Morphogenic Responses Research Articles

Modeling the mechanosensitive collective migration of cells on the surface and the interior of morphing soft tissues.

Cellular contractility, migration, and extracellular matrix (ECM) mechanics are critical for a wide range of biological processes including embryonic development, wound healing, tissue morphogenesis, and regeneration. Even though the distinct response of cells near the tissue periphery has been previously observed in cell-laden microtissues, including faster kinetics and more prominent cell-ECM interactions, there are currently no models that can fully combine coupled surface and bulk mechanics and kinetics to recapitulate the morphogenic response of these constructs. Mailand et al. (Biophys J 117(5):975-986, 2019) had shown the importance of active elastocapillarity in cell-laden microtissues, but modeling the distinct mechanosensitive migration of cells on the periphery and the interior of highly deforming tissues has not been possible thus far, especially in the presence of active elastocapillary effects. This paper presents a framework for understanding the interplay between cellular contractility, migration, and ECM mechanics in dynamically morphing soft tissues accounting for distinct cellular responses in the bulk and the surface of tissues. The major novelty of this approach is that it enables modeling the distinct migratory and contractile response of cells residing on the tissue surface and the bulk, where concurrently the morphing soft tissues undergo large deformations driven by cell contractility. Additionally, the simulation results capture the changes in shape and cell concentration for wounded and intact microtissues, enabling the interpretation of experimental data. The numerical procedure that accounts for mechanosensitive stress generation, large deformations, diffusive migration in the bulk and a distinct mechanism for diffusive migration on deforming surfaces is inspired from recent work on bulk and surface poroelasticity of hydrogels involving elastocapillary effects, but in this work, a two-field weak form is proposed and is able to alleviate numerical instabilities that were observed in the original method that utilized a three-field mixed finite element formulation.

Analysis of the potential involvement of lncRNAs in embryogenic competence of Solanum betaceum Cav. (tamarillo) calli

Somatic embryogenesis (SE) is a process by which somatic cells reprogram, acquire totipotency and embark on embryo formation. Although SE is a valuable tool for micropropagation in many crops, it presents specific challenges in woody species due to some bottlenecks, such as loss of embryogenic competence during subcultures and the often-low somatic embryo conversion into plantlets. Hence, great interest exists in exploring the regulatory networks involved on SE. As transcription modulators, long non-coding RNAs (lncRNAs) have been found essential in a wide range of biological processes. This work aimed to identify lncRNAs related to the embryogenic competence in Solanum betaceum Cav. (tamarillo). Nanopore® long-read sequencing was conducted in cell lines with distinct cell fates and, based on their coding potential, 60 transcripts were selected as lncRNA candidates. Similar expression patterns were found among embryogenic cell lines (EC) and cells that lost their embryogenic potential (herein long-term callus, LTC), whereas non-EC (NEC) showed differentially expressed lncRNAs. Whereas lncRNAs upregulated in EC and LTC were predicted to target embryogenesis-related genes, such as AGAMOUS-like 15 and WUSCHEL-related HOMEOBOX 2, lncRNAs upregulated in NEC were predicted to target mainly genes involved in carbohydrate metabolism, cell wall formation, auxin and ethylene signalling pathways. Altogether, these results show the involvement of lncRNA in the process of somatic embryogenesis in S. betaceum, indicating that EC present a pattern of lncRNA expression that suggests its action on genes that directly modulate the morphogenic response in vitro, while in NEC the modulation through this type of RNAs seems to be predominantly reflected in genes more related to cellular physiology.Graphical

Plant regeneration capacity in seeds of three species of Miconia (Melastomataceae) may be related to endogenous polyamine profiles.

