Occurrence of 5-methoxypodophyllotoxin in plants,cell cultures and regenerated plants of Linum flavum

The 5-methoxypodophyllotoxin contents of plants, cell cultures and regenerated plants of Linum flavum are compared. It is demonstrated that cell cultures are able to produce amounts of 5-methoxypodophyllotoxin that are comparable to the concentration in fully differentiated plants. The production of 5-methoxy-podophyllotoxin depends on the hormonal balance of the growth medium. The use of 2,4-dichlorophenoxyacetic acid as the growth regulator is favourable for 5-methoxypodophyllotoxin production when compared to naphthylacetic acid. The 5-methoxypodophyllotoxin accumulation appears to be positively related to the internal cell volume.     

Control of root-knot nematode,Meloidogyne incognita and reniform nematode,Rotylenchulus reniformis on pigeonpea and linseed

Abstract

Pigeonpea (Cajanus cajan) and linseed (Linum usitatissimum) are susceptible to Meloidogyne incognita and Rotylenchulus reniformis nematodes. Reduction in different growth parameters (length and weight of plant, number of pods), bulk density of pigeonpea stem, oil content of linseed, chlorophyll content of leaf and water absorption of roots caused by M. incognita and R. reniformis were statistically significant. Similar effects were also observed in plants raised from seeds soaked in different concentrations of water soluble fractions (WSF) of rice polish and pyridoxine solutions, however, the reductions were of a comparatively lesser extent. Higher concentrations of the solutions were more effective when compared to lower ones and pyridoxine was more beneficial than WSF for improving plant growth and reducing disease incidence.     

Habitat matters – Strong genetic and epigenetic differentiation in Linum catharticum from dry and wet grasslands

Plant species differ in their ecological amplitude, with some species occurring in very different habitats under strongly differentiated environmental conditions. We were interested in to what extent the occurrence of Linum catharticum in dry calcareous grasslands (Bromion) and wet litter meadows (Molinion), two habitats on opposing ends concerning, for example, moisture level, is reflected on the genetic and epigenetic level. Using AFLP (amplified fragment length polymorphisms) and MSAP (methylation sensitive amplification polymorphisms) analyses, we studied the genetic and epigenetic variation of L. catharticum from calcareous grasslands and litter meadows. From each habitat, we included five study sites with 16 individuals per sampling location. We observed lower genetic than epigenetic diversity, but considerable differentiation among habitats, which was stronger on the genetic than the epigenetic level. Additionally, we observed a strong correlation of genetic and epigenetic distance, irrespective of geographic distance. The dataset included a large portion of fragments exclusively found in individuals from one or the other habitat. Some epigenetic fragments even occurred in different methylation states depending on the habitat. We conclude that environmental effects act on both the genetic and epigenetic level, producing the clear differentiation among plant individuals from calcareous grasslands and litter meadows. These results may also point into the direction of ecotype formation in this species.     

Cloning of a Novel Omega-6 Desaturase from Flax (<Emphasis Type="Italic">Linum usitatissimum</Emphasis> L.) and Its Functional Analysis in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

The Δ12 desaturase represents a diverse gene family in plants and is responsible for conversion of oleic acid (18:1) to linoleic acid (18:2). Several members of this family are known from plants like Arabidopsis and Soybean. Using primers from conserved C- and N-terminal regions, we have cloned a novel Δ12 desaturase gene amplified from flax genomic DNA, denoted as LuFAD2-2. This intron-less gene is 1,149-base pair long encoding 382 amino acids—putative membrane-bound Δ12 desaturase protein. Sequence comparisons show that the novel sequence has 85% similarity with previously reported flax Δ12 desaturase at amino acid level and shows typical features of membrane-bound desaturase such as three conserved histidine boxes along with four membrane-spanning regions that are universally present among plant desaturases. The signature amino acid sequence ‘YNNKL’ was also found to be present at the N terminus of the protein, which is necessary and sufficient for ER localization of enzyme. Neighbor-Joining tree generated from the sequence alignment grouped LuFAD2-2 among the other FAD2 sequences from Ricinus, Hevea, Jatropha, and Vernicia. When LuFAD2-2 and LuFAD2 were expressed in Saccharomyces cerevisiae, they could convert the oleic acid to linoleic acid, with an average conversion rate of 5.25 and 8.85%, respectively. However, exogenously supplied linoleic acid was feebly converted to linolenic acid suggesting that LuFAD2-2 encodes a functional FAD2 enzyme and has substrate specificity similar to LuFAD2.     

