Profiling secondary metabolites of plant roots inoculated with Phytophthora cinnamomi

The soil-borne pathogen, Phytophthora cinnamomi, continues to cause severe dieback in Australian native forest species and is of great international significance due to its global distribution. This research established a protocol to successfully identify phyto-chemicals associated with the defense response of plants challenged by the disease caused by Phytophthora cinnamomi.

Variation in Cyclaneusma minus isolates

Cyclaneusma minus is a plant pathogen that has financial impacts on the forestry industry. This study characterised the genetic variation in Australian and New Zealand isolates of Cyclaneusma minus using both molecular and morphological techniques and developed a PCR detection test for the presence of Cyclaneusma minus in tree plantations.

Antibody-mediated protection of plants against infection from potyviruses

Transgenic plants expressing single-chain antibodies have been produced to investigate the feasibility of antibody-mediated broad-spectrum protection against plant virus infections. This study indicates that protection against a wide range of plant viruses can be achieved in transgenic plants expressing a single antibody construct.

Can phylogeny predict chemical diversity and potential medicinal activity of plants? A case study of amaryllidaceae

Background During evolution, plants and other organisms have developed a diversity of chemical defences, leading to the evolution of various groups of specialized metabolites selected for their endogenous biological function. A correlation between phylogeny and biosynthetic pathways could offer a predictive approach enabling more efficient selection of plants for the development of traditional medicine and lead discovery. However, this relationship has rarely been rigorously tested and the potential predictive power is consequently unknown.
Results We produced a phylogenetic hypothesis for the medicinally important plant subfamily Amaryllidoideae (Amaryllidaceae) based on parsimony and Bayesian analysis of nuclear, plastid, and mitochondrial DNA sequences of over 100 species. We tested if alkaloid diversity and activity in bioassays related to the central nervous system are significantly correlated with phylogeny and found evidence for a significant phylogenetic signal in these traits, although the effect is not strong.
Conclusions Several genera are non-monophyletic emphasizing the importance of using phylogeny for interpretation of character distribution. Alkaloid diversity and in vitro inhibition of acetylcholinesterase (AChE) and binding to the serotonin reuptake transporter (SERT) are significantly correlated with phylogeny. This has implications for the use of phylogenies to interpret chemical evolution and biosynthetic pathways, to select candidate taxa for lead discovery, and to make recommendations for policies regarding traditional use and conservation priorities.

Morbis artis: diseases of the arts

What constitutes life, what counts as a sentient being, and who gets to determine what lives are saved, punished, exploited and destroyed?

Composed of eleven separate but connected installation works, Morbis Artis explores the question of organic life through particular artistic lenses, each taking on the moniker of disease to represent and embody the issues that challenge bare life today.

Drawing upon Frances Stracey, the artists working on this exhibition consider Bio-art to represent ‘a crossover of art and the biological sciences, with living matter, such as genes, cells or animals, as its new media’.

Detection and measurement of Plasmodiophora brassicae

Clubroot, caused by Plasmodiophora brassicae, is one of the most important diseases of brassicas. Management of clubroot is difficult, and the best means of avoiding the disease include planting in areas where P. brassicae is not present and using plants and growing media free from pathogen inoculum. As P. brassicae is not culturable, its detection has traditionally relied on plant bioassays, which are time-consuming and require large amounts of glasshouse space. More recently, fluorescence microscopy, serology, and DNA-based methods have all been used to test soil, water, or plant samples for clubroot. The use of fluorescence microscopy to detect and count pathogen spores in the soil requires significant operator skill and is unlikely to serve as the basis for a routine diagnostic test. By contrast, serologic assays are inexpensive and amenable to high-throughput screening but need to be based on monoclonal antibodies because polyclonal antisera cannot be reproduced and are therefore of limited quantity. Several polymerase chain reaction (PCR)-based assays have also been developed; these are highly specific for P. brassicae and have been well-correlated with disease severity. As such, PCR-based diagnostic tests have been adopted to varying extents in Canada and Australia, but wide implementation has been restricted by sample processing costs. Efforts are underway to develop inexpensive serologic on-farm diagnostic kits and to improve quantification of pathogen inoculum levels through real-time PCR. Proper detection and quantification of P. brassicae will likely play an increasingly important role in the development of effective clubroot management strategies.

Effect of soil texture and wheat plants on N₂O fluxes: a lysimeter study

Agricultural soils are a major source of nitrous oxide (N2O) emissions and an understanding of factors regulating such emissions across contrasting soil types is critical for improved estimation through modelling and mitigation of N2O. In this study we investigated the role of soil texture and its interaction with plants in regulating the N2O fluxes in agricultural systems. A measurement system that combined weighing lysimeters with automated chambers was used to directly compare continuously measured surface N2O fluxes, leaching losses of water and nitrogen and evapotranspiration in three contrasting soils types of the Riverine Plain, NSW, Australia. The soils comprised a deep sand, a loam and a clay loam with and without the presence of wheat plants. All soils were under the same fertilizer management and irrigation was applied according to plant water requirements. In fallow soils, texture significantly affected N2O emissions in the order clay loam > loam > sand. However, when planted, the difference in N2O emissions among the three soils types became less pronounced. Nitrous oxide emissions were 6.2 and 2.4 times higher from fallow clay loam and loam cores, respectively, compared with cores planted with wheat. This is considered to be due to plant uptake of water and nitrogen which resulted in reduced amounts of soil water and available nitrogen, and therefore less favourable soil conditions for denitrification. The effect of plants on N2O emissions was not apparent in the coarse textured sandy soil probably because of aerobic soil conditions, likely caused by low water holding capacity and rapid drainage irrespective of plant presence resulting in reduced denitrification activity. More than 90% of N2O emissions were derived from denitrification in the fine-textured clay loam-determined for a two week period using K15NO3 fertilizer. The proportion of N2O that was not derived from K15NO3 was higher in the coarse-textured sand and loam, which may have been derived from soil N through nitrification or denitrification of mineralized N. Water filled pore space was a poorer predictor of N2O emissions compared with volumetric water content because of variable bulk density among soil types. The data may better inform the calibration of greenhouse gas prediction models as soil texture is one of the primary factors that explain spatial variation in N2O emissions by regulating soil oxygen. Defining the significance of N2O emissions between planted and fallow soils may enable improved yield scaled N2O emission assessment, water and nitrogen scheduling in the pre-watering phase during early crop establishment and within rotations of irrigated arable cropping systems.