Turnip mosaic virus pathogenesis and host resistance mechanisms in Brassica

Turnip mosaic virus(TuMV)is a devastating potyvirus pathogen that infects a wide variety of both cultivated and wild Brassicaceae plants.We urgently need more information and understanding of TuMV pathogenesis and the host responses involved in disease development in cruciferous crops.TuMV displays great versatility in viral pathogenesis,especially in its replication and intercellular movement.Moreover,in the coevolutionary arms races between TuMV and its hosts,the virus has evolved to co-opt host factors to facilitate its infection and counter host defense responses.This review mainly focuses on recent advances in understanding the viral factors that contribute to the TuMV infection cycle and the host resistance mechanism in Brassica.Finally,we propose some future research directions on TuMV pathogenesis and control strategies to design durable TuMV-resistant Brassica crops.

Isolation and Identification of Pandora neoaphidis and Its Pathogenicity against Turnip Aphid(Lipaphis erysimi)

[Objective] The study was to isolate and identify the pathogen of Pandora neoaphidis and to determine its pathogenicity against turnip aphid （Lipaphis erysimi）.[Method] Based on the morphological characteristics,the species of pathogenic fungus was identified.Spore shower method was used to carry out bioassay on the pathogen against turnip aphid.[Result] Primary conidia were ovoid,bitunicate and uninucleate,（24.7±1.4）μm×（10.7±0.9）μm,L/D=2.3±0.2.Secondary conidia had the similar shape with the primary ones,（18.6±2.1）μm×（13.3±1.3）μm,L/D=1.4±0.2.Hyphal body was like mycelium with the diameter of （10.6±0.8）μm.Conidiophores had palmate branch with the diameter of （10.0±0.9）μm.Pseudocystidia was not branched,which had rough base with the diameter of （19.2±1.7）μm,and gradually became more angular towards the apex with the diameter of （8.0±0.9）μm at tips.Rhizoid was like monohyphal shape with the diameter of （21.0±3.0）μm at base,the terminal apex had regular discoid holdfast.No resting spores were observed.The lethal dose of the pathogen against turnip aphid was 18.2/mm2.[Conclusion] The entomopathogenic fungus against turnip aphid was identified to be Pandora neoaphidis,and the pathogen was confirmed to have strong pathogenicity against turnip aphid.

Control Effect of Methanol Extract of Blumea megacephala Chang et Tseng against Turnip Aphid (Lipaphis erysimi Kaltenbach)

[ Objective ] The paper was to explore the application of botanical pesticides on controlling turnip aphid （ Lipaphis erysimi Kaltenbach）. [ Method ] Through potting efficacy experiment of Chinese cabbage, the control effects of two preparations（20% EC and 10% EW）of methanol extract of Blumea megacephala Chang et Tseng against turnip aphid, as well as leaf-protection effect on Chinese cabbage were determined. [ Result] 20% EC of B. megacephala had the highest efficacy in 10-fold dilution, and its control effects against turnip aphid were 57.78%, 77.19% and 84.79% after pesticide spraying for 24, 48 and 72 h; 10% EW of B. megacephala had the highest efficacy in 5-fold dilution, and its control effects against turnip aphid were 74.44%, 84.79% and 89.14% after pesticide spra- ying for 24, 48 and 72 h. The leaf-protection rates of 20% EC orB. megacephala in 10-fold dilution were 89.31% and 94.80% after pesticide spraying for 3 and 5 d; the leaf-protection rates of 10% EW of B. megacephala in 5-fold dilution were 93.50% and 97.83% after pesticide spraying for 3 and 5 d. [ Condusion] The methanol extract of B. megacephala had good control effect against turnip aphid and good protection rate on crops.

The Effect of Different Formulations on Turnip Juice Production in Controlled Conditions

Black carrots （Daucus earota L. spp. sativus. ） were fermented for 4 weeks by using six different starter dough formulations. Some of the samples were pasteurized to detemaine the effects of heat treatment on fermentation. Fermentation was followed by physicochemical and microbiological analysis. Some characteristics such as dry matter, crude fiber, water soluble extract, alcohol soluble extract, ether soluble extract, crude energy, total sugar, pH, salt and colour values and mineral contents of black carrot were determined. In the beginning of the fermentation, dry matter is highest in the brines with coriandrium and dry matter of the other brines are close to each other and lower than that of the brines with coriander. The number of Lactic acid bacteria, total bacteria, moulds-yeasts and coliform bacteria decreased through the end of fermentation. Heat treatment had a considerable effect on microbial growth. The microbial growth was higher in the nnpastenrized samples. Total bacteria number reached the highest level for the pasteurized samples （ 104 cfu/mL - 105 cfu/mL ） and for the unpasteurized samples （106 cfu/mL - 107 cfu/mL） in the second day. After the fermentation, sensory analyses were carried out to determine the storage stability of the last products. While ＂a＂ value increased, ＂b＂ and ＂L＂ values decreased during storage time. Yoghurt inoculated brine were preferred from the colour, odour and acceptability points of view.

