In this current study, we examined all 14 known members of the A. thaliana HSP70 gene family in response to CMV or ORMV infection in the wild-type ecotype Columbia-0 (Col-0) and SA, JA, and/or ET defense signaling mutants. Expression of all HSP70 family members in response to virus infection was of interest because only those predicted to encode cytosolic proteins were previously studied (Aparicio et al., 2005). In A. thaliana, HSP70s localize to the cytoplasm, chloroplast, mitochondrion or endoplasmic reticulum (ER). Thus profiling different classes of plant HSP70s in particular those encoding non-cytoplasmic proteins was necessary to determine the specificity or generality of their induction by viruses. Defense signaling mutants were selected to investigate whether HSP70s induced by viruses are reflective of a defense-related response requiring SA, JA and/or ET signaling pathways. This question is of interest because a N. benthamiana cytosolic HSP70 was reported to be essential for resistance to a bacterial pathogen (Kanzaki et al., 2003). Although we are studying compatible plant-virusinteractions that allow systemic virus infections, basal defense pathways are induced in virus-infected plants (Huang et al., 2005). In our study we also profiled two A. thaliana HSFs previously studied for their roles in regulating the heat stress-induced pathway to determine if they were virus-inducible. In A. thaliana, their are at least 21 HSFs (von Koskull-Doring et al., 2007). To gain further insight into HSP70 induction, an inducible promoter system was used to express viral proteins or non-viral proteins of interest to identify specific viral elicitors.
Plants exhibit specific responses when challenged with vi- ruses. Compatible host-virusinteractions result in systemic infections leading to the development of characteristic symptoms. The magnitude of physiological and phenotypic changes in the host during viral infection suggests the acti- vation and suppression of global gene expressions in the host . In incompatible interaction, the expression of host resistance (R) gene is triggered by specific molecular inter- actions with viral avirulence (Avr) proteins and activates a cascade of genes to induce defense mechanisms including synthesis of pathogenesis-related (PR) proteins [2,3]. The accumulation of PR proteins is also associated with sys- temic acquired resistance (SAR) against a wide range of pathogens . During incompatible interaction the virus replication is ceased and the movement is arrested at or near the sites of infection. The ‘ oxidative burst ’ by the pro- duction of reactive oxygen species (ROS) is one of the earliest cellular responses following pathogen infection. The sequential reduction of molecular oxygen to super- oxide radical (.O 2 - ), hydrogen peroxide (H 2 O 2 ) and hydroxyl
Both resource availability and coinfection play prominent roles in a variety of disease systems (Dordas 2009, Johnson et al. 2010, Griffiths et al. 2011, Seabloom et al. 2015), but the potential for these ecological factors to alter both host and pathogen fitness makes predicting their effects on virulence challenging (Lafferty and Holt 2003, Paull et al. 2012a). For our empirical case study of two plant viruses in oats, nutrient addition that promoted plant growth partially offset infection-induced mass loss and counteracted the negative effects of infection on chlorophyll content. Facilitation between the viruses may have contributed to higher symptom intensity observed in coinfected plants. However, the effects of nutrients on virus growth rates did not appear to meaningfully affect virulence, likely due to a weak connection between virus density and host traits. Through analysis of a mathematical model, we determined that
For the sake of model simplicity, spatial components associated with host- specific anatomy will be neglected, and the cell populations are assumed to uniformly distributed within the plant. Despite potentially overlooking some aspects of the dynamics, the assumption of spatial uniformity has been very eﬀectively used to understand viral dynamics [56, 57]. Non-spatial mod- els can provide significant insights into the dynamics and become the basis upon which more detailed models can be built on. Additionally, in the case of field plants, it is biologically reasonable to assume that multiple infection sites could be distributed all over the host. Targeted plants could be exposed multiple times during vector movement or feeding, as vector-borne pathogens have been found capable of even altering the phenotypes of their hosts and vectors in such a way that the frequency and the nature of interactions be- tween them promotes the transmission of the disease [58, 59]. Furthermore, all plant cells are connected through plasmodesmata, the phloem and the xylem vessels responsible for resource translocation , and these pathways can also be used by viruses for systemic infections of their host [61, 62].