In plant tissue culture, differences in endogenous levels of species-specific plant growth regulators (PGRs) may explain differences in regenerative capacity. In the case of polyamines (PAs), their dynamics and distribution may vary between species, genotypes, tissues, and developmental pathways, such as sexual reproduction and apomixis. In this study, for the first time, we aimed to assess the impact of varying endogenous PAs levels in seeds from distinct reproductive modes in Miconia spp. (Melastomataceae), on their in vitro regenerative capacity. We quantified the free PAs endogenous content in seeds of Miconia australis (obligate apomictic), Miconia hyemalis (facultative apomictic), and Miconia sellowiana (sexual) and evaluated their in vitro regenerative potential in WPM culture medium supplemented with a combination of 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BAP). The morphogenic responses were characterized by light microscopy and scanning electron microscopy and discussed regarding the endogenous PAs profiles found. Seeds of M. sellowiana presented approximately eight times more putrescine than M. australis, which was associated with a higher percentage of regenerated calluses (76.67%) than M. australis (5.56%). On the other hand, spermine levels were significantly higher in M. australis. Spermine is indicated as an inhibitor of auxin-carrying gene expression, which may have contributed to its lower regenerative capacity under the tested conditions. These findings provide important insights into in vitro morphogenesis mechanisms in Miconia and highlight the significance of endogenous PA levels in plant regeneration. These discoveries can potentially optimize future regeneration protocols in Miconia, a plant group still underexplored in this area.

Seasonal variation in contamination and browning of Acacia nilotica nodal explants in vitro

Major problems encountered in establishing axenic cultures are contamination and browning of explants and media. Contamination is initiated in explants excised from soil-borne tissues or adult trees. Several sterilizing agents (Tween 20, chlorine water, silver nitrate, mercuric chloride, etc.) or a wash in antibiotic solution are recommended to reduce this. . Establishing in vitro cultures of Acacia nilotica old tree nodal explants was a serious problem. The present study was undertaken to create a suitable protocol for in vitro micropropagation of nodal explants of Acacia nilotica subsp. indica. Contamination was controlled by sterilizing the explants by washing in polysan (5%, v/v along with 500mg/l PVP), thorough washing under tap water, 70% alcohol treatment and 0.1% HgCl2 treatment. Plant tissues release phenolic substances through their cut ends, which turn the media dark brown and toxic. Addition of various antioxidants or/and transfer of explants to fresh medium twice or thrice, at a few days’ intervals may overcome the problem. Collection of explants in antioxidant solution and a wash in antioxidant solution prior to inoculation was helpful in reducing the phenolic exudation in the present investigations. The addition of antioxidant (citric acid) to the medium also checked browning to some extent. The rate of infection and browning of explants varied in different seasons, the maximum being during winters and the minimum during summers of 2019. This was inversely related to the morphogenic response of explants i.e. maximum caulogenesis occurred in vitro during July (6.3±1.4 shoots per explant). The in vitro raised shoots showed 100% rooting on 2mg/l IBA augmented Nitsch’s (N) medium.

Morphogenic responses of two potato cultivars explants to sucrose, photoperiods and growth regulators

Morphogenic responses of two potato cultivars explants to sucrose, photoperiods and growth regulators

Environmentally adaptive reshaping of plant photomorphogenesis by karrikin and strigolactone signaling.

Coordinated morphogenic adaptation of growing plants is critical for their survival and propagation under fluctuating environments. Plant morphogenic responses to light and warm temperatures, termed photomorphogenesis and thermomorphogenesis, respectively, have been extensively studied in recent decades. During photomorphogenesis, plants actively reshape their growth and developmental patterns to cope with changes in light regimes. Accordingly, photomorphogenesis is closely associated with diverse growth hormonal cues. Notably, accumulating evidence indicates that light-directed morphogenesis is profoundly affected by two recently identified phytochemicals, karrikins (KARs) and strigolactones (SLs). KARs and SLs are structurally related butenolides acting as signaling molecules during a variety of developmental steps, including seed germination. Their receptors and signaling mediators have been identified, and associated working mechanisms have been explored using gene-deficient mutants in various plant species. Of particular interest is that the KAR and SL signaling pathways play important roles in environmental responses, among which their linkages with photomorphogenesis are most comprehensively studied during seedling establishment. In this review, we focus on how the phytochemical and light signals converge on the optimization of morphogenic fitness. We also discuss molecular mechanisms underlying the signaling crosstalks with an aim of developing potential ways to improve crop productivity under climate changes.

