Phloem Fibers Research Articles

Morphological, Histobiochemical and Molecular Characterisation of Low Lignin Phloem Fibre (llpf) Mutant of Dark Jute (Corchorus olitorius L.).

Lignin is a versatile plant metabolite challenging high-end industrial applications of several plant products including jute. Application of developmental mutant in regulation of lignification in jute may open up door for much awaited jute based diversified products. In the present study, a novel dark jute (Corchorus olitorius L.) mutant with low lignin (7.23%) in phloem fibre being compared to wild-type JRO 204 (13.7%) was identified and characterised. Unique morphological features including undulated stem, petiole and leaf vein distinguished the mutant in gamma ray irradiated mutant population. Histological and biochemical analysis revealed reduced lignification of phloem fibre cellsof the plant. RT-PCR analysis demonstrated temporal transcriptional regulation of CCoAMT1 gene in the mutant. The mutant was found an extremely useful model to study phloem fibre developmental biology in the crop besides acting as a donor genetic stock for low lignin containing jute fibre in dark jute improvement programme.

The influence of slope on Spartium junceum root system: morphological, anatomical and biomechanical adaptation.

Root systems have a pivotal role in plant anchorage and their mechanical interactions with the soil may contribute to soil reinforcement and stabilization of slide-prone slopes. In order to understand the responses of root system to mechanical stress induced by slope, samples of Spartium junceum L., growing in slope and in plane natural conditions, were compared in their morphology, biomechanical properties and anatomical features. Soils sampled in slope and plane revealed similar characteristics, with the exception of organic matter content and penetrometer resistance, both higher in slope. Slope significantly influenced root morphology and in particular the distribution of lateral roots along the soil depth. Indeed, first-order lateral roots of plants growing on slope condition showed an asymmetric distribution between up- and down-slope. Contrarily, this asymmetric distribution was not observed in plants growing in plane. The tensile strength was higher in lateral roots growing up-slope and in plane conditions than in those growing down-slope. Anatomical investigations revealed that, while roots grown up-slope had higher area covered by xylem fibers, the ratio of xylem and phloem fibers to root diameter did not differ among the three conditions, as also, no differences were found for xylem fiber cell wall thickness. Roots growing up-slope were the main contributors to anchorage properties, which included higher strength and higher number of fibers in the xylematic tissues. Results suggested that a combination of root-specific morphological, anatomical and biomechanical traits, determines anchorage functions in slope conditions.

Phloem fibres as motors of gravitropic behaviour of flax plants: level of transcriptome.

Restoration of stem vertical position after plant inclination is a widely spread version of plant orientation in accordance with gravity vector direction. Gravitropic behaviour of flax plants involves the formation of curvature in stem region that has ceased elongation long in advance of stem inclination. The important participants of such behaviour are phloem fibres with constitutively formed tertiary cell wall (G-layer). We performed the large-scale transcriptome profiling of phloem fibres isolated from pulling and opposite sides of gravitropic curvature and compared with control plant fibres. Significant changes in transcript abundance take place for genes encoding proteins of several ion channels, transcription factors and other regulating elements. The largest number of upregulated genes belonged to the cell wall category; many of those were specifically upregulated in fibres of pulling stem side. The obtained data permit to suggest the mechanism of fibre participation in gravitropic reaction that involves the increase of turgor pressure and the rearrangements of cell wall structure in order to improve contractile properties, and to identify the regulatory elements that operate specifically in the fibres of the pulling stem side making gelatinous phloem fibres an important element of gravitropic response in herbaceous plants.