Studies carried out in a wide array of ecosystems and regions in East Asia are required because the research on plant- pollinator interactions done so far has not been evenly distributed geographically. The majority of pollination studies in China have conducted in mountainous regions (Ren et al. 2018). In East Asia, relatively few studies have been conducted in the subtropics, coastal ecosystems, and wetland ecosystems. Although the Korean peninsula and Taiwan are biologically diverse and biogeographically important components of East Asia (Kong & Watts 1999; Choe et al. 2016; Zhu 2016; Tojo et al. 2017), very few studies on plant- pollinator interactions have been conducted in these regions. The relationship between habitat type and the composition of pollinator fauna in East Asia is still unclear because few community-level studies that were comparable among habitat types have been conducted. However, some trends can be observed (Fig. 2). Although very few studies have been conducted in wetland habitats, dipteran pollinators are known to be abundant in wetland habitats (Kato & Miura 1996). Bees, especially bumblebees, and Diptera are dominant flower visitors in alpine regions (Yumoto 1986; Fang & Huang 2012; Mizunaga & Kudo 2017; Ishii et al. 2019). Wasps tend to be more abundant in coastal sand dunes than in other habitats (Inoue & Endo 2006b; Hiraiwa & Ushimaru 2017). More studies are needed to definitively elucidate the relationships between different habitat types and their pollinator fauna.
While studies on the effect of neighbor identity through volatile cues are un- common, the observed elongated phenotypes of receiver plants could be consi- dered analogous to shade avoidance or competitive phenotypes. Changes in plant structure such as elongated height are characteristic responses to the pres- ence of competitors    , and A . thaliana has been shown to ex- press petiole elongation and increased canopy height in response to competition . Increasing the height of photosynthetic surfaces and root branching pro- mote competitive ability, ultimately allowing plants to gather more resources such as sunlight aboveground, and water or nutrients belowground  . Even though competition was not manipulated in our study (as plants were not allowed to directly interact with neighbors), the observed increase in growth-related traits of receiver plants of a different genotype than emitter plants resembled a plant-plant competition-like response. Since volatile composition differs be- tween the genotypes selected for this study  , it could be speculated that receiver plants could “recognize” a genetically distinct neighbor through air- borne volatiles. This could, in turn, elicit receiver phenotypes to mount a re- sponse to a potential stressor such as competition. It has been previously dem- onstrated that airborne chemical cues can activate shade avoidance responses, and thus, facilitate competitive preparedness between neighboring plants . Ethylene emission, for instance, may induce shade avoidance syndromes such as elongation and narrowing leaf blades  . Therefore, chemical communica- tion provides a mechanism that could potentially explain plant genotype-specific responses to neighbors.
The aim of this study was to assess whether water avail- ability differentially affects the biotic effects of BSCs and pioneer shrubs on the early plant life-history stage of tree seedling growth. This study uses Nothofagus pumilio (Poepp. et Endl.) Krasser seedlings as a focal organism, since this species is one of the most widely distributed trees in the Patagonian forests. Furthermore, N. pumilio has great eco- logical and economic relevance; it is the species that com- monly forms the altitudinal tree line, protecting the heads of watersheds, and at lower elevation it produces valuable timber and summer grazing grounds. Patagonian forests are already facing a desiccating trend in climatic conditions: de- crease in precipitation and increase in temperature, which is expected to intensify according to climate change scenarios, especially toward the north of their distribution (Barros et al., 2014). This can have important ecological consequences since N. pumilio forest dynamics and establishment patterns are greatly shaped by climatic trends (Rodríguez-Catón et al., 2016; Srur et al., 2016). We hypothesized that the cover of shrubs and the BSC have a facilitative effect on N. pumilio seedlings under water shortage since they modulate abiotic stress by increasing soil water availability. In addition, we hypothesized that the BSC would have an additional positive effect by increasing soil fertility while shrubs compete with seedlings for nutrient resources. Exploring this topic could improve our understanding of biotic interactions and help predict the ecological responses of these forests to climate change.
