Teores de proteína bruta na silagem de azevém (Lolium multiflorum, Lam.) em estágio vegetativo, submetida a diferentes tempos de murcha.

2015

Resistência de biótipos de azevém ao herbicida iodosulfurom-metílico sódio e herbicidas alternativos para o controle. ALS, Lolium multiflorum, plantas daninhas, sulfonilureia Sulfonylurea, weed

2016

Resistance characterization of Italian ryegrass (Lolium multiflorum) biotypes to clethodim herbicide.

2016

Adaptive potential of Lolium multiflorum L. biotypes susceptible and resistant to glyphosate.

2016

Evaluating temperate species for the subtropics. 1. Annual ryegrasses

In the subtropics of Australia, irrigated temperate species are the key to reliable cool season feed on dairy farms. Persistence of perennial species is a major limitation to achieving reliable production from irrigated areas and yearly sowings of annual ryegrasses have replaced them as the most productive cool season forage production system in the subtropics. This series of experiments evaluated the yield, and resistance to rust damage, of commercially available cultivars and breeders' lines of annually sown ryegrasses (Lolium multiflorum, L. rigidum, L. x boucheanum and L perenne) in pure, nitrogen-fertilised swards under irrigation in the subtropics over a 22-year period. Barberia and Aristocrat 2 were the most adapted cultivars for subtropical conditions, producing high yields (119 and 114% of mean yield, respectively) and demonstrating the least rust damage. Newer selections from New Zealand, South African, United States of America and European breeding programs are performing better under subtropical conditions than older cultivars, particularly if a component of the selection process has been conducted in that environment. Cultivars such as Passerei Plus, Crusader, Hulk, Status and Warrior are examples of this process, producing between 105 and 115% of mean yield. Yields of annual ryegrass cultivars, which have been available or still are available for sale in Australia, ranged from 14-30 t/ha DM, depending on cultivar, site and seasonal conditions. Yields were lower at the site, which had inferior soil structure and drainage. Up to 50% of yield was produced in the 3 winter months. There was a trend towards improved yields and better tolerance of crown rust from experimental lines in the subtropics, as breeders strive for wider adaptation. Around 70% of the variation in total yield of annual ryegrass and 50 and 60% of the variation in winter and spring yield, respectively, were significantly explained by cultivar, site and climatic variables in autumn, winter and spring. While level of rust damage had no effect on total or seasonal yields, it affected the amount of green leaf available in spring. Under subtropical conditions, winter, spring and overall (autumn to mid-summer) temperatures influenced the- development of rust, which along with cultivar, accounted for 46% of the variation in rust damage. Cultivars showed a range of adaptation, with some performing well only under adverse conditions, some being well adapted to all conditions and some which performed well only under favoured conditions. Cultivars with high winter yields were most suited to subtropical conditions and included Aristocrat 2 (now released as CM 108), Barberia, Warrior, Crusader, Status, Passerei Plus and Hulk. Short growing season types such as Winter Star and T Rex performed well in winter but achieved lower total production, and long season cultivars such as Flanker rarely achieved their potential because of unfavourable conditions in late summer.

Ruminal protein degradability of a range of tropical pastures

The rumen degradability parameters of the diet selected by two to four oesophageal-fistulated Brahman steers grazing a range of tropical pastures were determined by incubation of extrusa in nylon bags suspended in the rumen of rumen-fistulated (RF) Brahman steers. The effective protein degradability (Edg) was determined by measuring the rate of disappearance of neutral detergent insoluble nitrogen (NDIN) less acid detergent insoluble nitrogen (ADIN) in the incubated extrusa. Six to eight RF steers also grazed each of the pastures along with the oesophageal-fistulated steers, to allow determination of key rumen parameters and rumen particulate matter fractional outflow rates (FOR). The seven pastures studied included: native tropical grass (C4) pasture (major species Heteropogon contortus and Bothriochloa bladhii), studied in the early wet (NPEW), the wet/dry transition (NPT) and the dry (NPD) seasons; introduced tropical grass (C4) pasture (Bothriochloa insculpta), studied in the mid wet season (BB); the introduced tropical legumes (C3), Lablab purpureus (LL) and Clitoria ternatea (BP); and the temperate grass (C3) pasture, ryegrass (Lolium multiflorum, RG). Using the measured particle FOR values in calculations, the Edg estimates were very high for both C4 and C3 species: 0.82–0.91 and 0.95–0.98 g/g crude protein (CP), respectively. Substitution of an assumed FOR (kp = 0.02/h) for the measured values for each pasture type did not markedly affect estimates of Edg. However, C4 tropical grasses had much lower effective rumen degradable protein (ERDP) fractions (23–66 g/kg DM) than the C3 pasture species RG and LL (356 and 243 g/kg DM, respectively). This was associated with a lower potential degradability and degradation rate of organic matter (OM) in sacco, lower in vitro organic matter digestibility (IVOMD) and CP concentrations in the extrusa, and lower ammonia-N and branched-chain fatty acid concentrations in rumen fluid for the tropical grasses. As tropical grass pastures senesced, there was a decline in Edg, the ERDP and rumen undegradable protein (UDP) fractions, the potential degradability and degradation rate of OM and the IVOMD. These results provide useful data for estimating protein supply to cattle grazing tropical pastures.

