The rolB plant oncogene affects multiple signaling protein modules related to hormone signaling and plant defense

Isolation and Characterization of Extracellular Vesicles from Arabidopsis thaliana Cell Culture and Investigation of the Specificities of Their Biogenesis

Over recent years, extracellular vesicles (EVs), commonly termed exosomes, have gained prominence for their potential as natural nanocarriers. It has now been recognized that plants also secrete EVs. Despite this discovery, knowledge about EV biogenesis in plant cell cultures remains limited. In our study, we have isolated and meticulously characterized EVs from the callus culture of the model plant, Arabidopsis thaliana. Our findings indicate that the abundance of EVs in calli was less than that in the plant's apoplastic fluid. This difference was associated with the transcriptional downregulation of the endosomal sorting complex required for transport (ESCRT) genes in the calli cells. While salicylic acid increased the expression of ESCRT components, it did not enhance EV production. Notably, EVs from calli contained proteins essential for cell wall biogenesis and defense mechanisms, as well as microRNAs consistent with those found in intact plants. This suggests that plant cell cultures could serve as a feasible source of EVs that reflect the characteristics of the parent plant species. However, further research is essential to determine the optimal conditions for efficient EV production in these cultured cells.

Proteome-Level Investigation of Vitis amurensis Calli Transformed with a Constitutively Active, Ca2+-Independent Form of the Arabidopsis AtCPK1 Gene

Calcium-dependent protein kinases (CDPKs) are one of the main Ca2+ decoders in plants. Among them, Arabidopsis thaliana AtCPK1 is one of the most studied CDPK genes as a positive regulator of plant responses to biotic and abiotic stress. The mutated form of AtCPK1, in which the autoinhibitory domain is inactivated (AtCPK1-Ca), provides constitutive kinase activity by mimicking a stress-induced increase in the Ca2+ flux. In the present study, we performed a proteomic analysis of Vitis amurensis calli overexpressing the AtCPK1-Ca form using untransformed calli as a control. In our previous studies, we have shown that the overexpression of this mutant form leads to the activation of secondary metabolism in plant cell cultures, including an increase in resveratrol biosynthesis in V. amurensis cell cultures. We analyzed upregulated and downregulated proteins in control and transgenic callus cultures using two-dimensional gel electrophoresis, and Matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF). In calli transformed with AtCPK1-Ca, an increased amounts of pathogenesis-related proteins were found. A quantitative real-time PCR analysis confirmed this result.

Lessons learned from metabolic engineering in hairy roots: Transcriptome and metabolic profile changes caused by Rhizobium-mediated plant transformation in Cucurbitaceae species

Cucurbitaceae species are used in traditional medicine around the world. Cucurbitacins are highly oxygenated triterpenoids found in Cucurbitaceae species and exhibit potent anticancer activity alone and in combination with other existing chemotherapeutic drugs. Therefore, increasing production of these specialized metabolites is of great relevance. We recently showed that hairy roots of Cucurbita pepo can be used as a platform for metabolic engineering of cucurbitacins to modify their structure and increase their production. To study the changes in cucurbitacin accumulation upon formation of hairy roots, an empty vector (EV) control and Cucurbitacin inducing bHLH transcription factor 1 (CpCUCbH1)-overexpressing hairy roots of C. pepo were compared to untransformed (WT) roots. Whilst CpCUCbH1-overexpression increased production of cucurbitacins I and B by 5-fold, and cucurbitacin E by 3-fold when compared to EV lines, this increase was not significantly different when compared to WT roots. This indicated that Rhizobium rhizogenes transformation lowered the cucurbitacins levels in hairy roots, but that increasing expression of cucurbitacin biosynthetic genes by CpCUCbH1-overexpression restored cucurbitacin production to WT levels. Subsequent metabolomic and RNA-seq analysis indicated that the metabolic profile and transcriptome of hairy roots was significantly changed when compared to WT roots. Interestingly, it was observed that 11% of the differentially expressed genes were transcription factors. It was noteworthy that the majority of transcripts showing highest Pearson correlation coefficients to the Rhizobium rhizogenes genes rolB, rolC and ORF13a, were predicted to be transcription factors. In summary, hairy roots are an excellent platform for metabolic engineering of plant specialized metabolites, but these extensive transcriptome and metabolic profile changes should be considered in subsequent studies.

