A Moricandia arvensis– based cytoplasmic male sterility and fertility restoration system in Brassica juncea

 A cytoplasmic male-sterility system has been developed in mustard (Brassica juncea) following repeated backcrossings of the somatic hybrid Moricandia arvensis (2n=28, MM)+B. juncea (2n=36, AABB), carrying mitochondria and chloroplasts from M. arvensis, to Brassica juncea. Cytoplasmic male-sterile (CMS) plants are similar to normal B. juncea; however, the leaves exhibit severe chlorosis resulting in delayed flowering. Flowers are normal with slender, non-dehiscent anthers and excellent nectaries. CMS plants show regular meiosis with pollen degeneration occurring during microsporogenesis. Female fertility was normal. Genetic information for fertility restoration was introgressed following the development of a M. arvensis monosomic addition line on CMS B. juncea. The additional chromosome paired allosyndetically with one of the B. juncea bivalents and allowed introgression. The putative restorer plant also exhibited severe chlorosis similar to CMS plants but possessed 89% and 73% pollen and seed fertility, respectively, which subsequently increased to 96% and 87% in the selfed progeny. The progeny of the cross of CMS line with the restorer line MJR-15, segregated into 1 fertile : 1 sterile. The CMS (Moricandia) B. juncea, the restorer (MJR-15), and fertility restored F₁ plants possess similar cytoplasmic organellar genomes as revealed by ‘Southern’ analysis. Received: 17 September 1997 / Accepted: 18 February 1998     

Isolation and Preliminary Characterization of Differential Displayed cDNAs in Brassica juncea Exposed to Heavy Metal

Heavy metal contamination of soil has become a major environmental concern worldwide over the past several decades,the exploitation and application of heavy metal hyperaccumulating plants will defend the safety of food and environment on which human life relied,whereas using natural hyperaccumulators is insufficient,due to     

Access and Identification of Intergeneric Hybrid Between Brassica juncea×Crambe abyssinica

An intergeneric hybrid between Brassica juncea (L.) Coss. x Crambe abyssinica Hochst. ex R. E. Fries was obtained for the first time through routine method combined with embryo rescue. The inductivity of hybrids was 2.1%. In many respects the Fl hybrid resembled either its maternal or paternal parent br both. Consequenfiy, retarded growth, wrinkled leaves and rudimentary anthers in Fl plant were observed. Fl pollen varied in size and 10% ~ 15% were of the paternal pollen type,i.e. ,4-colpate. Fl pollen viability was low and 12% ~ 25% of pollens was viable, with a mean of 18.5%. The chromosome number of Fl somatic cell was 63 which was intermediate between the two parents. Most of pollen mother cells had 63 chromosomes. Analysis of isozymes further confirmed that the F1 hybrid combined the paternal characteristic bands.     

Modification of erucic acid content in Indian mustard (Brassica juncea) by up-regulation and down-regulation of the Brassica juncea FAT TY ACID ELONGATION1 (BjFAE1) gene

In Brassicas, the Fatty Acid Elongation1 (FAE1) gene product, a 3-ketoacyl-CoA synthase, is the first in a 4-enzyme complex involved in the synthesis of erucic acid from oleic acid. The FAE1 homologue from Brassica juncea cv. Pusa Bold was cloned in a binary vector both in sense and antisense orientations under the control of the CaMV35S promoter. The recombinant binary vectors were used to transform B. juncea cv. RLM 198 via Agrobacterium tumefaciens. The presence of the transgene was confirmed by polymerase chain reaction and Southern hybridization. Northern and western analyses showed the expression of the gene and protein, respectively, in the transgenic plants. Analyses of the fatty acid profile of the seed oil from homozygous T4 generation seeds revealed that over-expression of the FAE1 gene caused a 36% increase in the percent of erucic acid (37–49% compared to 36% in untransformed control). The down-regulation of FAE1 caused an 86% decrease in the percent of erucic acid to as low as 5% in the seed oil of transgenic plants. Thus, it is clearly possible to alter erucic acid content of mustard by altering the expression level of the FAE 1 gene. S. Kanrar and J. Venkateswari equally contributed to this work.     