Many pathogens establish their first contact with plant cells in the apoplast, the extracellular space in plant tissue that con- stitutes a source of nutrients and shelter for many microbial inhabitants. At the same time the apoplast is a hostile envi- ronment that contains hydrolytic enzymes and toxins that may challenge microbial growth. Furthermore, host hydrolytic activ- ities establish decomposition of microbial matrices to generate soluble PRR ligands (Liu et al., 2014 ). For instance, apoplastic glu- canases and chitinases disrupt the integrity of fungal walls and release chitin and glucan MAMPs. In response, several strategies evolved in plant pathogens in order to prevent recognition and MAMP-triggered activation of immune responses, including al- terations in the composition and structure of cell walls, modifi- cation of carbohydrate chains and secretion of effectors to pro- vide protection to the cell wall or target host immune responses (Fig. 2 ). Conversion of chitin to chitosan by deacetylation dur- ing host invasion may protect hyphae of pathogenic fungi from being hydrolyzed by extracellular plant chitinases, as chitosan is a poor substrate for chitinases, and consequently will reduce the release of elicitors (Ride and Barber 1990 ). Moreover, chi- tosan is a weak inducer of immune responses in many plant species (Baureithel, Felix and Boller 1994 ; Vander et al., 1998 ), although it has been reported as a strong inducer of immu- nity in others (Rabea et al., 2003 ; Iriti and Faoro 2009 ). Indeed, it has been demonstrated that chitin in the invasive hyphae of the rust fungi Puccinia graminis f.sp. tritici and Uromyces fabae and of the anthracnose fungus C. graminicola is not accessible to the chitin-binding probe wheat germ agglutinin, but is labeled by a chitosan-specific antibody (El Gueddari et al., 2002 ). In addition to chitin deacetylation, also other changes in cell wall compo- sition may occur during fungal infection. For instance, the rice blast pathogen M. oryzae specifically accumulates α-1,3-glucan
Most of our current knowledge on large multi-component protein complexes comes from biochemical experiments involving high quantity and high quality affinity purification of the protein of interest and inter- acting partners. Almost exclusively, studies with this objective have em- ployed strong cross linking agents to stabilise protein-protein and DNA- protein interactions, in an attempt to maximise the number of purified interactors and to also create a snapshot of protein networks in living sys- tems. One potential limitation arising from this methodology is the iden- tification of false positive interactions between proteins functioning in close proximity. In support of the cross-linking technique, the Allis lab who were responsible for several seminal papers in histone acetylation and the characterisation of the SAGA complex, also employed cross-link- ing agents such as formaldehyde. Two additional significant aspects of the experimental procedure include the quantity of material and the purifica- tion method. We attempted to scale up the purification by extracting pro- tein from at least 70 rosettes per treatment resulting in at least 30g of plant tissue. To put this into perspective, purifications from yeast to char- acterise the SAGA complex involved cultures ranging from 5-20 litres. This is significantly higher than the 30g of plant tissue employed in our experiments and highlights that the identification of multi protein com- plexes (potentially >1MDa in size) may require very large quantities of plant tissue. To our knowledge not many studies in plant research have attempted to fully characterize multi-protein chromatin remodelling com-
Considering only those papers that deal with mycorrhizal fungi-PGPR mixtures, we observed that one of the main research efforts is concentrated on the possible use of phosphate-solubilizing bacteria to enhance the advantage of mycorrhizal with respect to plant phosphorus nutrition, as exemplified by Roesti et al. (2006). In this paper, the authors obtained 3000 isolates from wheat (Triticum aestivum) fields in India, and selected 20 of those considered to be the most promising from both phosphate-solubilization and IAA production standpoints. These strains were selected from areas with different management strategies (low input and yield; low input with average yield and high input and yield), and although the authors found that plant growth stadium, crop management history and PGPR mix had significant effects, altogether they explained less than 60 % of the overall variation, even though the effect of PGPR inoculation was stronger than that observed for mycorrhizal inoculation.
