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In this study, the effects of the allelochemical coumarin through a metabolomic, proteomic and morpho-physiological approach in Arabidopsis adult plants (25days old) were investigated. Metabolomic analysis evidenced an increment of amino acids and a high accumulation of soluble sugars, after 6days of coumarin treatment. This effect was accompanied by a strong decrease on plant fresh and dry weights, as well as on total protein content. On the contrary, coumarin did not affect leaf number but caused a reduction in leaf area. An alteration of water status was confirmed by a reduction of relative water content and an increase in leaf osmotic potential. Moreover, coumarin impaired plant bio-membranes through an increase of lipid peroxidation and H 2 O 2 content suggesting that coumarin treatment might induce oxidative stress. Coumarin reduced the effective quantum yield of the photosystem II, the energy dissipation in the form of heat, the maximum PSII efficiency, the coefficient of the photochemical quenching and the estimated electron transport rate, while it significantly stimulated the fluorescence emission and the coefficient of the non photochemical quenching. Finally, the proteomic characterization of coumarin-treated plants revealed a down-regulation of the ROS detoxifying proteins, responsible of oxidative damage and consequently of physiological cascade effects., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Dittrichia viscosa (L.) W. Greuter is a pioneer species belonging to the Compositae family. It is widespread in the Mediterranean basin, where it is considered invasive. It is a source of secondary metabolites, playing an important ecological role. D. viscosa plant extracts showed a phytotoxic activity on several physiological processes of different species. In the current study, the allelopathic potential of D. viscosa VOCs, released by its foliage, was evaluated on seed germination and root growth of lettuce. The VOCs effect was also studied on lettuce adult plants in microcosm systems, which better mimicked the open field conditions. D. viscosa VOCs inhibited both seed germination and root growth of lettuce. The VOCs composition revealed a large presence of terpenoids, responsible of the effects observed. Moreover, D. viscosa VOCs caused an alteration on plant water status accompanied by oxidative damages and photoinhibition on lettuce adult plants., Competing Interests: The authors have declared that no competing interests exist.

Boron (B) is an essential plant nutrient, but when present in excess it is toxic. Morphological measurements were made to assess the impact of B toxicity on the growth of two different tomato hybrids, Losna and Ikram. Contrasting long and short-term B responses in these tomato hybrids, were observed. Losna showed less toxicity symptoms, maintaining higher growth and showing much less B content in both root and shoot tissues compared to Ikram. Root morphological differences did not explain the tolerance between the two hybrids. Under excess B supply, a significant inhibition on net nitrate uptake rate was observed in Ikram, but not in Losna. This effect may be explained by a decrease of nitrate transporter transcripts in Ikram, which was not measured in Losna. There was a different pattern of B transporter expression in two tomatoes and this can explain the contrasting tolerance observed. Indeed, Losna may be able to exclude or efflux B resulting in less accumulation in the shoot. Particularly, SlBOR4 expression showed significant differences between the tomato hybrids, with higher expression in Losna explaining the improved B-tolerance., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Nitrogen (N) supply usually limits crop production and optimizing N-use efficiency (NUE) to minimize fertilizer loss is important. NUE is a complex trait that can be dissected into crop N uptake from the soil (NUpE) and N utilization (NUtE). We compared NUE in 14 genotypes of three week old tomatoes grown in sand or hydroponic culture supplied with nitrate (NO3(-)). Culture method influenced measured NUE for some cultivars, but Regina Ostuni (RO) and UC82 were consistently identified as high and low NUE genotypes. To identify why these genotypes had contrasting NUE some traits were compared growing under 0.1 and 5 mM NO3(-) supply. UC82 showed greater root (15)NO3(-) influx at low and high supply, and stronger SlNRT2.1/NAR2.1 transporter expression under low supply when compared with RO. Conversely, RO showed a higher total root length and thickness compared to UC82. Compared with UC82, RO showed higher shoot SlNRT2.3 expression and NO3(-) storage at high supply, but similar NO3(-) reductase activity. After N-starvation, root cell electrical potentials of RO were significantly more negative than UC82, but nitrate elicited similar responses in both root types. Overall for UC82 and RO, NUtE may play a greater role than NUpE for improved NUE., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Current phylogenetic sampling reveals that dioecy and an XY sex chromosome pair evolved once, or possibly twice, in the genus Asparagus Although there appear to be some lineage-specific polyploidization events, the base chromosome number of 2n = 2× = 20 is relatively conserved across the Asparagus genus. Regardless, dioecious species tend to have larger genomes than hermaphroditic species. Here, we test whether this genome size expansion in dioecious species is related to a polyploidization and subsequent chromosome fusion, or to retrotransposon proliferation in dioecious species. We first estimate genome sizes, or use published values, for four hermaphrodites and four dioecious species distributed across the phylogeny, and show that dioecious species typically have larger genomes than hermaphroditic species. Utilizing a phylogenomic approach, we find no evidence for ancient polyploidization contributing to increased genome sizes of sampled dioecious species. We do find support for an ancient whole genome duplication (WGD) event predating the diversification of the Asparagus genus. Repetitive DNA content of the four hermaphroditic and four dioecious species was characterized based on randomly sampled whole genome shotgun sequencing, and common elements were annotated. Across our broad phylogenetic sampling, Ty-1 Copia retroelements, in particular, have undergone a marked proliferation in dioecious species. In the absence of a detectable WGD event, retrotransposon proliferation is the most likely explanation for the precipitous increase in genome size in dioecious Asparagus species., (Copyright © 2016 Harkess et al.)

