RsGLK2.1-RsNF-YA9a module positively regulates the chlorophyll biosynthesis by activating RsHEMA2 in green taproot of radish.

Radish (Raphanus sativus L.) is an economically important and widely cultivated root vegetable crop. The coloration of the green skin and green flesh is an important trait influencing the nutrition and flavor quality in fruit radish. GOLDEN2-LIKEs (GLKs) play critically important roles in plastid development and chlorophyll biosynthesis in plants. However, the molecular mechanism underlying chlorophyll biosynthesis still remain elusive in green fruit radish taproot. Herein, the RsGLK2.1 gene exhibited higher expression level in taproot with a green skin (GS) and green flesh (GF) than that in taproot of the white or red radish genotypes. RsGLK2.1 is a nuclear transcription factor that has intrinsic transcriptional activation activity. Overexpression of RsGLK2.1 increased the total chlorophyll content of 20.68%-45.84% in radish leaves. Knockout of the RsGLK2.1 gene via CRISPR/Cas9 technology resulted in a significant decrease in the chlorophyll content. Overexpression of the RsGLK2.1 gene could restore the phenotype of the glk1glk2 mutant Arabidopsis. RsGLK2.1 was participated in regulating the chlorophyll biosynthesis by directly binding to the promoter of RsHEMA2 and activating its transcription. The interaction of RsNF-YA9a with RsGLK2.1 increased the transcriptional activity of the downstream gene RsHEMA2 under the light condition rather than the dark condition, indicating that both of them regulate the chlorophyll biosynthesis in a light-dependent manner of radish. Overall, these results provided insights into the molecular framework of the RsGLK2.1-RsNF-YA9a module, and could facilitate dissecting the regulatory mechanism underlying chlorophyll biosynthesis in green taproot of radish, and genetic improvement of quality traits in fruit radish breeding programs.

Oxidative stress response and programmed cell death guided by NAC013 modulate pithiness in radish taproots.

Radish, Raphanus sativus L., is an important root crop that is cultivated worldwide. Owing to its evolutionary proximity to Arabidopsis thaliana, radish can be used as a model root crop in research on the molecular basis of agronomic traits. Pithiness is a significant defect that reduces the production of radish with commercial value; however, traditional breeding to eliminate this trait has thus far been unsuccessful. Here, we performed transcriptomics and genotype-by-sequencing (GBS)-based quantitative trait locus (QTL) analyses of radish inbred lines to understand the molecular basis of pithiness in radish roots. The transcriptome data indicated that pithiness likely stems from the response to oxidative stress, leading to cell death of the xylem parenchyma during the root-thickening process. Subsequently, we narrowed down a list of candidates responsible for pithiness near a major QTL and found polymorphisms in a radish homologue of Arabidopsis ANAC013 (RsNAC013), an endoplasmic reticulum bound NAC transcription factor that is targeted to the nucleus to mediate the mitochondrial retrograde signal. We analysed the effects of polymorphisms in RsNAC013 using Arabidopsis transgenic lines overexpressing RsNAC013 alleles as well as in radish inbred lines bearing these alleles. This analysis indicated that non-synonymous variations within the coding sequence result in different levels of RsNAC013 activities, thereby providing a genetic condition for root pithiness. The elevated oxidative stress or hypoxia that activates RsNAC013 for mitochondrial signalling enhances this process. Collectively, this study serves as an exemplary case of translational research taking advantage of the extensive information available from a model organism.

The radish Ogura fertility restorer impedes translation elongation along its cognate CMS-causing mRNA.

