Plants that are adapted to waterlogged conditions develop aerenchyma in roots for ventilation. Some wetland plant species also form an apoplastic barrier at the outer cell layers of roots that reduces radial oxygen loss (ROL) from the aerenchyma and to prevent toxic compounds from entering the root. The composition of the apoplastic barrier is not well understood. One potential component is suberin, which accumulates at the hypodermal/exodermal cell layers of the roots under waterlogged soil conditions or in response to other environmental stimuli. However, differences in suberin content and composition between plant species make it difficult to evaluate whether suberin has a role in preventing ROL. In this article, we summarize recent advances in understanding apoplastic barrier formation in roots and, between various plant species, compare the chemical compositions of the apoplastic barriers in relation to their permeability to oxygen. Moreover, the relationship between suberin accumulation and the barrier to ROL is discussed.

Alzheimer’s disease (AD) is the most common form of dementia that usually occurs among older people. AD results from neuronal degeneration that leads to the cognitive impairment and death. AD is incurable, typically develops over the course of many years and is accompanied by a loss of functional autonomy, making a patient completely dependent on family members and/or healthcare workers. Critical features of AD are pathological polymerization of Aβ peptide and microtubule-associated protein tau, accompanied by alterations of their conformations and resulting in accumulation of cross-β fibrils (amyloids) in human brains. AD apparently progresses asymptomatically for years or even decades before the appearance of symptoms. Therefore, development of the early AD diagnosis at a pre-symptomatic stage is essential for potential therapies. This review is focused on current and potential molecular tools (including non-invasive methods) that are based on detection of amyloidogenic proteins and can be applicable to early diagnosis of AD. Abbreviations: Aβ – amyloid-β peptide; AβO – amyloid-β oligomers; AD – Alzheimer’s disease; ADRDA – Alzheimer’s Disease and Related Disorders Association; APH1 - anterior pharynx defective 1; APP – amyloid precursor protein; BACE1 – β-site APP-cleaving enzyme 1; BBB – brain blood barrier; CJD - Creutzfeldt-Jakob disease; CRM – certified reference material; CSF – cerebrospinal fluid; ELISA – enzyme-linked immunosorbent assay; FGD – ¹⁸F-fluorodesoxyglucose (2-deoxy-2-[¹⁸F]fluoro-D-glucose); IP-MS – immunoprecipitation-mass spectrometry assay; MCI – mild cognitive impairment; MDS – multimer detection system; MRI – magnetic resonance imaging; NIA-AA – National Institute on Ageing and Alzheimer’s Association; NINCDS – National Institute of Neurological and Communicative Disorders and Stroke; PEN2 – presenilin enhancer 2; PET – positron emission tomography; PiB – Pittsburgh Compound B; PiB-SUVR - PIB standardized uptake value ratio; PMCA – Protein Misfolding Cycling Amplification; PrP – Prion Protein; P-tau – hyperphosphorylated tau protein; RMP – reference measurement procedure; RT-QuIC - real-time quaking-induced conversion; SiMoA – single-molecule array; ThT – thioflavin T; TSEs – Transmissible Spongiform Encephslopathies; T-tau – total tau protein

Rice coleoptiles, renowned for anoxia tolerance, were hypoxically pretreated, excised, ‘healed’, and then exposed to a combination of anoxia and pH 3.5. The putative acid load was confirmed by net effluxes of K⁺ to the medium, with concurrent net decreases of H⁺ in the medium, presumably mainly due to H⁺ influx. Yet the coleoptiles survived the combination of anoxia and pH 3.5 for at least 90 h, and even for at least 40 h when the energy crisis, inherent to anoxia, had been aggravated by supplying the coleoptiles with 2.5 mM rather than 50 mM glucose. Even in the case of coleoptiles with 2.5 mM glucose, an accumulation ratio of 6 for Cl^– was attained at 4 h after the start of re-aeration, implying plasma membrane integrity was either maintained during anoxia, or rapidly restored after a return to aerated conditions. Cytoplasmic pH and vacuolar pH were measured using in vivo³¹P nuclear magnetic resonance spectroscopy with 50 mM glucose in the basal perfusion medium. After 60 h in anoxia, external pH was suddenly decreased from 6.5 to 3.5, but cytoplasmic pH only decreased from 7.35 to 7.2 during the first 2 h and then remained steady for the next 16 h. During the first 3 h at pH 3.5, vacuolar pH decreased from 5.7 to 5.25 and then stabilized. After 18 h at pH 3.5, the initial values of cytoplasmic pH and vacuolar pH were rapidly restored, both upon a return to pH 6.5 while maintaining anoxia and after subsequent return to aerated solution. Summing up, rice coleoptiles exposed to a combination of anoxia and pH 3.5 retained pH regulation and cellular compartmentation, demonstrating tolerance to anoxia even during the acid load imposed by exposure to pH 3.5.