susceptibility of the host plant to subsequent attack (Chen, 2008). Three main signalling pathways are known to be involved in the defence response to pathogens and insects; jasmonic acid (JA), salicylic acid (SA) and ethylene (ET). The extent to which each pathway is activated appears to be attacker specific (Reymond & Farmer, 1998) which may result in antagonistic or synergistic interactions between plant attackers (Koornneef & Pieterse, 2008). For example, plant pathogens are usually associated with an SA- mediated response which may act to suppress the JA-mediated response to insect herbivores (Stout et al., 1999). These types of interaction between signalling pathways are often referred to as ‘cross-talk’ (Kunkel & Brooks, 2002). In addition, plants have also been found to possess receptors which are capable of recognising the type of organism which is attacking e.g. mitogen-activated protein kinase (MAPK) proteins (Jonak et al., 2002; Nakagami et al., 2005) which activate a signalling cascade which regulates cellular activities such as gene expression. Plants therefore exhibit a complex array of biochemical responses and the result of this ‘induced resistance’ ultimately leads to alterations in the underlying plant chemistry which can subsequently exert a range of effects on a secondary attacker, such as an insect herbivore (Karban & Baldwin, 1997).
Lexical arbitrariness leads to confusion in the biotic interaction literature. An established definition of the existing terms referring to biotic interaction levels and mechanisms would make literature clearer and more comprehensible (Trinder et al. 2013). A paradigmatic example illustrating this confusion is the word competition, which is used interchangeably to refer to different things. In community-level biotic interaction charts, competition refers to the negative pairwise interaction (-/-), as opposed to, for instance, mutualism (+/+) (e.g., in Godsoe et al. 2017). In some fields, such as plant positive interactions research, it is common to use competition to refer to a negative net interaction instead of facilitation (Filazzola and Lortie 2014). Finally, in an ecophysiology context, competition is the fight among individuals for a specific resource (Grime 1973), regardless of whether the net interactive effect is positive or negative, hence being an interaction force. The Merriam Webster dictionary goes in this same direction and defines competition as the "active demand by two or more organisms or kinds of organisms for some environmental resource in short supply." This problem similarly affects other related terms (West et al. 2007). To avoid confusion within this text, and hopefully to contribute a more precise use of the words across sub-disciplines, we propose the following glossary of biotic interaction terms.
The 8 th Seili Virus-Cell Interactions Symposium (generally known as “Seili meeting”) will focus on the current and future trends in virus research including structural, biochemical, cellular and systems biological approaches, and applications within diagnostics and biomedicine
A19-interacting proteins. HeLa cells were infected with vFS- A19, and the tagged A19 protein was captured with affinity beads to copurify any associated proteins. We also infected cells with two control viruses to evaluate nonspecific interactions: WT VACV, which has no affinity tag; and vFS-A11, which has the same FS affinity tag as A19. Lysates from cells infected with the three vi- ruses were prepared in the same manner and bound to streptavi- din-agarose beads. The bound proteins were eluted with biotin and resolved by SDS-PAGE. The absence of any intense bands in the WT lane was expected, as there was no affinity tag (Fig. 5). Surprisingly, the A11 lane had only one intense band correspond- ing in size to FS-A11, suggesting no strong, stable interactions (Fig. 5). Inspection of the A19 lane, however, revealed many bands that were unique or greatly enriched (Fig. 5). The intense band near the bottom of the gel corresponds in size to FS-A19. To iden- tify proteins, each lane was cut into 20 equal size gel slices and FIG 1 ClustalW alignment of A19 chordopoxvirus orthologs. (A) Amino acid sequences of A19 orthologs from each representative genus of Chordopoxvirinae were aligned using the ClustalW program. VACV, vaccinia virus Western Reserve; VARV, variola virus Bangladesh; DPV, deerpox virus strain W-1170-84; YMTV, Yaba monkey tumor virus Amano; CRV, crocodilepox virus Zimbabwe; SWPV, swinepox virus Nebraska; ORV, Orf virus OV-SA00; MOCV, molluscum contagiosum virus subtype1; MYXV, myxoma virus Lausanne; SPPV, sheeppox virus strain NISKHI; FWPV, fowlpox virus Iowa. Completely conserved amino acids are denoted by asterisks, and highly conserved amino acids are indicated by dots. Gaps introduced to maximize alignment are indicated by the dashes. The bar above the sequences indicates a sequence of positively charged amino acids. (B) Tabulation of the pairwise percent identity and similarity of A19 sequences between different genera.
