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Liparis loeselii (L.) Rich, an endangered member of the Orchidaceae family, is found in alkaline fens. With the declining populations of L. loeselii, there is a pressing need to reintroduce this species in Central Europe. As in vitro germination is a crucial tool for obtaining plants for introduction into the environment, we looked at the morphological changes occurring during the early stages of L. loeselii development in vitro. As the early stages of orchid development, especially the protocorm stage, are thought to be responsible for SAM formation and the initiation of symbiotic association, we focused on cell wall elements whose epitopes have been found in similar processes in other species: the extensin and pectin rhamnogalacturonan I (RG-I) side chain epitopes. We addressed the following questions: Does the cell wall of L. loeselii change its composition during the early stages of development, as noted in other species? Are there noticeable similarities in the cell wall to organs of different species whose function is to contact microorganisms? Are there regularities that allow the recognition of individual structures on this basis? Immunolocalization revealed changes in the distribution of certain extensins (JIM11 and JIM20) and RG-I (LM5 and LM6) side chain epitopes. Extensins, a type of cell wall protein, were observed during the initial stages of the formation of PLB and the shoot apical meristem of protocorms and PLBs. RG-I, on the other hand, was found to play a significant role in the development of the protocorm and PLB. In pseudobulbs, which appeared on the protocorms, extensins occurred in their storage part. However, RG-I side chains (1→4)-β-galactans (LM5), and (1→5)-α-L-arabinans (LM6) were not found in pseudobulbs. We revealed that a common feature of protocorms and PLBs was an increased amount of extensins, which were detected with the JIM11 antibody, and pectins, which were detected with the LM5 antibody, that were present together, which may prove helpful in determining the identity of the induced structures and distinguishing them from pseudobulbs. Thus, our study unveiled the role of extensins and RG-I during the growth of protocorms and PLBs. We suggest that PLBs may mimic the wall remodelling that occurs in protocorms, which indicates that using cell wall components is an invitation to be colonised by a fungal partner. However, this needs to be tested in future research. The findings of this research can help interpret future studies on the propagation, acclimatisation, and introduction of L. loeselii into the natural environment. [ABSTRACT FROM AUTHOR]

Liparis loeselii (L.) Rich, an endangered member of the Orchidaceae family, is found in alkaline fens. With the declining populations of L. loeselii, there is a pressing need to reintroduce this species in Central Europe. As in vitro germination is a crucial tool for obtaining plants for introduction into the environment, we looked at the morphological changes occurring during the early stages of L. loeselii development in vitro. As the early stages of orchid development, especially the protocorm stage, are thought to be responsible for SAM formation and the initiation of symbiotic association, we focused on cell wall elements whose epitopes have been found in similar processes in other species: the extensin and pectin rhamnogalacturonan I (RG-I) side chain epitopes. We addressed the following questions: Does the cell wall of L. loeselii change its composition during the early stages of development, as noted in other species? Are there noticeable similarities in the cell wall to organs of different species whose function is to contact microorganisms? Are there regularities that allow the recognition of individual structures on this basis? Immunolocalization revealed changes in the distribution of certain extensins (JIM11 and JIM20) and RG-I (LM5 and LM6) side chain epitopes. Extensins, a type of cell wall protein, were observed during the initial stages of the formation of PLB and the shoot apical meristem of protocorms and PLBs. RG-I, on the other hand, was found to play a significant role in the development of the protocorm and PLB. In pseudobulbs, which appeared on the protocorms, extensins occurred in their storage part. However, RG-I side chains (1→4)-β-galactans (LM5), and (1→5)-α-L-arabinans (LM6) were not found in pseudobulbs. We revealed that a common feature of protocorms and PLBs was an increased amount of extensins, which were detected with the JIM11 antibody, and pectins, which were detected with the LM5 antibody, that were present together, which may prove helpful in determining the identity of the induced structures and distinguishing them from pseudobulbs. Thus, our study unveiled the role of extensins and RG-I during the growth of protocorms and PLBs. We suggest that PLBs may mimic the wall remodelling that occurs in protocorms, which indicates that using cell wall components is an invitation to be colonised by a fungal partner. However, this needs to be tested in future research. The findings of this research can help interpret future studies on the propagation, acclimatisation, and introduction of L. loeselii into the natural environment.