Suppression of the HOS1 Gene Affects the Level of ROS Depending on Light and Cold

The E3 ubiquitin-protein ligase HOS1 is an important integrator of temperature information and developmental processes. HOS1 is a negative regulator of plant cold tolerance, and silencing HOS1 leads to increased cold tolerance. In the present work, we studied ROS levels in hos1^Cas9Arabidopsis thaliana plants, in which the HOS1 gene was silenced by disruption of the open reading frame via CRISPR/Cas9 technology. Confocal imaging of intracellular reactive oxygen species (ROS) showed that the hos1 mutation moderately increased levels of ROS under both low and high light (HL) conditions, but wild-type (WT) and hos1^Cas9 plants exhibited similar ROS levels in the dark. Visualization of single cells did not reveal differences in the intracellular distribution of ROS between WT and hos1^Cas9 plants. The hos1^Cas9 plants contained a high basal level of ascorbic acid, maintained a normal balance between reduced and oxidized glutathione (GSH and GSSG), and generated a strong antioxidant defense response against paraquat under HL conditions. Under cold exposure, the hos1 mutation decreased the ROS level and substantially increased the expression of the ascorbate peroxidase genes Apx1 and Apx2. When plants were pre-exposed to cold and further exposed to HL, the expression of the NADPH oxidase genes RbohD and RbohF was increased in the hos1^Cas9 plants but not in WT plants. hos1-mediated changes in the level of ROS are cold-dependent and cold-independent, which implies different levels of regulation. Our data indicate that HOS1 is required to maintain ROS homeostasis not only under cold conditions, but also under conditions of both low and high light intensity. It is likely that HOS1 prevents the overinduction of defense mechanisms to balance growth.

Proteomic Analysis of Proteins Related to Defense Responses in Arabidopsis Plants Transformed with the rolB Oncogene

During Agrobacterium rhizogenes-plant interaction, the rolB gene is transferred into the plant genome and is stably inherited in the plant's offspring. Among the numerous effects of rolB on plant metabolism, including the activation of secondary metabolism, its effect on plant defense systems has not been sufficiently studied. In this work, we performed a proteomic analysis of rolB-expressing Arabidopsis thaliana plants with particular focus on defense proteins. We found a total of 77 overexpressed proteins and 64 underexpressed proteins in rolB-transformed plants using two-dimensional gel electrophoresis and MALDI mass spectrometry. In the rolB-transformed plants, we found a reduced amount of scaffold proteins RACK1A, RACK1B, and RACK1C, which are known as receptors for activated C-kinase 1. The proteomic analysis showed that rolB could suppress the plant immune system by suppressing the RNA-binding proteins GRP7, CP29B, and CP31B, which action are similar to the action of type-III bacterial effectors. At the same time, rolB plants induce the massive biosynthesis of protective proteins VSP1 and VSP2, as well as pathogenesis-related protein PR-4, which are markers of the activated jasmonate pathway. The increased contents of glutathione-S-transferases F6, F2, F10, U19, and DHAR1 and the osmotin-like defense protein OSM34 were found. The defense-associated protein PCaP1, which is required for oligogalacturonide-induced priming and immunity, was upregulated. Moreover, rolB-transformed plants showed the activation of all components of the PYK10 defense complex that is involved in the metabolism of glucosinolates. We hypothesized that various defense systems activated by rolB protect the host plant from competing phytopathogens and created an effective ecological niche for A. rhizogenes. A RolB → RACK1A signaling module was proposed that might exert most of the rolB-mediated effects on plant physiology. Our proteomics data are available via ProteomeXchange with identifier PXD037959.