The control of messenger RNA (mRNA) translation has been increasingly recognized as a key regulatory step for gene control, but clear examples in eukaryotes are still scarce. Nucleo-cytoplasmic male sterilities (CMS) represent ideal genetic models to dissect genetic interactions between the mitochondria and the nucleus in plants. This trait is determined by specific mitochondrial genes and is associated with a pollen sterility phenotype that can be suppressed by nuclear genes known as restorer-of-fertility (Rf). In this study, we focused on the Ogura CMS system in rapeseed and showed that reversion to male sterility by the PPR-B fertility restorer (also called Rfo) occurs through a specific translation inhibition of the mitochondria-encoded CMS-causing mRNA orf138 We also demonstrate that PPR-B binds within the coding sequence of orf138 and acts as a ribosome blocker to specifically impede translation elongation along the orf138 mRNA. Rfo is the first recognized fertility restorer shown to act this way. These observations will certainly facilitate the development of synthetic fertility restorers for CMS systems in which efficient natural Rfs are lacking.

Protocol of European Radish (Raphanus sativus L.) Microspore Culture for Doubled Haploid Plant Production.

Here, we describe the first protocol of European radish (Raphanus sativus L. subsp. sativus convar. radicula) for obtaining doubled haploid plants through in vitro microspore culture, in which the full cycle of doubled haploid formation was successfully achieved. Using this protocol, a yield of up to eight embryoids per Petri dish can be obtained. Effectiveness of this protocol was confirmed for several genotypes of European radish.

Genome-wide transcriptome analysis of microspore abortion initiation in radish (Raphanus sativus L.).

The use of male sterile lines is one of the ideal means in hybrid seed production. Despite the widespread application of Ogura cytoplasmic male sterile (CMS) lines, the molecular mechanisms remain largely unknown. In this study, histological analyses of floral buds from a CMS line 40MA and its corresponding maintainer line 40MB were conducted, which indicate that microspore abortion was initiated shortly after the tetrad stage. RNA sequencing was performed to analyze the transcriptomes of floral buds from the tetrad stage and the early microspore stages of these two lines. More than 39 million clean reads were generated for each library, and the portions mapped to the reference genome were all above 70.60%. To further analyze the differentially expressed genes (DEGs), the samples were grouped into four pairs, of which the pair of 40MA and 40MB at the early microspore stage showed the most DEGs (5100 members). According to the abnormal appearance of the tapetum cells in 40MA, a series of tapetum development related genes were screened and analyzed. In addition, a total of 623 genes with differential expressions in the tetrad stage, but not in the early microspore stage between the two lines were filtered as the microspore abortion initiation related candidates. Twelve genes were selected to validate the sequencing result by quantitative RT-PCR. In this study, we identified a number of candidate genes involved in the initiation of microspore degeneration, which may provide a new perspective to unravel the molecular mechanism of Ogura CMS.

Effect of co-application of wastewater and freshwater on the physiological properties and trace element content in Raphanus sativus: soil contamination and human health.

Nowadays, the use of wastewater for crop irrigation is increasing at global scale mainly due to freshwater scarcity and economic benefits. However, the presence of different types of pollutants including the trace elements (TEs) poses a serious threat to environmental and human health. This pot study evaluated the effect of alone and mixed irrigation water [wastewater (WW) with canal water (CW) and tube-well water (TW)] on TEs build-up in the soil, their soil-plant transfer and allied health hazards in District Vehari. The WW samples were mainly contaminated with Cd (0.03 mg/L), Cr (1.45 mg/L), Cu (0.35 mg/L) and Ni (0.40 mg/L). The CW contained high levels of Cr and Fe, while TW was contaminated with Pb and Cr. In soil, the concentrations of Cd, Fe and Mn exceeded their respective limit values for all the treatments. Among all the treatments, TEs concentration was found highest in WW-3 irrigated soil. Application of all the treatments resulted in TEs (Cu, 60.1 mg/kg; Cd, 8.2 mg/kg; Ni, 39.9 mg/kg; Fe, 4411 mg/kg; Zn, 111.3 mg/kg and Pb, 44.5 mg/kg) accumulation mainly in the edible parts of Raphanus sativus. Compared to other treatments, TW and TW + CW irrigated plants accumulated higher levels of TEs. Results showed linear trends among TEs accumulation and alterations in physiological attributes of R. sativus. High TEs accumulation in TW irrigated treatments (TW + WW-1 and TW + CW) caused maximum H2O2 production, lipid peroxidation and decline in plant pigments. Risk assessment parameters showed both carcinogenic and non-carcinogenic risks for all the irrigation treatments due to high TEs contents in edible tissues. It is concluded that alone or combined application of WW, TW and CW is not fit for vegetable irrigation, in the studied area, due to high TEs contents.

