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Plants show varied cellular responses to salinity that are partly associated with maintaining low cytosolic Na+ levels and a high K+/Na+ ratio. Plant metabolites change with elevated Na+, some changes are likely to help restore osmotic balance while others protect Na+-sensitive proteins. Metabolic responses to salt stress are described for two barley (Hordeum vulgare L.) cultivars, Sahara and Clipper, which differed in salinity tolerance under the experimental conditions used. After 3 weeks of salt treatment, Clipper ceased growing whereas Sahara resumed growth similar to the control plants. Compared with Clipper, Sahara had significantly higher leaf Na+ levels and less leaf necrosis, suggesting they are more tolerant to accumulated Na+. Metabolite changes in response to the salt treatment also differed between the two cultivars. Clipper plants had elevated levels of amino acids, including proline and GABA, and the polyamine putrescine, consistent with earlier suggestions that such accumulation may be correlated with slower growth and/or leaf necrosis rather than being an adaptive response to salinity. It is suggested that these metabolites may be an indicator of general cellular damage in plants. By contrast, in the more tolerant Sahara plants, the levels of the hexose phosphates, TCA cycle intermediates, and metabolites involved in cellular protection increased in response to salt. These solutes remain unchanged in the more sensitive Clipper plants. It is proposed that these responses in the more tolerant Sahara are involved in cellular protection in the leaves and are involved in the tolerance of Sahara leaves to high Na+.

The walls of grasses and related members of the Poales are characterized by the presence of the polysaccharide (1,3, 1,4)-β-D-glucan (β-glucan). To date, only members of the grass-specific cellulose synthase-like F (CSLF) gene family have been implicated in its synthesis. Assuming that other grass-specific CSL genes also might encode synthases for this polysaccharide, we cloned HvCSLH1, a CSLH gene from barley (Hordeum vulgare L.), and expressed an epitope-tagged version of the cDNA in Arabidopsis, a species with no CSLH genes and no β-glucan in its walls. Transgenic Arabidopsis lines that had detectable amounts of the epitope-tagged HvCSLH1 protein accumulated β-glucan in their walls. The presence of β-glucan was confirmed by immunoelectron microscopy (immuno-EM) of sectioned tissues and chemical analysis of wall extracts. In the chemical analysis, characteristic tri- and tetra-saccharides were identified by high-performance anion-exchange chromatography and MALDI-TOF MS following their release from transgenic Arabidopsis walls by a specific β-glucan hydrolase. Immuno-EM also was used to show that the epitope-tagged HvCSLH1 protein was in the endoplasmic reticulum and Golgi-associated vesicles, but not in the plasma membrane. In barley, HvCSLH1 was expressed at very low levels in leaf, floral tissues, and the developing grain. In leaf, expression was highest in xylem and interfascicular fiber cells that have walls with secondary thickenings containing β-glucan. Thus both the CSLH and CSLF families contribute to β-glucan synthesis in grasses and probably do so independently of each other, because there is no significant transcriptional correlation between these genes in the barley tissues surveyed.

The composition and relative abundance of airborne pollen in urban areas of Australia and New Zealand are strongly influenced by geographical location, climate and land use. There is mounting evidence that the diversity and quality of airborne pollen is substantially modified by climate change and land-use yet there are insufficient data to project the future nature of these changes. Our study highlights the need for long-term aerobiological monitoring in Australian and New Zealand urban areas in a systematic, standardised, and sustained way, and provides a framework for targeting the most clinically significant taxa in terms of abundance, allergenic effects and public health burden.

