Rhizosphere microbial communities play an important role in maintaining the health and productivity of the plant host. The rhizobacteria
Pseudomonas putida
P2 of
Ramonda serbica
and
Bacillus cereus
...P5 of
R. nathaliae
were selected for treatment of the Belija wheat cultivar because of their plant growth-promoting (PGP) properties. Compared to the non-treated drought-stressed plants, the plants treated with rhizobacteria showed increased activity of the two major antioxidant enzymes, superoxide dismutase, and ascorbate peroxidase. Plants treated with the
B. cereus
P5 strain exhibited higher proline content under drought stress, suggesting that proline accumulation depends on the relative water content (RWC) status of the plants studied. Inoculation of wheat seeds with the
P. putida
P2 strain improved water status by increasing RWC and alleviating oxidative stress by reducing H
2
O
2
and malondialdehyde concentrations in plants exposed to severe drought, possibly also helping plants to overcome drought through its 1-aminocyclopropane-1-carboxylic acid deaminase activity. Analysis of data from Next Generation sequencing (NGS) revealed that the dominant bacterial taxa in the rhizosphere of resurrection plants
R. serbica
and
R. nathaliae
were extremophilic, thermotolerant,
Vicinamibacter silvestris, Chthoniobacter flavus
, and
Gaiella occulta.
From the fungi detected
Penicillium
was the most abundant in both samples, while
Fusarium
and
Mucor
were present only in the rhizosphere of
R. serbica
and the entomopathogenic fungi
Metarhizium
, and
Tolypocladiumu
only in the rhizosphere of
R. nathaliae
. The fungal communities varied among plants, suggesting a stronger environmental influence than plant species. Our study demonstrates the importance of in vivo experiments to confirm the properties of PGP bacteria and indicates that the rhizosphere of resurrection plants is a valuable source of unique microorganisms that can be used to improve the drought stress tolerance of crops.
Paleoendemic species of the monophyletic genus Ramonda (R. myconi, R. serbica and R.~nathaliae) are the remnants of the Tertiary tropical and subtropical flora in Europe. They are the rare ...resurrection plants of Northern Hemisphere temperate zone. Ramonda serbica and R. nathaliae are chorologically differentiated in the Balkan Peninsula and occupy similar habitats in calcareous, northward slopes in canyons and mountainsides. They remain well-hydrated during spring, late autumn and even in winter. In summer and early autumn when plants are subjected to drought and thermal stress, their desiccation tolerance comes into operation and they fall into anabiosis. Investigations revealed the permanent presence of ubiquitine and its conjugates, high amounts of oxalic acid and proline. Both species are homoiochlorophyllous. It enables them to rapidly resume photosynthesis upon rehydration, but also makes them susceptible to reactive oxygen species formation. Dehydration induces activation of antioxidative enzymes (ascorbate peroxidase, glutathione reductase, polyphenol oxidase), increase in amounts of AsA and GSH, phenolic acids, dehydrins, sucrose, and inorganic ions. Plasma membranes, characterized by high amount of cholesterol, are subjected to decrease in membrane fluidity mostly on account of increased level of lipid saturation. Cytogenetic analysis revealed that R. nathaliae is a diploid (2n = 48) and probably evolutionary older species, while R. serbica is a hexaploid (2n = 144). Two species live together in only two localities forming hybrid individuals (2n = 96). Polyploidization is the major evolutionary mechanism in the genus Ramonda that together with hybridization ability indicates that these relict species which have preserved an ancient survival strategy are not the evolutionary "dead end."The species of the genus Ramonda are promising sources of data important for understanding the complex strategy of resurrection plants' survival, appraised through a prism of their evolutionary and adaptive potential for multiple environmental stresses.
Born to revive Fernández-Marín, Beatriz; Nadal, Miquel; Gago, Jorge ...
The New phytologist,
20/May , Letnik:
226, Številka:
3
Journal Article
Recenzirano
Odprti dostop
• Resurrection plants recover physiological functions after complete desiccation. Almost all of them are native to tropical warm environments. However, the Gesneriaceae include four genera, remnant ...of the past palaeotropical flora, which inhabit temperate mountains. One of these species is additionally freezing-tolerant: Ramonda myconi. We hypothesise that this species has been able to persist in a colder climate thanks to some resurrection-linked traits.
• To disentangle the physiological mechanisms underpinning multistress tolerance to desiccation and freezing, we conducted an exhaustive seasonal assessment of photosynthesis (gas exchange, limitations to partitioning, photochemistry and galactolipids) and primary metabolism (through metabolomics) in two natural populations at different elevations.
• R. myconi displayed low rates of photosynthesis, largely due to mesophyll limitation. However, plants were photosynthetically active throughout the year, excluding a reversible desiccation period. Common responses to desiccation and low temperature involved chloroplast protection: enhanced thermal energy dissipation, higher carotenoid to Chl ratio and de-epoxidation of the xanthophyll cycle. As specific responses, antioxidants and secondary metabolic routes rose upon desiccation, while putrescine, proline and a variety of sugars rose in winter.