Reconsidering Hydrosols as Main Products of Aromatic Plants Manufactory: The Lavandin (Lavandula intermedia) Case Study in Tuscany.

: The present work evaluates for the first time two Lavandin (Lavandula × intermedia Emeric ex Loisel.) aromatic waters obtained from different plant organs, the flowers and the stems. Both extracts were analysed by GC-MS, which indicates semi-quantitative differences between the major metabolites including linalool, 1,8-cineole, camphor, linalyl acetate and 4-terpineol. 1H-NMR and LC-MS investigation confirmed the presence of these compounds. Moreover, behavioural tests with the food insect pest Tribolium confusum (Coleoptera Tenebrionidae) showed a good repellency for both hydrosols extracts with RD50 values of 3.6 and 3.3 µL cm-2 for the flowers and stems, respectively; at the higher concentrations, however, the hydrosol extract from the flowers is expected to be more effective than the one from the stems. The effect of the flowers and stems aromatic water of Lavandin on seed germination of Raphanus sativus was also evaluated. Results showed that seed germination was completely inhibited by flowers hydrolate, having a possible application as natural herbicide. The overall experience with these Lavandin extracts indicates the potential of improved hydrolates to become the main distillation products, rather than by-products, of the aromatic plants manufacturing; this stimulates further discussions about the potential positive impacts that such a shift could have in the context of ecopharmacognosy.

Quantitative Trait Loci (QTLs) Associated with Microspore Culture in Raphanus sativus L. (Radish).

The radish is a highly self-incompatible plant, and consequently it is difficult to produce homozygous lines. Bud pollination in cross-fertilization plants should be done by opening immature pollen and attaching pollen to mature flowers. It accordingly takes a lot of time and effort to develop lines with fixed alleles. In the current study, a haploid breeding method has been applied to obtain homozygous plants in a short period of time by doubling chromosomes through the induction of a plant body in the haploid cells, in order to shorten the time to breed inbred lines. We constructed genetic maps with an F1 population derived by crossing parents that show a superior and inferior ability to regenerate microspores, respectively. Genetic maps were constructed from the maternal and parental maps, separately, using the two-way pseudo-testcross model. The phenotype of the regeneration rate was examined by microspore cultures and a quantitative trait loci (QTL) analysis was performed based on the regeneration rate. From the results of the culture of microspores in the F1 population, more than half of the group did not regenerate, and only a few showed a high regeneration rate. A total of five significant QTLs were detected in the F1 population, and five candidate genes were found based on the results. These candidate genes are divided into two classes, and appear to be related to either PRC2 subunits or auxin synthesis.

Bioinformatics Analysis of the Lipoxygenase Gene Family in Radish (Raphanus sativus) and Functional Characterization in Response to Abiotic and Biotic Stresses.

Lipoxygenases (LOXs) are non-heme iron-containing dioxygenases involved in many developmental and stress-responsive processes in plants. However, little is known about the radish LOX gene family members and their functions in response to biotic and abiotic stresses. In this study, we completed a genome-wide analysis and expression profiling of RsLOX genes under abiotic and biotic stress conditions. We identified 11 RsLOX genes, which encoded conserved domains, and classified them in 9-LOX and 13-LOX categories according to their phylogenetic relationships. The characteristic structural features of 9-LOX and 13-LOX genes and the encoded protein domains as well as their evolution are presented herein. A qRT-PCR analysis of RsLOX expression levels in the roots under simulated drought, salinity, heat, and cold stresses, as well as in response to a Plasmodiophora brassicae infection, revealed three tandem-clustered RsLOX genes that are involved in responses to various environmental stresses via the jasmonic acid pathway. Our findings provide insights into the evolution and potential biological roles of RsLOXs related to the adaptation of radish to stress conditions.