Rhizogenic Agrobacterium protein RolB interacts with the TOPLESS repressor proteins to reprogram plant immunity and development

Rhizogenic Agrobacterium strains comprise biotrophic pathogens that cause hairy root disease (HRD) on hydroponically grown Solanaceae and Cucurbitaceae crops, besides being widely explored agents for the creation of hairy root cultures for the sustainable production of plant-specialized metabolites. Hairy root formation is mediated through the expression of genes encoded on the T-DNA of the root-inducing (Ri) plasmid, of which several, including root oncogenic locus B (rolB), play a major role in hairy root development. Despite decades of research, the exact molecular function of the proteins encoded by the rol genes remains enigmatic. Here, by means of TurboID-mediated proximity labeling in tomato (Solanum lycopersicum) hairy roots, we identified the repressor proteins TOPLESS (TPL) and Novel Interactor of JAZ (NINJA) as direct interactors of RolB. Although these interactions allow RolB to act as a transcriptional repressor, our data hint at another in planta function of the RolB oncoprotein. Hence, by a series of plant bioassays, transcriptomic and DNA-binding site enrichment analyses, we conclude that RolB can mitigate the TPL functioning so that it leads to a specific and partial reprogramming of phytohormone signaling, immunity, growth, and developmental processes. Our data support a model in which RolB manipulates host transcription, at least in part, through interaction with TPL, to facilitate hairy root development. Thereby, we provide important mechanistic insights into this renowned oncoprotein in HRD.

The RolB/RolC homolog from sweet potato promotes early flowering and triggers premature leaf senescence in transgenic Arabidopsis thaliana plants

Expression of the root oncogenic loci (rol) genes from Agrobacterium rhizogenes provokes multiple divergent effects on physiological properties in transgenic plants and cell cultures. Recently, the homolog of the rolB and rolC oncogenes, named Ib-rolB/C, has been identified in the genome of a naturally transgenic food crop, i.e. sweet potato. In this study, we revealed that the Ipomoea batatas genome contains two full-length copies of Ib-rolB/C. The expression level of Ib-rolB/C in leaves of sweet potato showed a clear age-dependent pattern and increased as leaves senesce. Moreover, dark-induced senescence strongly up-regulates transcription of the Ib-rolB/C gene. Though Ib-rolB/C shares homology with its counterparts in A. rhizogenes, this gene was not capable to induce hairy roots or tumors in kalanchoe and tobacco plants. The Ib-rolB/C gene induced early-flowering phenotype, altered leaf morphology, and promoted premature leaf senescence in transgenic Arabidopsis thaliana plants. At the same time, Ib-rolB/C did not affect root morphology and biomass. Our results suggest that Ib-RolB/RolC participates in both age- and dark-triggered leaf senescence programs.

Effect of Stress Signals and Ib-rolB/C Overexpression on Secondary Metabolite Biosynthesis in Cell Cultures of Ipomoea batatas

Ipomoea batatas is a vital root crop and a source of caffeoylquinic acid derivatives (CQAs) with potential health-promoting benefits. As a naturally transgenic plant, I. batatas contains cellular T-DNA (cT-DNA) sequence homologs of the Agrobacterium rhizogenes open reading frame (ORF)14, ORF17n, rooting locus (Rol)B/RolC, ORF13, and ORF18/ORF17n of unknown function. This study aimed to evaluate the effect of abiotic stresses (temperature, ultraviolet, and light) and chemical elicitors (methyl jasmonate, salicylic acid, and sodium nitroprusside) on the biosynthesis of CQAs and cT-DNA gene expression in I. batatas cell culture as a model system. Among all the applied treatments, ultraviolet irradiation, methyl jasmonate, and salicylic acid caused the maximal accumulation of secondary compounds. We also discovered that I. batatas cT-DNA genes were not expressed in cell culture, and the studied conditions weakly affected their transcriptional levels. However, the Ib-rolB/C gene expressed under the strong 35S CaMV promoter increased the CQAs content by 1.5-1.9-fold. Overall, our results show that cT-DNA-encoded transgenes are not involved in stress- and chemical elicitor-induced CQAs accumulation in cell cultures of I. batatas. Nevertheless, overaccumulation of RolB/RolC transcripts potentiates the secondary metabolism of sweet potatoes through a currently unknown mechanism. Our study provides new insights into the molecular mechanisms linked with CQAs biosynthesis in cell culture of naturally transgenic food crops, i.e., sweet potato.