Spatial and temporal fluctuations in nitrate (NO3(-)) availability are very common in agricultural soils. Therefore, understanding the molecular and physiological mechanisms involved in regulating NO3(-) uptake in regions along the primary root is important for improving the NO3(-) uptake efficiency (NUpE) in crops. Different regions of maize primary root, named R1, R2 and R3, NO3(-) starved for 3 days, were exposed to 50 μM NO3(-). Electrophysiological measurements (membrane potential and H(+) and NO3(-) fluxes) and NPF6.3, NRT2.1, NAR2.1, MHA1, MHA3 and MHA4 gene expression analyses were carried out. The results confirmed variable spatial and temporal patterns in both NO3(-) and H(+) fluxes and gene expression along the primary maize root. A significant correlation (P = 0.0023) between nitrate influx and gene transcript levels was observed only when NAR2.1 and NRT2.1 co-expression were considered together, showing for the first time the NRT2.1/NAR2.1 functional interaction in nitrate uptake along the root axis. Taken together these results suggest differing roles among the primary root regions, in which the apical part seem to be involved to sensing and signaling in contrast with the basal root which appears to be implicate in nitrate acquisition., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

In a field experiment conducted in a Mediterranean area of inner Sicily, durum wheat was inoculated with plant growth-promoting rhizobacteria (PGPR), with arbuscular mycorrhizal fungi (AMF), or with both to evaluate their effects on nutrient uptake, plant growth, and the expression of key transporter genes involved in nitrogen (N) and phosphorus (P) uptake. These biotic associations were studied under either low N availability (unfertilized plots) and supplying the soil with an easily mineralizable organic fertilizer. Regardless of N fertilization, at the tillering stage, inoculation with AMF alone or in combination with PGPR increased the aboveground biomass yield compared to the uninoculated control. Inoculation with PGPR enhanced the aboveground biomass yield compared to the control, but only when N fertilizer was added. At the heading stage, inoculation with all microorganisms increased the aboveground biomass and N. Inoculation with PGPR and AMF+PGPR resulted in significantly higher aboveground P compared to the control and inoculation with AMF only when organic N was applied. The role of microbe inoculation in N uptake was elucidated by the expression of nitrate transporter genes. NRT1.1, NRT2, and NAR2.2 were significantly upregulated by inoculation with AMF and AMF+PGPR in the absence of organic N. A significant down-regulation of the same genes was observed when organic N was added. The ammonium (NH4 (+)) transporter genes AMT1.2 showed an expression pattern similar to that of the NO3 (-) transporters. Finally, in the absence of organic N, the transcript abundance of P transporters Pht1 and PT2-1 was increased by inoculation with AMF+PGPR, and inoculation with AMF upregulated Pht2 compared to the uninoculated control. These results indicate the soil inoculation with AMF and PGPR (alone or in combination) as a valuable option for farmers to improve yield, nutrient uptake, and the sustainability of the agro-ecosystem.