Development of regenerated plants of interspecific wheat hybrids using immature embryos as explants

Nowadays particular attention in winter wheat breeding is paid to the introduction of biotechnological methods. The culture of immature embryos in vitro is an alternative way to produce hybrids that often do not develop fully in vivo. The purpose of the current study was to estimate the ability of immature embryos of interspecific winter wheat hybrids for callus induction, morphogenesis, and plant regeneration on artificial nutrient media, as well as to select optimal conditions for obtaining full-fledged plants with all the botanical characteristics of the species. The research material included 5 hybrid combinations of interspecific crosses between durum (Triticum durum DESF.) and common (Triticum aestivum L.) winter wheat. The material was collected during one field season (2022). Immature embryos were used as explants. Culture media were according to Murashige-Skoog (MS), and they differed in the content of hormones and organic substances. There has been found that the hybrid combinations were characterized by a variety of morphogenic responses. The manifestation of callusogenesis was not high enough and averaged 22–32 % depending on the nutrient medium. Rhizogenesis averaged from 1–6.7 %, and ended with the formation of roots. The process of formation of embryoid- and hemmorizogenesis was best demonstrated by the hybrid combination No.1, and on two media. All processes of morphogenesis excepting ‘rhizogenesis’ varied greatly among hybrid combinations. The largest number of regenerated plants was obtained from hybrid combination No.1 (61 pcs., 54.5 %). After vernalization and acclimatization, 38 % of the plants survived from the number of planted embryos. The largest number of heads (79 pcs.) was formed according to hybrid combination No.1, on average 1.46 heads per plant. However, not all heads were fertile. The results of the correlation analysis made it possible to identify indicators that closely correlated with the amount of plant regeneration, namely, the high yield of embryoid- and hemmorizogenic structures ensured a high frequency of plant regeneration (r = 0.769).

A liquid culture system for plantlet conversion and slow growth storage of encapsulated shoot tips of Justicia adhatoda L.

The present article demonstrates the applicability of liquid medium in propagation and short-term storage of synthetic seed of Justicia adhatoda L., a medicinally important plant used in many ayurvedic drugs. Shoot tips and nodal segments excised from shoots regenerated on meta-topolin (mT) containing medium were encapsulated in 3% Na-alginate and 100 mM CaCl2.2 H2O for the preparation of artificial seeds. Irrespective of media composition, shoot tips performed better than nodal segments with respect to shoot emergence from alginate beads and further conversion into plantlets in a single step. Morphogenic responses of encapsulated shoot tips in liquid as well as on agar-solidified medium were evaluated and maximum plantlet conversion was observed on PGR-free MS liquid medium. Encapsulated shoot tips were stored for 60 days using slow-growth storage approaches which were induced by a reduction of sucrose concentration (1%) in the medium and reducing MS medium strength to half. After storage, more than 50% synthetic seeds were converted into plantlets when transferred to a regrowth medium. This slow-growth approach may be applied for the short-term storage of synthetic seeds for a reasonable period that is sufficient for the exchange of germplasm for distant places.

Modulation in the enzymatic antioxidants, MDA level and elicitation in conessine biomolecule in Holarrhena pubescens (medicinal tree) cultures exposed to different heavy metals: Ni, Co, Cr and As.

