cell-wall invertase (CWI) gene GIF1 that plays an important role in the grain-filling process was most likely subjected to domestication selection in the promoter region. Here, we report that GIF1 and another CWI gene OsCIN1 constitute a pair of duplicate genes with differentiated expression and function through independent selection. RESULTS: Through synteny analysis, we show that GIF1 and another cell-wall invertase gene OsCIN1 were paralogues derived from a segmental duplication originated during genome duplication of grasses. Results based on analyses of population genetics and gene phylogenetic tree of 25 cultivars and 25 wild rice sequences demonstrated that OsCIN1 was also artificially selected during rice domestication with a fixed mutation in the coding region, in contrast to GIF1 that was selected in the promoter region. GIF1 and OsCIN1 have evolved into different expression patterns and probable different kinetics parameters of enzymatic activity with the latter displaying less enzymatic activity. Overexpression of GIF1 and OsCIN1 also resulted in different phenotypes, suggesting that OsCIN1 might regulate other unrecognized biological process. CONCLUSION: How gene duplication and divergence contribute to genetic novelty and morphological adaptation has been an interesting issue to geneticists and biologists. Our discovery that the duplicated pair of GIF1 and OsCIN1 has experienced sub-functionalization implies that selection could act independently on each duplicate towards different functional specificity, which provides a vivid example for evolution of genetic novelties in a model crop. Our results also further support the established hypothesis that gene duplication with sub-functionalization could be one solution for genetic adaptive conflict.

Polyploidy origin of wheatgrass Douglasdeweya wangii (Triticeae, Poaceae): evidence from nuclear ribosomal DNA internal transcribed spacer and chloroplast trnL-F sequences.

To study hybrid speciation in wheatgrass Douglasdeweya wangii and to investigate the evolutionary pattern of nuclear ribosomal DNA (nrDNA) internal transcribed spacer sequences (ITSs) in allotetraploids, DNA sequence variation of ITSs and chloroplast trnL-F sequences from D. wangii and its putative donors were analyzed. The ITSs revealed that D. wangii had an StP genome composition. Most accessions of D. wangii had one parental ITS copy in their genome, one accession had two parental ITSs. The trnL-F sequences revealed an especially close relationship of Pseudoroegneria to all D. wangii individuals included, and the two accessions of Pseudoroegneria tauri (PI401324 and PI401331) were maternal candidates of the studied D. wangii individuals. Both of ITS and trnL-F trees suggested multiple origins and recurrent hybridization of D. wangii. Thus, the results suggested that: (1) the St and P genome in allotetraploid D. wangii were donated by Pseudoroegneria and Agropyron, respectively;(2) Pseudoroegneria was the maternal donor of D. wangii, and P. tauri 26 (accession PI401324) and P. tauri 27 (accession PI401331) were most likely the potential candidates of maternal donors; (3) D. wangii individuals studied here showed multiple origins and experienced recurrent hybridization; and (4) bidirectional interlocus concerted evolution of ITSs had occurred in most D. wangii accessions, while in one accession concerted evolution among homeologous loci did not occur.

Modelling pollen-mediated gene flow in rice: risk assessment and management of transgene escape.

Fast development and commercialization of genetically modified plants have aroused concerns of transgene escape and its environmental consequences. A model that can effectively predict pollen-mediated gene flow (PMGF) is essential for assessing and managing risks from transgene escape. A pollen-trap method was used to measure the wind-borne pollen dispersal in cultivated rice and common wild rice, and effects of relative humidity, temperature and wind speed on pollen dispersal were estimated. A PMGF model was constructed based on the pollen dispersal pattern in rice, taking outcrossing rates of recipients and cross-compatibility between rice and its wild relatives into consideration. Published rice gene flow data were used to validate the model. Pollen density decreased in a simple exponential pattern with distances to the rice field. High relative humidity reduced pollen dispersal distances. Model simulation showed an increased PMGF frequency with the increase of pollen source size (the area of a rice field), but this effect levelled off with a large pollen-source size. Cross-compatibility is essential when modelling PMGF from rice to its wild relatives. The model fits the data well, including PMGF from rice to its wild relatives. Therefore, it can be used to predict PMGF in rice under diverse conditions (e.g. different outcrossing rates and cross-compatibilities), facilitating the determination of isolation distances to minimize transgene escape. The PMGF model may be extended to other wind-pollinated plant species such as wheat and barley.

Antioxidant activity of oligosaccharide ester extracted from Polygala tenuifolia roots in senescence-accelerated mice.

The constituents of the ethanol extract from the root of Polygala tenuifolia Willd. (Polygalaceae) were investigated for antioxidant activity in senescence-accelerated mice. Consequently, two relevant samples were obtained, a fraction separated by macroporous resin (YZ-OE), and a major pure crystal of 3,6'-disinapoyl sucrose (DISS). Based on HPLC-ESI-MS analysis, the most constituents in the YZ-OE fraction from the extract of P. tenuifolia were oligosaccharide esters. The antioxidant activities of these two samples were evaluated using the accelerated senescence-prone, short-lived mice (SAMP) in vivo. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) were increased significantly in SAMP mice fed oligosaccharide esters (YZ-OE 50 mg/kg) and its constituents (DISS 50 mg/kg). However, the content of malondialdehyde (MDA) was increased in the blood and liver of SAMP mice. But when given YZ-OE, it could be decreased, by 44.3% and 47.5%, respectively, compared with the SAMP model. Results from the analyses indicated that the oligosaccharide esters (YZ-OE) from roots of P. tenuifolia had a high in vivo antioxidant activity.