Summary
The perception of pathogen‐associated molecular patterns (PAMPs) by immune receptors launches defence mechanisms referred to as PAMP‐triggered immunity (PTI). Successful pathogens must ...suppress PTI pathways via the action of effectors to efficiently colonize their hosts. So far, plant PTI has been reported to be active against most classes of pathogens, except viruses, although this defence layer has been hypothesized recently as an active part of antiviral immunity which needs to be suppressed by viruses for infection success. Here, we report that Arabidopsis PTI genes are regulated upon infection by viruses and contribute to plant resistance to Plum pox virus (PPV). Our experiments further show that PPV suppresses two early PTI responses, the oxidative burst and marker gene expression, during Arabidopsis infection. In planta expression of PPV capsid protein (CP) was found to strongly impair these responses in Nicotiana benthamiana and Arabidopsis, revealing its PTI suppressor activity. In summary, we provide the first clear evidence that plant viruses acquired the ability to suppress PTI mechanisms via the action of effectors, highlighting a novel strategy employed by viruses to escape plant defences.
Plums are the predominant fruit crop in Serbia. In the period under consideration (2012–2021), the Serbian plum area accounted for, on average, 42.52 % of the total fruit area in the country, far ...surpassing all other fruit crops. The Republic of Serbia is one of the leading plum producers in the world. With an average annual plum production of 440.91 thousand tons, Serbia ranks third in the world (following only China and Romania), contributing 3.77% to the world’s total plum production. Nevertheless, the country faces challenges such as low yields per unit area, approximately 5.35 t/ha (FAO, 2023). Presently, the economic significance of plum production is not as high as in previous decades, and cultivation potential remains underutilized. To revitalize plum production in Serbia and reclaim its historical prominence, it is imperative to assess the current state of plum production both globally and regionally and implement appropriate measures to enhance economic performance in this traditional fruit sector.
Cracking fruit is a serious quality change phenomenon in the storage and transportation of postharvest plum fruit. To reduce the cracking rate of plum fruit during cold storage, the 'Guofeng No.7′ ...plum was sprayed with chitosan with 1.5% concentration 30d from preharvest. The postharvest plum fruit was stored at (0 ± 0.5) °C and (85–90) % relative humidity. The results showed that chitosan treatment could reduce the reactive oxygen species (ROS) level of plum fruit, effectively delaying the fruit cracking. Compared with the control, chitosan treated fruits inhibited the increase of free radical content such as O2−· and H2O2 and delayed the increase of membrane permeability and the accumulation of MDA (from 71.9 mmol/g to 53.5 mmol/g). It also regulates lipoxygenase (LOX), peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) (enzymatic activity from 34.15 g/min to 42.21 g/min) and ascorbate peroxidase (APX) activity and gene expression during fruit cracking to maintain membrane integrity and intracellular compartmentalization, thereby increasing the crack tolerance of plum fruit during cold storage. These results indicate that preharvest chitosan treatment can inhibit the metabolism of active oxygen species, increase the activity of ROS scavenging enzymes and gene expression, and delay the postharvest cracking of plum fruit.
•Fruit cracking during postharvest storage and transportation largely challenges quality control requiring new strategies.•The technique of spraying chitosan preharvest was selected to control the cracking of plum fruit.•It surprisingly delayed the cracking of plum fruits and maintained postharvest quality.•This control was related to regulation of reactive oxygen species metabolism.
The potyviral RNA genome encodes two polyproteins that are proteolytically processed by three viral protease domains into 11 mature proteins. Extensive molecular studies have identified functions for ...the majority of the viral proteins. For example, 6K2, one of the two smallest potyviral proteins, is an integral membrane protein and induces the endoplasmic reticulum (ER)-originated replication vesicles that target the chloroplast for robust viral replication. However, the functional role of 6K1, the other smallest protein, remains uncharacterized. In this study, we developed a series of recombinant full-length viral cDNA clones derived from a Canadian Plum pox virus (PPV) isolate. We found that deletion of any of the short motifs of 6K1 (each of which ranged from 5 to 13 amino acids), most of the 6K1 sequence (but with the conserved sequence of the cleavage sites being retained), or all of the 6K1 sequence in the PPV infectious clone abolished viral replication. The trans expression of 6K1 or the cis expression of a dislocated 6K1 failed to rescue the loss-of-replication phenotype, suggesting the temporal and spatial requirement of 6K1 for viral replication. Disruption of the N- or C-terminal cleavage site of 6K1, which prevented the release of 6K1 from the polyprotein, either partially or completely inhibited viral replication, suggesting the functional importance of the mature 6K1. We further found that green fluorescent protein-tagged 6K1 formed punctate inclusions at the viral early infection stage and colocalized with chloroplast-bound viral replicase elements 6K2 and NIb. Taken together, our results suggest that 6K1 is required for viral replication and is an important viral element of the viral replication complex at the early infection stage.
