Pectin Deposition Research Articles

Nickel oxide nanoparticles induce cell wall modifications, root anatomical changes, and nitrosative signaling in ecotypes of Ni hyperaccumulator Odontarrhena lesbiaca

The industrial application and environmental release of nickel oxide NPs (NiO NPs) is increasing, but the details of their relationship with plants are largely unknown. In this work, the cellular, tissue, organ, and molecular level responses of three ecotypes of Ni hyperaccumulator Odontarrhena lesbiaca grown in the presence of high doses of NiO NP (250 mg/L and 500 mg/L) were studied. All three ecotypes showed a similar accumulation of Ni in the presence of nano Ni, and in the case of NiO NPs, the root-to-shoot Ni translocation was slighter compared to the bulk Ni. In all three ecotypes, the walls of the root cells effectively prevented internalization of NiO NPs, providing cellular defense against Ni overload. Exposure to NiO NP led to an increase in cortex thickness and the deposition of lignin-suberin and pectin in roots, serving as a tissue-level defense mechanism against excessive Ni. Exposure to NiO NP did not modify or cause a reduction in some biomass parameters of the Ampeliko and Loutra ecotypes, while it increased all parameters in Olympos. The free salt form of Ni exerted more negative effects on biomass production than the nanoform, and the observed effects of NiO NPs can be attributed to the release of Ni ions. Nitric oxide and peroxynitrite levels were modified by NiO NPs in an ecotype-dependent manner. The changes in the abundance and activity of S-nitrosoglutathione reductase protein triggered by NiO NPs suggest that the enzyme is regulated by NiO NPs at the post-translational level. The NiO NPs slightly intensified protein tyrosine nitration, and the slight differences between the ecotypes were correlated with their biomass production in the presence of NiO NPs. Overall, the Odontarrhena lesbiaca ecotypes exhibited tolerance to NiO NPs at the cellular, tissue, organ/organism and molecular levels, demonstrating various defense mechanisms and changes in the metabolism of reactive nitrogen species metabolism and nitrosative protein modification.

Pectin degree of esterification influences rheology and digestibility of whey protein isolate-pectin stabilized bilayer oil-in-water nanoemulsions

Gelation in nanoemulsions happens at a lower oil volume fraction ( φ ) compared to conventional emulsions due to the increasing contribution of interfacial shell-layer thickness. In this study, the shell-layer thickness was increased by depositing a second layer of pectin on whey protein isolate (WPI)-stabilized nanodroplets. Pectin with two different degrees of esterification (DE), 33% and 73%, was used to investigate the effect of interfacial charge on the repulsive shell layer thickness. Excess WPI was removed from the primary 20 wt% canola oil-in-water nanoemulsion stabilized with 4 wt% WPI (pH 7) by ultracentrifugation before pectin addition. At pH 7, the added pectin remained in the continuous phase and led to almost two orders of magnitude increase in emulsion viscosity, but they were flowable. Changing to pH 3 led to electrostatic complexation of pectin with WPI either mostly in the aqueous phase for the emulsions with excess proteins (WTEP) or at the oil droplet surface for the emulsions without excess proteins (WOEP). The addition of pectin transformed the liquid primary emulsions into viscoelastic gels at only 20 wt% oil due to extensive droplet aggregation for the emulsion WTEP. For the emulsion WOEP, gelation was manifested by the close packing of repulsive droplets. The higher pectin charge (DE33) increased the gel strength of bilayer emulsions compared to the lower pectin charge (DE73) due to the charge cloud-induced enhanced interfacial repulsive barrier. The deposition of pectin also reduced lipid digestibility from 37.2% for the monolayer emulsions to 24.0% and 16.1% for DE73 and DE33-coated bilayer emulsions, respectively. Such findings can be used to better understand and modify the rheological and digestion properties of repulsive emulsion gels for application in reduced fat foods. • WPI-pectin bilayer nanoemulsion was created using layer-by-layer electrostatic deposition. • Excess whey protein in the continuous phase led to attractive gelation in nanoemulsion. • Removal of excess protein led to repulsive gelation in bilayer nanoemulsion. • Higher pectin charge was more effective in enhancing repulsive gelation in bilayer nanoemulsions. • Lipid digestibility was reduced with pectin bilayer and increasing pectin charge.