Nodal explants of Holarrhena pubescens, an important medicinal tree, were cultured on Murashige and Skoog's medium (MS) containing 15µM BA (control) alone and on medium supplemented with different concentrations (0, 1, 5, 25, 50, 100 and 200mg/L) of heavy metals such as NiCl2, CoCl2, As2O3 and CrO3 to study their toxic effect. After 28days of treatments, the nodal segments were harvested to assess the average number of shoots per explants, average shoot length, malondialdehyde content, proline content, conessine accumulation and antioxidant enzymatic activity. Among all the metals tried, best morphogenic response was achieved at 5mg/L CrO3 where 80% culture differentiated an average of 3.21 ± 0.08 shoots per explant having 0.95 ± 0.018cm average shoot length. Highest concentration (200mg/L) of all the heavy metals proved lethal for morphogenesis. Maximum inhibition in average shoot number and average shoot length was observed in nodal explants treated with 25mg/L As2O3 where an average of 0.49 ± 0.047 shoots having an average shoot length of 0.3 ± 0.02cm. Contrarily, addition of heavy metals in culture medium proved strong elicitors, exhibiting significant enhancement in the biosynthesis of conessine, an important bioactive compound. HPLC analysis of the crude extract of in vitro grown untreated nodal cultures revealed an average of 117.06 ± 2.59µg/g d. w. of conessine, whereas those treated with 100mg/L of CoCl2 accounted for 297.1 ± 7.76µg/g d. w. (an increase of 156% over control). Among the heavy metals tried, CoCl2 proved to be the best for conessine enhancement which was in the order of CoCl2 > Cr2O3 > NiCl2 > As2O3 in the nodal explants. Concomitantly, MDA content, the antioxidant enzymes activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GR) and ascorbate peroxidase (APX) were also observed to be differentially expressed with the increase in the heavy metals concentration from 1 to 200mg/L. Free proline, too, increased up to 3.5-fold over control. The results obtained during the present investigation revealed that the overall response of the nodal explants in terms of morphogenesis, conessine content and antioxidant enzyme activities was metal specific as well as dose dependent.

Overexpression of Brassica napus COMT1 in Arabidopsis heightens UV-B-mediated resistance to Plutella xylostella herbivory.

UV-B radiation regulates numerous morphogenic, biochemical and physiological responses in plants, and can stimulate some responses typically associated with other abiotic and biotic stimuli, including invertebrate herbivory. Removal of UV-B from the growing environment of various plant species has been found to increase their susceptibility to consumption by invertebrate pests, however, to date, little research has been conducted to investigate the effects of UV-B on crop susceptibility to field pests. Here, we report findings from a multi-omic and genetic-based study investigating the mechanisms of UV-B-stimulated resistance of the crop, Brassica napus (oilseed rape), to herbivory from an economically important lepidopteran specialist of the Brassicaceae, Plutella xylostella (diamondback moth). The UV-B photoreceptor, UV RESISTANCE LOCUS 8 (UVR8), was not found to mediate resistance to this pest. RNA-Seq and untargeted metabolomics identified components of the sinapate/lignin biosynthetic pathway that were similarly regulated by UV-B and herbivory. Arabidopsis mutants in genes encoding two enzymes in the sinapate/lignin biosynthetic pathway, CAFFEATE O-METHYLTRANSFERASE 1 (COMT1) and ELICITOR-ACTIVATED GENE 3-2 (ELI3-2), retained UV-B-mediated resistance to P. xylostella herbivory. However, the overexpression of B. napus COMT1 in Arabidopsis further reduced plant susceptibility to P. xylostella herbivory in a UV-B-dependent manner. These findings demonstrate that overexpression of a component of the sinapate/lignin biosynthetic pathway in a member of the Brassicaceae can enhance UV-B-stimulated resistance to herbivory from P. xylostella.

