Marine heatwave and reduced light scenarios cause species-specific metabolomic changes in seagrasses under ocean warming.

Climate change and extreme climatic events, such as marine heatwaves (MHWs), are threatening seagrass ecosystems. Metabolomics can be used to gain insight into early stress responses in seagrasses and help to develop targeted management and conservation measures. We used metabolomics to understand the temporal and mechanistic response of leaf metabolism in seagrasses to climate change. Two species, temperate Posidonia australis and tropical Halodule uninervis, were exposed to a combination of future warming, simulated MHW with subsequent recovery period, and light deprivation in a mesocosm experiment. The leaf metabolome of P. australis was altered under MHW exposure at ambient light while H. uninervis was unaffected. Light deprivation impacted both seagrasses, with combined effects of heat and low light causing greater alterations in leaf metabolism. There was no MHW recovery in P. australis. Conversely, the heat-resistant leaf metabolome of H. uninervis showed recovery of sugars and intermediates of the tricarboxylic acid cycle under combined heat and low light exposure, suggesting adaptive strategies to long-term light deprivation. Overall, this research highlights how metabolomics can be used to study the metabolic pathways of seagrasses, identifies early indicators of environmental stress and analyses the effects of environmental factors on plant metabolism and health.

Sugar transporter Slc37a2 regulates bone metabolism in mice via a tubular lysosomal network in osteoclasts.

Osteoclasts are giant bone-digesting cells that harbor specialized lysosome-related organelles termed secretory lysosomes (SLs). SLs store cathepsin K and serve as a membrane precursor to the ruffled border, the osteoclast's 'resorptive apparatus'. Yet, the molecular composition and spatiotemporal organization of SLs remains incompletely understood. Here, using organelle-resolution proteomics, we identify member a2 of the solute carrier 37 family (Slc37a2) as a SL sugar transporter. We demonstrate in mice that Slc37a2 localizes to the SL limiting membrane and that these organelles adopt a hitherto unnoticed but dynamic tubular network in living osteoclasts that is required for bone digestion. Accordingly, mice lacking Slc37a2 accrue high bone mass owing to uncoupled bone metabolism and disturbances in SL export of monosaccharide sugars, a prerequisite for SL delivery to the bone-lining osteoclast plasma membrane. Thus, Slc37a2 is a physiological component of the osteoclast's unique secretory organelle and a potential therapeutic target for metabolic bone diseases.

Volatile biomarkers for non-invasive detection of American foulbrood, a threat to honey bee pollination services.

Honey bees provide essential environmental services, pollinating both agricultural and natural ecosystems that are crucial for human health. However, these pollination services are under threat by outbreaks of the bacterial honey bee disease American foulbrood (AFB). Caused by the bacterium, Paenibacillus larvae, AFB kills honey bee larvae, converting the biomass to a foul smelling, spore-laden mass. Due to the bacterium's tough endospores, which are easily spread and extremely persistent, AFB management requires the destruction of infected colonies in many countries. AFB detection remains a significant problem for beekeepers: diagnosis is often slow, relying on beekeepers visually identifying symptoms in the colony and molecular confirmation. Delayed detection can result in large outbreaks during high-density beekeeping pollination events, jeopardising livelihoods and food security. In an effort to improve diagnostics, we investigated volatile compounds associated with AFB-diseased brood in vitro and in beehive air. Using Solid Phase Microextraction and Gas Chromatography Mass-Spectrometry, we identified 40 compounds as volatile biomarkers for AFB infections, including 16 compounds previously unreported in honey bee studies. In the field, we detected half of the biomarkers in situ (in beehive air) and demonstrated their sensitivity and accuracy for diagnosing AFB. The most sensitive volatile biomarker, 2,5-dimethylpyrazine, was exclusively detected in AFB-disease larvae and hives, and was detectable in beehives with <10 AFB-symptomatic larvae. These, to our knowledge, previously undescribed biomarkers are prime candidates to be targeted by a portable sensor device for rapid and non-invasive diagnosis of AFB in beehives.

Effect of chitosan and gum Arabic with natamycin on the aroma profile and bacterial community of Australian grown black Périgord truffles (Tuber melansoporum) during storage.

This study aimed to assess the effect of chitosan or gum Arabic edible coatings, with natamycin (200, 300, 400 mg/L) on the aroma profiles of Western Australian grown truffles at five storage intervals: 0, 7, 14, 21, and 28 days using solid-phase microextraction (SPME)-followed by gas chromatography-mass spectrometry (GC-MS). The population structure of the bacterial community of both untreated and chitosan-natamycin (400 mg/L) coated truffles were assessed using metagenomic sequencing analysis alongside GC-MS. The results demonstrated that all the coating treatments were able to have a positive impact in halting or delaying the changes of truffle aroma throughout the storage period, with chitosan-natamycin (400 mg/L) coating having the best preservation results compared to the other coatings. Only 9 volatile organic compounds (VOCs) were found to have significant changes in chitosan-natamycin (400 mg/L) coated truffles throughout the storage period compared to 11 VOCs in untreated controls. The result also demonstrated the gradual change of fresh truffle's bacteria communities over the storage period. Over 4 weeks of storage, the dominant bacterial classes of the truffles (α-Proteobacteria, Bacteroidia or Actinobacteria classes) were replaced by Bacteroidia, Actinobacteria, Deltaprotobacteria and γ-Proteobacteria classes. The preliminary results from this study show that edible coatings can affect the VOC and bacterial communities of the truffles which may have implications for future research into truffle preservation techniques.

Developmental programming of adult adrenal structure and steroidogenesis: effects of fetal glucocorticoid excess and postnatal dietary omega-3 fatty acids.

Fetal glucocorticoid excess programs a range of detrimental outcomes in the adult phenotype, at least some of which may be due to altered adult adrenocortical function. In this study, we determined the effects of maternal dexamethasone treatment on offspring adrenal morphology and function, as well as the interactive effects of postnatal dietary omega-3 (n-3) fatty acids. This postnatal dietary intervention has been shown to alleviate many of the programming outcomes in this model, but whether this is via the effects on adrenal function is unknown. Dexamethasone acetate was administered to pregnant rats (0.75 microg/ml drinking water) from day 13 to term. Cross-fostered offspring were raised on either a standard or high-n-3 diet. Adrenal weight (relative to body weight) at 6 months of age was unaffected by prenatal dexamethasone, regardless of postnatal diet, and stereological analysis showed no effect of dexamethasone on the volumes of adrenal components (zona glomerulosa, zona fasciculata/reticularis or adrenal medulla). Expression of key steroidogenic genes (Cyp11a1 and Star) was unaffected by either prenatal dexamethasone or postnatal diet. In contrast, adrenal expression of Mc2r mRNA, which encodes the ACTH receptor, was higher in offspring of dexamethasone-treated mothers, an effect partially attenuated by the Hn3 diet. Moreover, stress-induced levels of plasma and urinary corticosterone and urinary aldosterone were elevated in offspring of dexamethasone-treated mothers, indicative of enhanced adrenal responsiveness. In conclusion, this study shows that prenatal exposure to dexamethasone does not increase basal adrenocortical activity but does result in a more stress-responsive adrenal phenotype, possibly via increased Mc2r expression.