Increase in glutathione S-transferase activity and antioxidant damage ability drive resistance to bensulfuron-methyl in Sagittaria trifolia.

Weeds tend to develop resistance to herbicides with time. Understanding the resistance mechanisms evolved by weeds would help manage weed infestation. Sagittaria trifolia, a paddy weed found in the rice fields of Liaoning, China, has developed resistance to bensulfuron-methyl, causing severe yield losses in rice. This study deciphers the underlying mechanisms in terms of non-target-site resistance toward bensulfuron-methyl. We compared the ability of glutathione S-transferase (GST) mediated detoxification metabolism and reactive oxygen species (ROS) scavenging between sensitive (NHS) and resistant (NHR) populations of S. trifolia. The resistance ratio of NHR was 210; but the ratio was significantly decreased after GST-inhibitor treatment (44.9). This indicated that a GST-mediated enhancement of detoxification metabolism stimulated the development of resistance. Similarly, higher GST activity was observed in NHR; but the activity equaled that of NHS after GST-inhibitor treatment. However, treatment with the GST-inhibitor did not completely reverse bensulfuron-methyl resistance in NHR, indicating that additional factors contributed to herbicide resistance in these plants. We observed a rapid increase in H2O2 and malondialdehyde accumulation in the case of NHS after bensulfuron-methyl application, whereas those of NHR remained relatively stable, implying that NHR exhibited higher ROS-scavenging capacity under herbicide stress. Further, NHR showed higher glutathione and ascorbic acid contents and higher activities of glutathione reductase and dehydrogenase reductase, all of which contribute towards herbicide resistance in these plants. Our results indicate that GST-mediated detoxification metabolism of bensulfuron-methyl and ROS scavenging capacity contributed to the development of resistance in S. trifolia.

[Sagittaria sagittifolia polysaccharides regulates Nrf2/HO-1 to relieve liver injury caused by multiple heavy metals in vivo and in vitro].

This study explored whether Sagittaria sagittifolia polysaccharides(SSP) activates the nuclear factor erythroid-2-related factor2(Nrf2)/heme oxygenase-1(HO-1) signaling pathway to protect against liver damage jointly induced by multiple heavy metals. First, based on the proportion of dietary intake of six heavy metals in rice available in Beijing market, a heavy metal mixture was prepared for inducing mouse liver injury and HepG2 cell injury. Forty male Kunming mice were divided into five groups: control group, model group, glutathione positive control group, and low-and high-dose SSP groups, with eight mice in each group. After 30 days of intragastric administration, the liver injury in mice was observed by HE staining. In the in vitro experiment, MTT assay was conducted to detect the effects of SSP at 0.25, 0.5, 1, and 2 mg·mL~(-1) on HepG2 cell survival at different time points. The content of alanine transaminase(ALT) and aspartate aminotransferase(AST) in the 48-h cell culture fluid was measured using micro-plate cultivation method, followed by the detection of the change in reactive oxygen species(ROS) content by flow cytometry. The mRNA expression levels of Nrf2 and HO-1 in cells were determined by RT-PCR, and their protein expression by Western blot. HE staining results showed that compared with the model group, the SSP administration groups exhibited significantly alleviated inflammatory cell infiltration and fatty infiltration in the liver, with better outcomes observed in the high-dose SSP group. In the in vitro MTT assay, compared with the model group, SSP at four concentrations all significantly increased the cell survival rate, decreased the ALT, AST, and ROS content(P<0.05), and down-regulated Nrf2 and HO-1 mRNA and protein expression(P<0.05). SSP significantly improves inflammatory infiltration in the liver tissue of mice exposed to a variety of heavy metals and corrects the liver fat degeneration, which may be related to its regulation of the Nrf2/HO-1 signaling pathway, reduction of ROS, and alleviation of oxidative damage.

Sagittaria sagittifolia polysaccharide protects against six-heavy-metal-induced hepatic injury associated with the activation of Nrf2 pathway to regulate oxidative stress and apoptosis.