(ii ) Trochetia. An endemic Mascarene genus encompass- ing six species of shrubs and small trees; five species in Mauritius and one in La Re´union. All six species have coloured nectar, and show a remarkable variation in flower morphology and colour among species (Fig. 2G; Table 1; Friedmann, 1987). Their proposed closest rela- tives include several Malagasy Dombeyoid genera (Fried- mann, 1987). The most commonly reported pollinators of the Mauritian Trochetia species are two nectarivorous endemic bird species: the Mauritius grey white-eye, Zoster- ops mauritianus, has been observed visiting T. blackburniana, and the Mauritius olive white-eye, Z. chloronothos, has been observed on T. uniflora and has repeatedly been suggested as the main pollinator of T. blackburniana (Gill, 1971; Staub, 1988; Safford, 1991; Hansen et al., 2002). Further- more, Z. chloronothos has been suggested as a pollinator of the endangered T. boutoniana (Staub, 1988). In La Re´union, both endemic species of Zosterops have been observed visiting T. granulata (Gill, 1971; D. M. Hansen, personal observations). An anecdotal observation of an endemic diurnal gecko visiting a flower of T. blackburniana (Staub, 1988) has recently been confirmed by a study which shows that Mauritian Phelsuma geckos are important pollinators of T. blackburniana (Fig. 2Q; Hansen et al., in press). Phelsuma geckos have been confirmed to visit a wide range of other Mauritian endemic plant species (Nyhagen et al., 2001; Olesen et al., 2002; D. M. Hansen, personal observations; C. N. Kaiser, personal communication), and in a recent study P. ornata geckos strongly preferred col- oured over clear nectar in experimental artificial flowers (Hansen et al., 2006). More studies on how Phelsuma geckos interact with Mauritian plants with coloured nectar in the wild are needed to assess the effect of coloured nec- tar on reproductive success. Trochetia blackburniana may be well suited for such studies, as its nectar naturally varies from clear to deep yellow or orange, even within small populations, while variation in nectar colour of flowers on the same plant seems to be smaller (D. M. Hansen, per- sonal observations).
lymphoid aggregates in the dermis associated with capil- laries upon microscopic examination. The presence of MDV in tumor-like lesions was subsequently confirmed by isolation of the virus in culture . However, in situ, these cells do not generally harbor viral antigens detect- able by immunofluorescence , and therefore appear to be latently infected-tumor cells. Interestingly, cutane- ous tumors with large accumulations of lymphoblasts expressing the viral oncoprotein Meq have been ob- served in the dermis of scaleless chickens, suggesting that the presence of feather follicles is not required for the development of skin tumors . Among non tumor-like lesions are the nuclear inclusion bodies typic- ally found during lytically herpesvirus infections. These nuclear inclusions are only found in the upper layers of the feather follicle epithelium, and never in the basal layer [42,45,75]. The lesions are associated with the pres- ence of viral antigens. Analysis of the distribution of fea- ther follicles positive for MDV antigens and lymphoid cell aggregates shows that these two features are associ- ated , and suggests that lymphoid cells could be the source of feather follicle infection, although this has not been demonstrated. Macroscopic and microscopic le- sions associated with the presence of MDV antigens have been described in cutaneous structures other than feather follicles, including the comb, barbs, and leg skin that harbors scales without feathers . For more de- tails on these skin lesions, we refer the reader to two re- views [20,77].