The use of temperate species in the Australian subtropics.

Temperate species and tropical crop silage are the basis for forage production for the dairy industry in the Australian subtropics. Irrigation is the key resource needed for production, with little survival of temperate species under rain-grown conditions except for lucerne. Annual ryegrass (Lolium multiflorum), fertilised with either inorganic nitrogen or grown with clovers, is the main cool season forage for the dairy industry. It is sown into fully prepared seedbeds, oversown into tropical grasses, especially kikuyu (Pennisetum clandestinum) or sown after mulching. There has been a continual improvement in the performance of annual and hybrid ryegrass cultivars over the last 25 years. In small plot, cutting experiments, yields of annual ryegrass typically range from 15 to 21 t DM/ha, with equivalent on-farm yields of 7 to 14 t DM/ha of utilised material. Rust (Puccinia coronata) remains the major concern although resistance is more stable than in oats. There have also been major improvements in the performance of perennial ryegrass (L. perenne) cultivars although their persistence under grazing is insufficient to make them a reliable forage source for the subtropics. On the other hand, tall fescue (Festuca arundinacea) and prairie grass (Bromus willdenowii) cultivars perform well under cutting and grazing, although farmer resistance to the use of tall fescue is strong. White clover (Trifolium repens) is a reliable and persistent performer although disease usually reduces its performance in the third year after sowing. Persian (Shaftal) annual clover (T. resupinatum) gives good winter production but the performance of berseem clover (T. alexandrinum) is less reliable and the sub clovers (T. subterraneum) are generally not suited to clay soils of neutral to alkaline pH. Lucerne (Medicago sativa), either as a pure stand or in mixtures, is a high producing legume under both irrigation and natural rainfall. Understanding the importance of leaf and crown diseases, and the development of resistant cultivars, have been the reasons for its reliability. Insects on temperate species are not as serious a problem in the subtropics as in New Zealand (NZ). Fungal and viral diseases, on the other hand, cause many problems and forage performance would benefit from more research into resistance.