Coumarin is a natural compound well known for its phytotoxic potential. In the search for new herbicidal compounds to manage weeds, three synthetic derivatives bearing the coumarin scaffold (1-3), synthesized by a carbonylative organometallic approach, were in vitro assayed on germination and root growth of two noxious weeds, Amaranthus retroflexus and Echinochloa crus-galli. Moreover, the synthetic coumarins 1-3 were also in vitro assayed on seedlings growth of the model species Arabidopsis thaliana to identify the possible physiological targets. All molecules strongly affected seed germination and root growth of both weeds. Interestingly, the effects of synthetic coumarins on weed germination were higher than template natural coumarin, pointing out ED50 values ranging from 50-115 µM. Moreover, all synthetic coumarins showed a strong phytotoxic potential on both Arabidopsis shoot and root growth, causing a strong reduction in shoot fresh weight (ED50 values ≤ 60 µM), accompanied by leaf development and a decrease in pigment content. Furthermore, they caused a strong alteration in root growth (ED50 values ≤ 170 µM) and morphology with evident alterations in root tip anatomy. Taken together, our results highlight the promising potential herbicidal activity of these compounds.

Sex chromosomes have evolved independently in phylogenetically diverse flowering plant lineages. The genes governing sex determination in dioecious species remain unknown, but theory predicts that the linkage of genes influencing male and female function will spur the origin and early evolution of sex chromosomes. For example, in an XY system, the origin of an active Y may be spurred by the linkage of female suppressing and male promoting genes. Garden asparagus (Asparagus officinalis) serves as a model for plant sex chromosome evolution, given that it has recently evolved an XX/XY sex chromosome system. In order to elucidate the molecular basis of gender differences and sex determination, we used RNA-sequencing (RNA-Seq) to identify differentially expressed genes between female (XX), male (XY) and supermale (YY) individuals. We identified 570 differentially expressed genes, and showed that significantly more genes exhibited male-biased than female-biased expression in garden asparagus. In the context of anther development, we identified genes involved in pollen microspore and tapetum development that were specifically expressed in males and supermales. Comparative analysis of genes in the Arabidopsis thaliana, Zea mays and Oryza sativa anther development pathways shows that anther sterility in females probably occurs through interruption of tapetum development before microspore meiosis., (© 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.)

A novel class of potential herbicides, the 3-(methoxycarbonylmethylene) isobenzofuran-1-imines, has been discovered. The herbicidal activity has been tested on two particular molecules, (E)-methyl 2-[3-(butylimino)isobenzofuran-1(3H)-ylidene]acetate (1) and (E)-methyl 2-phenyl-2-[3-(phenylimino)isobenzofuran-1(3H)-ylidene]acetate (2), prepared by palladium-catalyzed oxidative carbonylation of 2-alkynylbenzamides. Both compounds 1 and 2 showed a strong phytotoxic effect on both shoot and root systems of Arabidopsis thaliana. The effects observed on the shoot were similar for both molecules, but while compound 1 showed a stronger effect on root parameters (such as primary root length, root hair and density, showing lower ED50 values), compound 2 caused important malformations in root morphology. Our results indicate that these molecules are very promising synthetic herbicides.