Anatomical Study of the desert shrub Fagonia L. in Libya

Ten Fagonia species grown in the Libyan Desert were subjected in this study. Fagonia arabica L., Fagonia bruguieri DC, Fagonia cretica L., Fagonia glutinosa Delile, Fagonia indica Burm., Fagonia microphylla Pomel, Fagonia sinaica Boiss, Fagonia schweinfurthii Hadidi, Fagonia tenuifolia Steud. and Fagonia thebaica Boiss. Anatomical characters, include internal structures of both stem and leaves have been subjected in this study. Taxonomical key has been constructed according to internal structure of the stem. The result of the ANOVA tests indicate that five characters; stem outline, number of phloem fiber patches in the cortex, number of parenchyma layers in the cortex, ratio between xylem and vascular bundle; ratio between phloem and stem and ratio between xylem and stem; are highly significant different within the studied species. The previous trials of classification have been discussed according to the obtained results.

Cellulosic fibres of flax recruit both primary and secondary cell wall cellulose synthases during deposition of thick tertiary cell walls and in the course of graviresponse.

Cellulose synthesising complex consists of cellulose synthase (CESA) subunits encoded by a multigene family; different sets of CESA genes are known to be expressed during primary and secondary cell wall formation. We examined the expression of LusCESAs in flax (Linum usitatissimum L.) cellulosic fibres at various stages of development and in the course of graviresponse by means of RNA-Seq and quantitative PCR. Transcripts for both primary and secondary cell wall-related CESAs were abundant in fibres depositing highly cellulosic tertiary cell walls. Gravistimulation of flax plants temporally increased the abundance of CESA transcripts, specifically in phloem fibres located at the pulling stem side. Construction of coexpression networks for LusCESAs revealed that both primary and secondary cell wall-related CESAs were involved in the joint coexpression group in fibres depositing tertiary cell walls, as distinct from other tissues, where these genes were within separate groups. The obtained data suggest that fibres depositing tertiary cell walls have a specific mechanism of cellulose biosynthesis and a specific way of its regulation.

Transcriptome portrait of cellulose-enriched flax fibres at advanced stage of specialization.

Functional specialization of cells is among the most fundamental processes of higher organism ontogenesis. The major obstacle to studying this phenomenon in plants is the difficulty of isolating certain types of cells at defined stages of in planta development for in-depth analysis. A rare opportunity is given by the developed model system of flax (Linum usitatissimum L.) phloem fibres that can be purified from the surrounding tissues at the stage of the tertiary cell wall deposition. The performed comparison of the whole transcriptome profile in isolated fibres and other portions of the flax stem, together with fibre metabolism characterization, helped to elucidate the general picture of the advanced stage of plant cell specialization and to reveal novel participants potentially involved in fibre metabolism regulation and cell wall formation. Down-regulation of all genes encoding proteins involved in xylan and lignin synthesis and up-regulation of genes for the specific set of transcription factors transcribed during tertiary cell wall formation were revealed. The increased abundance of transcripts for several glycosyltransferases indicated the enzymes that may be involved in synthesis of fibre-specific version of rhamnogalacturonan I.

Flowers regulate the growth and vascular development of the inflorescence rachis in Vitis vinifera L.

The rachis, the structural framework of the grapevine (Vitis vinifera L.) inflorescence (and subsequent bunch), consists of a main axis and one or more orders of lateral branches with the flower-bearing pedicels at their fine tips. The rachis is crucial both for support, and transport from the shoot. Earlier suggestions that the flowers per se affect normal rachis development are investigated further in this study. Different percentages (0, 25, 50, 75 or 100) of flowers were removed manually one week before anthesis on field-grown vines. Treatment effects on subsequent rachis development (curvature, vitality, anatomy, starch deposit) were assessed. Sections, both fixed and embedded, and fresh hand-cut were observed by fluorescence and bright-field optics after appropriate staining. Emphasis was on measurement of changes in cross-sectional area of secondary xylem and phloem, and on maturation of fibres and periderm. Specific defects in rachis development were dependent on the percent and location of flower removal one week prior to anthesis. The rachises curved inwards where most of the flowers were removed. When fully de-flowered, they became progressively necrotic from the laterals back to the primary axes and from the distal to the proximal end of those axes, with a concurrent disorganisation of their anatomy. A few remaining groups of flowers prevented desiccation and abscission of the rachis axes proximal to the group, but not distally. Flower removal (50%) reduced rachis elongation, while 75% removal reduced xylem and phloem area and delayed phloem fibre and periderm development. 75% flower removal did not affect starch present in the rachis during berry development. Developing flowers affect the growth and vitality of the rachis and the development of its vascular and support structures. The extent of these effects depends on the cultivar and the number and position of flowers remaining after some are removed one week before anthesis.

