Barriers to Gait Training among Stroke Survivors: An Integrative Review.

Gait recovery is vital for stroke survivors' ability to perform their activities associated with daily living. Consequently, a gait impairment is a significant target for stroke survivors' physical rehabilitation. This review aims to identify barriers to gait training among stroke survivors. An integrative review was conducted following Whittemore and Knafl's methodology. The research was carried out on the electronic databases Scopus, PubMed, and B-on, applying a time span of 2006 to 2022. A total of 4189 articles were initially identified. After selecting and analyzing the articles, twelve studies were included in the sample. This review allowed for the identification of several barriers to gait training among stroke survivors, which can be grouped into three categories: individual, environmental, and rehabilitation workforce-related barriers. These findings highlight that participation in gait training is not solely dependent on the stroke survivor. Instead, the uptake of rehabilitation programs may also depend on environmental and rehabilitation workforce-related factors.

Newly identified miRNAs may contribute to aerenchyma formation in sugarcane roots.

Small RNAs comprise three families of noncoding regulatory RNAs that control gene expression by blocking mRNA translation or leading to mRNA cleavage. Such post-transcriptional negative regulation is relevant for both plant development and environmental adaptations. An important biotechnological application of miRNA identification is the discovery of regulators and effectors of cell wall degradation, which can improve/facilitate hydrolysis of cell wall polymers for second-generation bioethanol production. The recent characterization of plant innate cell wall modifications occurring during root aerenchyma development triggered by ethylene led to the possibility of prospection for mechanisms of cell wall disassembly in sugarcane. By using next-generation sequencing, 39 miRNAs were identified in root segments along the process of aerenchyma development. Among them, 31 miRNAs were unknown to the sugarcane miRBase repository but previously identified as produced by its relative Sorghum bicolor. Key putative targets related to signal transduction, carbohydrate metabolic process, and cell wall organization or biogenesis were among the most representative gene categories targeted by miRNA. They belong to the subclasses of genes associated with the four modules of cell wall modification in sugarcane roots: cell expansion, cell separation, hemicellulose, and cellulose hydrolysis. Thirteen miRNAs possibly related to ethylene perception and signaling were also identified. Our findings suggest that miRNAs may be involved in the regulation of cell wall degradation during aerenchyma formation. This work also points out to potential molecular tools for sugarcane improvement in the context of second-generation biofuels.

Cell wall hydrolases act in concert during aerenchyma development in sugarcane roots.

BACKGROUND AND AIMS: Cell wall disassembly occurs naturally in plants by the action of several glycosyl-hydrolases during different developmental processes such as lysigenous and constitutive aerenchyma formation in sugarcane roots. Wall degradation has been reported in aerenchyma development in different species, but little is known about the action of glycosyl-hydrolases in this process. METHODS: In this work, gene expression, protein levels and enzymatic activity of cell wall hydrolases were assessed. Since aerenchyma formation is constitutive in sugarcane roots, they were assessed in segments corresponding to the first 5 cm from the root tip where aerenchyma develops. KEY RESULTS: Our results indicate that the wall degradation starts with a partial attack on pectins (by acetyl esterases, endopolygalacturonases, ß-galactosidases and α-arabinofuranosidases) followed by the action of ß-glucan-/callose-hydrolysing enzymes. At the same time, there are modifications in arabinoxylan (by α-arabinofuranosidases), xyloglucan (by XTH), xyloglucan-cellulose interactions (by expansins) and partial hydrolysis of cellulose. Saccharification revealed that access to the cell wall varies among segments, consistent with an increase in recalcitrance and composite formation during aerenchyma development. CONCLUSION: Our findings corroborate the hypothesis that hydrolases are synchronically synthesized, leading to cell wall modifications that are modulated by the fine structure of cell wall polymers during aerenchyma formation in the cortex of sugarcane roots.

The control of endopolygalacturonase expression by the sugarcane RAV transcription factor during aerenchyma formation.

The development of lysigenous aerenchyma starts with cell expansion and degradation of pectin from the middle lamella, leading to cell wall modification, and culminating with cell separation. Here we report that nutritional starvation of sugarcane induced gene expression along sections of the first 5 cm of the root and between treatments. We selected two candidate genes: a RAV transcription factor, from the ethylene response factors superfamily, and an endopolygalacturonase (EPG), a glycosyl hydrolase related to homogalacturonan hydrolysis from the middle lamella. epg1 and rav1 transcriptional patterns suggest they are essential genes at the initial steps of pectin degradation during aerenchyma development in sugarcane. Due to the high complexity of the sugarcane genome, rav1 and epg1 were sequenced from 17 bacterial artificial chromosome clones containing hom(e)ologous genomic regions, and the sequences were compared with those of Sorghum bicolor. We used one hom(e)olog sequence from each gene for transactivation assays in tobacco. rav1 was shown to bind to the epg1 promoter, repressing ß-glucuronidase activity. RAV repression upon epg1 transcription is the first reported link between ethylene regulation and pectin hydrolysis during aerenchyma formation. Our findings may help to elucidate cell wall degradation in sugarcane and therefore contribute to second-generation bioethanol production.