The hepatic protective role of Sagittaria sagittifolia polysaccharide (SSP) and its possible mechanism were discussed in mice and L02 hepatocytes injured by heavy metals mixture of Cd + Cr (VI) + Pb + Mn + Zn + Cu. After 30-day intervention, blood and liver samples were collected for the relevant assessments. Methyl thiazolyl tetrazolium (MTT) assay showed 24 h was the best protecting point and the SSP protection at 1 mg/mL was strongest in L02 hepatocytes. SSP can alleviated hepatic injury, as evidenced by significantly decreased the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and the malondialdehyde (MDA) content, also increased the superoxide dismutase (SOD) activity and glutathione (GSH), total sulphydryl (T-SH) contents. SSP effectively reduced pathological damage of mice and accumulation of heavy metals in liver, as well as decreased the level of reactive oxygen species (ROS) in L02 hepatocytes. After SSP treatment, the protein expressions or gene transcription of nuclear factor erythroid 2-related factor 2 (Nrf2), NAD(P)H dehydrogenase, quinone 1 (NQO1) and heme oxygenase1 (HO-1) decreased in L02. The protein expression of Nrf2 and NQO1 were increased while HO-1 was decreased in liver. Besides, SSP can attenuates apoptosis through reducing the protein expression of Bcl-2-associated X protein (Bax) and caspase-3, and increasing B-cell lymphoma gene 2 (Bcl-2) and B-cell lymphoma-extra large (Bcl-xl). SSP protects against six-heavy-metal-induced hepatic injury in mice and L02 hepatocytes. Supported by Nrf2 gene silencing, the mechanisms may correlate with activating Nrf2 pathway to mitigate oxidative stress and apoptosis.

Sagittaria trifolia tuber: bioconstituents, processing, products, and health benefits.

Sagittaria trifolia is an aquatic plant that is distributed worldwide. The edible tuber part of S. trifolia is a very common and popular vegetable in China. The aim of the present review is to discuss the discovery of nutraceuticals from S. trifolia tuber by reviewing its major constituents, food processing, food products, and health-promoting benefits. Sagittaria trifolia tuber comprises a series of nutritional and bioactive constituents, including dietary fibers, amino acids, minerals, starches, non-starch polysaccharides, diterpenoids, colchicine, phenols, and organic acids. Food processing affects its flavor, biocomponents, and bioactivity. Numerous S. trifolia tuber-based food products and nutraceuticals have been developed, but new categories of products and the anticipated functions still need to be explored. The non-starch polysaccharides could be the central ingredients that contribute to the plant's antioxidant, hepatoprotective, hypoglycemic, lipid-regulating, and immunostimulatory properties. Of these, antioxidant and hepatoprotective effects have been thoroughly investigated. Procedures for the extraction and purification of polysaccharides influence their health-promoting actions. Overall, S. trifolia tuber is an underutilized aquatic vegetable species that is an emerging subject for nutraceutical research. © 2020 Society of Chemical Industry.

Resource reallocation patterns within Sagittaria trifolia inflorescences following differential pollination.

PREMISE OF THE STUDY: Understanding resource allocation to reproduction, a key factor in life history tradeoffs, has long intrigued plant ecologists. Despite the recognized importance of understanding the movement of resources among flowers following variable pollination, the patterns of resource reallocation to plant reproductive organs have not been thoroughly addressed. In this study, we aimed to empirically explore how resources redistribute within inflorescences in response to differential pollination intensities. METHODS: Using a common herb, Sagittaria trifolia, we conducted supplemental and controlled pollination for single, some, or all flowers in simple and complex inflorescences, and compared their resulting fruiting probabilities, seed production, and average seed masses. KEY RESULTS: Pollen supplementation of a single flower significantly increased its fruiting probability; however, the same manipulation of an inflorescence did not increase its overall reproduction. Single pollen-supplemented flowers had a higher percentage fruit set than inflorescences receiving supplemental pollination. In complex inflorescences, supplemental pollination had no effect on the reproductive success of flowers on the lateral or main branches. CONCLUSIONS: We provided evidence of resource reallocation from controlled to pollen-supplemented flowers in simple inflorescences; however, resources were unlikely to be reallocated between the main and lateral branches in the complex inflorescences, suggesting that flowering branches represent integrated physiological units in S. trifolia. The results also demonstrated that single-flower supplemental pollination would exaggerate pollen limitation and lead to a biased understanding of a plant's reproductive status.