• The data suggest conserved mechanisms to cope with photo-oxidation during desiccation and cold events, while additional metabolic mechanisms may have evolved as specific adaptations to cold during recent glaciations
Resurrection plants have the unique ability to restore normal physiological activity after desiccation to an air-dry state. In addition to their desiccation tolerance, some of them, such as
and
, are ...also freezing-tolerant species, as they survive subzero temperatures during winter. Here, we compared the response of the photosynthetic apparatus of two other Gesneriaceae species,
and
, together with
, to cold and freezing temperatures. The role of some protective proteins in freezing tolerance was also investigated. The water content of leaves was not affected during cold acclimation but exposure of plants to -10 °C induced dehydration of plants. Freezing stress strongly reduced the quantum yield of PSII photochemistry (Y(II)) and stomatal conductance (
) on the abaxial leaf side. In addition, the decreased ratio of F
/F
suggested photoinhibition or sustained quenching. Freezing-induced desiccation resulted in the inhibition of PSII activity, which was accompanied by increased thermal energy dissipation. In addition, an increase of dehydrins and ELIPs was detected, but the protein pattern differed between species. During recovery, the protein abundance decreased and plants completely recovered their photosynthetic activity. Thus, our results showed that
and
survive freezing stress due to some resurrection-linked traits and confirmed their freezing tolerance.
Resurrection plants are unique among higher plants because of their ability to withstand long periods of dehydration without damages. In this study, leaf epidermis and palisade mesophyll of three ...resurrection species, Haberlea rodopensis, Ramonda serbica and Ramonda myconi, grown under full desiccation and benign conditions, were analyzed by differential interference contrast microscopy. Detailed investigation of adaxial and abaxial leaf surfaces revealed species-specific differences in the size and number of epidermal cells and stomatal density. The applied full desiccation did not cause any significant deviations of these parameters from the controls. There were no changes in the size and number of mesophyll cells as well. Analysis of stomatal patterning displayed essentially hypostomatic leaves, having stomata mainly abaxially positioned. The most significant change detected in the leaves of dehydration-treated plants was the increased formation of adaxially positioned trichomes. This increase was very high in R. myconi, where the adaxial leaf surface was fully covered by trichomes. Despite the existence of small species-specific differences, the results showed uniform desiccation-related responses of the studied resurrection species. The quantified leaf epidermal and mesophyll features are discussed with respect to their possible contribution to the desiccation tolerance of resurrection species.
Introduction
Ramonda serbica and R. nathaliae are resurrection plants that have the remarkable ability to survive the complete desiccation of their vegetative organs (i.e. leaves, stem, roots) during ...periods of drought and rapidly revive when rewatered and rehydrated.
Objective
To investigate metabolic changes in R. serbica and R. nathaliae during their desiccation and recovery process
Methods
Proton nuclear magnetic resonance (1H‐NMR) and gas chromatography–mass spectrometry (GC–MS)‐based metabolomics approach coupled with multivariate data analysis was utilised to identify the metabolomes of the plants from 90 biological replicates.
Results
Sucrose and the polyphenolic glycoside myconoside were predominant in almost equal amounts in all samples studied, regardless of their water content at sampling. During the dehydration process, a decrease in the relative content of fructose, galactose, and galactinol was observed while the contents of those metabolites were preserved in the partially rehydrated plants. Raffinose and myo‐inositol were accumulated in dry samples.
Conclusion
Using 1H‐NMR and GC–MS as two complementary analytical platforms provided a more complete picture of the metabolite composition for investigation of the desiccation and recovery process in resurrection plants.
Metabolic changes in resurrection plants Ramonda serbica and R. nathaliae during their desiccation and recovery process are investigated. Proton nuclear magnetic resonance (1H‐NMR) and gas chromatography–mass spectrometry (GC–MS)‐based metabolomics approach coupled with multivariate data analysis were utilized to identify the metabolomes. Sucrose and the polyphenolic glycoside myconoside were predominant compounds in all samples studied. During the dehydration process, a decrease of fructose, galactose, and galactinol was observed while their contents were preserved in the partially rehydrated plants. Raffinose and myo‐inositol were accumulated in dry samples.