RNASeq Analysis of the Shoot Apex of Flax (Linum usitatissimum) to Identify Phloem Fiber Specification Genes.

All of the post-embryonic, above-ground structures of seed plants are generated from the shoot apical meristem (SAM), which acts as a reservoir of stem cells. Members of the flax genus (Linum spp.) have been used historically as models for the study of SAMs (Esau, 1942). Cultivated flax (Linum usitatissimum) is grown in more than 50 countries for its seeds or its stem phloem (bast) fibers (Rubilar et al., 2010). Due to prolonged intrusive growth, and a highly crystalline cellulosic secondary wall, flax phloem fibers are among the longest and strongest cells in plants (Mohanty et al., 2000). In flax, all phloem fibers are derived from primary growth in the shoot apex. Specification of phloem fibers occurs in the apical-most 0.5 mm of the stem, since young phloem fibers can be anatomically distinguished starting 0.4–0.5 mm from the shoot apex (Gorshkova et al., 2003). The molecular mechanisms that govern fiber identity are almost entirely unknown (Gorshkova et al., 2012). Also, in contrast to the significant progress obtained in the past decade toward understanding xylem differentiation, information about the phloem fiber differentiation is very scarce (De Rybel et al., 2016). In the past decade, shoot apex transcriptomes have been described in various plants, including maize, pea, soybean, rice, Arabidopsis and chickpea, but none of these produce significant primary phloem fibers (Ohtsu et al., 2007; Wong et al., 2008; Haerizadeh et al., 2009; Jiao et al., 2009; Yadav et al., 2009; Wang et al., 2014). Most molecular and cellular research on flax fiber has thus far focused on later stages of development (Day et al., 2005; Roach and Deyholos, 2007; Fenart et al., 2010). Differential transcript expression data from the region of the shoot apex in which fiber specification occurs would complement other approaches (e.g., mutant screening) aimed at understanding primary phloem fiber differentiation.

Development of gravitropic response: unusual behavior of flax phloem G-fibers.

The major mechanism of gravitropism that is discussed for herbal plants is based on the nonuniform elongation of cells located on the opposite stem sides, occurring in the growing zone of an organ. However, gravitropic response of flax (Linum usitatissimum L.) is well-pronounced in the lower half of developing stem, which has ceased elongation long in advance of plant inclination. We have analyzed the stem curvature region by various approaches of microscopy and found the undescribed earlier significant modifications in primary phloem fibers that have constitutively developed G-layer. In fibers on the pulling stem side, cell portions were widened with formation of "bottlenecks" between them, leading to the "sausage-like" shape of a cell. Lumen diameter in fiber widening increased, while cell wall thickness decreased. Callose was deposited in proximity to bottlenecks and sometimes totally occluded their lumen. Structure of fiber cell wall changed considerably, with formation of breaks between G- and S-layers. Thick fibrillar structures that were revealed in fiber cell wall by light microscopy got oblique orientation instead of parallel to the fiber axis one in control plants. The described changes occurred at various combinations of gravitational and mechanical stimuli. Thus, phloem fibers with constitutively formed gelatinous cell wall, located in nonelongating parts of herbal plant, are involved in gravitropism and may become an important element in general understanding of the gravity effects on plants. We suggest flax phloem fibers as the model system to study the mechanism of plant position correction, including signal perception and transduction.