Single nucleotide polymorphisms (SNPs) and simple sequence repeats (SSR) are abundant and evenly distributed co-dominant molecular markers in plant genomes. SSRs are valuable for marker assisted breeding and positional cloning of genes associated traits of interest. Although several high throughput platforms have been developed to identify SNP and SSR markers for analysis of segregant plant populations, breeding in garden asparagus (Asparagus officinalis L.) has been limited by a low content of such markers. In this study massively parallel GS-FLX pyro-sequencing technology (454 Life Sciences) has been used to sequence and compare transcriptome from two genotypes: a rust tolerant male (1770) and a susceptible female (G190). A total of 122,963 and 99,368 sequence reads, with an average length of 245.7bp, have been recovered from accessions 1770 and 190 respectively. A computational pipeline has been used to predict and visually inspect putative SNPs and SSR sequences. Analysis of Gene Ontology (GO) slim annotation assignments for all assembled uniscripts indicated that the 24,403 assemblies represent genes from a broad array of functions. Further, over 1800 putative SNPs and 1000 SSRs were detected. One hundred forty-four SNPs together with 60 selected SSRs were validated and used to develop a preliminary genetic map by using a large BC(1) population, derived from 1770 and G190. The abundance of SNPs and SSRs provides a foundation for the development of saturated genetic maps and their utilization in assisted asparagus breeding programs., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Coumarin effects on gravitropic responses of Arabidopsis thaliana roots were here evaluated. Coumarin alone did not cause any alteration on gravitropic response showing a behavior similar to control plants. In contrast, TIBA and NPA, two auxin transport inhibitors, strongly modified root gravitropic responses. The addition of coumarin to the medium together with TIBA or NPA partially restored the effect of both inhibitors. Simultaneously, a semi-quantitative evaluation of ROS distribution was performed on root tips. TIBA and NPA caused a wide distribution of O 2(-), ROS oxidant species, around the root tip which disappeared with coumarin addition to both treatments, restoring ROS localized distribution. These results indicated a strong correlation between ROS distribution and coumarin-mediated recovery of root gravitropism.

The spatial variability of the nitrate (NO₃-) uptake along the maize primary root axis was investigated at physiological and molecular levels. Net NO₃- uptake rate (NNUR) and its kinetic parameters, together with the gene expression of a high-affinity NO₃- transporter (NRT2.1), were evaluated. The activity and the expression of plasma membrane H⁺ -ATPase (PM H⁺ -ATPase), key enzyme in plant nutrition, were also analysed. The NNUR showed a heterogeneous spatial pattern along the root, where the regions closer to the root tip early exhibited higher capacity to absorb NO₃- than the basal regions, because of a higher maximum NNUR and faster induction of the inducible high-affinity transport system (iHATS), the presence of the high-affinity transport system (HATS) also at external NO₃- concentrations >100 µm and an improved NO₃- transport because of lower K(m) values. ZmNRT2.1 transcript abundances were not spatially correlated with NNUR, suggesting that post-translational effects or NAR2 protein co-expression could be involved. By contrast, PM H⁺ -ATPase displayed a similar spatial-temporal pattern as that of nitrate uptake, resulting in higher activity in the root tip than in the basal regions. Increased activities of the enzyme after nitrate supply resulted in enhanced expression of MAH3 and MAH4, PM H⁺ -ATPase subfamily II genes, while MAH1 was not expressed., (© 2011 Blackwell Publishing Ltd.)

A plant regeneration methodvia somatic embryogenesis of severalHelianthus annuus L. genotypes was developed. Starting from cotyledonary explants high frequency embryo induction was obtained following several subcultures on defined media. An appropriate cotyledon developmental stage was identified. Etiolated explants and darkness treatment were necessary to obtain somatic embryos in all tested genotypes. After 20-25 days on somatic induction medium containing an auxin:cytokinin ratio of 1:1, the germination of embryos was induced by a reduction of the hormonal ratio (1:2). Shoots were excised from callus and transferred onto a medium containing various vitamins. The range of embryogenesis frequency was 33-72%, depending on the genotype. High frequency of rooting (49-82%) was obtained using a medium supplemented with 0.5 mg/L of ancymidol and by a reduction of photoperiod. A large percentage of somatic embryos developed into normal regenerated plants producing viable seeds.