Comparison Between a Tetraploid Turnip and Its Diploid Progenitor(Brassica rapa L.):The Adaptation to Salinity Stress

Polyploidy is pursued in plant breeding programs due mainly to its ability to yield larger vegetative or reproductive organs. In controlled growth chamber experiments, a tetraploid turnip （cv. Aijiaohuang, 4n） and its diploid progenitor （cv. Aijiaohuang, 2n） were evaluated for their tolerance to salinity stress via investigations on a group of physiological parameters. The results indicate that the tetraploid turnip exhibit better adaptation to a high concentration salt medium （200 mmol L-1）, as evidenced by a less-affected germination rate and a healthier morphological appearance at the seedling stage. Furthermore, an extension of salinity stress up to a certain period of time at the 5-7-leaf stage shows differences between the tetraploid turnip and its diploid progenitor. The former had a higher K＋/Na＋ ratio in the roots, higher glutathione concentration and antioxidant activities in the leaves, and smaller reductions in photosynthetic capacity in terms of leaf chlorophyll content. Studies on the differences between an autopolyploid and its respective relative, from which the autopolyploid originated, in terms of their tolerance to salinity and/or other abiotic stresses, have remained rather limited. The comparison is interesting due to a homogenous genetic background.

Effect of vernalization on tuberization and flowering in the Tibetan turnip is associated with changes in the expression of FLC homologues

The turnip(Brassica rapa var. rapa) is a biennial crop that is planted in late summer/early fall and forms fleshy tubers for food in temperate regions. The harvested tubers then overwinter and are planted again the next spring for flowering and seeds. FLOWERING LOCUS C(FLC) is a MADS-box transcription factor that acts as a major repressor of floral transition by suppressing the flowering promoters FT and SOC1. Here we show that vernalization effectively represses tuber formation and promotes flowering in Tibetan turnip. We functionally characterized four FLC homologues(BrrFLC1,FLC2, FLC3, and FLC5), and found that BrrFLC2 and BrrFLC1 play a major role in repressing flowering in turnip and in transgenic Arabidopsis. In contrast, tuber formation was correlated with BrrFLC1 expression in the hypocotyl and was repressed under cold treatment following the quantitative downregulation of BrrFLC1. Grafting experiments of non-vernalized and vernalized turnips revealed that vernalization independently suppressed tuberization in the tuber or hypocotyl of the rootstock or scion, which occurred in parallel with the reduction in BrrFLC1 activity. Together, our results demonstrate that the Tibetan turnip is highly responsive to cold exposure, which is associated with the expression levels of BrrFLC genes.

Genome-wide analysis indicates diverse physiological roles of the turnip (Brassica rapa var. rapa) oligopeptide transporters gene family

Oligopeptide transporters(OPTs) encode integral membrane-localized proteins and have a broad range of substrate transport capabilities. Here, 28 BrrOPT genes were identified in the turnip. Phylogenetic analyses revealed two well-supported clades in the OPT family, containing 15 BrrOPTs and 13 BrrYSLs.The exon/intron structure of OPT clade are conserved but the yellow stripe-like(YSL) clade was different.The exon/intron of the YSL clade possesses structural differences, whereas the YSL class motifs structure are conserved. The OPT genes are distributed unevenly among the chromosomes of the turnip genome.Phylogenetic and chromosomal distribution analyses revealed that the expansion of the OPT gene family is mainly attributable to segmental duplication. For the expression profiles at different developmental stages, a comprehensive analysis provided insights into the possible functional divergence among members of the paralog OPT gene family. Different expression levels under a variety of ion deficiencies also indicated that the OPT family underwent functional divergence during long-term evolution.Furthermore. BrrOPT8.1, BrrYSL1.2, BrrYSL1.3, BrrYSL6 and BrrYSL9 responded to Fe(Ⅱ) treatments and BrrYSL7 responded to calcium treatments, BrrYSL6 responded to multiple treatments in root, suggesting that turnip OPTs may be involved in mediating cross-talk among different ion deficiencies. Our data provide important information for further functional dissection of BrrOPTs, especially in transporting metal ions and nutrient deficiency stress adaptation.

