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PAPERS PUBLISHED IN INTERNATIONAL SCIENTIFIC JOURNALS DURING 2018

Chimona, C., Koukos, D., Meletiou-Christou, M. S., Spanakis, E., Argiropoulos, A., Rhizopoulou, S. (2018) Functional traits of floral and leaf surfaces of the early spring flowering Asphodelus ramosus in the Mediterranean region. Flora, 248, 10-21.
 

Abstract: In this study functional micromorphological traits and water repellent attributes of floral and leaf surfaces of Asphodelus ramosus are presented. The branched inflorescences of A. ramosus bear numerous short-lived flowers arranged on tall flowering stalks, while the basal long-tapered leaves are long-lived. The most striking feature of the short-lived flowers of A. ramosus is the surface structure of the coloured midrib and the white bilateral sections of tepals, revealing different functionality between the two sections of tepals and the two sides of the corollas. Structural features of adaxial and abaxial epidermal cells may function predominantly for water repellence of floral tissues expanded during the humid period of the year. The leaves are more water repellent than the tepals and display declining water retention on their surfaces. It appears that micro- and nano-scale patterns observed on leaf and tepal surfaces of A. ramosus are linked to hydrophobic properties, which are important adaptive traits contributing to the seasonal performance of A. ramosus in the field, particularly in regard to water adhesion. 

https://www.sciencedirect.com/science/article/pii/S0367253018300689
 

A. Christopoulou, D. Kazanis, N.M. Fyllas, M. Arianoutsou 2018. Post-fire recovery of Abies cephalonica forest communities: the case of Mt Parnitha National Park, Attica, Greece, i-Forest, doi: 10.3832/ifor2744-011
 

Abstract: Mountain coniferous forests of Southern Europe seem to be increasingly affected by large fires. Endemic Greek fir (Abies cephalonica) forests were among the most affected ecosystems by the 2007 extreme wildfires in Greece. The aim of this study is to investigate the pattern of post-fire regeneration of fir forest plant communities of Mount Parnitha National Park, in Attica (Greece), after a large wildfire. A network of 8 severely burned sites across the mountain ridge was established in order to monitor natural regeneration of A. cephalonica as well as post-fire floristic composition and species richness. Field campaigns took place in two distinct time periods, one close to the fire event and one 8 to 10 years after. Generalized linear models were used to explore the effects of distance and microhabitat variables on the post-fire regeneration of the Greek fir. Distance from the unburned patches, slope and cover of woody species significantly affected A. cephalonica seedling establishment and hence its natural post-fire regeneration. Floristic composition and plant species richness of the recovering fir communities changed through time. During the initial phase, high species richness was recorded, mainly because of the high contribution of herbaceous species. During the second period, species richness was lower and similar to that recorded in the unburned fir communities. It is during this period when the first seedlings of the Greek fir managed to establish, although their density is rather low to ensure full recovery of the forest.
 

Gavriil ES, Dimitrakis S, Papadaki G, Balaska S, Lambrinidis G, Lougiakis N, Marakos P, Diallinas G., Pouli N, Mikros E (2018) Structure-activity relationships in fungal nucleobases transporters as dissected by the inhibitory effects of novel purine analogues. Eur J Med Chem. 2018 Aug 5;156:240-251. doi: 10.1016/j.ejmech.2018.06.038. Epub 2018 Jun 18.
 

Abstract: We have previously rationally designed, synthesized and tested a number of 3-deazapurine analogues, which inhibit the ubiquitous fungal nucleobase transporter FcyB, through binding in its major substrate binding site, by specifically interacting with Asn163. Here, in an effort to further understand the molecular details of structure-activity relationships in all three major nucleobase transporters of fungi, we extend this study by designing, based on our previous experience, synthesizing and testing further 3-deazapurine analogues. We thus identify seven new compounds with relatively high affinity (19-106 μΜ) for the FcyB binding site. Importantly, four of these compounds can also efficiently inhibit AzgA, a structurally and evolutionary distinct, but functionally similar, purine transporter. Contrastingly, none of the new compounds tested had any effect on the transport activity of the uric acid-xanthine transporter UapA, albeit this being a structural homologue of AzgA. Besides the apparent importance for understanding how nucleobase transporter specificity is determined at the molecular level, our work might constitute a critical step in the design of novel purine-related antifungals.
 

