Carrot protoplast fusion

Conclusion Carrot protoplasts have been used successfully in many protoplast fusion studies. These studies have demonstrated 1) whether or not the expression of certain resistances is dominant or recessive, 2) the development of a “universla hybridzer,” 3) the use of chemicals to inactivate one parent, 50 the complementation of albino mutants, 5) interspecific, intergeneric, and interkingdom fusions, and 6) the dominant expression of plant regeneration ability, and 7) the occurrence of somatic segregation in fusion hybrids.     

Carrot yellow leaf virus Is Associated with Carrot Internal Necrosis

Internal necrosis of carrot has been observed in UK carrots for at least 10 years, and has been anecdotally linked to virus infection. In the 2009 growing season some growers had up to 10% of yield with these symptoms. Traditional diagnostic methods are targeted towards specific pathogens. By using a metagenomic approach with high throughput sequencing technology, other, as yet unidentified causes of root necrosis were investigated. Additionally a statistical analysis has shown which viruses are most closely associated with disease symptoms. Carrot samples were collected from a crop exhibiting root necrosis (102 Affected: 99 Unaffected) and tested for the presence of the established carrot viruses: Carrot red leaf virus (CtRLV), Carrot mottle virus (CMoV), Carrot red leaf associated viral RNA (CtRLVaRNA) and Parsnip yellow fleck virus (PYFV). The presence of these viruses was not associated with symptomatic carrot roots either as single viruses or in combinations. A sub-sample of carrots of mixed symptom status was subjected to MiSeq sequencing. The results from these tests suggested Carrot yellow leaf virus (CYLV) was associated with symptomatic roots. Additionally a novel Torradovirus, a novel Closterovirus and two novel Betaflexiviradae related plant viruses were detected. A specific diagnostic test was designed for CYLV. Of the 102 affected carrots, 98% were positive for CYLV compared to 22% of the unaffected carrots. From these data we conclude that although we have yet to practically demonstrate a causal link, CYLV appears to be strongly associated with the presence of necrosis of carrots.     

Some Effects of 'Hardening' Carrot Seed

Carrot seed and water were mixed in the ratio of 100 : 70 byweight, kept in a covered petri-dish for 24 h at 20 °C andthen dried by exposure to the atmosphere at 20 °C. Threecycles of this ‘hardening’ treatment gave seed havingembryos 51 per cent longer than those in untreated seed. Thisincrease in embryo length was due mainly to cell division duringhardening rather than to cell expansion. Hardened seed imbibedwater more quickly to start with and germinated and producedseedlings which emerged in the field 3–4 days earlierthan untreated seed. Relative growth-rates during early growthwere similar from both types of seed. At harvests 14 to 21 weeksafter sowing the mean yields of roots from the hardened seedwas 64.0 compared to 59.2 tons per hectare from the untreatedseed. Variations of the hardening treatment were tried but it appearedthat the above treatment was the most effective for enhancingthe rate of germination, although embryo length and numbersof cells per embryo increased progressively with cycles of hardeningup to six cycles. The moisture content of seed ripening in a field at Wellesbournefluctuated diurnally over the same range as that used in theexperiments to produce a hardening effect, but the embryos didnot increase in length during field ripening.     

胡萝卜优良品种比较试验

在厦门市翔安区对引进的17个胡萝卜新品种进行比较试验,旨在筛选出适宜当地的、优质高产的胡萝卜品种。结果表明,YZS08-863、YZS09-983两个品种分别比对照SK4-316每hm2增产14.0%、28.5%,成熟期提前15～20 d,综合性状表现较为突出,适宜推广应用。     

用衔接头PCR克隆新的胡萝卜Ⅱ型转化酶基因启动子

 为克隆新的胡萝卜 型转化酶基因启动子 ,将胡萝卜基因组 DNA分别用 Pvu 、Eco R 、Dra 和 Sma 酶切 ,酶切片段与一特殊的衔接头连接 .取连接产物作模板 ,以衔接头引物和基因特异引物做 PCR,得到的主要 PCR产物分别为 3.4kb、1 .3kb、0 .4kb和 0 .6kb.将 Eco R -衔接头体系的 PCR产物克隆和测序 ,并将其序列与 Gen Bank中的已知序列进行比较分析 ,发现了一个新的胡萝卜 型转化酶启动子序列 ,它含有类似于 TATA box和 CAAT box的元件 ,在启动子的远上游区域还含有多个 AT富含区 .该启动子的发现对于研究植物中糖代谢具有重要意义 .     