More plant growth but less plant defence? First global gene expression data for plants grown in soil amended with biochar

Biochar is a carbon (C)-rich solid formed when biomass is used to produce bioenergy. This ‘black carbon’ has been suggested as a solution to climate change, potentially reducing global anthropogenic emissions of greenhouse gases by 12%, as well as promoting increased crop growth. How biochar application to soil leads to better crop yields remains open to speculation. Using the model plant Arabidopsis and the crop plant lettuce (Lactuca sativa L.), we found increased plant growth in both species following biochar application. Statistically significant increases for Arabidopsis in leaf area (130%), rosette diameter (61%) and root length (100%) were observed with similar findings in lettuce, where biochar application also increased leaf cell expansion. For the first time, global gene expression arrays were used on biochar-treated plants, enabling us to identify the growth-promoting plant hormones, brassinosteroid and auxin, and their signalling molecules, as key to this growth stimulation, with limited impacts on genes controlling photosynthesis. In addition, genes for cell wall loosening were promoted as were those for increased activity in membrane transporters for sugar, nutrients and aquaporins for better water and nutrient uptake and movement of sugars for metabolism in the plant. Positive growth effects were accompanied by down-regulation of a large suite of plant defence genes, including the jasmonic acid biosynthetic pathway, defensins and most categories of secondary metabolites. Such genes are critical for plant protection against insect and pathogen attack, as well as defence against stresses including drought. We propose a conceptual model to explain these effects in this biochar type, hypothesizing a role for additional K⁺ supply in biochar amended soils, leading to Ca²⁺ and Reactive Oxygen Species (ROS) –mediated signalling underpinning growth and defence signalling responses.     

Heterotrimeric Gα subunit regulates plant architecture,organ size and seed weight in the oilseed Brassica juncea

Plant Molecular Biology - Two BjuGα proteins exhibit conserved GTP-binding and GTP-hydrolysis activities, and function in maintaining overall plant architecture and controlling multiple...     

A complex interplay of Gβ and Gγ proteins regulates plant growth and defence traits in the allotetraploid Brassica juncea

Plant Molecular Biology - Gene expression analysis coupled with in-planta studies showed that specific Gβγ combination regulates plant growth and defence traits in the allotetraploid...     

Overcoming prefertilization barriers in the crossDiplotaxis siettiana × Brassica juncea using irradiated mentor pollen

Hybridization between the nearly extinct speciesDiplotaxis siettiana andBrassica juncea is prevented because of strong prefertilization barriers. Use of mentor pollen ofD. siettiana irradiated with 1000 Gy gamma radiation before the incompatible pollination led to fertilization. 5 d after pollination 17% ovules showed entry of pollen tubes, 10 d after pollination 27% ovules showed small globular embryos which grew no further. No embryos were found in control pollinations. Thus , use of irradiated mentor pollen brings about fertilization in this difficult cross and hybrids can be obtained if embryos are rescued.     

Accumulation and translocation of heavy metals in the canola (Brassica napus L.)—soil system in Yangtze River Delta, China

Aims and methods

Concentrations of heavy metals such as Cd, As, Hg, Pb, Cr, Cu, Zn and Ni in different tissues (seeds, roots and shoots) of the mature canola (Brassica napus L.) plants and in the associated rhizosphere soils from Yangtze River Delta (YRD) region of China, were determined to evaluate the heavy metals’ pollution in the soils and the canola seeds, and to discuss their accumulation and translocation characteristics in canola plants. At the same time, the phytoextraction potential of the canola plant for the above heavy metals was theoretically calculated and discussed on the basis of above measured data.

Results

The results showed that the concentration ranges of Cd, As, Hg, Pb, Cr, Cu, Zn and Ni in the rhizosphere soils were 0.115–0.481, 3.40–20.5, 0.069–0.682, 9.92–27.4, 46.8–86.6, 17.7–253.3, 65.2–511.7 and 16.0–37.8?mg?kg^?1, respectively. The concentrations of Cu, Zn and Hg at some sampling sites exceeded the 2nd grade threshods of Chinese national environmental quality standard for soils. The potential ecological risk of heavy metals in the canola rhizosphere soils decreased in the order of Zhejiang > Shanghai > Jiangsu provinces. The concentration ranges of above heavy metals in the canola seeds were 0.032–0.067, 0.002–0.005, 0.001–0.005, 0.053–0.165, 0.191–0.855, 3.01–13.20, 34.82–96.95 and 0.343–2.86?mg?kg^?1, respectively, with Cu and Zn at some sampling sites exceeding the permissible concentrations in foods of China. Heavy metals’ concentrations in canola seeds didn’t increase with their increasing concentrations in the rhizosphere soils. The bioconcentration factors (BCFs) of most heavy metals in the canola seeds decreased with their increasing concentrations in the associated rhizosphere soils. The average BCFs of heavy metals decreased in the order of Zn (0.488)>Cd (0.241)>Cu (0.145)>Ni (0.038)>Hg (0.021)>Pb (0.005)=Cr (0.005)>As (0.000) in the canola seeds, Cd (1.550)>Cu (0.595)>Zn (0.422)>Hg (0.138)>Ni (0.085)>Pb (0.080)>As (0.035)>Cr (0.031) in the roots, and Cd (0.846)>Zn (0.242)>Cu (0.205)>Hg (0.159)>Ni (0.031)>Pb (0.025)>As (0.012)>Cr (0.007) in the shoots, respectively. The accumulation capacity for most of the above heavy metals in the mature canola tissues was root > shoot > seed, with the exceptions of seed > root > shoot for Zn and shoot > root > seed for Hg. Except Hg from root to shoot and Zn from root to seed, translocation factors (TFs) of above heavy metals were lower than 1.0.