Transcriptome analysis of starch and sucrose metabolism across bulb development in Sagittaria sagittifolia.

Sagittaria sagittifolia L is an important bulb vegetable that has high nutritional and medical value. Bulb formation and development are crucial to Sagittaria sagittifolia; however, its sucrose metabolism is poorly understood and there are a lack of sufficient transcriptomic and genomic data available to fully understand the molecular mechanisms underlying bulb formation and development as well as the bulb transcriptome. Five cDNA libraries were constructed at different developmental stages and sequenced using high-throughput Illumina RNA sequencing. From approximately 63.53 Gb clean reads, a total of 60,884 unigenes, with an average length of 897.34 bp and N50 of 1.368 kb, were obtained. A total of 36,590 unigenes were successfully annotated using five public databases. Across different developmental stages, 4195, 827, 832, 851, and 1494 were differentially expressed in T02, T03, T04, T05, and T06 libraries, respectively. Gene ontology (GO) analysis revealed several differentially-expressed genes (DEGs) associated with catalytic activity, binding, and transporter activity. The Kyoto encyclopedia of genes and genomes (KEGG) revealed that these DEGs are involved in physiological and biochemical processes. RT-qPCR was used to profile the expression of these unigenes and revealed that the expression patterns of the DEGs were consistent with the transcriptome data. In this study, we conducted a comparative gene expression analysis at the transcriptional level using RNA-seq across the different developmental stages of Sagittaria sagittifolia. We identified a set of genes that might contribute to starch and sucrose metabolism, and the genetic mechanisms related to bulblet development were also explored. This study provides important data for future studies of the genetic and molecular mechanisms underlying bulb formation and development in Sagittaria sagittifolia.

Potential of Sagittaria trifolia for Phytoremediation of Diesel.

The phytoremediation potential and responses of Sagittaria trifolia to diesel were investigated. In order to elucidate the biochemical and physiological responses of S. trifolia to diesel, the chlorophyll content, root vitality, soluble protein content and antioxidant enzymes activity (peroxidase (POD), catalase (CAT) and antioxidant enzymes superoxide dismutase (SOD)) were determined in the plant tissues after 50 d of diesel treatment. The results showed the presence of S. trifolia significantly improved the removal ratios of diesel, from 21∼36% in the control soils to 54∼85% in the planted soils. The chlorophyll content, root vitality and soluble protein content all increased at low diesel concentration, then decreased at high diesel concentration. The activities of CAT and POD exhibited peak values at 5 g·kg(-1) diesel treatment and declined at higher diesel concentrations. However, the activity of SOD kept stable at lower diesel concentration (1 and 5 g·kg(-1)), and also declined at higher diesel concentration. Collectively, S. trifolia had the ability to tolerate certain amount of diesel, but when the concentration was up to 10 g·kg(-1), the growth of S. trifolia would be restrained. The results also showed that variation of antioxidant enzyme activity was an important response in plants to diesel pollution.

Identification of differentially expressed genes relevant to corm formation in Sagittaria trifolia.

Sagittaria trifolia is a good model of wetland plants to elucidate the formation of corm. However, few studies have been conducted to uncover the complexity of gene expression involved in corm formation. In this study, high-throughput tag-sequencing based on Solexa Genome Analyzer Platform was applied to monitor the changes in gene expression with three libraries of differentially expressed genes (DEGs) (C1 library: stolon stage, C2 library: initial swelling stage and C3 library: swelling stage) during corm formation in Sagittaria trifolia. Approximately 6.0 million tags were sequenced, and 5854021, 5983454, and 5761079 clean tags including 138319, 116804, and 101739 distinct tags were obtained after removal of low quality tags from each library, respectively. About 46% distinct tags were unambiguous tags mapping to the reference genes, and 33% were unambiguous tag-mapped genes. Totally, 20575, 19807, and 18438 were annotated in C1, C2, and C3 libraries, respectively, after mapping their functions in existing databases. In addition, we found that profiling of gene expression in C1/C2 and C2/C3 libraries were different among most of the selected 20 DEGs. Most DEGs in C1/C2 libraries were relevant to hormone synthesis and response; energy metabolism and stress response, while most of the genes in C2/C3 libraries were involved in carbohydrate metabolism. All up-regulated transcriptional factors and 16 important genes relevant to corm formation in three libraries were also identified. To further analyze the expression of 9 genes, from the results of tag-sequencing, qRT-PCR was applied. In summary, this study provides a comprehensive understanding of gene expression, during the formation of corm in Sagittaria trifolia.