Improving rooting of Lobostemon fruticosus L. cuttings with delayed auxin treatment

Lobostemon fruticosus is a semi-woody shrub used medicinally for treating wounds, blood poisoning, ringworms, skin diseases and syphilis. The material used is mostly wild harvested, leading to decline in natural populations. Propagation and cultivation methods to establish commercial production can assist in conservation of the species. The objective of this study was to determine the effect of delaying rooting hormone application on the success of vegetative propagation of L. fruticosus using basal stem cutting, cut at an angle of 30° at the base. It was done in a mist bed at the Agricultural Research Council-Vegetable and Ornamental Plant Institute (ARC-VOPI) (Pretoria, South Africa) in a factorial randomized complete block design with two growth media (cocopeat and cocopeat+potting soil1:1; v/v), rooting hormone (Seradix No. 1 and control) and six application times, with five replications. The parameters assessed were callus development, rooting percentage, shoot and root length, survival rate and stem cutting anatomical analysis. Rooting percentage significantly increased with delaying the application of rooting hormone for one to two weeks from planting, as compared to the control (without hormone) and hormone application at the time of planting (week zero). Cocopeat medium gave the highest rooting percentage (67.1%) and lowest mortality rate (18%), whereas potting soil+cocopeat medium gave the lowest root development (31.5%). Anatomical observations in this study showed that with delayed auxin application up to two weeks after planting, the callus tissue started to develop from the vascular cambium close to the cut end of the cutting. Parenchyma gaps in the phloem fiber ring close to the cut end of the cuttings was also observed. This study concludes that delaying hormone application for two weeks after planting improved rooting of L. fruticosus cuttings.

Interaction between secondary phloem and xylem in gravitropic reaction of lateral branches of Tilia cordata Mill. trees

Abstract The tension wood (TW) of Tilia cordata (lime tree) does not contain gelatinous fibers. Based on anatomical studies of secondary phloem (secPhl) and xylem by means of microscopy, digital imaging, and biomechanical tests, it was hypothesized that there is an interaction between the phloem and xylem as a response of gravitropic forces on lateral branches. The goal of the present study was to check this hypothesis. The results demonstrated that dilated phloem rays are longer and wider on the upper side (US) of a branch compared to the lower side (LS) and that the ratio of fiber/ray parenchyma in the phloem is lower on the US of the branches. Bark strips consisting of secPhl with periderm have higher elastic modulus (MOE) on the US of branches. The results support the hypothesis that the compression stress of ray parenchyma may cause phloem fibers to stretch, which may result in the development of axial tensile stresses that are higher on the US of branches. However, the wider rings of xylem formed on the US of branches and the results of biomechanical tests can be interpreted that a higher MOE of wood in the US of lateral branch are the main factors responsible for gravitropic reaction of Tilia branches. TW can be considered as a kind of biotensegrity.

Lignin Deposition in Cotton Cells ? Where is the lignin?

and poplar have been investigated, detailed examination of lignin deposition in agriculturally important crops such as cotton has been very limited. Lignin is a complex polymeric structure of phenolic compounds containing monolignols (coniferyl alcohol (guaiacyl, G-lignin monomer), sinapyl alcohol (sinapyl, S-lignin monomer), p-coumaryl alcohol (hydroxyphenyl, H-lignin monomer) and 5-OH coniferyl alcohol (5-hydroxyguaiacyl, 5-OH G-lignin monomer)) [1]. The key genes involved in lignin biosynthesis have been identified and functionally characterized in model plants allowing the realisation of lignin manipulation for potential useful application in plants (reviewed by Bedon and Legay) [2]. The lignin monomers are generally associated with the plant secondary cell wall (SCW) typified by specialised cells such as xylem vessels, xylem fibres in angiosperms, and tracheids in gymnosperms. The SCWs in these cells function to allow water transport via xylem vessels and tracheids, to provide mechanical support via tracheids, xylem fibres and phloem fibres, and to protect against biotic attack and abiotic stresses. The physical properties of lignin that contribute to its roles in different cell types is highly dependent on its quantity and quality, the latter determined by the ratio of the monolignols and how they are covalently linked. Cotton