Corrigendum: Pectins, Endopolygalacturonases, and Bioenergy.

[This corrects the article on p. 1401 in vol. 7, PMID: 27703463.].

Pectins, Endopolygalacturonases, and Bioenergy.

The precise disassembly of the extracellular matrix of some plant species used as feedstocks for bioenergy production continues to be a major barrier to reach reasonable cost effective bioethanol production. One solution has been the use of pretreatments, which can be effective, but increase even more the cost of processing and also lead to loss of cell wall materials that could otherwise be used in industry. Although pectins are known to account for a relatively low proportion of walls of grasses, their role in recalcitrance to hydrolysis has been shown to be important. In this mini-review, we examine the importance of pectins for cell wall hydrolysis highlighting the work associated with bioenergy. Here we focus on the importance of endopolygalacturonases (EPGs) discovered to date. The EPGs cataloged by CAZy were screened, revealing that most sequences, as well as the scarce structural work performed with EPGs, are from fungi (mostly Aspergillus niger). The comparisons among the EPG from different microorganisms, suggests that EPGs from bacteria and grasses display higher similarity than each of them with fungi. This compilation strongly suggests that structural and functional studies of EPGs, mainly from plants and bacteria, should be a priority of research regarding the use of pectinases for bioenergy production purposes.

Do plant cell walls have a code?

A code is a set of rules that establish correspondence between two worlds, signs (consisting of encrypted information) and meaning (of the decrypted message). A third element, the adaptor, connects both worlds, assigning meaning to a code. We propose that a Glycomic Code exists in plant cell walls where signs are represented by monosaccharides and phenylpropanoids and meaning is cell wall architecture with its highly complex association of polymers. Cell wall biosynthetic mechanisms, structure, architecture and properties are addressed according to Code Biology perspective, focusing on how they oppose to cell wall deconstruction. Cell wall hydrolysis is mainly focused as a mechanism of decryption of the Glycomic Code. Evidence for encoded information in cell wall polymers fine structure is highlighted and the implications of the existence of the Glycomic Code are discussed. Aspects related to fine structure are responsible for polysaccharide packing and polymer-polymer interactions, affecting the final cell wall architecture. The question whether polymers assembly within a wall display similar properties as other biological macromolecules (i.e. proteins, DNA, histones) is addressed, i.e. do they display a code?

How endogenous plant cell-wall degradation mechanisms can help achieve higher efficiency in saccharification of biomass.

Cell-wall recalcitrance to hydrolysis still represents one of the major bottlenecks for second-generation bioethanol production. This occurs despite the development of pre-treatments, the prospect of new enzymes, and the production of transgenic plants with less-recalcitrant cell walls. Recalcitrance, which is the intrinsic resistance to breakdown imposed by polymer assembly, is the result of inherent limitations in its three domains. These consist of: (i) porosity, associated with a pectin matrix impairing trafficking through the wall; (ii) the glycomic code, which refers to the fine-structural emergent complexity of cell-wall polymers that are unique to cells, tissues, and species; and (iii) cellulose crystallinity, which refers to the organization in micro- and/or macrofibrils. One way to circumvent recalcitrance could be by following cell-wall hydrolysis strategies underlying plant endogenous mechanisms that are optimized to precisely modify cell walls in planta. Thus, the cell-wall degradation that occurs during fruit ripening, abscission, storage cell-wall mobilization, and aerenchyma formation are reviewed in order to highlight how plants deal with recalcitrance and which are the routes to couple prospective enzymes and cocktail designs with cell-wall features. The manipulation of key enzyme levels in planta can help achieving biologically pre-treated walls (i.e. less recalcitrant) before plants are harvested for bioethanol production. This may be helpful in decreasing the costs associated with producing bioethanol from biomass.

An Acidic Thermostable Recombinant Aspergillus nidulans Endoglucanase Is Active towards Distinct Agriculture Residues.

Aspergillus nidulans is poorly exploited as a source of enzymes for lignocellulosic residues degradation for biotechnological purposes. This work describes the A. nidulans Endoglucanase A heterologous expression in Pichia pastoris, the purification and biochemical characterization of the recombinant enzyme. Active recombinant endoglucanase A (rEG A) was efficiently secreted as a 35 kDa protein which was purified through a two-step chromatography procedure. The highest enzyme activity was detected at 50°C/pH 4. rEG A retained 100% of activity when incubated at 45 and 55°C for 72 h. Purified rEG A kinetic parameters towards CMC were determined as K m = 27.5 ± 4.33 mg/mL, V max = 1.185 ± 0.11 mmol/min, and 55.8 IU (international units)/mg specific activity. Recombinant P. pastoris supernatant presented hydrolytic activity towards lignocellulosic residues such as banana stalk, sugarcane bagasse, soybean residues, and corn straw. These data indicate that rEG A is suitable for plant biomass conversion into products of commercial importance, such as second-generation fuel ethanol.