With the discovery in 2015 of the ability to induce somatic embryos in Cyathea delgadii, learning more about the relationship between the structure of apoplast and cell differentiation has become possible among ferns. In this study, the distribution of arabinogalactan proteins, pectins, extensins, and callose with specific epitopes recognized by monoclonal antibodies was investigated during direct somatic embryogenesis (SE) of C. delgadii. Eight antigens against the arabinogalactan proteins (JIM8, JIM13, LM2), pectins (JIM5, JIM7), extensins (JIM11, JIM12), and callose (anti-1 → 3-β-glucan) were selected. Two types of explants were analyzed, i.e. stipe fragments and internodes, which give rise to embryos of unicellular and multicellular origin, respectively. The study showed that embryogenic transition in C. delgadii is preceded by cell wall remodeling of initial explants. Dynamic changes in JIM13, JIM12, and anti-1 → 3-β-glucan localization were observed. The differences in the distribution of studied epitopes were observed between the cell walls of the epidermis and those located in the other layers of the explant. Moreover, within the somatic embryos, a stronger fluorescence of the examined antibodies was observed, mainly those reacting with arabinogalactan proteins, extensins, and callose. These results also implicated that, with the exception of the earlier appearance of callose in the stipe explants, the uni- and multicellular pathways of somatic embryo differentiation do not differ in the quality of cell wall components. The presented studies document the first time that SE in ferns can be regulated by changes in apoplast structure and they provide a basis for more detailed research. Key Message: The cell wall plays a significant role in somatic embryogenesis of Cyathea delgadii and changes in its composition may be a marker of embryogenicity for this species. [ABSTRACT FROM AUTHOR]

Root hair cells are important sensors of soil conditions. They grow towards and absorb water-soluble nutrients. This fast and oscillatory growth is mediated by continuous remodeling of the cell wall. Root hair cell walls contain polysaccharides and hydroxyproline-rich glycoproteins, including extensins (EXTs). Class-III peroxidases (PRXs) are secreted into the apoplastic space and are thought to trigger either cell wall loosening or polymerization of cell wall components, such as Tyr-mediated assembly of EXT networks (EXT-PRXs). The precise role of these EXT-PRXs is unknown. Using genetic, biochemical, and modeling approaches, we identified and characterized three root-hair-specific putative EXT-PRXs, PRX01, PRX44, and PRX73. prx01,44,73 triple mutation and PRX44 and PRX73 overexpression had opposite effects on root hair growth, peroxidase activity, and ROS production, with a clear impact on cell wall thickness. We use an EXT fluorescent reporter with contrasting levels of cell wall insolubilization in prx01,44,73 and PRX44-overexpressing background plants. In this study, we propose that PRX01, PRX44, and PRX73 control EXT-mediated cell wall properties during polar expansion of root hair cells. [ABSTRACT FROM AUTHOR]

We recently showed that yellow lupine is highly sensitive to soil water deficits since this stressor disrupts nodule structure and functioning, and at the same time triggers flower separation through abscission zone (AZ) activation in the upper part of the plant. Both processes require specific transformations including cell wall remodeling. However, knowledge about the involvement of particular cell wall elements in nodulation and abscission in agronomically important, nitrogen-fixing crops, especially under stressful conditions, is still scarce. Here, we used immuno-fluorescence techniques to visualize dynamic changes in cell wall compounds taking place in the root nodules and flower AZ of Lupinus luteus following drought. The reaction of nodules and the flower AZ to drought includes the upregulation of extensins, galactans, arabinans, xylogalacturonan, and xyloglucans. Additionally, modifications in the localization of high- and low-methylated homogalacturonans and arabinogalactan proteins were detected in nodules. Collectively, we determined for the first time the drought-associated modification of cell wall components responsible for their remodeling in root nodules and the flower AZ of L. luteus. The involvement of these particular molecules and their possible interaction in response to stress is also deeply discussed herein. [ABSTRACT FROM AUTHOR]