A Brief Review on Pharmacognosy, Phytochemistry and Therapeutic Potential ofSolanum IndiumL. used in Indian Systems of Medicine

Solanum indicum L. (Fam. Solanaceae) commonly known as poison berry in English is a prickly, much branched perennial under shrub, nearly upto 1m high, mostly found throughout India in warmer parts upto an elevation of 1500 m. This important medicinal plant is widely used in folk and traditional Indian systems of medicine for poisonous affections, skin diseases, ulcers difficult breathing, abdominal pain, cough and dyspepsia. In Ayurveda and Siddha. It is an important ingredient of dasamoola group of plants. The review attempts to highlight various available literature with respect to the therapeutic uses, enthno-medicinal uses, pharmacognostic studies, chemical constitutes and various reported pharmacological activities. Some steroidal alkaloids/glycoalkaloids such as Solasodine, Solasonine, Solamargine, Solanidine and Solanine were reported by various investigators. Pharmacognostic studies revealed the presence black powdery depositions of sandy crystals, throughout the root, sclerieds in the cortical region, phloem fibres towards the periphery and uni to biseriate medullary rays in xylem and phloem as the diagnostic characters of root of S. indicum. It is reported to have hepatoprotective, anthelmintic, antioxident and antimicrobial activity.

Pharmacognostic studies of the stem bark of Chloroxylon swietenia DC

Chloroxylon swietenia DC. (Family: Rutaceae) is an important traditional medicinal plant used in the treatment of various ailments like fungal infection of skin, rheumatism, common cold, cough, ophthalmic infection and cataract, wounds and as an astringent. However, detailed scientific information is not available to identify the plant material, in order to ascertain its quality and purity. In this paper, we report the pharmacognostic evaluation of the bark for the purpose of its identification and differentiation from related species. The macroscopy, microscopy, physicochemical parameters such as moisture content, ash values, extractive values, fluorescence analysis and preliminary phytochemical analysis of the bark were investigated. Transverse section of the bark shows presence of cork, cortex, medullary rays, and stone cells. Presence of cork, stone cells, phloem fibres and parenchyma cells which were also observed in the powdered sample of the bark. The result of preliminary phytochemical screening indicated presence of alkaloids, steroids, carbohydrates, proteins, phenolic compounds, tannins flavonoids and triterpenoids. The present study will be useful for its identification prior to carrying out further research work. The findings of this study will facilitate pharmacognostic standardization of the plant material and aid in the preparation of a herbal monograph for the species.

Comparative study on secondary xylem and formation of successive cambia in stems and roots of Antigonon leptopus Hook. & Arn. (Polygonaceae)

Antigonon leptopus Hook. & Arn. (Polygonaceae) being a climbing member increases their stem and root diameter by forming successive cambia. The first successive ring of cambium initiates as small segments from the parenchymatous cells located on the inner side of group of primary phloem fibres. These small arcs of cambia produced secondary xylem internally and phloem externally while portion between newly initiated cambial arcs exclusively produce thin walled parenchyma cells on either side. With the increase in age, vessel diameter and their frequency not only decreased in roots but also showed complete absence of wider vessels or observed occasionally in thick roots. In thick stems, strands of lignified derivatives once closely arranged became separated and appeared as embedded in parenchymatous ground mass. At this stage, these parenchyma cells underwent proliferation and formed small arcs of meristematic cells and produce vascular elements. Formation of xylem and phloem from these arcs appear like vascular bundles embedded in conjunctive tissue. Since, major portion of the stem is composed of parenchyma cells, presence of fibre with distinct bordered pits instead of wider vessels might be related with additional mechanical support and to provide additional path for the water conduction in absence of wider vessels in roots.