Kalanchoë blossfeldiana naturally transformed with Rhizobium rhizogenes exhibits superior root phenotype

Plant transformation with root oncogenic loci (rol) genes and open reading frames (ORFs) from Rhizobium rhizogenes have not yet targeted the underground root phenotype of these transformants. Hence, there is a need to develop plants with more efficient root system architecture (RSA). Here, RSA was assessed in naturally transformed (NT) and single rol/ORF Kalanchoë blossfeldiana 'Molly' lines in an aeroponic growth system combined with gene expression analysis. Three NT lines; 306, 324 and 331; exhibited better-developed RSA with longer roots and increased root biomass. In line 306, longest root was 6.3 ± 0.3 cm while WT had 4.8 ± 0.1 cm. However, root length of all overexpressing lines was ca. 30% shorter than WT. Root fresh weight of NT lines was 4.5-fold higher than WT. The expression of rolB, ∆ORF13a and ORF14 in the leaves of overexpressing lines was many folds higher than in NT lines. Increased expression of ∆ORF13a and ORF14 in leaves and roots may contribute more to a stronger compact phenotype than previously assumed. The moderate compact phenotype of NT lines combined with improved RSA compared to the overexpressing lines and WT strongly indicate that the use of R. rhizogenes has great potential to produce Kalanchoë phenotypes with enhanced RSA.

Overexpression of the A4-rolB gene from the pRiA4 of Rhizobium rhizogenes modulates hormones homeostasis and leads to an increase of flavonoid accumulation and drought tolerance in Arabidopsis thaliana transgenic plants

Increased flavonol accumulation and enhanced drought tolerance in A4-rolB-overexpressing plants can be explained by the cooperative action of the SA and ROS signalling pathways. Clarification of function of the A4-rolB plast gene from pRiA4 of Rhizobium rhizogenes will allow a better understanding of the biological principles of the natural transformation process and its use as a tool for plant bioengineering. In the present study, we investigated whether the overexpression of A4-rolB gene could regulate two important processes, flavonoid biosynthesis and drought tolerance. In addition, we investigated some aspects of the possible machinery of the A4-rolB-induced changes in plant physiology, such as crosstalk of the major signalling systems. Based on the data obtained in this work, it can be presumed that constitutive overexpression of A4-rolB leads to the activation of the salicylic acid signalling system. An increase in flavonol accumulation and enhanced drought tolerance can be explained by the cooperative action of SA and ROS pathways.

Effects of various Agrobacterium rhizogenes strains on hairy root induction and analyses of primary and secondary metabolites in Ocimum basilicum