Kalampokis IF, Kapetanakis GC, Aliferis KA, Diallinas G. (2018) Multiple nucleobase transporters contribute to boscalid sensitivity in Aspergillus nidulans.  Fungal Genet Biol. 2018 Jun;115:52-63. doi: 10.1016/j.fgb.2018.02.004
 

Abstract: The development of fungicide-resistant fungal populations represents a major challenge for the agrochemical and agri-food sectors, which threatens food supply and security. The issue becomes complex for fungi that cause quantitative and qualitative losses due to mycotoxin biosynthesis. Nonetheless, currently, the molecular details underlying fungicide action and fungal resistance mechanisms are partially known. Here, we have investigated whether plasma membrane transporters contribute to specific fungicide uptake in the model fungus Aspergillus nidulans. Independent physiological tests and toxicity screening of selected fungicides provided evidence that the antifungal activity of Succinate Dehydrogenase Inhibitors (SDHIs) is associated with the expression of several nucleobase-related transporters. In particular, it was shown that a strain genetically inactivated in all seven nucleobase-related transporters is resistant to the fungicide boscalid, whereas none of the single null mutants exhibited significant resistance level. By constructing and testing isogenic strains that over-express each one of the seven transporters, we confirmed that five of them, namely, UapC, AzgA, FycB, CntA, and FurA, contribute to boscalid uptake. Additionally, by employing metabolomics we have examined the effect of boscalid on the metabolism of isogenic strains expressing or genetically lacking boscalid-related nucleobase transporters. The results confirmed the involvement of specific nucleobase transporters in fungicide uptake, leading to the discovery of corresponding metabolites-biomarkers. This work is the first report on the involvement of specific transporters in fungicide uptake and toxicity and their impact on fungal metabolism regulation and results might be further exploited towards the deeper understanding of fungal resistance to fungicides.
 

Kourkoulou A, Pittis AA, Diallinas G. (2018) Evolution of substrate specificity in the Nucleobase-Ascorbate Transporter (NAT) protein family.  Microb Cell. 2018 Mar  22;5(6):280-292. doi: 10.15698/mic2018.06.636.
 
Abstract: L-ascorbic acid (vitamin C) is an essential metabolite in animals and plants due to its role as an enzyme co-factor and antioxidant activity. In most eukaryotic organisms, L-ascorbate is biosynthesized enzymatically, but in several major groups, including the primate suborder Haplorhini, this ability is lost due to gene truncations in the gene coding for L-gulonolactone oxidase. Specific ascorbate transporters (SVCTs) have been characterized only in mammals and shown to be essential for life. These belong to an extensively studied transporter family, called Nucleobase-Ascorbate Transporters (NAT). The prototypic member of this family, and one of the most extensively studied eukaryotic transporters, is UapA, a uric acid-xanthine/H+symporter in the fungus Aspergillus nidulans. Here, we investigate molecular aspects of NAT substrate specificity and address the evolution of ascorbate transporters apparently from ancestral nucleobase transporters. We present a phylogenetic analysis, identifying a distinct NAT clade that includes all known L-ascorbate transporters. This clade includes homologues only from vertebrates, and has no members in non-vertebrate or microbial eukaryotes, plants or prokaryotes. Additionally, we identify within the substrate-binding site of NATs a differentially conserved motif, which we propose is critical for nucleobase versus ascorbate recognition. This conclusion is supported by the amino acid composition of this motif in distinct phylogenetic clades and mutational analysis in the UapA transporter. Together with evidence obtained herein that UapA can recognize with extremely low affinity L-ascorbate, our results support that ascorbate-specific NATs evolved by optimization of a sub-function of ancestral nucleobase transporters..
 