Effects of soil properties on accumulation characteristics of copper,manganese, zinc, and cadmium in Chinese turnip

Clarifying the mechanisms of heavy metal(HM)accumulation and translocation from soil-root-leaf is crucial to coping with soil HM pollution.In this study,we analysed copper(Cu),manganese(Mn),zinc(Zn)and cadmium(Cd)accumulation characteristics in Chinese turnips and the effect of soil physicochemical properties on both HM accumulation and translocation.Our results indicate that Chinese turnips absorb and translocate Mn,Zn,and Cd at much higher levels than they do Cu.When we measured bioconcentration factors in Chinese turnips for different HMs in the same soil,we found Chinese turnip capacities for HM accumulation decrease from Zn>Mn>Cd>Cu.In addition,the translocation factor for these HMs decreases from Mn>Cd>Zn>Cu.Correlation analysis indicates that soil p H and various soil components are either negatively or positively correlated with Mn,Zn,and Cd accumulation;also,soil properties are correlated with Mn translocation from root to leaf.These findings may help evaluate HM accumulation and translocation mechanisms as well as artificially regulate HM uptake levels from soils to turnips.

Comparative expression analysis of heavy metal ATPase subfamily genes between Cd-tolerant and Cd-sensitive turnip landraces

The heavy metal ATPase(HMA)subfamily is mainly involved in heavy metal(HM)tolerance and transport in plants,but an understanding of the definite roles and mechanisms of most HMA members are still limited.In the present study,we identified 14 candidate HMA genes named BrrHMAl—BrrHMA8 from the turnip genome and analyzed the phylogeny,gene structure,chromosome distribution,and conserved domains and motifs of HMAs in turnip(Brassica rapa var.rapa).According to our phylogenetic tree,the BrrHMAs are divided into a Zn/Cd/Co/Pb subclass and Cu/Ag subclass.The BrrHMA members show similar structural characteristics within subclasses.To explore the roles of BrrHMAs in turnip,we compared the gene sequences and expression patterns of the BrrHMA genes between a Cd-tolerant landrace and a Cd-sensitive landrace.Most BrrHMA genes showed similar spatial expression patterns in both Cd-tolerant and Cd-sensitive turnip landraces;some BrrHMA genes,however,were differentially expressed in specific tissue in Cd-tolerant and Cd-sensitive turnip.Specifically,BrrHMA genes in the Zn/Cd/Co/Pb subclass shared the same coding sequence but were differentially expressed in Cd-tolerant and Cd-sensitive turnip landraces under Cd stress.Our findings suggest that the stable expression and up-regulated expression of BrrHMA Zn/Cd/Co/Pb subclass genes under Cd stress may contribute to the higher Cd tolerance of turnip landraces.

Chemical Constituents from Turnip and Their Effects on α-Glucosidase

Brassica rapa var.rapa(turnip)is an important crop in Qinghai-Tibet Plateau(QTP)with anti-hypoxic effect.Turnip is rich in glucosinolates,isothiocyanates and phenolic compounds with diverse biological activities,involving anti-oxidant,anti-tumor,anti-diabetic,anti-inflammatory,anti-microbial,hypolipidemic,cardioprotective,hepatoprotective,nephroprotective and analgesic properties.In this study,the ethyl acetate(EtOAc)and butanol parts of Brassica rapa were first revealed with inhibitory effects onα-glucosidase,whereas the water part was inactive.Subsequent bioassay-guided isolation on the EtOAc and butanol parts yielded 12 compounds,involving three indole derivatives,indole-3-acetonitrile(1)4-methoxyindole-3-acetonitrile(2)and indole-3-aldehyde(3)two flavonoids,liquiritin(4)and licochalcone A(5)two phenylpropanoids,sinapic acid(6)and caffeic acid(7)two phenylethanol glycosides,2-phenylethylβ-glucopyranoside(8)and salidroside(9)and three other compounds,syringic acid(10)adenosine(11)and(3β,20E)-ergosta-5,20(22)-dien-3-ol(12)Licochalcone A(5)and caffeic acid(7)showedα-glucosidase inhibitory activity with IC 50 values of 62.4±8.0μM and 162.6±3.2μM,comparable to the positive control,acarbose(IC 50=142±0.02μM).Docking study suggested that licochalcone A(5)could well align in the active site ofα-glucosidase(docking score=-52.88)by forming hydrogen bonds(Gln1372,Asp1420,Gln1372,Arg1510),hydrophobic effects(Tyr1251,Tyr1251,Trp1355,Phe1560,Ile1587,Trp1355,Phe1559,Phe1559)andπ-πstacking interaction(Trp1355).This study provides valuable information for turnip as a new resource in searching anti-diabetic candidates.