The hairy root (HR) culture system is an excellent alternative strategy to the whole plant system for producing valuable compounds. However, selection of suitable Agrobacterium strain for the successful induction of HR is an essential step for enhanced production of beneficial secondary metabolites. In this study, we examined the transformation efficiency of various A. rhizogenes strains (ATCC 13333, ATCC 15834, A4, R1000, R1200, and R1601) for transgenic HRs induction in Ocimum basilicum. Among the tested strains, the R1601 was found to be one of the most promising strain for mass production of HR in terms of transformation efficiency (94%) and the number and length of HR (8.4 ± 0.52 and 1.68 ± 0.14 cm). The HR induced by the same strain exhibited highest levels of rosmarinic acid level (62.05 ± 4.94 µg/g DW) and total phenolic content (62.3 ± 4.95 µg/g DW). A total of 55 metabolites were identified using high-performance liquid chromatography (HPLC) and gas chromatography-time-of-flight mass spectrometry (GC-TOFMS). The PCA and PLS-DA plot of the identified metabolites showed that HR induced by A4 and ATCC 15834 displayed variation in primary and secondary metabolite contents. Analysis of the metabolic pathway identified a total of 56 pathways, among which 35 were found to be impacted. A heat map and hierarchical clustering analysis indicated that HR induced by different Agrobacterium strains exhibited differential metabolites profiles. In conclusion, Agrobacterium strains R1601 is one of the best and most promising strains for inducing mass HR production and enhanced levels of secondary metabolites in O. basilicum.

Response of physiological parameters in Dionaea muscipula J. Ellis teratomas transformed with rolB oncogene

BACKGROUND

Plant transformation with rol oncogenes derived from wild strains of Rhizobium rhizogenes is a popular biotechnology tool. Transformation effects depend on the type of rol gene, expression level, and the number of gene copies incorporated into the plant's genomic DNA. Although rol oncogenes are known as inducers of plant secondary metabolism, little is known about the physiological response of plants subjected to transformation.

RESULTS

In this study, the physiological consequences of rolB oncogene incorporation into the DNA of Dionaea muscipula J. Ellis was evaluated at the level of primary and secondary metabolism. Examination of the teratoma (transformed shoots) cultures of two different clones (K and L) showed two different strategies for dealing with the presence of the rolB gene. Clone K showed an increased ratio of free fatty acids to lipids, superoxide dismutase activity, synthesis of the oxidised form of glutathione, and total pool of glutathione and carotenoids, in comparison to non-transformed plants (control). Clone L was characterised by increased accumulation of malondialdehyde, proline, activity of superoxide dismutase and catalase, total pool of glutathione, ratio of reduced form of glutathione to oxidised form, and accumulation of selected phenolic acids. Moreover, clone L had an enhanced ratio of total triglycerides to lipids and accumulated saccharose, fructose, glucose, and tyrosine.

CONCLUSIONS

This study showed that plant transformation with the rolB oncogene derived from R. rhizogenes induces a pleiotropic effect in plant tissue after transformation. Examination of D. muscipula plant in the context of transformation with wild strains of R. rhizogenes can be a new source of knowledge about primary and secondary metabolites in transgenic organisms.

Agrobacterium rhizogenes rolB oncogene: An intriguing player for many roles

The rolB oncogene is one of the so-called rol genes found in the T-DNA region of the Agrobacterium rhizogenes Ri plasmid and involved in the hairy root syndrome, a tumour characterized by adventitious root overgrowth on plant stem. rolB produces in plants a peculiar phenotype that, together with its root-inducing capacity, has been connected to auxin sensitivity. The gene is able to modify the plant genetic programme to induce meristem cells and direct them to differentiate not only roots, but also other cells, tissues or organs. Besides its essential function in hairy root pathogenesis, the rolB role has been progressively extended to cover several physiological aspects in the transgenic plants: from secondary metabolites production and ROS inhibition, to abiotic and biotic stress tolerance and photosynthesis improvement. Some of the observed effects could be determined, at least in part, through microRNAs molecules, suggesting an epigenetic control rolB-mediated. These multifaceted capacities could allow plants to withstand adverse environmental conditions, enhancing fitness. In spite of this expanding knowledge, functional analyses did not detect yet any definitive rolB-derived biochemical product, even if more than one enzymatic activity has been ascribed to it. Moreover, phylogenetic and evolutionary studies evidenced no homology with any plant sequences but, otherwise, it belongs to the Plast family, a group of rolB-homologous bacterial genes. Finally, the finding of sequences similar to rolB in plants not infected by A. rhizogenes suggests a hypothetical plant origin for this gene, implying different possibilities about its evolution.