Potyviruses account for more than 30% of known plant viruses and consist of many agriculturally important viruses. The genomes of potyviruses encode two polyproteins that are proteolytically processed into 11 mature proteins, with the majority of them having been at least partially functionally characterized. However, the functional role of a small protein named 6K1 remains obscure. In this study, we showed that deletion of 6K1 or a short motif/region of 6K1 in the full-length cDNA clones of plum pox virus abolishes viral replication and that mutation of the N- or C-terminal cleavage sites of 6K1 to prevent its release from the polyprotein greatly attenuates or completely inhibits viral replication, suggesting its important role in potyviral infection. We report that 6K1 forms punctate structures and targets the replication vesicles in PPV-infected plant leaf cells at the early infection stage. Our data reveal that 6K1 is an important viral protein of the potyviral replication complex.
It has been hypothesized that plants can get beneficial trade‐offs from viral infections when grown under drought conditions. However, experimental support for a positive correlation between ...virus‐induced drought tolerance and increased host fitness is scarce. We investigated whether increased virulence exhibited by the synergistic interaction involving Potato virus X (PVX) and Plum pox virus (PPV) improves tolerance to drought and host fitness in Nicotiana benthamiana and Arabidopsis thaliana. Infection by the pair PPV/PVX and by PPV expressing the virulence protein P25 of PVX conferred an enhanced drought‐tolerant phenotype compared with single infections with either PPV or PVX. Decreased transpiration rates in virus‐infected plants were correlated with drought tolerance in N. benthamiana but not in Arabidopsis. Metabolite and hormonal profiles of Arabidopsis plants infected with the different viruses showed a range of changes that positively correlated with a greater impact on drought tolerance. Virus infection enhanced drought tolerance in both species by increasing salicylic acid accumulation in an abscisic acid‐independent manner. Viable offspring derived from Arabidopsis plants infected with PPV increased relative to non‐infected plants, when exposed to drought. By contrast, the detrimental effect caused by the more virulent viruses overcame potential benefits associated with increased drought tolerance on host fitness.
It has been hypothesized that tolerance of virus‐infected plants to abiotic stresses is a conditional phenotype that could act as a pay‐off that offsets the detrimental effect of virus infection on plant fitness. However, this might not be the case if fitness costs associated with virulence outweigh the beneficial effects conferred by stress tolerance on plant growth. We experimentally tested the hypothesis that virus infection would increase the reproductive fitness of Arabidopsis thaliana and Nicotiana benthamiana under variable drought conditions. Our results challenge the general validity of the hypothesis that viruses behave as conditionally beneficial to their hosts and emphasize the need of considering the effect of virulence in the analysis of plant responses to combined abiotic and biotic stress.
Abstract Unusual Plum pox virus (PPV) isolates (named Tat isolates) were discovered on sour cherry ( Prunus cerasus ) in Russia. They failed to be recognized by RT-PCR using commonly employed primers ...specific to the strains C or CR (the only ones that proved able to infect sour cherry) as well as to the strains M and W. Some of them can be detected by RT-PCR using the PPV-D-specific primers P1/PD or by TAS-ELISA with the PPV-C-specific monoclonal antibody AC. Phylogenetic analysis of the 3′-terminal genomic region assigned the Tat isolates into the cluster of cherry-adapted strains. However, they grouped separately from the C and CR strains and from each other as well. The sequence divergence of the Tat isolates is comparable to the differences between the known PPV strains. They may represent new group(s) of cherry-adapted isolates which do not seem to belong to any known strain of the virus.