Molecular cloning and expression analysis of turnip (Brassica rapa var. rapa) sucrose transporter gene family

In higher plants, sugars （mainly sucrose） are produced by photosynthetically assimilated carbon in mesophyll cells of leaves and translocated to heterotrophic organs to ensure plant growth and devel- opment. Sucrose transporters, or sucrose carriers （SUCs）, play an important role in the long-distance transportation of sucrose from source organs to sink organs, thereby affecting crop yield and quality. The identification, characterization, and molecular function analysis of sucrose transporter genes have been reported for monocot and dicot plants. However, no relevant study has been reported on sucrose transporter genes in Brassica rapa vat. rapa, a cruciferous root crop used mainly as vegetables and fodder. We identified and cloned 12 sucrose transporter genes from turnips, named BrrSUC1.1 to BrrSUCB.2 according to the SUC gene sequences of B. rapa pekinensis. We constructed a phylogenetic tree and analyzed conserved motifs for all 12 sucrose transporter genes identified. Real-time quantitative poly- merase chain reaction was conducted to understand the expression levels of SUC genes in different tissues and developmental phases of the turnip. These findings add to our understanding of the genetics and physiology of sugar transport during taproot formation in turnips.

BAK1在减弱拟南芥对Turnip crinkle virus感病性作用中的影响

以Turnip crinkle virus(TCV)-拟南芥(Col-0)为互作系统,研究了跨膜蛋白BAK1是否参与拟南芥对TCV的防御作用。接种试验结果表明,bak1-4突变体对TCV更加敏感,叶片易褪绿枯萎;而过量表达植株在接种TCV后受损程度较小。H2O2检测表明,严重的病症伴随有较多活性氧积累,提示该亲和互作系统中,活性氧有利于症状的形成,BAK1对活性氧产生有负调控作用。半定量RT-PCR分析表明,BAK1过表达有利于MAPK途径下游与防御相关MPK和WRKY转录因子的激活;但不影响与病程相关水杨酸途径PR1和PR2基因的表达,它们没有介导对TCV的抗性。

Effect of SO_2－polluted rape plant on growth and reproduction of the turnip aphid，Lipaphis erysimi（Kaltenbach）

A series of experiments using open-top fumigation chambers was carried out to investi gate the effect of SO2-polluted rape on performance of the turnip aphid, Lipaphis erysimi(Kaltenbach).Proper SO2 concentrations significantly enhances growth and reproduction of the aphid. Nymph MRGR and adult fecundity reached their maxima at 116 nl/L and 80 nl/L of the pollutant, respectively. Potential of the population growth got fully displayed at the latter dose because the highest survival rate of the nymphs also took place at this concentration.It is suggested according to changes in the plant chemistry that this indirect effect of SO2 pollution on the turnip aphid might involve variation in content of individual key free amino acid rather than total amount of all the amino acids in the leaves induced by the air pollutant.

Effect of airborne SO_2 on performance of the turnip moth,Agrotis segetum Schiff

Effect of SO_2-enriched air on the turnip moth, Agrotis segetum Schiff.was investigated by rearing the larvae on rape leaves that had been exposed to 40 or 80 ppb of the air pollutant in field fumigation chambers. An examination on the 11th day showed that the larvae in both treatments survived more, developed markedly faster, their fresh v/eig'ht and mean relative growth rate were significantly greater than those of control insect. Improvement of their growth and development resulted in decrease of total larval duration by 0.5 - 1.0 day. Pupal and adult performances were little affected by SO2 level to which larval food plant was exposed. Possible reason responsible for enhanced growth and development of the insect species was discussed.

Physiological and biochemical analysis of mechanisms underlying cadmium tolerance and accumulation in turnip