Lacomucinaea, a new monotypic genus in Thesiaceae (Santalales)

A new monotypic genus from southern Africa is described based on Thesium lineatum. Lacomucinaea lineata has a number of vegetative and floral morphological features that differ from Thesium and other members of Thesiaceae. An apparently unique feature of the plant is the presence of succulent, fusiform, terete leaves that are caducous, eventually leaving a persistent petiolar stub. The stem surface shows striations formed by cortical fibers inside raised ridges. Anatomically, this type of primary phloem fiber bundle also occurs in Osyridicarpos. A molecular phylogenetic analysis using nuclear ribosomal ITS and the chloroplast trnLF spacer for representatives of all genera in Thesiaceae showed that Lacomucinaea is sister to Osyridicarpos, further supporting this relationship suggested by stem anatomy characters. Recognizing this taxon as a distinct genus results in the genus Thesium being monophyletic. A key to all genera in Thesiaceae is provided.

Secondary phloem diversity and evolution in Bignonieae (Bignoniaceae).

Phloem evolution has been explored in the literature across very broad scales, either for vascular plants as a whole or for major plant groups, such as the monocotyledons or the former dicotyledons. However, it has never been examined in a way that would elucidate evolutionary shifts leading to the diversification of phloem in single lineages. Therefore, the present study explores in detail the patterns of phloem evolution in the tribe Bignonieae (Bignoniaceae). This group represents a particularly good model for phloem studies since it is known to have a very conspicuous and diverse phloem. A total of 19 phloem characters were coded in 56 species from all 21 genera currently recognized in the tribe Bignonieae, accounting for phloem wedge growth and for all the anatomical cell diversity encountered in the phloem. Phloem evolution was explored by reconstructing ancestral character states using maximum-likelihood assumptions with a time-calibrated molecular phylogeny for the group. Directionality and the effect of phylogenetic transformations in the current variation of quantitative traits and evolutionary correlations of selected discrete phloem traits were also tested under a maximum-likelihood approach. Individual phloem features are quite diverse in the tribe, but generally conserved within smaller clades. Contrasting phloem patterns were found when comparing major groups, with certain lineages having the phloem marked by a background of phloem fibres where all other cells are embedded, tangentially arranged sieve tubes and sieve-tubecentric parenchyma. In contrast, other lineages exhibited a scarcely fibrous phloem, regularly stratified phloem, sieve tube elements in radial or diffuse arrangement, and diffuse parenchyma. We found signals of directional evolution in fibre abundance and number of sieve areas, which increased in the 'Fridericia and allies extended clade' and decreased in the 'Multiples of four extended clade', resulting in no signal of directionality when the whole Bignonieae was considered. In contrast, no indication of directional evolution was found for the axial parenchyma, either in single clades within Bignonieae or in the entire tribe. Positive correlation was found between sieve element length and both sieve plate type and the presence of a storied structure. Correlated evolution was also found between fibre abundance and several traits, such as sieve tube arrangement, sieve plate type, parenchyma arrangement, ray lignification and number of companion cells. The secondary phloem of Bignonieae is extremely diverse, with sister lineages exhibiting distinct phloem anatomies derived from contrasting patterns of evolution in fibre abundance. Fibre abundance in the tribe has diversified in correlation with sieve tube arrangement, sieve tube morphology, number of companion cells and parenchyma type. The results challenge long-standing hypotheses regarding general trends in cell abundance and morphological cell evolution within the phloem, and demonstrate the need to expand studies in phloem anatomy both at a narrow taxonomic scale and at a broad one, such as to families and orders.