Nicotiana alata pollen tubes are a widely used model for studies of polarized tip growth and cell wall synthesis in plants. To better understand these processes, RNA-Seq and de novo assembly methods were used to produce a transcriptome of N. alata pollen grains. Notable in the reconstructed transcriptome were sequences encoding proteins that are involved in the synthesis and remodelling of xyloglucan, a cell wall polysaccharide previously not thought to be deposited in Nicotiana pollen tube walls. Expression of several xyloglucan-related genes in actively growing pollen tubes was confirmed and xyloglucan epitopes were detected in the wall with carbohydrate-specific antibodies: the major xyloglucan oligosaccharides found in N. alata pollen grains and tubes were fucosylated, an unusual structure for the Solanaceae, the family to which Nicotiana belongs. Finally, carbohydrate linkages consistent with xyloglucan were identified chemically in the walls of N. alata pollen grains and pollen tubes grown in culture. The presence of a fucosylated xyloglucan in Nicotiana pollen tube walls was thus confirmed. The consequences of this discovery to models of pollen tube growth dynamics and more generally to polarised tip-growing cells in plants are discussed.

Self-incompatibility (SI) is a genetic mechanism that restricts inbreeding in flowering plants. In the nightshade family (Solanaceae) SI is controlled by a single multiallelic S locus. Pollen rejection in this system requires the interaction of two S locus products: a stylar (S)-RNase and its pollen counterpart (pollen S). pollen S has not yet been cloned. Our understanding of how this gene functions comes from studies of plants with mutations that affect the pollen but not the stylar SI response (pollen-part mutations). These mutations are frequently associated with duplicated S alleles, but the absence of an obvious additional allele in some plants suggests pollen S can also be deleted. We studied Nicotiana alata plants with an additional S allele and show that duplication causes a pollen-part mutation in several different genetic backgrounds. Inheritance of the duplication was consistent with a competitive interaction model in which any two nonmatching S alleles cause a breakdown of SI when present in the same pollen grain. We also examined plants with presumed deletions of pollen S and found that they instead have duplications that included pollen S but not the S-RNase gene. This finding is consistent with a bipartite structure for the S locus. The absence of pollen S deletions in this study and perhaps other studies suggests that pollen S might be required for pollen viability, possibly because its product acts as an S-RNase inhibitor.

AbstractObjectivesTo describe the demand for emergency medical assistance during the largest outbreak of thunderstorm asthma reported globally, which occurred on 21 November 2016.DesignA time series analysis was conducted of emergency medical service caseload between 1 January 2015 and 31 December 2016. Demand during the thunderstorm asthma event was compared to historical trends for the overall population and across specific subgroups.SettingVictoria, Australia.Main outcome measuresNumber of overall cases attended by emergency medical services, and within patient subgroups.ResultsOn 21 November 2016, the emergency medical service received calls for 2954 cases, which was 1014 more cases than the average over the historical period. Between 6 pm and midnight, calls for 1326 cases were received, which was 2.5 times higher than expected. A total of 332 patients were assessed by paramedics as having acute respiratory distress on 21 November, compared with a daily average of 52 during the historical period. After adjustment for temporal trends, thunderstorm asthma was associated with a 42% (95% confidence interval 40% to 44%) increase in overall caseload for the emergency medical service and a 432% increase in emergency medical attendances for acute respiratory distress symptoms. Emergency transports to hospital increased by 17% (16% to 19%) and time critical referrals from general practitioners increased by 47% (21% to 80%). Large increases in demand were seen among patients with a history of asthma and bronchodilator use. The incidence of out-of-hospital cardiac arrest increased by 82% (67% to 99%) and pre-hospital deaths by 41% (29% to 55%).ConclusionsAn unprecedented outbreak of thunderstorm asthma was associated with substantial increase in demand for emergency medical services and pre-hospital cardiac arrest. The health impact of future events may be minimised through use of preventive measures by patients and predictive early warning systems.

Nicotiana section Suaveolentes (Solanaceae) currently includes 28 species and subspecies that are endemic to Australasia and the South Pacific and one African species, N. africana . The section is monophyletic and of allotetraploid origin, but relationships among the species in it and its diploid progenitors are poorly understood. Here we report chromosome numbers for 20 of the 29 taxa from the Suaveolentes , including a count for one recently proposed species for which no number has previously been available. Many of the published chromosome numbers for the Suaveolentes are confirmed in this study. However, six counts were different from the published numbers including n = 15 for N. maritima and N. suaveolens , which is a new chromosome number for the genus. Nicotiana goodspeedii and N. rotundifolia were n = 16, and the same number was found in the suggested species N. sp. ‘Corunna’. Nicotiana suaveolens contains polyploid races of n = 32 and here we report the probable existence of an n = 31 race as well. Karyotypic variation within species and within the section is apparently much greater than previously thought and further investigation is warranted.