MORPHOGENIC RESPONSE FROM LEAF EXPLANT OF Dendranthema grandiflora VAR MICROMARGARA

<p class="Default"><strong>Background:</strong> Chrysanthemum is one of the most popular landscape plants worldwide. Introducing desirable traits into this plant by conventional breeding has limitations due to cross-incompatibility. An approach to this problem is the introduction of resistance or tolerance traits via plant genetic transformation. <em>In vitro</em> regeneration of plants is necessary for implementing genetic transformation systems; therefore, regeneration via morphogenesis is required before any genetic transformation attempt. <strong>Objective</strong>: To induce morphogenesis from the leaf explant of <em>Dendranthema grandiflora</em> var Micromargara. <strong>Methodology</strong>: Micropropagation from node cuttings was induced from node cuttings of 3 cm in length from 6 months-old plants that were used as explants to produce seedlings as source explants. Morphogenesis experiments were done using leaf segments of 1 cm<sup>2</sup> from 8-weeks-old <em>in vitro </em>seedlings. The explants were transferred to basal medium Murashige and Skoog at 4.4 gL<sup>-1</sup> supplemented with different plant growth regulators. During the morphogenic process, leaves samples were collected to detect which morphogenic process was induced. <strong>Results: </strong>Node cuttings culture on Murashige and Skoog medium at 3.3 gL<sup>-1</sup> supplemented with benzylaminopurine at 2.2 µM yielded a vegetative growth increase from 1 to 7 shoots, 2 to 12 leaves per node cutting, and the stem length of 3 to 9.5 cm. The leaf explant induced three ways of <em>in vitro</em> morphogenesis: direct and indirect roots organogenesis (rhizogenesis) and, shoot organogenesis. Direct rhizogenesis was induced in plant growth regulator-free Murashige and Skoog medium (18 roots/explant). Indirect rhizogenesis from leaf explant was less efficient than direct rhizogenesis, get obtaining six roots per leaf explant cultured on Murashige and Skoog medium at 4.4 g L<sup>-1 </sup>supplemented with 0.4 µM thidiazuron and 4.5 µM 2,4-dichlorophenoxyacetic acid, and three roots per leaf explant cultured on Murashige and Skoog medium supplemented with 0.4 µM thidiazuron and 9.05 µM 2,4-dichlorophenoxyacetic acid. Indirect shoot organogenesis was induced from leaf explants cultured on Murashige and Skoog at 4.4 g L<sup>-1</sup> supplemented with 13.32 µM benzylaminopurine and 4.83 µM naphthalene acetic acid; 50% of explants with callus formed shoots (2 shoots/leaf explant). Through histological analysis it was possible to verify that the morphogenic response obtained was organogenesis. <strong>Implications:</strong> Regeneration of <em>Dendranthema grandiflora</em> var. Micromargara established herein will allow improvement of the variety through techniques of genetic transformation mediated by Agrobacterium and any other strategy to incorporate or silence genes of interest in the plant. <strong>Conclusion</strong>: The high capacity to induce roots of <em>Dendranthema grandiflora</em> var Micromargara, may provide an efficient model for further investigating the mechanism of rhizogenesis from leaf explants cultured without plant growth regulators.</p>

Acceleration of Callus Formation in Date Palm (Phoenix dactylifera L.) Zygotic Embryos

This study was carried out to test the effect of water soaking ofseeds of date palm ( P. dactylifera L.) as a pre-empryo excision treatment,on in vitro culture of zygotic empryos. The objective was optimization oforganogenic callus formation. Mature seeds of “Barakawi” and “MishrigWad Laggi” date palm cultivars were used as sources of embryos.Durations of 0- up to 9-days of seed water soaking, prior to embryoexcision and culture, were tested. Murashige and Skoog (1962) mediumwas used as basal medium. The cultures responded positively to the watersoaking treatments and resulted in the organogenic responses of swelling,germination, callus and adventitious roots formation were obtained. Themagnitude and type of response varied with cultivar and soaking duration.All water soaking treatments increased the measured responses relative tothe control. The results showed that a 6-day soaking treatment wasoptimal for all measured responses compared with the other periods ofsoaking tested. Calli formation in 6-day water soaking treatment were50% and 70% for “Barakawi” and “Mishrig Wad Laggai” ,respectively.However, increasing the soaking duration beyond the 6-day had a markednegative effect on morphogenic response regardless of cultivar. The bestresults for all measured parameters were obtained with embryos of“Mishrig Wad Laggi” compared with embryos excised from “Barakawi”.It seems that soaking date palm seeds in water prior to embryo excisionplay an important role, in enhancing morphogenic response and callusformation in date palm tissue culture.

