Micropropagation of the rare species Stylidium coroniforme and other Stylidium species

The number of plants in the gazetted rare species Stylidium coroniforme was increased through micropropagation. A method was first developed using the common species S. brunonianum. It was found that for both species, rapid propagation could be obtained by excising shoots from sterile seedlings and inducing shoot proliferation on Murashige and Skoog medium supplemented with 1 M BAP. Rooting was achieved using 1 M IBA and over 100 plants of each species were successfully established in soil. Leaf pieces could also be used to initiate cultures. In media with 20–25 M BAP and 1–5 M IBA, leaf pieces of S. brunonianum, S. piliferum, S. caricifolium and S. crassifolium produced adventitious buds, thus providing another method of micropropagation.     

Tissue culture of Ecklonia radiata (Phaeophyceae,Laminariales): effects on growth of light,organic carbon source and vitamins

The effects of light quality and irradiance, and supply of organic carbon and vitamins on the growth of two forms of Ecklonia radiata in tissue culture were examined. A callus of unpigmented cells developed over the cut surface of newly excised explants of stipe. This growth was best in the dark but stopped after 10 weeks. Pigmented, mainly filamentous clumps of cells developed from explants after several weeks in culture. These required light for growth, with growth being enhanced by increasing photon flux density up to 30 μmol photon m^-2 s^-1, with the active spectral component being red light (> 600 nm). The addition to the medium of a range of organic carbon sources or vitamins did not stimulate growth of either culture type in the dark. author for correspondence     

Growth and swainsonine production of Swainsona galegifolia (Andr.) R. Br. untransformed and transformed root cultures

Untransformed and transformed root cultures of Swainsona galegifollawere established for swainsonine production. Transformed rootsgrew faster and produced higher swainsonine levels (62.3 µgg^–1 DW) than untransformed roots (23.6 ,µg g^–1DW) or roots of intact plants (8.7 µg g^–1 DW). Transformationof a number of plant genotypes using A. rhizogenes strain LBA9402 showed that plant genotype Influences swainsonine levelin transformed roots but that a wide range of swainsonine levelscan be induced by separate transformation events in the samegenotype. Enhancement of swainsonine production was attemptedby treatment with sugars and induction of polyploid roots. Key words: Agrobacterium rhizogenes, root cultures, Swainsona galegifolia, swainsonine     

An Ustilago maydis Mutant Partially Blocked in P45014DM Activity Is Hypersensitive to Azole Fungicides

An Ustilago maydis ergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14alpha-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14alpha-methyl sterols, eburicol, 14alpha-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.     

Selection for NaCl tolerance in cell cultures of Medicago sativa and recovery of plants from a NaCl-tolerant cell line

Medicago sativa lines with a high incidence of regeneration were established as suspension cultures and used to select for NaCl tolerant lines. Attempts were then made to regenerate plants from these lines. Regeneration was severely depressed in NaCl tolerant calli and the only plants that were successfully regenerated were from one callus of M. sativa cv. Regen S which grew in 62.5 mM NaCl. Plants from this callus, and new calli derived from the recovered plants, have shown a tolerance to NaCl comparable to calli and plants from the initial seed stock rather than an improved level of tolerance.     

Investigations on the influence of headgroup substitution and isoprene side-chain length in the function of primary and secondary quinones of bacterial reaction centers

The contributions of headgroup and side-chain in the binding and function of the primary (QA) and secondary (QB) quinones of isolated reaction centers (RCs) from Rhodobacter sphaeroides were investigated. Various ubiquinones and structurally similar quinones were reconstituted into RCs depleted of one (1Q-RCs) or both (0Q-RCs) quinones. The influence of partition coefficients on the apparent binding affinities was minimized by expressing dissociation constants in terms of the mole fraction of quinone partitioned into the detergent. It was then apparent that the size of the isoprenyl side-chain was of little consequence in determining the binding affinity or the functional competence of either QA or QB, although an alkyl chain of equivalent size was a poor substitute. The degree of substitution of the headgroup, however, was a sensitive determinant of binding. For both quinone sites, the trisubstituted plastoquinones bond more weakly than the fully substituted ubiquinones. Similarly, for binding to the QA site, duroquinone (tetramethylbenzoquinone) bound much more strongly than trimethylbenzoquinone. The affinity of the QA site for ubiquinones was about 20-times stronger than the QB site, but the QB site is probably not more specific than the QA site. However, QB function depends on a suitable redox free-energy drop from QA as well as binding, and of all the quinones tested only the ubiquinones simultaneously supported full QA and QB activity. Even plastoquinone-A, which fills both roles in Photosystem II, was unable to do so in bacterial RCs, although it did bind. The unique ability of ubiquinones to both bind and provide the appropriate redox span is discussed. The temperature dependence of binding of the isoprenyl ubiquinones at the QA site changed markedly with chain length. For Q-10-Q-7, the binding enthalpy was positive and net binding was entirely driven by entropic factors. For the shorter-chain ubiquinones, Q-6-Q-1, both entropy and enthalpy of binding were favorable. This strong entropy-enthalpy compensation is suggested to arise from antagonistic interactions (anticooperativity) between headgroup and tail binding. For QB function by hydrophobic quinones, the temperature dependence of the micelle properties prevented easy access to thermodynamic parameters. However, for water-soluble Q-0, binding to the QB site was determined to be enthalpically driven.(ABSTRACT TRUNCATED AT 400 WORDS)     