Genome-wide characterization and evolutionary analysis of heat shock transcription factors (HSFs) to reveal their potential role under abiotic stresses in radish (Raphanus sativus L.).

BACKGROUND: Abiotic stresses due to climate change pose a great threat to crop production. Heat shock transcription factors (HSFs) are vital regulators that play key roles in protecting plants against various abiotic stresses. Therefore, the identification and characterization of HSFs is imperative to dissect the mechanism responsible for plant stress responses. Although the HSF gene family has been extensively studied in several plant species, its characterization, evolutionary history and expression patterns in the radish (Raphanus sativus L.) remain limited. RESULTS: In this study, 33 RsHSF genes were obtained from the radish genome, which were classified into three main groups based on HSF protein domain structure. Chromosomal localization analysis revealed that 28 of 33 RsHSF genes were located on nine chromosomes, and 10 duplicated RsHSF genes were grouped into eight gene pairs by whole genome duplication (WGD). Moreover, there were 23 or 9 pairs of orthologous HSFs were identified between radish and Arabidopsis or rice, respectively. Comparative analysis revealed a close relationship among radish, Chinese cabbage and Arabidopsis. RNA-seq data showed that eight RsHSF genes including RsHSF-03, were highly expressed in the leaf, root, cortex, cambium and xylem, indicating that these genes might be involved in plant growth and development. Further, quantitative real-time polymerase chain reaction (RT-qPCR) indicated that the expression patterns of 12 RsHSF genes varied upon exposure to different abiotic stresses including heat, salt, and heavy metals. These results indicated that the RsHSFs may be involved in abiotic stress response. CONCLUSIONS: These results could provide fundamental insights into the characteristics and evolution of the HSF family and facilitate further dissection of the molecular mechanism responsible for radish abiotic stress responses.

Early Response of Radish to Heat Stress by Strand-Specific Transcriptome and miRNA Analysis.

Radish is a crucial vegetable crop of the Brassicaceae family with many varieties and large cultivated area in China. Radish is a cool season crop, and there are only a few heat tolerant radish varieties in practical production with little information concerning the related genes in response to heat stress. In this work, some physiological parameter changes of young leaves under short-term heat stress were detected. Furthermore, we acquired 1802 differentially expressed mRNAs (including encoding some heat shock proteins, heat shock factor and heat shock-related transcription factors), 169 differentially expressed lncRNAs and three differentially expressed circRNAs (novel_circ_0000265, novel_circ_0000325 and novel_circ_0000315) through strand-specific RNA sequencing technology. We also found 10 differentially expressed miRNAs (ath-miR159b-3p, athmiR159c, ath-miR398a-3p, athmiR398b-3p, ath-miR165a-5p, ath-miR169g-3p, novel_86, novel_107, novel_21 and ath-miR171b-3p) by small RNA sequencing technology. Through function prediction and enrichment analysis, our results suggested that the significantly possible pathways/complexes related to heat stress in radish leaves were circadian rhythm-plant, photosynthesis-antenna proteins, photosynthesis, carbon fixation in photosynthetic organisms, arginine and proline metabolism, oxidative phosphorylation, peroxisome and plant hormone signal transduction. Besides, we identified one lncRNA-miRNA-mRNAs combination responsive to heat stress. These results will be helpful for further illustration of molecular regulation networks of how radish responds to heat stress.

Evaluating resistant brassica trap crops to manage Heterodera schachtii (Schmidt) infestations in eastern England.

