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Povzetek: Abscission occurs specifically in the abscission zone (AZ) tissue as a natural stage of plant development. Previously, we observed delay of tomato (Solanum lycopersicum) leaf abscission when the LX ribonuclease (LX) was inhibited. The known association between LX expression and programmed cell death (PCD) suggested involvement of PCD in abscission. In this study, hallmarks of PCD were identified in the tomato leaf and flower AZs during the late stage of abscission. These included loss of cell viability, altered nuclear morphology, DNA fragmentation, elevated levels of reactive oxygen species and enzymatic activities, and expression of PCD-associated genes. Overexpression of antiapoptotic proteins resulted in retarded abscission, indicating PCD requirement. PCD, LX, and nuclease gene expression were visualized primarily in the AZ distal tissue, demonstrating an asymmetry between the two AZ sides. Asymmetric expression was observed for genes associated with cell wall hydrolysis, leading to AZ, or associated with ethylene biosynthesis, which induces abscission. These results suggest that different abscission-related processes occur asymmetrically between the AZ proximal and distal sides. Taken together, our findings identify PCD as a key mechanism that occurs asymmetrically during normal progression of abscission and suggest an important role for LX in this PCD process.
Ključne besede: plant cell, cell death, abscission
Objavljeno v DiRROS: 05.08.2024; Ogledov: 98; Prenosov: 69
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Povzetek: Physiological studies in plants often require enzyme extraction from tissues containing high concentrations of phenolsand polyphenols. Unless removed or neutralized, such compounds may hinder extraction, inactivate enzymes, and inter-fere with enzyme detection. The following protocol for activity assays for enzymes of primary carbohydrate metabo-lism, while based on our recently published one for quantitative measurement of activities using coupled spectrophoto-metric assays in a 96-well format, is tailored to the complexities of phenolic- and anthocyanin-rich extracts from grape-vine leaf. As a case study we applied the protocol to grapevine leaf samples infected with plant pathogenic bacteriašCandidatusPhytoplasma solani’, known to alter carbohydrate metabolism in grapevine. The described adaptations maybe useful for determination of metabolic fingerprints for physiological phenotyping of other plant species with inhe-rently high levels of phenolic compounds.
Ključne besede: AGPase, carbohydrates, invertases, sucrose synthase, panel of enzyme activity assays, phytoplasma
Objavljeno v DiRROS: 25.07.2024; Ogledov: 125; Prenosov: 75
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Povzetek: Ethylene has impact on several physiological plant processes, including abscission, during which plants shed both their vegetative and reproductive organs. Cell separation and programmed cell death are involved in abscission, and these have also been correlated with ethylene action. However, the detailed spatiotemporal pattern of the molecular events during abscission remains unknown. We examined the expression of two tomato ACO genes, LeACO1, and LeACO4 that encode the last enzyme in ethylene biosynthesis, 1-aminocyclopropane-1-carboxylate oxidase (ACO), together with the expression of other abscission-associated genes involved in cell separation and programmed cell death, during a period of 0–12 h after abscission induction in the tomato flower pedicel abscission zone and nearby tissues. In addition, we determined their localization in specific cell layers of the flower pedicel abscission zone and nearby tissues obtained by laser microdissection before and 8 h after abscission induction. The expression of both ACO genes was localized to the vascular tissues in the pedicel. While LeACO4 was more uniformly expressed in all examined cell layers, the main expression site of LeACO1 was in cell layers just outside the abscission zone in its proximal and distal part. We showed that after abscission induction, ACO1 protein was synthesized in phloem companion cells, in which it was localized mainly in the cytoplasm. Samples were additionally treated with 1-methylcyclopropene (1-MCP), a competitive inhibitor of ethylene actions, and analyzed 8 h after abscission induction. Cell-layer-specific changes in gene expression were observed together with the specific localization and ethylene sensitivity of the hallmarks of cell separation and programmed cell death. While treatment with 1-MCP prevented separation of cells through inhibition of the expression of polygalacturonases, which are the key enzymes involved in degradation of the middle lamella, this had less impact on the occurrence of different kinds of membrane vesicles and abscission-related programmed cell death. In the flower pedicel abscission zone, the physical progressions of cell separation and programmed cell death are perpendicular to each other and start in the vascular tissues.
Ključne besede: abscission, ACO, cell separation, ethylene, laser microdissection, programmed cell death, tomato, ultrastructure
Objavljeno v DiRROS: 24.07.2024; Ogledov: 106; Prenosov: 123
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Povzetek: Phytoplasmas from the 16Sr-X apple proliferation (AP) group are quarantine species in Europe and causal agents of the most important diseases of fruit trees within the family Rosaceae, namely apple proliferation, European stone fruit yellows and pear decline. In this study, a detailed insight into the molecular diversity of isolates of two phytoplasmas from the AP group, i. e. ‘Candidatus Phytoplasma mali’ and ‘Ca. P. prunorum’ obtained from different orchards in Slovenia, was estimated by a multilocus sequence typing, based on analysis of the genomic regions of aceF, pnp, secY and imp. With seven and five genotypes defined for ‘Ca. P. mali’ and ‘Ca. P. prunorum’ isolates, respectively, imp was the most variable among the applied markers. On the other hand, pnp was the least variable with three genotypes defined for ‘Ca. P. mali’ isolates and only one for ‘Ca. P. prunorum’ isolates. The presented results complete the survey of the AP group phytoplasma diversity in Slovenia, which has started with the recent analysis of the ‘Ca. P. pyri’. The comparison of results with those from several European countries shows an important genetic diversity of the Slovenian genotypes with some previously unknown. The genotype distribution reflects the geographic position of Slovenia. Additional grafting experiments with apricot trees tolerant to ‘Ca. P. prunorum’ demonstrated that the tolerance status is transmissible. Some possible mechanisms involved in the process are discussed.
Ključne besede: apple proliferation, multilocus sequence typing, phytoplasma diversity, Slovenia
Objavljeno v DiRROS: 24.07.2024; Ogledov: 98; Prenosov: 69
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Povzetek: Bois noir (BN) is the most widespread European grapevine yellows disease caused by ‘Candidatus Phytoplasma solani’. Although our knowledge of the mechanisms of interactions of this pathogenic bacteria with host is largely unknown, the plant-pathogen system of BN is commonly used as a model system for studying grapevine yellows diseases. We applied here a conceptual model of general plant pathology – a disease triangle for describing interactions among the host plant, the pathogen and the environment. We generated a proof-of-concept statistical model for disease triangle using original experimental data and different statistical and data mining approaches for a selected system of ‘Ca. P. solani’ infection of cv. ‘Chardonnay’ grapevine plants. We monitored individual plants from a single vineyard over a period of six years. Phytoplasma content, the expression of 21 selected grapevine genes and environmental conditions were recorded and related to disease severity. Our model predicts that in described conditions BN is a function of the expression of grapevine gene VvDMR6, summer rainfall and abundance of ‘Ca. P. solani’. The greatest impact among elements of the disease triangle is attributed to the pathogen, and is independent of the pathogen titer. We showed that this first de facto representation of the disease triangle is useful for showing disease dynamics over several years and could be applied to other plant-pathogen systems. The overall results of this study will contribute to understanding of ‘Ca. P. solani’ biology and its interactions with grapevine host.
Ključne besede: plant diseases, plant pathology
Objavljeno v DiRROS: 24.07.2024; Ogledov: 118; Prenosov: 102
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