Projected climate and land use change alter western blacklegged tick phenology,seasonal host‐seeking suitability and human encounter risk in California

Global environmental change is having profound effects on the ecology of infectious disease systems, which are widely anticipated to become more pronounced under future climate and land use change. Arthropod vectors of disease are particularly sensitive to changes in abiotic conditions such as temperature and moisture availability. Recent research has focused on shifting environmental suitability for, and geographic distribution of, vector species under projected climate change scenarios. However, shifts in seasonal activity patterns, or phenology, may also have dramatic consequences for human exposure risk, local vector abundance and pathogen transmission dynamics. Moreover, changes in land use are likely to alter human–vector contact rates in ways that models of changing climate suitability are unlikely to capture. Here we used climate and land use projections for California coupled with seasonal species distribution models to explore the response of the western blacklegged tick (Ixodes pacificus), the primary Lyme disease vector in western North America, to projected climate and land use change. Specifically, we investigated how environmental suitability for tick host‐seeking changes seasonally, how the magnitude and direction of changing seasonal suitability differs regionally across California, and how land use change shifts human tick‐encounter risk across the state. We found vector responses to changing climate and land use vary regionally within California under different future scenarios. Under a hotter, drier scenario and more extreme land use change, the duration and extent of seasonal host‐seeking activity increases in northern California, but declines in the south. In contrast, under a hotter, wetter scenario seasonal host‐seeking declines in northern California, but increases in the south. Notably, regardless of future scenario, projected increases in developed land adjacent to current human population centers substantially increase potential human–vector encounter risk across the state. These results highlight regional variability and potential nonlinearity in the response of disease vectors to environmental change.     

Timing and abundance of sporangia production and zoospore release influences the recovery of different Phytophthora species by baiting

Analysis of soil samples using High Throughput Sequencing (HTS) frequently detects more Phytophthora species compared with traditional soil baiting methods. This study investigated whether differences between species in the timing and abundance of sporangial production and zoospore release could be a reason for the lower number of species isolated by baiting. Stems of Eucalyptus marginata were inoculated with ten Phytophthora species (P. nicotianae, P. multivora, P. pseudocryptogea, P. cinnamomi, P. thermophila, P. arenaria, P. heveae, P. constricta, P. gondwanensis and P. versiformis), and lesioned sections for each species were baited separately in water. There were significant differences between species in timing of sporangia production and zoospore release. P. nicotianae, P. pseudocryptogea, P. multivora and P. thermophila released zoospores within 8–12 h and could be isolated from lesioned baits within 1–2 days. In contrast, P. constricta did not produce zoospores for over 48 h and was only isolated 5–7 days after baiting. P. heveae and P. versiformis did not produce zoospores and were not recovered from the baits. When species were paired in the same baiting tub, those that produced zoospores in the shortest time were isolated most frequently, while species slow to produce zoospores, or which produced them in lower numbers, were isolated from few baits or not at all. Thus, species differences in the timing of sporangia production and zoospore release may contribute to the ease of isolation of some Phytophthora species when they are present together with other Phytophthora species in an environmental sample.     

Hexazonium pararosaniline as a fixative for animal tissues

Hexazonium pararosaniline is a valuable reagent that has been used in enzyme activity histochemistry for 50 years. It is an aqueous solution containing the tris-diazonium ion derived from pararosaniline, an aminotriarylmethane dye, and it contains an excess of nitrous acid that was not consumed in the diazotization reaction. Other investigators have found that immersion for 2 min in an acidic (pH 3.5) 0.0015 M hexazonium pararosaniline solution can protect cryostat sections of unfixed animal tissues from the deleterious effects of aqueous reagents such as buffered solutions used in immunohistochemistry, while preserving specific affinities for antibodies. In the present investigation hexazonium pararosaniline protected lymphoid tissue and striated muscle against the damaging effects of water or saline. The same protection was conferred on unfixed sections treated with dilute nitrous or hydrochloric acid in concentrations similar to those in hexazonium pararosaniline solutions. Model tissues (solutions, gels or films containing gelatin and/or bovine albumin) responded predictably to well known cross-linking (formaldehyde) or coagulant (mercuric chloride) fixatives. Hexazonium pararosaniline solutions prevented the dissolution of protein gels in water only after 9 or more days of contact, during which time considerable swelling occurred. It is concluded that there is no evidence for a “fixative” action of hexazonium pararosaniline. The protective effect on frozen sections of unfixed tissue is attributable probably to the low pH of the solution.