High Frequency Direct Organogenesis in Five Romanian Tomato (Lycopersicon esculentum Mill.) Cultivars

Tomato (Lycopersicon esculentum Mill.) as the most economically important vegetable crop worldwide has been investigated intensively for the development of new and improved varieties. Most of these technologies require efficient protocols for in vitro regeneration and propagation of plant material. In the present study, an efficient and reproducible in vitro regeneration system for five Romanian tomato genotypes (cvs. ‘Capriciu’, ‘Darsirius’, ‘Kristin’, ‘Pontica’ and ‘Siriana’) has been established. The tomato genotypes were selected based on their horticultural and economically valuable traits. To study the in vitro morphogenic response, various explants, such as cotyledons, cotyledonary nodes, hypocotyls, leaf explants, internodes, stem nodes and apical buds have been selected. The highest efficiency in terms of direct shoot organogenesis was obtained in cv. ‘Capriciu’ (98% for apical buds and 94% for stem nodes) on culture media with zeatin and indole-3-butyric acid. One advantage of this regeneration procedure is beside its feasibility in handling, the high percentage of regenerated shoots and their rooting. The present protocol contributes to the existing information regarding the response of tomato cultivars to in vitro culture conditions.

Disparity in pseudohyphal morphogenic switching response to the quorum sensing molecule 2-phenylethanol in commercial brewing strains of Saccharomyces cerevisiae.

Saccharomyces cerevisiae can undergo filamentous growth in response to specific environmental stressors, particularly nitrogen-limitation, whereby cells undergo pseudohyphal differentiation, a process where cells transition from a singular ellipsoidal appearance to multicellular filamentous chains from the incomplete scission of the mother-daughter cells. Previously, it was demonstrated that filamentous growth in S. cerevisiae is co-regulated by multiple signaling networks, including the glucose-sensing RAS/cAMP-PKA and SNF pathways, the nutrient-sensing TOR pathway, the filamentous growth MAPK pathway, and the Rim101 pathway, and can be induced by quorum-sensing aromatic alcohols, such as 2-phenylethanol. However, the prevalent research on the yeast-pseudohyphal transition and its induction by aromatic alcohols in S. cerevisiae has been primarily limited to the strain Σ1278b. Due to the prospective influence of quorum sensing on commercial fermentation, the native variation of yeast-to-filamentous phenotypic transition and its induction by 2-phenylethanol in commercial brewing strains was investigated. Image analysis software was exploited to enumerate the magnitude of whole colony filamentation in 16 commercial strains cultured on nitrogen-limiting SLAD medium; some supplemented with exogenous 2-phenylethanol. The results demonstrate that phenotypic switching is a generalized, highly varied response occurring only in select brewing strains. Nevertheless, strains exhibiting switching behavior altered their filamentation response to exogenous concentrations of 2-phenylethanol.

Prominent Effects of Zinc Oxide Nanoparticles on Roots of Rice (Oryza sativa L.) Grown under Salinity Stress