Conclusions

The concentrations, BCFs and TFs of above heavy metals in the canola tissues indicated that the investigated canola plants did not meet the criteria of hyperaccumulators for the above heavy metals. The phytoextracton potential of the studied canola plants for the above heavy metals from the polluted soils was very limited. It would take 920, 3,170 and 3,762?years (assuming two crops per year) to reduce the initial soil Zn, Cu and Hg concentrations, respectively, from the most polluted soil concentrations to the 2nd grade thresholds of Chinese national environmental quality standard for soils.     

Does far-red light affect growth and mycorrhizas of Scots pine seedlings grown in forest soil?

We studied the response of Scots pine (Pinus sylvestris L.) to supplementary far-red sidelight in seedlings grown in a forest soil substrate without additional nutrient supply. Our aim was to determine possible changes in the accumulation and allocation of dry weight and mineral nutrients and the presence of mycorrhizas. Half of the seedlings were grown in light conditions simulating reflected far-red light (FR) from neighbouring plants and the other half were controls not receiving additional FR. PAR irradiance was kept constant in both treatments. At the first harvest (41 d of treatment), FR+ had no effect on stem height, biomass accumulation or allocation. However, at the end of the experiment (93 d of treatment), an increase in stem extension rate and stem dry weight was observed in FR+ seedlings when compared to controls. Both control and treated plants had several morphological types of ectomycorrhizas, but no effect of FR+ on the frequency of these morphotypes was observed. Nor was the concentration of ergosterol or estimated mycorrhizal fungal biomass affected. Nutrients were more responsive to the light quality treatment: P concentration in roots and N and P contents in stems and roots were higher in FR+ plants than in control seedlings. These results are in contrast to those of a previous study in which the root system of pine seedlings, which were fertilised and had less developed mycorrhizas, was reduced by FR+. This revised version was published online in June 2006 with corrections to the Cover Date.     

Protozoan grazing of bacteria in soil—impact and importance

Interactions between bacteria and protozoa in soil were studied over 2-week periods in the field and in a pot experiment. Under natural conditions the total biological activity was temporarily synchronized by a large rainfall, and in the laboratory by the addition of water to dried-out soil, with or without plants. In the field, peaks in numbers and biomass of bacteria appeared after the rain, and a peak of naked amoebae quickly followed. Of the three investigated groups—flagellates, ciliates, and amoebae—only populations of the latter were large enough and fluctuated in a way that indicated a role as bacterial regulators. The bacterial increase was transient, and the amoebae alone were calculated to be able to cause 60% of the bacterial decrease. The same development of bacteria and protozoa was observed in the pot experiment: in the presence of roots, amoebic numbers increased 20 times and became 5 times higher than in the unplanted soil. In the planted pots, the amoebic increase was large enough to cause the whole bacterial decrease observed; but in the unplanted soil, consumption by the amoebae caused only one-third of the bacterial decrease.     

Uptake and distribution of zinc,cadmium, lead and copper in Brassica napus var. oleífera and Helianthus annus grown in contaminated soils

Brassica napus var. oleifera and Helianthus annus were grown in artificially contaminated soils. Accumulation and translocation of the environmental pollutants zinc, cadmium, lead, and copper, was evaluated in different portions of the plants at two harvesting times. The distribution into the plants of these metal ions, as well as their capacity for contaminant phytoextraction and accumulation was assessed. For this purpose, an analytical method utilizing focused ultrasound employed for extraction and stripping voltammetry for measurement has been optimized and validated for the simultaneous measurement of Zn, Cd, Pb, and Cu in plant extracts.     