Agronomic challenges for organic crop husbandry

With respect to resource management and environmental impact, organic farming offers rationales for agricultural sustainability. However, agronomic productivity is usually higher with conventional farming. This work aimed at investigating two factors of major importance for the agronomic productivity of organic crop husbandry, nitrogen (N) supply through symbiotic N fixation (SNF) and weed occurrence. Perennial red clover-grass leys and spring cereal crops subjected to regular agricultural practices were studied on 34 organic farms located in the southern and the north-western coastal regions of Finland. Herbage growth, clover content as a proportion of the ley and extent of SNF in perennial leys, and the occurrence of weed species and weed-crop competition in spring cereal stands were related to climate conditions, soil properties, and management measures. The herbage accumulated from the first and the second cut of one- and two-year-old leys averaged 7.5 t DM ha-1 (SD ± 1.7 t DM ha-1); the clover content averaged 43.9% (SD ± 18.8%). Along with the clover content, herbage production decreased with ley age. Radiation use efficiency (RUE) correlated positively with clover proportion but despite low clover contents, three-year-old leys were still productive with regard to RUE. SNF in the accumulated annual growth of one- and two-year-old leys averaged 247.5 kg N ha-1 yr-1 (SD ± 114.4 kg N ha-1 yr-1). It was supposed that if red clover-grass leys constituted 40% of the rotation, then the mean N supply by SNF would be able to sustain two or three succeeding cereal crops (green manure and forage ley, respectively), yielding 3.0 to 4.0 t grain ha-1. Being a function of clover biomass, the SNF increased from the first to the second cut and thereafter declined with ley age. Coefficients of variation of clover contents (and SNF) between and within fields were around 50%, which was about twice as high as those of herbage production. The lower were the clover contents, the higher were the within-field variations of clover as a proportion of the ley. Low clover contents in one-year-old leys and increasing variability with ley age suggested that red clover growth was limited by poor establishment and poor overwintering. The proportions of clover in leys were lower and their variability was higher in the northwest than in the south. Soil properties, primarily texture and structure, had a major impact on clover proportion and herbage production, which largely explained regional differences in ley growth. Within-field variability of soil properties can be amended through site-specific measures, including drainage, liming, and applications of organic manures and mineral fertilizers. Overwintering and the persistence of leys can be improved by the choice of winter-hardy varieties, careful establishment and the appropriate harvest regime. Mean grain yields of spring cereal crops amounted to 3.2 t ha-1 in the south and 3.6 t ha-1 in the northwest. At 570 and 565 m-2 for the south and northwest respectively, mean weed densities did not differ between the regions, whereas the respective mean weed biomass of 697 and 1594 kg dry weight ha-1, respectively did differ. Weed abundance varied remarkably between single fields. The number of weed species was higher in the south than in the northwest. For example, Fumaria officinalis and Lamium spp. were found only in the south. Frequencies and abundances of Lapsana communis, Myosotis arvensis, Polygonum aviculare, Tripleurospermum inodorum, and Vicia spp. were higher in the south, whereas those of Elymus repens, Persicaria spp. and Spergula arvensis were higher in the northwest. The number of years since conversion to organic farming, i.e. long-term management, was one of the variables that explained the abundance of single weed species. E. repens was the weed species whose biomass increased most with the duration of organic farming. Another significant variable was crop biomass, which was affected by short-term management. The presence of different weed species was related to the duration of organic farming and to low crop yield. This finding demonstrated that it was not the organic farming regime per se, which resulted in high weed infestation and low yielding crops, but failures in the understanding and the management of organic farming systems. Successful weed control relies on farm- and field-specific long- and short-term management approaches. The agronomic productivity of ley and spring cereal crops managed by full-time farmers with an interest in organic farming was on the same level as of the mean for conventional farming. Given the many options for further improvements of the agronomic performance of organic arable systems, organic farming offers foundations for the development of sustainable agriculture. The main threat to the sustainability of farming in Finland, both conventional and organic, is the spatial separation of crop production and animal husbandry by region, along with the simplification of associated crop rotations.

Undersowing in a northern climate: effects on spring cereal yield and risk of nitrate leaching

Disadvantages of invariable cereal cropping, concern of nutrient leaching and prices of nitrogen (N) fertilizer have all increased during last decades. An undersown crop, which grows together with a main crop and after harvest, could mitigate all those questions. The aim of this study was to develop undersowing in Finnish conditions, so that it suits for spring cereal farming as well as possible and enhances taking care of soil and environment, especially when control of N is concerned. In total, 17 plant species were undersown in spring cereals during the field experiments between 1991-1999 at four sites in South and Central Finland, but after selection, eight of them were studied more thoroughly. Two legumes, one grass species and one mixture of them were included in long-term trials in order to study annually repeated undersowing. Further, simultaneous broadcasting of seeds instead of separate undersowing was studied. Grain yield response and the capacity of the undersown crop to absorb soil N or fix N from atmosphere, and the release of N were of greatest interest. Seeding rates of undersown crops and N fertilization rates during annually repeated undersowing were also studied. Italian ryegrass (Lolium multiflorum Lam., IR) absorbed soil nitrate N (NO3-N) most efficiently in autumn and timothy (Phleum pratense L.) in spring. The capacity of other grass species to absorb N was low, or it was insufficient considering the negative effect on grain yield. Red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) suited well in annually repeated undersowing, supplying fixed N for cereals without markedly increased risk of N leaching. Autumn oriented growth rhythm of the studied legumes was optimal for undersowing, whereas the growth rhythm of grasses was less suited but varied between species. A model of adaptive undersowing system was outlined in order to emphasize allocation of measures according needs. After defining the goal of undersowing, many decisions are to be done. When diminishing N leaching is primarily sought, a mixture of IR and timothy is advantageous. Clovers suit for replacing N fertilization, as the positive residual effect is greater than the negative effect caused by competition. A mixture of legume and non legume is a good choice when increased diversity is the main target. Seeding rate is an efficient means for adjusting competition and N effects. Broadcasting with soil covering equipment can be used to establish an undersown crop. In addition, timing and method of cover crop termination have an important role in the outcome. Continuous observing of the system is needed as for instance conditions significantly affect growth of undersown crop and on the other hand N release from crop residues may increase in long run.