The morphological plasticity of plant roots is a key factor in their ability to tolerate a wide range of edaphic stresses. There are many unanswered questions relating to nanotechnology and its potential uses for sustainable agriculture. The main purpose of this study was to examine the effects of salinity-induced morphogenic responses and zinc oxide nanoparticles (ZnO-NPs) on root characteristics, growth, MDA content, antioxidant enzymatic activity, and root ion accumulation in rice (Oryza sativa L.). The experiment was conducted in a hydroponic culture containing 50 mg/L of ZnO-NPs and different concentrations (60, 80, and 100 mM) of NaCl for 14 days. The results indicated a decrease in rice root growth due to exposure to salinity (length, fresh, and root dry weight). The results showed that salinity caused a reduction in rice root growth (length, fresh, and root dry weight). Higher root sodium (Na+) accumulation, MDA content, and potassium level decreased with increasing salinity. Root length, root fresh weight, root dry weight, root K+ content, and root antioxidant enzymatic activity were all enhanced by applying 50 mg/L ZnO-NPs often in salinity. SEM analysis revealed that ZnO-NPs treatments significantly improved root morphology. There was a notable decrease in root Na+ content as a result, which improved the K+/Na+ ratio in the rice’s root system. These findings suggest that O. sativa, when treated with ZnO-NPs, can thrive under salt-stress conditions, opening up the possibility of cultivating the plant in extreme climates.

Ex Situ Conservation of Atriplex taltalensis I.M. Johnst. via In Vitro Culturing of Its Axillary Shoots

Atriplex taltalensis is an endangered shrub endemic to northern Chile. Sparse populations of this species can be found in areas with extreme edaphoclimatic conditions in the Atacama desert, and its seeds have a poor germination rate. Consequently, mass-cultivating it can be challenging. In this study, the vegetative propagation mechanisms of A. taltalensis were evaluated using an in vitro culture to aid in their conservation. A. taltalensis shoot explants were treated with two phytoregulators, indole-3-butyric acid (IBA) and 6-benzylaminopurine (BAP), to assess the morphogenic responses and their effects on the propagation of the species, based on shoot multiplication, elongation, and rooting, through subculturing. During multiplication, the treatment with IBA alone efficiently promoted explant elongation, lateral root formation, and axillary shoot proliferation, allowing for the rapid development of shoots into whole plants. Alternatively, treatment with IBA and BAP in combination stimulated the proliferation of basal shoots with little elongation and rooting and promoted shoot hyperhydricity at 0.25–1 mg L−1 BAP concentrations. Thus, we conclude that A. taltalensis propagation is viable through in vitro plant tissue culture using a rapid axillary shoot multiplication system, and this method could aid in the conservation of this species through in vitro propagation and rescue programs.

Evaluation of In Vitro Morphogenic Response of Triticum urartu, a Donor of Au Genome of Modern Wheat

Triticum urartu Thum. ex Gandil. is a wild diploid wheat species (2n = 2x = 14) that is an Au genome donor of modern polyploid cultivars of durum and bread wheat. In the last decade, this relict species has attracted breeders as donors of various agronomically important characteristics to broaden the genetic diversity of cultivated wheat. In addition, T. urartu can be considered as a model species for studying the evolution, biology and genomics of wheat without the cross-influence of homologous sub-genomes. Various genetic engineering technologies, including transgenesis and genome editing, may be applied to facilitate the functional characterization of genes located in A chromosomes. Such biotechnological techniques are still required for the efficient tissue culture systems to allow easy plant regeneration. The objective of our study was to assess the abilities of in vitro plant regeneration from zygotic immature embryo-derived tissues of spring and winter types of T. urartu. Three synthetic auxins, 2,4-D, Dicamba and Picloram, at four concentrations were studied to stimulate morphogenic responses in spring T. urartu. The induction medium supplemented with 4 mg·L−1 Dicamba stimulated the highest frequency of regenerable callus production (65.8%), promoting the generation of 5.7 plants. Although the presence of 2 mg·L−1 2,4-D was less effective in stimulating regenerable callus formation (53.2%) than Dicamba, it allowed the regeneration of more plants from one regenerable callus (9.3 plants). These two treatments also successfully initiated morphogenesis in winter assertions; however, their regenerative capacity was generally lower. The frequency of regenerable callus production was accession-dependent and fluctuated within 31.3 to 49.2%, with a formation of an average 2.2–5.8 plants per callus. The relatively simple and fast regeneration system described in this study could be further used as the basis for regenerating transgenic plants of T. urartu.