Living cells in wood. 2. Raylessness: histology and evolutionary significance

Raylessness occurs in several hundred species belonging to about 40 families (fewer depending on taxonomic delineation). Fibre distribution (raylessness at first, followed by origin of rays), fibre wall thickness and sclerenchyma at pith margins support the idea that rapid acquisition of mechanical strength is basic to most instances of raylessness. Raylessness may be the most readily available process for achieving mechanical strength in ancestrally herbaceous groups lacking large amounts of phloem and cortical fibres. Raylessness is not a uniform phenomenon and a small number of instances suggest alternative causation, as in two lianas (Cobaea, Thunbergia). Raylessness occurs in only a small number of trees and annuals, but is found in woody herbs, subshrubs and some shrubs. It is indicative of secondary woodiness and wood paedomorphosis. Raylessness would seem to block the radial flow that rays typically provide, but a surprising number of rayless woods have moderately pitted fibres (indicative of flow) and septate or non-septate living fibres. Three-dimensional networks of conjunctive tissues in rayless species with successive cambia (Aizoaceae, Amaranthaceae, Nyctaginaceae) could also provide radial flow avenues. Ontogenetic changes from raylessness to ray presence within the stem of a given species are described and illustrated. Pseudo-raylessness, late-onset raylessness and early-onset raylessness are recognized. Systematic distribution and pertinent literature are given for known instances of raylessness and pseudo-raylessness. Raylessness shows that wood evolution involves not merely change in the abundance and position of cell types, but also redesign and diversification in cell types. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178, 529–555.

Extraction of pectin from flax fiber by chemical means

Purpose – Building the relationship between retting termination and pectin content remained in the fiber is crucial for ensuring the identity quality of retted flax. In order to measure the pectin content, pectin must be removed thoroughly from the fiber. The purpose of this paper is to find the most suitable method to extract pectin from flax phloem fiber. Design/methodology/approach – Methods of extracting pectin from fruits were employed to ensure the complete removal of pectin from flax for the first time, including extraction with ethylene diamine tetraacetic acid, hydrochloric acid and ion exchange resin. Traditional ammonium oxalate-KOH method was adopted as control. Each procedure was optimized according to the yield of pectin. A characteristic chromogenic technique for determining the exact pectin amount was used, which ensured the precise measurement of pectin extracted. Findings – Results showed that comparing with the traditional ammonium oxalate-KOH method, methods of hydrochloric acid and ion exchange resin extract >95 percent (w/w) pectin and the extract conditions are much milder. Originality/value – Bulk of literatures have covered the problem of how to define the quality of retted flax. But the flax industry in China still uses sensory method to check the retting termination. Connect the fiber quality with pectin content is a brand new idea. Also, the exaction method employed from fruit pectin extract is applied in flax pectin for the first time. These methods are essential for building the relationship between the pectin content and retting termination and also significant for discovering the suitable enzyme for enzyme retting.

PtaRHE1, a Populus tremula×Populus alba RING-H2 protein of the ATL family, has a regulatory role in secondary phloem fibre development.

REALLY INTERESTING NEW GENE (RING) proteins play important roles in the regulation of many processes by recognizing target proteins for ubiquitination. Previously, we have shown that the expression of PtaRHE1, encoding a Populus tremula×Populus alba RING-H2 protein with E3 ubiquitin ligase activity, is associated with tissues undergoing secondary growth. To further elucidate the role of PtaRHE1 in vascular tissues, we have undertaken a reverse genetic analysis in poplar. Within stem secondary vascular tissues, PtaRHE1 and its corresponding protein are expressed predominantly in the phloem. The downregulation of PtaRHE1 in poplar by artificial miRNA triggers alterations in phloem fibre patterning, characterized by an increased portion of secondary phloem fibres that have a reduced cell wall thickness and a change in lignin composition, with lower levels of syringyl units as compared with wild-type plants. Following an RNA-seq analysis, a biological network involving hormone stress signalling, as well as developmental processes, could be delineated. Several candidate genes possibly associated with the altered phloem fibre phenotype observed in amiRPtaRHE1 poplar were identified. Altogether, our data suggest a regulatory role for PtaRHE1 in secondary phloem fibre development.