Ethnobotany of the Monpa ethnic group at Arunachal Pradesh, India

Background: The present paper documents the uses of plants in traditional herbal medicine for human and veterinary ailments, and those used for dietary supplements, religious purpose, local beverage, and plants used to poison fish and wild animals. Traditional botanical medicine is the primary mode of healthcare for most of the rural population in Arunachal Pradesh. Materials and methods: Field research was conducted between April 2006 and March 2009 with randomly selected 124 key informants using semi-structured questionnaire. The data obtained was analyzed through informant consensus factor (F(IC)) to determine the homogeneity of informant's knowledge on medicinal plants. Results: We documented 50 plants species belonging to 29 families used for treating 22 human and 4 veterinary ailments. Of the medicinal plants reported, the most common growth form was herbs (40%) followed by shrubs, trees, and climbers. Leaves were most frequently used plant parts. The consensus analysis revealed that the dermatological ailments have the highest F(IC) (0.56) and the gastro-intestinal diseases have F(IC) (0.43). F(IC) values indicated that there was high agreement in the use of plants in dermatological and gastro-intestinal ailments category among the users. Gymnocladus assamicus is a critically rare and endangered species used as disinfectant for cleaning wounds and parasites like leeches and lice on livestocks. Two plant species (Illicium griffithii and Rubia cordifolia) are commonly used for traditional dyeing of clothes and food items. Some of the edible plants recorded in this study were known for their treatment against high blood pressure (Clerodendron colebrookianum), diabetes mellitus (Momordica charantia), and intestinal parasitic worms like round and tape worms (Lindera neesiana, Solanum etiopicum, and Solanum indicum). The Monpas of Arunachal Pradesh have traditionally been using Daphne papyracea for preparing hand-made paper for painting and writing religious scripts in Buddhist monasteries. Three plant species (Derris scandens, Aesculus assamica, and Polygonum hydropiper) were frequently used to poison fish during the month of June-July every year and the underground tuber of Aconitum ferrox is widely used in arrow poisoning to kill ferocious animals like bear, wild pigs, gaur and deer. The most frequently cited plant species; Buddleja asiatica and Hedyotis scandens were used as common growth supplements during the preparation of fermentation starter cultures. Conclusion: The traditional pharmacopoeia of the Monpa ethnic group incorporates a myriad of diverse botanical flora. Traditional knowledge of the remedies is passed down through oral traditions without any written document. This traditional knowledge is however, currently threatened mainly due to acculturation and deforestation due to continuing traditional shifting cultivation. This study reveals that the rural populations in Arunachal Pradesh have a rich knowledge of forest-based natural resources and consumption of wild edible plants is still an integral part of their socio-cultural life. Findings of this documentation study can be used as an ethnopharmacological basis for selecting plants for future phytochemical and pharmaceutical studies.

Efecto de las frecuencias de pastoreo sobre un pastizal natural con presencia de Lotus tenuis en el partido de Olavarría, provincia de Buenos Aires

Resumen: La Pampa deprimida bonaerense está considerada la zona de cría más importante del país; el 85% de su superficie está cubierta por pastizales naturales, siendo éstos la principal fuente de alimento para la ganadería local. La productividad del pastizal natural, puede ser mejorada aplicando tecnología de procesos, al utilizar pastoreos en forma rotacional, en lugar del usual pastoreo continuo. El objetivo del presente trabajo, es evaluar el efecto en la producción bruta de materia seca del pastizal natural en un ambiente de un bajo dulce, en donde Lolium multiflorum y Lotus tenuis constituyen especies indicadoras, y cuya frecuencia en el tapiz vegetal es alta. Este ensayo se realizó en el establecimiento “El Fortín” ubicado en la Estación Pourtalé (Partido de Olavarría), durante un año, desde Mayo del 2014 hasta Mayo del 2015. Se utilizó un diseño experimental de bloques completamentes aleatorizados (DCBA), con dos tratamientos: frecuencia de 45 días y frecuencia de 90 días. Aleatorizados en tres bloques que corresponden al número de parcelas existentes dentro del potrero. Se realizaron en total 11 muestreos midiendo la producción de materia seca, siendo esta la variable en estudio. El análisis estadístico se realizó mediante un análisis de varianza, utilizando como software el programa Infostat. Los resultados sobre la producción en promedio, sostienen que existen diferencias significativas entre ambos tratamientos: de 45 días y de 90 días. La materia seca acumulada y anualizada, fue de 3306,7kg.MS ha-1 para el tratamiento de 45 días y de 3190,0 kg.MS ha-1 para el tratamiento de 90 días, entre pastoreos sucesivos. Mientras que la producción promedio acumulada entre cortes para cada tratamiento fue de 472,4kg.MS ha-1 para el tratamiento de 45 días y de 797,5 kg.MS ha-1 para el tratamiento de 90 días.