Changes of polyamine levels in roots of Sagittaria sagittifolia L. under copper stress.

INTRODUCTION: The goal of the present study was to investigate the effects of Cu contamination on the above-mentioned biochemical and physiological parameters in order to explore possible prevention strategies against heavy metal stress. MATERIALS AND METHODS: Effects of copper (Cu) on the roots of Sagittaria sagittifolia L. were studied after 10 days of treatment at five concentration levels. The accumulation of Cu, the generation rate of O(2) (·-), the contents of thiobarbituric acid reactive substances (TBARS) and polyamines, as well as the activities of arginine decarboxylase (ADC) and polyamine oxidase (PAO) in the roots were measured and analyzed. RESULTS AND DISCUSSION: It was observed that endogenous Cu content increased in roots of S. sagittifolia L. in a concentration-dependent manner, along with an increased production of O(2) (·-). TBARS content increased progressively up to 5 µmol l(-1) Cu. A constant increase in ADC activity was also observed. The results indicated that lower Cu concentrations (2.5 and 5 µmol l(-1), respectively) had greater enhancing effect on the contents of free Put and perchloric acid-soluble conjugated (PS-conjugated) putrescine (Put), while Cu treatments at different concentration levels had similar enhancing effect on the content of perchloric acid-insoluble bound Put. In total, Put content in each Cu-treated group was higher than that in the control group. PAO activity was inhibited up to 10 µmol l(-1) Cu but enhanced at higher Cu concentrations (20 and 40 µmol l(-1)). This explained the initial rise and subsequent decline of the contents of all forms of spermine (Spm), free and PS-conjugated spermidine (Spd). However, with the increase of Cu concentration, total Spm content increased gradually while total Spd content decreased. Our results suggest that Cu is phytotoxic to the roots of S. sagittifolia L. at high concentrations, and that the increased Spm level is not sufficient to resist Cu-induced oxidative damages.

[Phosphorus rhizosphere depletion effect of four aquatic plants].

Four aquatic plants (Alternanthera philoxeroides, Typha latifolia, Sagittaria sagittifolia, Phragmites communis ) were cultured on P-enriched soil in a pot experiment to assess the phosphorus rhizosphere depletion effect and analysis the ratio of root to shoot, root morphology, phosphorus uptake efficiency and phosphorus use efficiency. An obvious variation in P concentration of the soil in the rhizophere and non- rhizophere was observed. Compared with the non-rhizosphere (available P: 167.53 microg x g(-1)), the available P in the rhizosphere soil of Alternanthera philoxeroides, Typha latifolia, Sagittaria sagittifolia and Phragmites communis was reduced to 80.17, 124.37, 155.38 and 161.75 microg x g(-1) respectively, with 81%, 42%, 18% and 16% reduction ratio of water-soluble phosphorus. More effective phosphorus depletion was achieved in Alternanthera philoxeroides by higher phosphorus uptake efficiency (1.32 mg x m(-1)), while rooting system was small and phosphorus use efficiency was low (0.34 g x mg(-1)). Phosphorus uptake efficiency of Typha latjfolia is much lower (0.52 mg x m(-1)) than that of Alternanthera philoxeroides, however, its strong rooting system enhanced soil exploration, with higher phosphorus use efficiency (0.64 g x mg(-1)) and the ratio of root to shoot (0.35). Alternantshera philoxeroides and Typha latfolia were more effective in phosphorus depletion of the rhizosphere soil than that in Sagittaria sagittifolia and Phragmites communis.