The capacity of plants to accumulate cadmium(Cd) is significant for phytoremediation of Cd-polluted soils. Turnips cultivated in China include species featuring high Cd accumulation and some of these plants act as Cd hyperaccumulator landraces. These plants can accumulate over 100 mg Cd kg^(-1) dry weight in leaves without injury. Hence, studies that explore mechanisms underlying Cd detoxification and transport in turnip plants are essential. In the present study, we compared physiological and biochemical changes in turnip leaves treated with two Cd concentrations to controls. We discovered that Cd stress significantly increased the enzymatic activities or compound contents in the antioxidant system, including members of the glutathione-ascorbic acid cycle, whereas oxidation of reactive oxygen species(ROS) remained stable. Cd treatments also increased the contents of phytochelatins as well as a number of amino acids. Based on these results, we conclude that turnips initiate a series of response processes to manage Cd treatment. First, the antioxidant system maintaining ROS homeostasis and osmotic adjustment is excited to maintain stability of cell osmotic potential. Cd is chelated into its stable form to reduce its toxicity. Cd is possibly transported to vacuoles or non-protoplasts for isolation. Amino acid synthesis may directly and indirectly play an important role in these processes. This study partly revealed physiological and biochemical mechanisms underlying turnip response to Cd stress and provides information on artificially increasing or decreasing Cd accumulation in turnips and other plants.

The Defense Effect of ABA against Turnip crinkle virus (TCV)

[ Objective ] The paper was to understand whether abscisic acid （ABA） participates the defense effect of hosts against Turnip crinkle virus （TCV）. [ Method] By external application of ABA and using the corresponding mutants, TCV coat protein levels of various plants were detected by western-blot, and the expression of defense-related genes was analyzed by RT-PCR. [Result] After external application of SA, JA, ET and ABA, only SA and ABA could significantly inhibit TCV accumulation. In arabidopsis-TCV interaction system, SA and ABA had antagonistic effect with each other, the defense effect against TCV induced by ABA was independent on SA pathway. [ Conclusion] The plants could activate distinct signal pathways to adjust the defense of hosts against virus.

Glucosinolate Variation in Turnip (Brassica rapa L.) at Different Growing Stages

The seed, leaf and root parts of three turnip （ Brassica rapa L.） cultivars were analyzed for glucosinolates. The component and concentration of glucosinolates in the three cultivars were also analyzed at different growing stages. Eight kinds of glucosinolates were tested in turnip. They were PRO, NAP, 4OH, GBN, GBC, NAS, 4ME and NEO, respectively. The contents and kinds of glucosinolates varied at different growing stages. The content of NAS was the highest in the seed, GBC and NEO contents were the highest in the seedling, GBN and NEO contents were the highest in the leaf, while the highest NAS content was in the root.

Pulling the turnip

Hare:Oh,a turnip!A big turnip!I’m hungry.I’ll pull it out.Ai-Hay-Yo,Ai-Hay-Yo.The turnip is too heavy.I can’t pull it out.Dog:I’m a dog.I’m hungry.Oh,Miss Hare,What are you doing?

TURNIP MOSAIC VIRUS COAT PROTEIN GENE: CLONING AND CONSTRUCTION OF THE PLANT VECTOR

Complementary DNAs to turnip mosaic virus (a radish Raphanus stativus isolate) genomicRNA were synthesized using oligo (dT) as primer and cloned into the vector λ-ZAP Ⅱ. Afterhybridization with a single-stranded cDNA probe and the sequencing of inserted DNA,positive clones with poly--A tails were obtained. One clone containing 1429-base pair insertwas sequenced. The coat protein gene was identified based on the molecular weight of theTuMV coat protein and the consensus sequences of the polyprotein processing sites ofpotyviruses. The 5’ end of the coat protein gene was modified by PCR to introduce aninitiation codon, ATG, and two restriction enzyme sites. The gene was then manipulatedinto a binary vector pBIN437 which was derived from pBI121, and the plant expressionvector is being used to transform Brassica napus.

Magnetically treated water irrigation effect on turnip seed germination,seedling growth and enzymatic activities

Pre-sowing magnetic field seed treatment effects on biological characteristics of vegetables and crops have been studied well.However,studies reporting irrigation with magnetically treated water are scanty.Therefore,the effect of irrigation with magnetically treated water on turnip seed germination,seedling growth and enzymatic activities was evaluated.The tap water was treated at 211 mT for 30,45 and 60 min and used for irrigation of turnip seed and seedlings.Uniform and healthy turnip seed was sown under randomized complete block design(RCBD).The germination,emergence rate index,vigor index I and vigor index II increased up to 28.33%,11.54%,57.59%and 32.26%,respectively.The growth parameters such as seedling lengths,fresh&dry weights,chlorophyll content were also enhanced in response of irrigation with magnetically treated water.The seedlings irrigated with magnetically treated water showed 28.92%,11.36%and 14.76%higher protein content,alpha amylase and protease activities,respectively vs control.Results revealed that irrigation with magnetically treated water has potential to improve turnip germination,seedling growth and enzymatic activities and this study is also extendable to other vegetables and crops for the improvement of germination and growth.