Endothall species selectivity evaluation: northern latitude aquatic plant community

Species selectivity of the aquatic herbicide dipotassium salt of endothall (Aquathol® K) was evaluated on plant species typically found in northern latitude aquatic plant communities. Submersed species included Eurasian watermilfoil (Myriophyllum spicatum L.), curlyleaf pondweed (Potamogeton crispus L.), Illinois pondweed (Potamogeton illinoensis Morong.), sago pondweed (Potamogeton pectinatus L.), coontail (Ceratophyllum demersum L.), elodea (Elodea canadensis Michx.) and wildcelery (Vallisneria americana L.). Emergent and floating-leaf plant species evaluated were cattail (Typha latifolia L.), smartweed (Polygonum hydropiperoides Michx.), pickerelweed (Pontederia cordata L.) and spatterdock (Nuphar advena Aiton). The submersed species evaluations were conducted in 7000 L mesocosm tanks, and treatment rates included 0, 0.5 1.0, 2.0, and 4.0 mg/L active ingredient (ai) endothall (dipotassium salt of endothall). The exposure period consisted of a 24-h flow through half-life for 7 d. The cattail and smartweed evaluation was conducted in 860 L mesocosm tanks, and the spatterdock and pickerelweed evaluations were conducted in 1600 L mesocosm tanks. Treatment rates for the emergent and floating-leafed plant evaluations included 0, 0.5, 2.0 and 4.0 mg/L ai endothall, and the exposure period consisted of removing and replacing half the water from each tank, after each 24 h period for a duration of 120 h. Biomass samples were collected at 3 and 8 weeks after treatment (WAT). Endothall effectively controlled Eurasian watermilfoil and curlyleaf pondweed at all of the application rates, and no significant regrowth was observed at 8 WAT. Sago pondweed, wildcelery, and Illinois pondweed biomass were also significantly reduced following the endothall application, but regrowth was observed at 8 WAT. Coontail and elodea showed no effects from endothall application at the 0.5, 1.0, and 2.0 mg/L application rates, but coontail was controlled at 4.0 mg/L rate. Spatterdock, pickerelweed, cattail, and smartweed were not injured at any of the endothall application rates.

Macrophytes aquatiques dans les eaux "continentales" ivoiriennes

Inventory and socio-economic impacts of water weed are presented. Free-floating species (Eichhornia crassipes, Pistia strationes) floating leaves plants (Nymphaea lotus, Polygonum senegalense) as well as emerged species such as Echinochloa pyramidalis and Nelumbo nucifera are the most common species in the concerned aquatic environments. These plants have been colonizing these environments for about a decade and the colonized area are equivalent to 70 % of the whole of the water surface. Besides, these plants strongly affect water quality and constitute a nuisance for water uses.