Somatic Embryogenesis in Cultured Carrot Cells

Somatic embryogenesis in cultured plant cells is an ideal system for investigating the whole process of differentiation and development from single cells to whole plants, and especially the molecular mechanism of expression of totipotency. This review reports recent progress the studies on somatic embryogenesis.     

Biological Control of Carrot Black Rot

Diseased carrot seeds were treated with selected micro-organisms isolated from soils, carrot seeds and tap roots. The effects of those antagonists on the control of Alternaria radicina were evaluated by growing-on tests on water agar, filter paper, vermiculite and in a potting medium (BVB no. 4). The germination percentage, emergence percentage and the disease severity of those carrot seeds treated with Burkholderia (Pseudomonas) cepacia no.229 were significantly (P=0.05) differed from the non-treated seeds and the seed treated with other antagonists. The effects of B. cepacia no.229 in promoting seed emergence and controlling disease were as good as those seeds treated with iprodione (100 p.p.m.). Black rot lesions on carrot tap roots were significantly reduced (P=0.05) in size when roots were treated with B. cepacia no 229 or Bacillus amyloliquefaciens no. 224 compared to the nontreated roots. Also, B. cepacia no. 229 significantly (P=0.05) reduced black rot on the foliage of carrot compared to check.     

胡萝卜育种研究(综述)

胡萝卜是高度异花授粉作物,由于存在近交衰退,因而很难通过系内授粉培育出综合性状优良的品种。随着雄性不育系的发现,进而培育出整齐一致的一代杂种。本文综述国内外胡萝卜育种与科研现状,提出胡萝卜育种的主要目标,着重介绍雄性不育在胡萝卜育种中的应用,为加快胡萝卜育种研究提供思路。     

Carrot cells detoxify N-phosphonoacetyl-L-aspartate by esterification.

Unlike bacterial and mammalian cells, carrot cells are able to tolerate N-phosphonoacetyl-L-aspartate (PALA), a potential inhibitor of pyrimidine biosynthesis, by detoxifying the compound. Anion-exchange chromatography showed that detoxified PALA was less negatively charged than PALA, and allowed detoxified PALA to be isolated. Incubation of detoxified PALA with a low-specificity carboxylic-ester hydrolase fully restored the ability to inhibit aspartate transcarbamoylase, the target enzyme, indicating that the detoxification involves the formation of carboxylic ester. G.1.c. analysis of the alcohol products of enzymic hydrolysis, and of their ratio to PALA, showed that the detoxification produced a mixture of mono- and di-carboxylic esters and of methyl and ethyl esters. The detoxification mechanism showed considerable specificity towards PALA, since the analogous carboxy groups of succinate were not modified in the same way. Succinate was depleted much more slowly, no succinate esters could be detected, and the presence of a 10-fold excess of succinate did not inhibit the esterification rate of PALA. The possible significance of these results is discussed.     

Improved Nematode Extraction from Carrot Disk Culture

Radopholus spp. were reared in carrot tissue culture via established procedures, with slight modification. Several plant tissue maceration enzymes and flotation media (salts and sucrose) were evaluated with regard to nematode toxicity and extraction efficiency. Best extraction of viable nematodes and eggs was attained when carrot tissue infested with Radopholus citrophilus or R. similis was macerated with a mixture of 0.50% driselase and 0.50% cellulysin, w/v each, with 2.5 ml of enzyme solution based for each gram of carrot tissue. Maceration slurries containing carrot tissue and nematodes were maintained in open flasks on a rotary shaker (175 rpm) at 26 C for 24 hours. Nematodes and eggs were extracted from resultant culture slurries by flotation with MgSO₄-7H₂0 (sp gr 1.1). A protocol is presented to extract large quantities of viable burrowing nematodes and their eggs from carrot disk cultures.     

Ethylene-induced Isocoumarin Formation in Carrot Root Tissue

The concentrations of 3-methyl-6-methoxy-8-hydroxy-3,4-dihydroisocoumarin (MMHD) formed in carrot roots inoculated with certain fungi or treated with indole-3-acetic acid, 2,4-dichlorophenoxyacetic acid, or 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), were related to the amount of ethylene produced by the root tissue. Ethylene applied exogenously in concentrations above 0.3 ppm induced the formation of MMHD in carrot root discs. Continued production of MMHD required the continued presence of ethylene. The amounts of MMHD in the discs were reduced by CO₂, an inhibitor of ethylene action, and by reduction of the partial pressure of ethylene in fungus-inoculated or 2,4,5-T-treated carrot root discs. The results indicate that ethylene is required for the induction of MMHD formation by carrot root tissue.     