Transgenic Kalanchoë blossfeldiana, Containing Individual rol Genes and Open Reading Frames Under 35S Promoter, Exhibit Compact Habit, Reduced Plant Growth, and Altered Ethylene Tolerance in Flowers

Reduced growth habit is a desirable trait for ornamental potted plants and can successfully be obtained through Rhizobium rhizogenes transformation in a stable and heritable manner. Additionally, it can also be obtained by transformation with Agrobacterium tumefaciens harboring specific genes from R. rhizogenes. The bacterial T-DNA harbors four root oncogenic loci (rol) genes and 14 less known open reading frames (ORFs). The four rol genes, i.e., rolA, rolB, rolC, and rolD, are conceived as the common denominator for the compact phenotype and the other less characterized ORFs seem auxiliary but present a potential breeding target for less aberrant and/or more tailored phenotypes. In this study, Kalanchoë blossfeldiana 'Molly' was transformed with individual rol genes and selected ORFs in 35S overexpressing cassettes to comprehensively characterize growth traits, gene copy and expression, and ethylene tolerance of the flowers. An association of reduced growth habit, e.g. height and diameter, was observed for rolB2 and ORF14-2 when a transgene single copy and high gene expression were detected. Chlorophyll content was reduced in overexpressing lines compared to wild type (WT), except for one ΔORF13a (a truncated ORF13a, where SPXX DNA-binding motif is absent). The flower number severely decreased in the overexpressing lines compared to WT. The anthesis timing showed that WT opened the first flower at 68.9 ± 0.9 days and the overexpressing lines showed similar or up to 24 days delay in flowering. In general, a single or low relative gene copy insertion was correlated to higher gene expression, ca. 3 to 5-fold, in rolB and ΔORF13a lines, while in ORF14 such relation was not directly linked. The increased gene expression observed in rolB2 and ΔORF13a-2 contributed to reducing plant growth and a more compact habit. Tolerance of detached flowers to 0.5 μl L-1 ethylene was markedly higher for ORF14 with 66% less flower closure at day 3 compared to WT. The subcellular localization of rolC and ΔORF13a was investigated by transient expression in Nicotiana benthamiana and confocal images showed that rolC and ΔORF13a are soluble and localize in the cytoplasm being able to enter the nucleus.

Hairy Root Cultures-A Versatile Tool With Multiple Applications

Hairy roots derived from the infection of a plant by Rhizobium rhizogenes (previously referred to as Agrobacterium rhizogenes) bacteria, can be obtained from a wide variety of plants and allow the production of highly diverse molecules. Hairy roots are able to produce and secrete complex active glycoproteins from a large spectrum of organisms. They are also adequate to express plant natural biosynthesis pathways required to produce specialized metabolites and can benefit from the new genetic tools available to facilitate an optimized production of tailor-made molecules. This adaptability has positioned hairy root platforms as major biotechnological tools. Researchers and industries have contributed to their advancement, which represents new alternatives from classical systems to produce complex molecules. Now these expression systems are ready to be used by different industries like pharmaceutical, cosmetics, and food sectors due to the development of fully controlled large-scale bioreactors. This review aims to describe the evolution of hairy root generation and culture methods and to highlight the possibilities offered by hairy roots in terms of feasibility and perspectives.