In addition to microbes, over 100 species of vascular plants synthesize mannitol (17). Our recent research has focused on the role(s) of mannitol metabolism in plants, in particular celery, where mannitol serves as an alternate metabolic reserve, as well as an osmoprotectant. In celery, the enzyme mannitol dehydrogenase (MTD), a 1-oxidoreductase, catalyzes the direct conversion of mannitol to mannose, and is a key regulator of mannitol pool size (18). Characterization of a cDNA encoding MTD revealed a striking sequence similarity (>70% nt and >90% aa) to the Eli3 pathogen induced transcripts from parsley and Arabidopsis (19,20). The dramatic induction of MTD expression in celery cell suspensions upon treatment with SA provided further evidence that MTD and hence mannitol might play a role in plant-pathogen interactions. We originally hypothesized that, given its antioxidant properties, the large pools of mannitol in celery and parsley (up to 50 and 20%, respectively, of their soluble carbohydrate) would seriously handicap ROS-mediated plant resistance responses. However, removal of mannitol via the pathogen- induced production of MTD would allow these defense responses to proceed.
The hypothesis for a role for mannitol in host-pathogen interactions has come from direct and indirect observations. While some have reported mannitol accumulation in liver tissue and blood of rats suffering from aspergillosis (Wong, et al., 1989), others have shown that mutants of C. neoformans that produced less mannitol were found to be less virulent than wild type (Chaturvedi et al., 1996 a ). C. neoformans produces large amounts of the mannitol in culture and infected animals. A UV generated mutant of C. neoformans that produced less mannitol was more susceptible to stresses such as heat and high NaCl concentrations than wild type. In addition, mice that were inoculated with the mutant survived, while the ones inoculated with the wild type at the same inoculum concentration died. The same mutant and wild type were used in an assay with polymorphonuclear neutrophils. Polymorphonuclear neutrophils killed more mutants than wild type C. neoformans after 2 and 4 hrs of exposure (p < than 0.05). While the usage of catalase in the assay did not prevent the death of the two strains, using superoxide dismutase, mannitol, and DMSO prevented both strains from being killed. It was suggested that C. neoformans produced and secreted mannitol to protect itself against oxidative killing mechanisms of phagocytic cells (Chaturvedi et al., 1996 b ). The yeast C. albicans produces arabinitol in cultured, as well as in animals and humans suffering from candidiasis (Kiehn, et al., 1979). Link et al., 2005 recently showed that arabinitol, which is also made by the fungus U. fabae, can also quench ROS. However, similar studies as those with C. neoformans have not been done with C. albicans and arabinitol.
striking change was that a loop, designated B (Figure 3.2 A and B), had been transformed into an a-helix. This connected to existing a-helical regions A and C and probably acts to project the fusion peptide approximately 100A away from the virus surface. Also residues 106-112 convert from a helical configuration to an extended loop which causes the D helix to be flipped by 180°C. Interestingly, approximately 20 C-terminal amino acids which should not be present in the TBHA2 fragment were not resolved indicating that they possessed a disordered or flexible conformation and suggested that they may form the connection to the transmembrane region. (Bullough et al., 1994; Hernandez et al., 1996). Electron microscopic study of HA containing virosomes which had been pre-treated at low pH and reacted with an antibody that binds to residues surrounding HA2 107 indicated that this region had been inverted 180° and was now approximately llOA from the viral envelope (Wharton et al., 1995). The inverted structure is supported by a study that showed that treatment of virus at low pH in the absence of target membrane released fusion peptides that inserted in to the viral envelope and resembled its own HA2 transmembrane domain (Weber etal., 1994).