Ⅰ 虎杖聚酮类化合物生物合成相关基因的克隆及功能分析 Ⅱ 高山红景天酪醇生物合成代谢途径机制分析

Ⅰ 虎杖聚酮类化合物生物合成相关基因的克隆及功能分析 虎杖 (Polygonum cuspidatum Sieb. et Zucc) 属于蓼科蓼属多年生草本植物，在中国和日本民间曾被广泛用于动脉粥样硬化、高血压、咳嗽、化脓性皮肤炎以及淋病的治疗，具有祛风利湿、散瘀定痛、止咳化痰等功效。而在现代医学上最令人瞩目和具有发展前景的是其在抗肿瘤、心血管保护、抗氧化方面的作用，相关疗效主要来自于虎杖中结构迥异、种类丰富的聚酮化合物及其衍生物资源。这些聚酮类化合物主要包括蒽醌、大黄素、大黄素-甲醚、大黄酚、芪类以及类黄酮化合物等。其中，大部分聚酮类化合物生物合成途径机制尚不明确，但可以肯定的是植物类型III聚酮合酶type III polyketide synthases (PKSs) 在这些聚酮化合物的生物合成起始反应中行使着关键的作用。因此，除了我们所熟悉的类黄酮化合物、芪类化合物之外，进一步分离和分析虎杖中其它重要聚酮类化合物生物合成所涉及的类型III聚酮合酶基因的是非常值得期待的。 目前，已经有14个植物类型III PKS基因被克隆和功能分析。植物类型III PKS的共同特征包括基因结构、序列相似性、保守的活性中心、酶学性质以及共同的催化机制等。显花植物（裸子植物和被子植物）中，植物类型III PKS的基因结构绝对保守，除了一个早期报道的金鱼草（Antirrhinum majus）查尔酮合酶chalcone synthase (CHS) 含有第二个内含子外，迄今为止所有已知的植物类型III PKS基因均含有一个内含子且该内含子位置保守。有趣的是，在本研究中，两个含有3个内含子的类型III PKS基因从虎杖中被分离，且两个基因3个内含子的位置完全保守，这是三内含子类型III PKS基因首次得到分离。除了新奇的基因结构外，体外功能分析显示上述两个基因还具有特殊的酶学性质和功能。 本论文围绕上述2个三内含子基因开展了以下工作： 虎杖中一个由三内含子基因编码的新型类型III聚酮合酶 一个类型III PKS的cDNA及其相应的基因（PcPKS2）从药用植物虎杖中被克隆。序列分析结果表明，PcPKS2的开放阅读框被3个内含子分隔，这是一个出人意料的发现，因为截至到目前为止，除了金鱼草一个CHS基因外，所有已知的类型III PKS基因均在固定位置上含有一个内含子。除了特殊的基因结构外，PcPKS2显示了一些有趣的特性：(i) CHS“守卫”苯丙氨酸——Phe215和Phe265在PcPKS2中双双缺失，它们分别被亮氨酸和半胱氨酸取代;(ii) 体外功能分析结果表明，当酶促反应体系的pH值为6.5-8.5时，大肠杆菌中过表达的重组PcPKS2高效地合成丁烯酮非环化产物——4-香豆酰甘油酸内酯（4-coumaroyltriacetic acid lactone (CTAL)）为主产物，而丙烯酮非环化产物bis-noryangonin (BNY) 以及苯亚甲基丙酮为副产物;而当酶促反应体系的pH值为9.0时，PcPKS2高效地合成苯亚甲基丙酮为主产物，而CTAL、BNY为副产物。另外，除了上述3种产物外，在不同的pH条件下，还有痕量的柚皮素查尔酮能被检测到。此外，在4-香豆酰辅酶A（4-coumaroyl-CoA）的类似化合物中，除了4-香豆酰辅酶A外，只有feruloyl-CoA能够被PcPKS2接受作为起始底物。PcPKS2不接受脂肪酰辅酶A——异丁酰基辅酶A（isobutyryl-CoA）、异戊酰基辅酶A（isovaleryl-CoA）以及乙酰辅酶A（acetyl-CoA）作为起始底物。Southern blot杂交结果表明，在虎杖基因组中存在2-4个PcPKS2基因的拷贝。Northern blot杂交结果表明，在根茎和幼叶中，PcPKS2表达量很高，而在根中无表达。叶中的PcPKS2的表达受病原菌诱导，但不受伤诱导。 虎杖中一个编码双功能类型III聚酮合酶的三内含子基因的鉴定 显花植物中，所有已知的类型III PKS 基因均含有一个内含子且位置绝对保守。本研究中，综合运用PCR技术，从富含聚酮类化合物的植物虎杖中克隆得到一个类型III PKS 基因（PcPKS1）及其cDNA。序列分析结果表明，PcPKS1含有3个内含子。