Effect of nickel concentration and soil pH on metal accumulation and growth in tropical agromining ‘metal crops’

Plant and Soil - Phosphorus (P) deficiency is a major constraint for rice production in the tropics. Field-specific P management is key for resource-limited farmers to increase yields with minimal...     

Production and cytogenetics of the intergeneric hybrids Brassica juncea×Orychophragmus violaceus and B. carinata×O. violaceus

 Intergeneric hybrids between Brassica juncea (2n=36), B. carinata (2n=34) and Orychophragmus violaceus (2n=24) were produced when B. juncea and B. carinata cultivars were used as female parents. The hybrids between B. juncea and O. violaceus had an intermediate morphology except for petal colour and were partially fertile. The hybrids between B. carinata and O. violaceus had a matroclinous morphology and were nearly fertile. Cytological analysis of the hybrids and their progenies gave the following results. (1) In the hybrids between B. juncea and O. violaceus, the somatic tissues of the roots, leaves and styles were mixoploid (2n=12–42), and cells with 24, 30 or 36 chromosomes were the most frequent. Based on the recorded numbers and behaviour of the mitotic and meiotic chromosomes, complete and partial separation of the parental genomes was proposed to have occurred during mitosis. This resulted in the occurrence of cells with possibly complete and incomplete complements of the parental species and cells with parental complements and some additional chromosomes from the other parent. (2)  Pollen mother cells (PMCs) possibly with both parental chromosome complements, only B. juncea chromosomes or a complete B. juncea complement with additional O. violaceus chromosomes were more competitive in entering meiosis. The majority of fertile gametes were deduced to have been produced by PMCs with a B. juncea complement with or without additional O. violaceus chromosomes. (3) The progeny plants from selfed hybrids between B. juncea and O. violaceus were morphologically either of a B. juncea, hybrid or variable type. Cytologically they were grouped into six types according to the frequencies of cells with various chromosome numbers. All of the plants except 2 which constituted two types, were mixoploids, composed of cells with various chromosome numbers, mainly in a certain serial range. (4) The hybrid plants between B. carinata and O. violaceus were mixoploids with chromosome numbers in the range of 12–34, and cells with 2n=34 were the most frequent. The main categories of PMCs with 17 bivalents at metaphase I and 17 : 17 segregations at anaphase I contributed to the high fertility of the hybrids and the fact that their progeny after selfing were mainly plants with 2n=34. Somatic and meiotic separation of the parental genomes was proposed to have occurred in the hybrids between B. carinata and O. violaceus. (5) Mitotic and meiotic elimination of what could be O. violaceus chromosomes might also have contributed to the observed mitotic and meiotic cell types in the two kinds of hybrids studied. Finally, the possible mechanisms behind these cytological observations and their potential in the production of Brassica aneuploids were discussed. Received: 4 February 1997/Accepted: 29 July 1997     

Dynamics of vegetation and soil carbon and nitrogen accumulation over 26 years under controlled grazing in a desert shrubland

For decades, arid desert ecosystems in northwest China, covering one-fourth the country’s land surface, have experienced a rapid decline in plant species diversity, productivity and soil carbon stock owing to degradation by overgrazing. In this study, plant community composition, diversity and productivity, as well as soil carbon (C) and nitrogen (N) stocks, were monitored over 26 years from 1981 to 2006 in a severely degraded Haloxylon ammodendron-dominated shrubland where livestock densities were reduced from 4–5 to 1–2 dry sheep equivalent ha^-1. The objective was to assess long-term grazing effects on vegetation and soil C and N accumulation dynamics. Results showed that the reduction of grazing pressure significantly increased vegetation cover, plant diversity and productivity, resulting primarily from an increase in livestock-preferred species. Controlled grazing also led to marked increases in soil C and N stocks in the top 30 cm of soil. This increase was strongly associated with increased plant species richness, vegetation cover and biomass production. Averaged over 26 years, soil C and N accumulated at rates of 89.9 g?C and 8.4 g?N m^-2?year^-1, respectively, but rates of C and N accumulation varied greatly at different time periods. The greatest species regeneration occurred in the first 8 years, but the largest C and N accumulation took place during years 9–18, with a time-lag in response to changes in vegetation. Our results provide insights into the long-term recovery patterns of different ecosystem components from the influence of prolonged overgrazing disturbance that cannot be inferred from a short-term study. The findings are important for assessing the resilience of these livestock-disturbed desert ecosystems and developing a more effective strategy for the management of this important biome from a long-term perspective.     