Effect of a Bacillus subtilis strain on flax protection against Fusarium oxysporum and its impact on the root and stem cell walls

In Normandy, flax is a plant of important economic interest because of its fibres. Fusarium oxysporum, a telluric fungus, is responsible for the major losses in crop yield and fibre quality. Several methods are currently used to limit the use of phytochemicals on crops. One of them is the use of plant growth promoting rhizobacteria (PGPR) occurring naturally in the rhizosphere. PGPR are known to act as local antagonists to soil‐borne pathogens and to enhance plant resistance by eliciting the induced systemic resistance (ISR). In this study, we first investigated the cell wall modifications occurring in roots and stems after inoculation with the fungus in two flax varieties. First, we showed that both varieties displayed different cell wall organization and that rapid modifications occurred in roots and stems after inoculation. Then, we demonstrated the efficiency of a Bacillus subtilis strain to limit Fusarium wilt on both varieties with a better efficiency for one of them. Finally, thermo‐gravimetry was used to highlight that B. subtilis induced modifications of the stem properties, supporting a reinforcement of the cell walls. Our findings suggest that the efficiency and the mode of action of the PGPR B. subtilis is likely to be flax variety dependent.     

亚麻胚性细胞悬浮培养体系的建立和影响因素

亚麻品种‘双亚五号’的胚性愈伤组织诱导最佳培养基为MB（MS无机盐加B5维生素）＋1.0mg·L^-12,4-D;细胞初始悬浮培养的最佳培养基为MB＋0.2mg·L-16-BA;细胞继代悬浮培养的最佳培养基为改良的MB（NH4NO3减半,KNO3加倍）＋0.02mg·L^-12,4-D＋0.2mg·L^-16-BA;适宜的蔗糖量为50g·L^-1;适宜的继代接种量为1.0～1.5g·（25mL）^-1;继代间隔为5～7d。     

Ontogenic variations in n-alkanes during somatic embryogenesis of flax (Linum usitatissimum L.)

Hypocotyl segments (HS) of flax seedlings germinated in vitro, were used to induce indirect somatic embryogenesis on solid medium. The composition and distribution of n-alkanes in flax tissues collected at different developmental stages were studied by capillary gas chromatography (GC) and capillary gas chromatography-mass spectrometry (GC-MS). During induction and development of callus from hypocotyl tissues a decrease in the percentage of total lipids was observed. In all types of tissue sampled – HS used as primary explants, HS with differentiating calli at the cut ends (HSC), embryogenic (EC) and non-embryogenic calli (NEC) and somatic embryos (SE) – a skewed-normal distribution of n-alkanes with a low mass range (C₁₃–C₂₁) were found. The highest content of n-alkanes occurred in the primary hypocotyl explants and in the early stages of callus development. Longer carbon chain n-alkanes were observed only in the mature or differentiated tissues of hypocotyls and SE. Although the n-alkane contents decreased with time, in SE and calli, a significantly lower n-alkane content was observed in EC when compared to NEC independent of the time in culture. These results suggest the utilisation of n-alkanes for heterotrophic cellular growth as well as its mobilisation from EC to developing SE.     

Environmental factors affecting the cyanogenic potential of flax seedlings

The levels of cyanogenic glucosides (linamarin and lotaustralin) and the activity of linamarase were studied in 5-day old seedlings of oil flax (Linum usitatissimum L., cv. LCSD 200) under different environmental conditions. White light enhanced the cyanoglucosides content, and this effect depended on its intensity and the time of exposure. The level of cyanoglucosides rose with temperature, and it reached the highest level at the highest temperature (30 °C). Linamarase (EC. 3.2.1.21) activity was the highest at 20°C, especially in light-grown seedlings. Lower enzyme activity at the extreme temperature (15 and 30 °C) was observed. Water stress (low water potential, ω=−0.34 MPa) reduced by more than twice the cyanoglucoside level and linamarase activity. The possible protective, or/and regulatory roles of cyanogenic glucosides was discussed.