Martzoukou O, Diallinas G, Amillis S. (2018) Secretory Vesicle Polar Sorting, Endosome Recycling and Cytoskeleton Organization Require the AP-1 Complex in Aspergillus nidulans. Genetics. 2018 Aug;209(4):1121-1138. doi: 10.1534/genetics.118.301240. Epub 2018 Jun 20. PubMed PMID: 29925567; PubMed Central PMCID: PMC6063236
 
Abstract: The AP-1 complex is essential for membrane protein traffic via its role in the pinching-off and sorting of secretory vesicles (SVs) from the trans-Golgi and/or endosomes. While its essentiality is undisputed in metazoa, its role in simpler eukaryotes seems less clear. Here, we dissect the role of AP-1 in the filamentous fungus Aspergillus nidulans and show that it is absolutely essential for growth due to its role in clathrin-dependent maintenance of polar traffic of specific membrane cargoes toward the apex of growing hyphae. We provide evidence that AP-1 is involved in both anterograde sorting of RabERab11-labeled SVs and RabA/BRab5-dependent endosome recycling. Additionally, AP-1 is shown to be critical for microtubule and septin organization, further rationalizing its essentiality in cells that face the challenge of cytoskeleton-dependent polarized cargo traffic. This work also opens a novel issue on how nonpolar cargoes, such as transporters, are sorted to the eukaryotic plasma membrane..
 

Pyle E, Kalli AC, Amillis S, Hall Z, Lau AM, Hanyaloglu AC, Diallinas G, Byrne B, Politis A. (2018) Structural Lipids Enable the Formation of Functional Oligomers of the Eukaryotic Purine Symporter UapA.  Cell Chem Biol. 2018 Jul 19;25(7):840-848.e4. doi: 10.1016/j.chembiol.2018.03.011. Epub 2018 Apr 19. PubMed PMID: 29681524; PubMed Central PMCID: PMC6058078.
 
Abstract: The role of membrane lipids in modulating eukaryotic transporter assembly and function remains unclear. We investigated the effect of membrane lipids in the structure and transport activity of the purine transporter UapA from Aspergillus nidulans. We found that UapA exists mainly as a dimer and that two lipid molecules bind per UapA dimer. We identified three phospholipid classes that co-purified with UapA: phosphatidylcholine, phosphatidylethanolamine (PE), and phosphatidylinositol (PI). UapA delipidation caused dissociation of the dimer into monomers. Subsequent addition of PI or PE rescued the UapA dimer and allowed recovery of bound lipids, suggesting a central role of these lipids in stabilizing the dimer. Molecular dynamics simulations predicted a lipid binding site near the UapA dimer interface. Mutational analyses established that lipid binding at this site is essential for formation of functional UapA dimers. We propose that structural lipids have a central role in the formation of functional, dimeric UapA.
 

H. Seebens, T.M. Blackburn, E.E. Dyer, P. Genovesi, P.E. Hulme, J.M. Jeschkei, S. Pagad, P. Pysekm, M. van Kleunen, M. Winter, M. Ansong, M. Arianoutsou et al. 2018. Global rise in emerging alien species results from increased accessibility of new source pools Proceedings of the National Academy of Sciences, www.pnas.org/cgi/doi/10.1073/pnas.1719429115
 
Abstract: Our ability to predict the identity of future invasive alien species is largely based upon knowledge of prior invasion history. Emerging alien species—those never encountered as aliens before—therefore pose a significant challenge to biosecurity interventions worldwide. Understanding their temporal trends, origins, and the drivers of their spread is pivotal to improving prevention and risk assessment tools. Here, we use a database of 45,984 first records of 16,019 established alien species to investigate the temporal dynamics of occurrences of emerging alien species worldwide. Even after many centuries of invasions the rate of emergence of new alien species is still high: One-quarter of first records during 2000– 2005 were of species that had not been previously recorded anywhere as alien, though with large variation across taxa. Model results show that the high proportion of emerging alien species cannot be solely explained by increases in well-known drivers such as the amount of imported commodities from historically important source regions. Instead, these dynamics reflect the incorporation of new regions into the pool of potential alien species, likely as a consequence of expanding trade networks and environmental change. This process compensates for the depletion of the historically important source species pool through successive invasions. We estimate that 1–16% of all species on Earth, depending on the taxonomic group, qualify as potential alien species. These results suggest that there remains a high proportion of emerging alien species we have yet to encounter, with future impacts that are difficult to predict.