Activation of anthraquinone biosynthesis in long-cultured callus culture of Rubia cordifolia transformed with the rolA plant oncogene

The RolA protein belongs to the RolB class of plant T-DNA oncogenes, and shares structural similarity with the papilloma virus E2 DNA-binding domain. It has potentially as an inducer of plant secondary metabolism, although its role in biotechnology has yet to be realised. In this investigation, a Rubia cordifolia callus culture transformed with the rolA plant oncogene for more than 10 years was analysed. Expression of the rolA gene in the callus line was stable during long-term cultivation, and growth parameters were both elevated and stable, exceeding those of the non-transformed control culture. The rolA-transformed calli not only demonstrated remarkably stable growth, but also the ability to increase the yield of anthraquinones (AQs) in long-term cultivation. After ten years of cultivating rolA callus lines, we observed an activation of AQ biosynthesis from 200 mg/l to 874 mg/l. The increase was mainly due to activation of ruberitrinic acid biosynthesis. The expression of key AQ biosynthesis genes was strongly activated in rolA-transgenic calli. We compared the effects of the rolA gene with those of the rolB gene, which was previously considered the most potent inducer of secondary metabolism, and showed that rolA was more productive under conditions of long-term cultivation.

Coordination of ABA and Chaperone Signaling in Plant Stress Responses

The abscisic acid (ABA) and chaperone signaling pathways are the central regulators of plant stress defense. Despite their significance and potential overlap, these systems have been described separately. In this review, we summarize information about mechanisms by which the ABA and chaperone signaling pathways might be coregulated. The central factors that join the ABA and chaperone signaling systems are the SWI/SNF chromatin-remodeling proteins, which are involved in stress memory. A benefit from coordination is that the signals sensed through both the ABA and chaperone signaling systems are perceived and stored via chromatin-remodeling factors. For improving plant stress resistance, we propose new bioengineering strategies, which we term 'bioengineering memory'.

Dryas as a Model for Studying the Root Symbioses of the Rosaceae

The nitrogen-fixing root nodule symbiosis is restricted to four plant orders: Fabales (legumes), Fagales, Cucurbitales and Rosales (Elaeagnaceae, Rhamnaceae, and Rosaceae). Interestingly all of the Rosaceae genera confirmed to contain nodulating species (i.e., Cercocarpus, Chamaebatia, Dryas, and Purshia) belong to a single subfamily, the Dryadoideae. The Dryas genus is particularly interesting from an evolutionary perspective because it contains closely related nodulating (Dryas drummondii) and non-nodulating species (Dryas octopetala). The close phylogenetic relationship between these two species makes Dryas an ideal model genus to study the genetic basis of nodulation by whole genome comparison and classical genetics. Therefore, we established methods for plant cultivation, transformation and DNA extraction for these species. We optimized seed surface sterilization and germination methods and tested growth protocols ranging from pots and Petri dishes to a hydroponic system. Transgenic hairy roots were obtained by adapting Agrobacterium rhizogenes-based transformation protocols for Dryas species. We compared several DNA extraction protocols for their suitability for subsequent molecular biological analysis. Using CTAB extraction, reproducible PCRs could be performed, but CsCl gradient purification was essential to obtain DNA in sufficient purity for high quality de novo genome sequencing of both Dryas species. Altogether, we established a basic toolkit for the culture, transient transformation and genetic analysis of Dryas sp.

Influence of different Agrobacterium rhizogenes strains on hairy root induction and analysis of phenolic and flavonoid compounds in marshmallow (Althaea officinalis L.)

Hairy roots were induced in Althea officinalis using Agrobacterium rhizogenes, strains A4, A13, ATCC15834, and ATCC15834(GUS). The leaf, petiole and shoot explants of marshmallow were used for the hairy roots induction. When hairy roots appeared, cultures were established in MS (Murashige and Skoog) liquid medium without growth regulators. Hairy roots in explants appeared 5-12 days after inoculation. Maximum transformation frequency of 83% was observed on shoot explants with ATCC15834 strain. Among the strains, ATCC15834(GUS) strain showed better potential in the mass production of hairy roots in the hormone-free liquid medium after 50 days of culturing. The highest total phenolic and flavonoids content was found at 1.57 ± 0.1 mg/g dry weight in A13 strain and 3.47 ± 0.3 mg/g in A4 strain, respectively. Secondary metabolite content of hairy roots was found to be strain-specific.