BACKGROUND: The beet cyst nematode (BCN), Heterodera schachtii Schmidt, is a plant parasitic nematode that causes severe yield losses in sugar beet. Resistant brassicas (radish and mustard) have been bred to be planted after harvest of the main crop, for example a cereal, and encourage BCN juvenile hatching. The resistant plants stimulate juvenile hatching but are not suitable hosts. Juveniles are unable to complete their lifecycle and thus populations are lowered. This research aimed to investigate the effectiveness of a range of brassicas in terms of BCN control when grown in infested fields in eastern England. RESULTS: Experiments used four different radish cultivars, which differed in their resistance to BCN, and one resistant mustard variety. Field experiments were sown in early September in 2016 and 2017. Significant reductions in BCN populations were found only following resistant mustard and the radish with the greatest resistance level. CONCLUSIONS: Further research is needed to understand how best to utilize brassicas and whether they are economically viable when alternative management options for BCN are available. Time of planting may be crucial to fully achieve their BCN-reducing potential. © 2018 Society of Chemical Industry.

2,4-D and dicamba resistance mechanisms in wild radish: subtle, complex and population specific?

Background and Aims: Resistance to synthetic auxin herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D) is increasing in weed populations worldwide, which is of concern given the recent introduction of synthetic auxin-resistant transgenic crops. Due to the complex mode of action of the auxinic herbicides, the mechanisms of evolved resistance remain largely uncharacterized. The aims of this study were to assess the level of diversity in resistance mechanisms in 11 populations of the problem weed Raphanus raphanistrum, and to use a high-throughput, whole-genome transcriptomic analysis on one resistant and one susceptible population to identify important changes in gene expression in response to 2,4-D. Methods: Levels of 2,4-D and dicamba (3,6-dichloro-2-methoxybenzoic acid) resistance were quantified in a dose-response study and the populations were further screened for auxin selectivity, 2,4-D translocation and metabolism, expression of key 2,4-D-responsive genes and activation of the mitogen-activated proein kinase (MAPK) pathway. Potential links between resistance levels and mechanisms were assessed using correlation analysis. Key Results: The transcriptomic study revealed early deployment of the plant defence response in the 2,4-D-treated resistant population, and there was a corresponding positive relationship between auxinic herbicide resistance and constitutive MAPK phosphorylation across all populations. Populations with shoot-wide translocation of 2,4-D had similar resistance levels to those with restricted translocation, suggesting that reduced translocation may not be as strong a resistance mechanism as originally thought. Differences in auxin selectivity between populations point to the likelihood of different resistance-conferring alterations in auxin signalling and/or perception in the different populations. Conclusions: 2,4-D resistance in wild radish appears to result from subtly different auxin signalling alterations in different populations, supplemented by an enhanced defence response and, in some cases, reduced 2,4-D translocation. This study highlights the dangers of applying knowledge generated from a few populations of a weed species to the species as a whole.

DNA double-strand breaks promote endoreduplication in radish cotyledon.

KEY MESSAGE: DSBs differently affect endoreduplication and organ size in radish cotyledons and hypocotyls in different light conditions, suggesting that DSBs-mediated endoreduplication varies based on different developmental and environmental cues. Endoreduplication induced by DNA double strand breaks (DSBs) in Arabidopsis thaliana roots and cultured cells has been reported in recent years. In this study, we investigated whether DSBs-mediated endoreduplication also occurs in other tissues, such as cotyledons and hypocotyls of radish (Raphanus sativus var. longipinnatus) plants. To induce DSBs, UV irradiation and Zeocin treatment were applied to in vitro-cultured radish seedlings, and ploidy distribution of the treated tissues was analyzed by flow cytometry. Consequently, frequencies of the higher ploidy (8C) cells and cycle values in the cotyledon tissues increased with increasing doses of UV irradiation and concentrations of Zeocin, irrespective of light conditions. UV-stimulated endoreduplication was also observed in four Brassica species. In hypocotyls, UV treatments decreased the frequencies of higher ploidy (32C) cells and cycle values in dark-grown seedlings, whereas Zeocin treatments increased the frequencies of higher ploidy (16C and 32C) cells and cycle values in light- and dark-grown seedlings. Among the treatments, organ sizes did not simply correlate with cycle values. The effects of treatments on endoreduplication and organ size differed based on organ and light conditions, indicating that DSBs-mediated endoreduplication may involve a multifaceted response to different developmental and environmental cues.