Assessing the Role of Extreme Mediterranean Events on Coastal River Outlet Dynamics

River mouths are highly dynamic environments responding very rapidly to changes in wave energy or river floods. While the morphological response during floods or during marine storm events has been widely documented in the literature, little is known about the mechanisms acting during the co-occurrence of fluvial and marine hazards. This concomitance of river flood and marine storm is quite common in the western Mediterranean Sea, and was the case for the Gloria event, considered to be the most extreme event in recent decades. During this event, monitoring of hydrodynamics and morphological evolution was implemented, making it possible to better understand the impact of concomitant marine storm and fluvial flood during an extreme meteorological event on spit breaching of a small Mediterranean river mouth. Monitoring using a combination of high-resolution hydrodynamic measurements, topographic and bathymetric surveys, and sediment cores was used before, during, and after the storm “Gloria”. The results suggest an amplification of the morphological impact of the events and a different morphogenic response than if each of the events had acted independently on the system. The marine storm, occurring first, weakened the spit and initiated its breaching, which was continued by the extreme fluvial flood, thus leading to the complete destruction of the mouth. The destruction of the spit acted as a sediment source for subaqueous large delta deposition amounting to 50% of the total volume. The contribution of the river, estimated at 30%, was quite low for an exceptional event, showing the importance of locating rainfall in a catchment area controlled by a dam. For this event, extreme morphological evolution was observed, as well as the importance of water levels in the river mouth, which probably increased flood hazards, demonstrating the importance of including the compounding effect of extreme coastal water levels in river flood risk management.

Indirect effects of COVID-19 on the environment: How plastic contamination from disposable surgical masks affect early development of plants

Personal protective equipment, used extensively during the COVID-19 pandemic, heavily burdened the environment due to improper waste management. Owing to their fibrous structure, layered non-woven polypropylene (PP) disposable masks release secondary fragments at a much higher rate than other plastic waste types, thus, posing a barely understood new form of ecological hazard. Here we show that PP mask fragments of different sizes induce morphogenic responses in plants during their early development. Using in vitro systems and soil-filled rhizotrons, we found that several PP mask treatments modified the root growth of Brassica napus (L.) regardless of the experimental system. The environment around the root and mask fragments seemed to influence the effect of PP fabric fragment contamination on early root growth. In soil, primary root length was clearly inhibited by larger PP mask fragments at 1 % concentration, while the two smallest sizes of applied mask fragments caused distinct, concentration-dependent changes in the lateral root numbers. Our results indicate that PP can act as a stressor: contamination by PP surgical masks affects plant growth and hence, warrants attention. Further investigations regarding the effects of plastic pollution on plant-soil interactions involving various soil types are urgently needed.

Indirect organogenesis for high frequency shoot regeneration of two cultivars of Sansevieria trifasciata Prain differing in fiber production

Sansevieria trifasciata is used as an indoor plant, in traditional medicine and as a fiber source. Here we characterized fibers of two of varieties of S. trifasciata, Lorentii and Hahnii, and report a protocol for their propagation based on indirect shoot organogenesis. Structural and ribbon fibers were scattered within leaf parenchyma when viewed with confocal laser scanning microscopy. Chemical analysis of the fibers by mass spectrometry and high-performance chromatography revealed higher contents of cellulose and xylose in Lorentii than in Hahnii and significant differences for total lignin between both. A protocol for de novo shoot production was then developed using leaf explants. Time-course histological analyses showed that the first events of transdifferentiation were triggered preferentially in cells surrounding fibers and vascular bundles. Callogenesis and shoot performances were quantified for both varieties, and 2,4-D at 2 and 3 mg·L-1 yielded the best results for primary calli induction and fresh calli mass. The length, number, and mass of shoots produced did not differ significantly between the two cultivars. The fast morphogenic response of S. trifasciata to in vitro culture may be useful for mass propagation or other biotechnological purposes such as metabolite production.