Resurrection plant
Ramonda serbica
is a suitable model to investigate vegetative desiccation tolerance. However, the detailed study of these mechanisms at the protein level is hampered by the severe ...tissue water loss, high amount of phenolics and polysaccharide, and possible protein modifications and aggregations during the extraction and purification steps. When applied to
R
.
serbica
leaves, widely used protein extraction protocols containing polyvinylpolypyrrolidone and ascorbate, as well as the phenol/SDS/buffer–based protocol recommended for recalcitrant plant tissues failed to eliminate persistent contamination and ensure high protein quality. Here we compared three protein extraction approaches aiming to establish the optimal one for both hydrated and desiccated
R
.
serbica
leaves. To evaluate the efficacy of these protocols by shotgun proteomics, we also created the first
R
.
serbica
annotated transcriptome database, available at
http://www.biomed.unipd.it/filearrigoni/Trinity_Sample_RT2.fasta
. The detergent-free phenol-based extraction combined with dodecyl-β-
d
-maltoside-assisted extraction enabled high-yield and high-purity protein extracts. The phenol-based protocol improved the protein-band resolution, band number, and intensity upon electrophoresis, and increased the protein yield and the number of identified peptides and protein groups by LC-MS/MS. Additionally, dodecyl-β-
d
-maltoside enabled solubilisation and identification of more membrane-associated proteins. The presented study paves the way for investigating the desiccation tolerance in
R
.
serbica
, and we recommend this protocol for similar recalcitrant plant material.
Graphical abstract
The article presents the results of a study of the plant communities of Ramonda serbica, primarily intended to increase knowledge of their species and syntaxonomic diversity. The dataset included 204 ...vegetation plots (relevés) of the two Balkan Ramondas (R. serbica and R. nathaliae), 174 digitised from published literature sources and 30 new ones from field sampling of R. serbica in Montenegro and North Macedonia. Nineteen associations and subassociations of R. serbica were identified, using hierarchical cluster analysis (the Sørensen index as a distance measure and the Flexible Beta method, ß −0.25). Three associations (Micromerio julianae-Ramondetum serbicae, Hylocomio splendentis-Ramondetum serbicae, Neckero pumillae-Ramondetum serbicae), three subassociations (Micromerio julianae-Ramondetum serbicae subass. allosoretosum persicae, Ceterachi officinarum-Ramondetum serbicae subass. festucetosum dalmaticae and subass. hylotelephietosum maximi) and one alliance Exsertotheco crispae-Ramondion serbicae are described as new. Both hierarchical cluster analysis and non-metric multidimensional scaling ordination support the distinction of 3 chorological/ecological groups of R. serbica communities: Adriatic-Ionian (xerophilous), Moesian (xero and mesophilous communities) and Illyrian-Scardo-Pindic (hygromesophilous). Communities of the Adriatic-Ionian cluster belongs to alliances Edraianthion, Centaureo cuspidatae-Portenschagillion ramosissimae and Campanulion versicoloris, of the Moesian one to Edraiantho graminifolii-Erysimion comati, and the Illyrian-Scardo-Pindic one to novel alliance Exsertotheco crispae-Ramondion serbicae.
Ramonda sp. (Gesneriaceae) is an endemic and relic plant in a very small group of poikilohydric angiosperms that are able to survive in an almost completely dehydrated state. Senescence- and ...drought-related changes in the activity of peroxidase (POD; EC 1.11.1.7), ascorbate peroxidase (EC 1.11.1.11), and superoxide dismutase (SOD; EC 1.15.1.1) were determined in leaves of different age and relative water content. The results indicate that different POD isoforms were stimulated during senescence and dehydration. Two of the soluble POD isoforms were anionic with pI 4.5, and two were cationic with pI 9.3 and 9.0. The activity of ascorbate peroxidase remained unchanged either by drought or senescence. For the first time, SOD isoforms have now been determined in this resurrection plant. Several SOD isoforms, all of the Mn type, were found to be anionic with pI 4 and a few others had pI from 5 to 6, while one band of FeSOD with a lower molecular weight was neutral. Rehydration brought about a remarkable decrease over the first hour in the activity of all the antioxidant enzymes examined but activity recovered 1 d after rehydration. The results confirmed that dehydration and senescence caused disturbance in the redox homeostasis of Ramonda leaves, while inducing different POD isoforms. A physiological role of peroxidase reaction with hydroxycinnamic acids in conservation and protection of cellular constituents of desiccated Ramonda leaves is suggested.
The pollen and seeds of 3 paleoendemic resurrection species, Ramonda myconi (L.) Rchb. (Iberian Peninsula), R. nathaliae Pancic & Petrovic, and R. serbica Pancic (Balkan Peninsula), as well as of ...natural hybrids between the 2 last species, have been analyzed using light and scanning electron microscopy. Their general structural differences, taxonomic and phylogenetic significance, pollen viability, and seed germination capacity, as well as the correlation of pollen and seed characteristics and plant ploidy levels, have been studied. The pollen grains are small (R. myconi, R. nathaliae) to medium (R. serbica) in size, ranging from 10 to 28 µm, and 3-colporate, isopolar monads with microreticulate-perforate exine. Seeds are small, 309 to 1000 µm long and 80 to 425 µm wide, elongated, with a reticulate surface and auriculate ornamentation. Micromorphologies of the pollen exine ornamentation and seed surface revealed significant differences among the 3 species. Pollen from hybrid individuals was heterogeneous in size and morphology, and the germination of their tiny seeds was very low. A strong correlation was found between pollen size, DNA content, and chromosome number. The environmental influence on pollen and seeds of 3 species and especially of the R. nathaliae population growing on serpentine is also discussed.
PDF