系统发育分析结果表明，PcPKS1与其它植物的CHSs归为一类。然而，体外功能分析结果表明，当酶促反应体系pH值为7.0时，大肠杆菌中过表达的重组PcPKS1高效地合成柚皮素查尔酮（naringenin）为单一产物;而当pH值为9.0时，苯亚甲基丙酮（p-hydroxybenzalacetone）几乎为重组PcPKS1的唯一产物。后续的研究表明，与典型的CHSs相比，PcPKS1具有另外一些不同的特点：在pH值为9.0时（PcPKS1的苯亚甲基丙酮合成活性最适pH值），在4-香豆酰辅酶A的类似化合物中，只有feruloyl-CoA能够被PcPKS1接受作为起始底物。与CHSs展现出的对脂肪酰辅酶A宽泛的底物特异性不同，在不同的pH条件下，PcPKS1不接受异丁酰基辅酶A（isobutyryl-CoA）、异戊酰基辅酶A（isovaleryl-CoA）以及乙酰辅酶A（acetyl-CoA）作为起始底物。以上数据指出重组PcPKS1是一个具有查尔酮合酶（CHS）和苯亚甲基丙酮合酶（BAS）活性的双功能酶。Southern blot杂交结果表明，在虎杖基因组中存在2-4个PcPKS1基因的拷贝。Northern blot杂交结果表明，PcPKS1可能在防御病原菌和草食动物方面起着重要作用。PcPKS1和PcPKS2共同从虎杖中被分离的事实极有可能暗示了苯丁烷类化合物（phenylbutanoid）及其衍生物存在于虎杖中。 Ⅱ 高山红景天酪醇生物合成代谢途径机制研究 高山红景天（Rhodiola sachalinensis A. Bor）是景天科（Crassulaceae）红景天属多年生草本植物，作为一种适应原性中草药在中国的应用史已经超过800年。最近红景天提取物作为一种重要的商业药用制剂资源，其应用遍及欧洲、亚洲和美国，其主要治疗范围包括抗变应性和消炎，提高心理机敏性等。目前已经非常明确，红景天甙（salidroside）和甙元酪醇（tyrosol）是红景天属植物的主要功效成分，主要分布于这类植物的根中并且具有抗缺氧、抗疲劳、延缓衰老、预防紫外线辐射伤害等功效。红景天甙为酪醇8-O-β-D葡萄糖甙，是酪醇在葡萄糖基转移酶UDP-glucosyltransferase (UGT) 的催化下糖基化后形成的，可以认为是酪醇在植物体内的贮存形式。酪醇作为一种重要的活性分子，同样存在于橄榄树和葡萄酒中。 虽然已经非常明确酪醇来自于莽草酸代谢途径，然而其具体的生物合成途径及其调控仍不明确。总结以往的报道，在酪醇的生物合成上主要存在两种观点：一是酪醇可能来自于苯丙烷代谢途径产生的4-香豆酸（4-coumaric acid）前体;二是来自于酪氨酸的酪胺（tyramine）可能是酪醇生物合成的直接前体。我们的工作兴趣主要围绕着鉴别高山红景天中的酪醇生物合成途径展开： 高山红景天内源苯丙氨酸解氨酶PALrs1的过表达对红景天甙积累的影响 红景天甙是来自于药用植物高山红景天的一种适应原性新型药物，其生物合成途径可能起始于苯丙氨酸或酪氨酸。由于高山红景天野生植物资源的匮乏和相对含量很低，阐明红景天甙的生物合成途径对于增加红景天甙的供给至关重要。在我们以前的工作中，运用cDNA末端快速扩增技术（RACE），一个编码苯丙氨酸解氨酶phenylalanine ammonia-lyase (PAL)的cDNA从高山红景天中被克隆，命名为PALrs1。在本研究中，PALrs1置于35S启动子+Ω增强子序列的控制下通过农杆菌（Agrobacterium tumefaciens）介导法转化回高山红景天。PCR 和 PCR–Southern blot分析结果表明，PALrs1已经整合到了转基因植物的基因组上。Northern blot杂交结果表明，PALrs1已经获得在转录水平上的高水平表达。与预期的结果相同，高效液相色谱High-performance liquid chromatography (HPLC)测定结果显示PALrs1的过表达引起4-香豆酸含量增长3.3倍。然而，与之相反的是，酪醇和红景天甙含量与对照相比反而分别下降4.7和7.7倍。此外，我们发现PALrs1的过表达造成酪氨酸含量下降2.6倍。这些数据暗示着PALrs1的过表达和4-香豆酸的积累并不能促进酪醇的生物合成。酪醇，作为一种苯乙烷类衍生物并非来自苯丙氨酸，而酪氨酸含量的下降则极有可能是酪醇生物合成和红景天甙积累大规模下降的直接原因。