乙烯诱导胡萝卜原生质体凋亡

乙烯是一种参与多种重要生理学过程的植物激素。用乙烯利在密闭条件下处理胡萝卜（ＤａｕｃｕｓｃａｒｏｔａＬ．）原生质体（在ｐＨ＞４．１时释放乙烯）,发现随着乙烯利浓度增加,细胞死亡率逐渐增高。经乙烯利处理的胡萝卜原生质体出现核内染色质固缩,形成凋亡小体等典型的细胞凋亡的形态学特征。用中性法彗星电泳观测到彗星状的核ＤＮＡ片段的迁移。ＤＮＡ电泳分析观察到细胞凋亡时产生的典型的核小体间ＤＮＡ断裂所形成的梯状条带。结果表明,乙烯能诱导悬浮培养的胡萝卜原生质体凋亡     

Ethylene-induced Phenylalanine Ammonia-Lyase Activity in Carrot Roots

Ethylene enhanced the activity of phenylalanine ammonialyase in carrot (Daucus carota L., var. “Nauty”) root tissue. Slight increase in enzyme activity was exhibited by root discs incubated in ethylene-free air. It was probably due to the ethylene formed within the sliced tissue. Addition of ethylene to the air stream increased phenylalanine ammonia-lyase activity and the total protein content of the discs until maximum activity was reached after 36 to 48 hours of incubation. The continuous presence of ethylene was required to maintain high level of activity. Ethylene, at a concentration of 10 microliter per liter induced higher activity than at lower or higher concentrations. CO₂ partially inhibited the ethylene-induced activity. Cycloheximide or actinomycin D effectively inhibited the ethylene-induced activity in discs that had not previously been exposed to ethylene. The results appear to support the hypothesis that the mode of action of ethylene may involve both de novo synthesis of the enzyme protein and protection or regulation of activity of the induced enzyme.     

Partial Resistance of Carrot to Alternaria dauci Correlates with In Vitro Cultured Carrot Cell Resistance to Fungal Exudates

Although different mechanisms have been proposed in the recent years, plant pathogen partial resistance is still poorly understood. Components of the chemical warfare, including the production of plant defense compounds and plant resistance to pathogen-produced toxins, are likely to play a role. Toxins are indeed recognized as important determinants of pathogenicity in necrotrophic fungi. Partial resistance based on quantitative resistance loci and linked to a pathogen-produced toxin has never been fully described. We tested this hypothesis using the Alternaria dauci – carrot pathosystem. Alternaria dauci, causing carrot leaf blight, is a necrotrophic fungus known to produce zinniol, a compound described as a non-host selective toxin. Embryogenic cellular cultures from carrot genotypes varying in resistance against A. dauci were confronted with zinniol at different concentrations or to fungal exudates (raw, organic or aqueous extracts). The plant response was analyzed through the measurement of cytoplasmic esterase activity, as a marker of cell viability, and the differentiation of somatic embryos in cellular cultures. A differential response to toxicity was demonstrated between susceptible and partially resistant genotypes, with a good correlation noted between the resistance to the fungus at the whole plant level and resistance at the cellular level to fungal exudates from raw and organic extracts. No toxic reaction of embryogenic cultures was observed after treatment with the aqueous extract or zinniol used at physiological concentration. Moreover, we did not detect zinniol in toxic fungal extracts by UHPLC analysis. These results suggest that strong phytotoxic compounds are present in the organic extract and remain to be characterized. Our results clearly show that carrot tolerance to A. dauci toxins is one component of its partial resistance.     

Carrot arabinogalactan proteins are interlinked with pectins

Cell wall extracts from a carrot cell culture and tap roots were obtained by sequential extraction with water, EDTA buffer solution and cold sodium hydroxide solution. Arabinogalactan proteins (AGPs) were isolated from the extracts and from the medium of the cell culture and analysed for their molecular weight distribution and carbohydrate composition. Copper ions were used to separate the Yariv positive fractions into AGP fractions with a high and a low level of galacturonic acid (GalA). The GalA rich AGP fractions were incubated with pectin methylesterase and polygalacturonase. This enzyme incubation released GalA fragments from the AGP fractions as monitored by HPAEC and MALDI-TOF MS. At least part of carrot AGPs from the medium and cell walls may be covalently linked to pectin containing a homogalacturonan structural element.     

Chemical genetics: where genetics and pharmacology meet

Genetics and pharmacology can elicit surprisingly different phenotypes despite targeting the same protein. This Essay explores these unexpected differences and their implications for biology and medicine.