Distribution of 103Ru—chloride in tumor-bearing animals and the mechanism for accumulation in tumor and liver

Tumor uptake rates of ¹⁰³Ru—chloride were smaller than those for ⁶⁷Ga—citrate. In three tumors and liver, ¹⁰³Ru in the mitochondrial fraction containing lysosome increased with time after the administration of ¹⁰³Ru—chloride. The concentration of ¹⁰³Ru was more dominant in connective tissue (especially inflammatory tissue) than in viable tumor tissue or in necrotic tissue. Quite large amounts of ¹⁰³Ru in the tumor and liver were bound to the acid mucopolysaccharide whose molecular masses exceeded 40,000. Behavior of this nuclide was essentially similar to that of ⁶⁷Ga.     

Effects of AM colonization on “wild tobacco” plants grown in zinc-contaminated soil

This greenhouse study aimed to determine the effect of colonization by the arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & Smith) on the “wild” tobacco (Nicotiana rustica L. var. Azteca), under soil–zinc (Zn) conditions. Plants of N. rustica were grown in AM or non-AM inoculated substrate and subjected to four soil–[Zn] concentrations (0, 50, 100, and 250 mg Zn kg⁻¹ dry soil). The AM root colonization increased markedly from 14 to 81% with the increasing soil–[Zn] and the mycorrhizal structures were significantly more abundant at the highest soil–[Zn], suggesting that Zn may be involved directly or indirectly in AM root colonization. In addition, total Zn content or Zn concentrations in shoots and roots were shown to increase as soil–[Zn] increased in both AM and non-AM plants. As for the growth parameters studied, there were no significant differences between treatments despite the increase in Zn content or concentration. The AM roots subjected to the highest soil–[Zn] had a significant reduction by about 50% of total Zn content and Zn concentration compared to non-AM roots. Still, the relative extracted Zn percentage decreased dramatically as soil–[Zn] increased. Soil pH was significantly lower in non-AM than AM treatments at the highest soil–[Zn]. In summary, AM plants (particularly roots) showed lower Zn content and concentration than non-AM plants. In this regard, the AM fungi have a protective role for the host plant, thus playing an important role in soil-contaminant immobilization processes; and, therefore, are of value in phytoremediation, especially when heavy metals approach toxic levels in the soil.     

Effects of wild-type and α-tocopherol-enriched transgenic Brassica juncea on the components of xenobiotic metabolism, antioxidant status, and oxidative stress in the liver of mice

Alpha (α)-tocopherol is the most biologically active and preferentially retained form of vitamin E in the human body and is known for its antioxidant and gene regulatory functions. Its increased intake is implicated in protection against diseases that involve an oxidative stress component. We have evaluated the chemopreventive potential of a diet supplemented with natural α-tocopherol-enriched transgenic (TR) Brassica juncea seeds. The modulation of phase I and phase II xenobiotic metabolism and of antioxidative enzymes was compared in the livers of mice fed on a control diet or on a diet supplemented with 2, 4, and 6 % (w/w) of wild-type (WT) or TR seeds. A dose-dependent increase in the specific activities of these enzymes was observed in those animals fed on diet supplemented with TR seeds. In comparison, an increase in the specific activities of antioxidative enzymes was substantial only at higher doses of WT seeds. Consequently, oxidative stress measured in terms of lipid peroxidation and lactate dehydrogenase activity was found to be lower in the case of mice fed with the supplemented diet. However, the chemopreventive potential of TR seeds was more pronounced than that of WT seeds. This study demonstrates the feasibility of fortifying diets with natural α-tocopherol for chemopreventive benefits by means of transgenic manipulation of a commonly used oilseed crop.     

Intertribal somatic hybrids between Brassica napus and Barbarea vulgaris — production of in vitro plantlets

Intertribal somatic hybrids were produced between Brassica napus and Barbarea vulgaris. The two species belong to the tribes Arabidae and Brassiceae, respectively, B. vulgaris is known to be cold tolerant and of interest to use as a gene donor to rapeseed. Of the plants produced in five fusion experiments six plants were verified to be hybrids by RFLP analysis utilizing one B. vulgaris-specific repetitive DNA sequence and two nuclear probes (rDNA and cruciferin) as markers. When analysing nuclear DNA content in four of these six hybrids, all had a higher DNA content than B. napus. However, mature plants could not be established outside in vitro conditions, indicating problems with compatibility between the species.