Deciphering physio-biochemical, yield, and nutritional quality attributes of water-stressed radish (Raphanus sativus L.) plants grown from Zn-Lys primed seeds.

Water shortage appears to be expedited under the current climate change scenario worldwide. The present work was aimed to investigate the effects of zinc-chelated lysine (Zn-Lys) on germination and yield of water stressed radish plants. The research was comprised of two studies where the effect of Zn-Lys seed priming on germination attributes under PEG-induced water stress was investigated in the first experiment. In the second experiment, growth, physio-biochemical, and yield responses of water-stressed radish plants raised from Zn-Lys primed seeds were recorded. The seeds pre-conditioned with 0, 1.5, 3, 4.5, or 6 mg kg-1 of Zn-Lys was grown in petri-dishes and pots. Priming treatments significantly improved the germination attributes under water stress. Plants raised from primed seeds exhibited significant improvements in plant biomass production, leaf photosynthetic pigments, final root yield, and nutritional quality. Furthermore, the activities of superoxide dismutase (SOD) and peroxidase (POD) were increased, while the melondialdehyde (MDA) content decreased. Root flavonoids, ascorbic acid, carotenoids, protein, carbohydrates, fiber and lysine content were significantly improved due to Zn-Lys seed priming, both under water-stressed and non-stressed conditions. Moreover, plant's mineral nutrients such as K and Ca as well as Mg, Fe, P, and Zn of final harvested roots were also improved due to Zn-Lys seed priming. Overall, for the induction of drought tolerance and nutritional quality, Zn-Lys regimes of 3 and 4.5 mg kg-1 were most effective. It can be inferred that the Zn-Lys priming maintained a potential balance of nutrient uptake and translocation by preventing drought-induced lipid peroxidation of membranes.

Investigating long-term effect of nanoparticles on growth of Raphanus sativus plants: a trans-generational study.

In the past decade, there has been an unprecedented growth in the application of nanoparticles (NPs) worldwide. Even though the acute toxicity of CuO and ZnO NPs to plants has been investigated in past, the trans-generational effects of these NPs in the environment are still unknown. In this study, we investigated whether the treatment of radish plants with CuO and ZnO NPs as single compound and as a binary mixture (10, 100 and 1000 mg/Kg soil) through their lifecycle would affect the seed quality and the development of second-generation seedlings or not. Results showed reduced root length, shoot length and biomass in F1 seedlings of NPs treated plants. The treated F1 seeds had smaller seed weight with accumulated Cu and Zn. The effect of toxic interaction between CuO and ZnO on plant growth was antagonistic in nature. Evaluation of the trans-generational impact is important to understand the long-term effect of NPs on the environment.

Sink-Source Balance and Down-Regulation of Photosynthesis in Raphanus sativus: Effects of Grafting, N and CO2.

To clarify whether excessive accumulation of total non-structural carbohydrate (TNC) causes down-regulation of photosynthesis in Raphanus sativus, we manipulated sink-source balance to alter TNC levels in source leaves and examined its effects on photosynthetic characteristics, whole-plant biomass allocation and anatomical characteristics of leaves and petioles. Comet and Leafy varieties with large and small hypocotyls were reciprocally grafted to change hypocotyl sink strength. They were grown at high or low nitrogen (N) availability and at elevated or ambient CO2. Maximum photosynthetic rate, which was highly correlated with Rubisco and leaf N contents, was hardly correlated with TNC across the grafting combinations and growth conditions. Biomass allocation to petioles and hypocotyls and accumulation of TNC in each organ were significantly higher at low N. TNC and structural carbohydrates such as cellulose and hemicellulose were higher and the proportion of intercellular air space in source leaves was lower at low N and elevated CO2. We conclude that excess TNC does not cause severe down-regulation of photosynthesis, and cell walls and petioles are also major carbohydrate sinks responding to changes in sink-source and carbon-nitrogen balances, which contribute to alleviating further accumulation of TNC to avoid its negative effects in source leaves.