In November 2016, an unprecedented epidemic thunderstorm asthma event in Victoria, Australia, resulted in many thousands of people developing breathing difficulties in a very short period of time, including 10 deaths, and created extreme demand across the Victorian health services. To better prepare for future events, a pilot forecasting system for epidemic thunderstorm asthma (ETSA) risk has been developed for Victoria. The system uses a categorical risk-based approach, combining operational forecasting of gusty winds in severe thunderstorms with statistical forecasts of high ambient grass pollen concentrations, which together generate the risk of epidemic thunderstorm asthma. This pilot system provides the first routine daily epidemic thunderstorm asthma risk forecasting service in the world that covers a wide area, and integrates into the health, ambulance, and emergency management sector. Epidemic thunderstorm asthma events have historically occurred infrequently, and no event of similar magnitude has impacted the Victorian health system since. However, during the first three years of the pilot, 2017–19, two high asthma presentation events and four moderate asthma presentation events were identified from public hospital emergency department records. The ETSA risk forecasts showed skill in discriminating between days with and without health impacts. However, even with hindsight of the actual weather and airborne grass pollen conditions, some high asthma presentation events occurred in districts that were assessed as low risk for ETSA, reflecting the challenge of predicting this unusual phenomenon.

The T 2 family of nonspecific endoribonucleases (EC 3.1.27.1 ) is a widespread family of RNases found in every organism examined thus far. Most T 2 enzymes are secretory RNases and therefore are found extracellularly or in compartments of the endomembrane system that would minimize their contact with cellular RNA. Although the biological functions of various T 2 RNases have been postulated on the basis of enzyme location or gene expression patterns, the cellular roles of these enzymes are generally unknown. In the present work, we characterized Rny1, the only T 2 RNase in Saccharomyces cerevisiae . Rny1 was found to be an active, secreted RNase whose gene expression is controlled by heat shock and osmotic stress. Inactivation of RNY1 leads to unusually large cells that are temperature-sensitive for growth. These phenotypes can be complemented not only by RNY1 but also by both structurally related and unrelated secretory RNases. Additionally, the complementation depends on RNase activity. When coupled with a recent report on the effect of specific RNAs on membrane permeability [Khvorova, A., Kwak, Y-G., Tamkun, M., Majerfeld, I. & Yarus, M. (1999) Proc. Natl. Acad. Sci. USA 96, 10649–10654], our work suggests an unexpected role for Rny1 and possibly other secretory RNases. These enzymes may regulate membrane permeability or stability, a hypothesis that could present an alternative perspective for understanding their functions.

The S locus of Nicotiana alata encodes a polymorphic series of ribonucleases (S-RNases) that determine the self-incompatibility (SI) phenotype of the style. The pollen product of the S locus (pollen S) in N. alata is unknown, but in species from the related genus Petunia and in self-incompatible members of the Plantaginaceae and Rosaceae, this function has been assigned to an F-box protein known as SLF or SFB. Here we describe the identification of 10 genes (designated DD1–10) encoding SLF-related proteins that are expressed in N. alata pollen. Because our approach to cloning the DD genes was based on sequences of SLFs from other species, we presume that one of the DD genes encodes the N. alata SLF ortholog. Seven of the DD genes were exclusively expressed in pollen and a low level of sequence variation was found in alleles of each DD gene. Mapping studies confirmed that all 10 DD genes were linked to the S locus and that at least three were located in the same chromosomal segment as pollen S. Finally, the different topologies of the phylogenetic trees produced using available SLF-related sequences and those produced using S-RNase sequences suggests that pollen S and the S-RNase have different evolutionary histories.