Syzygium cumini(S.cumini)(L.) Skeels(jambolan) is one of the widely used medicinal plants in the treatment of various diseases in particular diabetes.The present review has been primed to describe ...the existing data on the information on botany,phytochemical constituents,traditional uses and pharmacological actions of 5.cumini(L.) Skeels(jambolan).Electronic database search was conducted with the search terms of Eugenia jambolana,S.cumini,jambolan,common plum and java plum.The plant has been viewed as an antidiabetic plant since it became commercially available several decades ago.During last four decades,numerous folk medicine and scientific reports on the antidiabetic effects of this plant have been cited in the literature.The plant is rich in compounds containing anthocyanins,glucoside,ellagic acid,isoquercetin,kaemferol and myrecetin.The seeds are claimed to contain alkaloid,jambosine,and glycoside jambolin or antimellin,which halts the diastalic conversion of starch into sugar.The vast number of literatures found in the database revealed that the extracts of different parts of jambolan showed significant pharmacological actions.We suggest that there is a need for further investigation to isolate active principles which confer the pharmacological action.Hence identification of such active compounds is useful for producing safer drugs in the treatment of various ailments including diabetes.
Numerous plum pox virus (PPV) strain D isolates have been found in geographically distant regions of European Russia and the Crimean peninsula on different stone fruit hosts. Phylogenetic analysis of ...their partial and complete genomes suggests multiple introductions of PPV-D into Russia. Distinct natural isolates from Prunus tomentosa were found to bear unique amino acid substitutions in the N-terminus of the coat protein (CP) that may contribute to the adaptation of PPV-D to this host. Serological analysis using the PPV-D-specific monoclonal antibody 4DG5 provided further evidence that mutations at positions 58 and 59 of the CP are crucial for antibody binding.
Plum pox virus (PPV) is the causal agent of sharka, the most detrimental virus disease of stone fruit trees worldwide. PPV isolates have been assigned into seven distinct strains, of which PPV-C ...regroups the genetically distinct isolates detected in several European countries on cherry hosts. Here, three complete and several partial genomic sequences of PPV isolates from sour cherry trees in the Volga River basin of Russia have been determined. The comparison of complete genome sequences has shown that the nucleotide identity values with other PPV isolates reached only 77.5 to 83.5%. Phylogenetic analyses clearly assigned the RU-17sc, RU-18sc, and RU-30sc isolates from cherry to a distinct cluster, most closely related to PPV-C and, to a lesser extent, PPV-W. Based on their natural infection of sour cherry trees and genomic characterization, the PPV isolates reported here represent a new strain of PPV, for which the name PPV-CR (Cherry Russia) is proposed. The unique amino acids conserved among PPV-CR and PPV-C cherry-infecting isolates (75 in total) are mostly distributed within the central part of P1, NIa, and the N terminus of the coat protein (CP), making them potential candidates for genetic determinants of the ability to infect cherry species or of adaptation to these hosts. The variability observed within 14 PPV-CR isolates analyzed in this study (0 to 2.6% nucleotide divergence in partial CP sequences) and the identification of these isolates in different localities and cultivation conditions suggest the efficient establishment and competitiveness of the PPV-CR in the environment. A specific primer pair has been developed, allowing the specific reverse-transcription polymerase chain reaction detection of PPV-CR isolates.
•Major anthocyanins in Taoxingli: cyanidin 3-o-glucoside and cyanidin 3-o-rutinoside.•1-MCP maintained the quality of chemical attributes in ‘Taoxingli’ plum fruit.•1-MCP regulated the expression of ...anthocyanin synthesis genes and PsMYB10.•1-MCP delayed in accumulation of anthocyanin in ‘Taoxingli’ plum fruit during storage.
The effects of 1methylcyclopropene (1-MCP) treatment on the quality attributes of ‘Taoxingli’ plum fruit, particularly on whole fruit anthocyanin content via anthocyanin biosynthesis during storage at the non-chilling temperature of 10 °C were investigated. The results showed that 1-MCP treatment effectively reduced weight loss and better maintained soluble solids content (SSC) and titratable acidity (TA), resulting in increased contents of fructose, glucose, sorbitol, and malic acid, and reduced decay during storage. Furthermore, major anthocyanins, including cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside, were detected. 1-MCP treatment delayed increases in total anthocyanins along with the major individual anthocyanins during storage, which was attributed to its effect in suppressing the expression of synthesis-related structural genes and the transcription factor PsMYB10 early in storage, enhancing their expression later in the storage period. Thus, 1-MCP treatment was beneficial for retaining the quality of ‘Taoxingli’ plums, particularly the chemical attributes, and extending the storage life with low economic loss during storage.
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