Measurement of thermal properties of white radish (R. raphanistrum) using easily constructed probes.

Thermal properties are necessary for the design and control of processes and storage facilities of food materials. This study proposes the measurement of thermal properties using easily constructed probes with specific heat capacity calculated, as opposed to the use of Differential Scanning Calorimeter (DSC) or other. These probes were constructed and used to measure thermal properties of white radish in the temperature range of 80-20°C and moisture content of 91-6.1% wb. Results showed thermal properties were within the range of 0.71-0.111 Wm-1 C-1 for thermal conductivity, 1.869×10-7-0.72×10-8 m2s-1 for thermal diffusivity and 4.316-1.977 kJ kg-1C-1for specific heat capacity. These results agree with reports for similar products studied using DSC and commercially available line heat source probes. Empirical models were developed for each property through linear multiple regressions. The data generated would be useful in modeling and control of its processing and equipment design.

Can selection on a male mating character result in evolutionary change? A selection experiment on California wild radish, Raphanus sativus.

PREMISE OF THE STUDY: Whenever more pollen grains arrive on stigmas than necessary to fertilize ovules, sexual selection is possible. However, the role of sexual selection remains controversial, in part because of lack of evidence on genetic bases of traits and the response of relevant characters to selection. METHODS: In an experiment with Raphanus sativus, we selected on tendency to sire seeds in the stylar or basal regions of fruits. This character is likely related to pollen tube growth rate, and seed position affects rates of abortion and seed predation. We measured differences among families in seed siring and related characters and evaluated responses to selection. KEY RESULTS: All replicates showed strong effects of pollen donor family on proportion of seeds sired per fruit in mixed pollinations. Most also showed effects of pollen donor family on number of pollen grains per flower and pollen diameter. Two of four replicates showed a response to selection on position of seeds sired. In responding replicates, we found trade-offs in pollen grain size and number; plants with larger pollen grains sired more seeds in the basal region. CONCLUSIONS: Our data suggest a genetic basis for pollen donor ability to sire seeds in competition. The significant response to selection in two replicates shows that position of seeds sired can respond to selection. Thus, all components for sexual selection to occur and affect traits are present. Variation in results among replicates might be due to changes in greenhouse conditions. Environmental effects may contribute to the maintenance of variation in these fitness-related characters.

De novo sequencing of root transcriptome reveals complex cadmium-responsive regulatory networks in radish (Raphanus sativus L.).

Cadmium (Cd) is a nonessential metallic trace element that poses potential chronic toxicity to living organisms. To date, little is known about the Cd-responsive regulatory network in root vegetable crops including radish. In this study, 31,015 unigenes representing 66,552 assembled unique transcripts were isolated from radish root under Cd stress based on de novo transcriptome assembly. In all, 1496 differentially expressed genes (DEGs) consisted of 3579 transcripts were identified from Cd-free (CK) and Cd-treated (Cd200) libraries. Gene Ontology and pathway enrichment analysis indicated that the up- and down-regulated DEGs were predominately involved in glucosinolate biosynthesis as well as cysteine and methionine-related pathways, respectively. RT-qPCR showed that the expression profiles of DEGs were in consistent with results from RNA-Seq analysis. Several candidate genes encoding phytochelatin synthase (PCS), metallothioneins (MTs), glutathione (GSH), zinc iron permease (ZIPs) and ABC transporter were responsible for Cd uptake, accumulation, translocation and detoxification in radish. The schematic model of DEGs and microRNAs-involved in Cd-responsive regulatory network was proposed. This study represents a first comprehensive transcriptome-based characterization of Cd-responsive DEGs in radish. These results could provide fundamental insight into complex Cd-responsive regulatory networks and facilitate further genetic manipulation of Cd accumulation in root vegetable crops.