The trans-Golgi-localized protein BICAT3 regulates manganese allocation and matrix polysaccharide biosynthesis.

Manganese (Mn2+) is essential for a diversity of processes, including photosynthetic water splitting and the transfer of glycosyl moieties. Various Golgi-localized glycosyltransferases that mediate cell wall matrix polysaccharide biosynthesis are Mn2+ dependent, but the supply of these enzymes with Mn2+ is not well understood. Here, we show that the BIVALENT CATION TRANSPORTER 3 (BICAT3) localizes specifically to trans-cisternae of the Golgi. In agreement with a role in Mn2+ and Ca2+ homeostasis, BICAT3 rescued yeast (Saccharomyces cerevisiae) mutants defective in their translocation. Arabidopsis (Arabidopsis thaliana) knockout mutants of BICAT3 were sensitive to low Mn2+ and high Ca2+ availability and showed altered accumulation of these cations. Despite reduced cell expansion and leaf size in Mn2+-deficient bicat3 mutants, their photosynthesis was improved, accompanied by an increased Mn content of chloroplasts. Growth defects of bicat3 corresponded with an impaired glycosidic composition of matrix polysaccharides synthesized in the trans-Golgi. In addition to the vegetative growth defects, pollen tube growth of bicat3 was heterogeneously aberrant. This was associated with a severely reduced and similarly heterogeneous pectin deposition and caused diminished seed set and silique length. Double mutant analyses demonstrated that the physiological relevance of BICAT3 is distinct from that of ER-TYPE CA2+-ATPASE 3, a Golgi-localized Mn2+/Ca2+-ATPase. Collectively, BICAT3 is a principal Mn2+ transporter in the trans-Golgi whose activity is critical for specific glycosylation reactions in this organelle and for the allocation of Mn2+ between Golgi apparatus and chloroplasts.

Effect of boron toxicity on pollen tube cell wall architecture and the relationship of cell wall components of Castanea mollissima Blume.

Boron (B) is essential to plant development. However, excessive B is toxic to plants. This research was performed to evaluate the effects of B toxicity on cell wall architecture of Chinese chestnut (Castanea mollissima Blume) pollen tubes with emphasis on the relationship among pectins, cellulose, and callose. Results showed that 0.8 mM H3BO3 inhibited pollen germination and led to abnormal morphology of the pollen tubes. B toxicity also affected the distribution of cell wall components of the pollen tube. In control pollen tube, esterified and acid pectins were distributed unevenly, with the former mainly at the tip and the latter on the distal region. Cellulose was distributed uniformly on the surface with less at the tip; callose reduced gradually from base to sub-tip of the pollen tubes and no callose at the tip of the tube was detected. B toxicity led to the deposition of esterified and acid pectins, cellulose, and callose at the tip of the pollen tube. Results from scanning electron microscopy and transmission electron microscopy showed that B toxicity also altered pollen tube wall ultrastructure. The results from enzymatic treatment illustrated that there existed a close relationship among pectins, cellulose, and callose. B toxicity also altered the relationship. In a word, B toxicity altered deposition and relationship of pectins, cellulose, and callose of pollen tube wall.

Edible multilayer coating using electrostatic layer‐by‐layer deposition of chitosan and pectin enhances shelf life of fresh strawberries

SummaryThis study aimed to develop an edible multilayer coating by electrostatic layer‐by‐layer deposition (LbL) of chitosan‐pectin biopolymers to extend the shelf life of strawberries. A fixed concentration of chitosan (2% w/v) and varying pectin concentrations (0.25–1% w/v) in an LbL sequence were initially applied to coat on the low‐density polyethylene (LDPE) film. The successful assembly of these biopolymers in the LDPE film was confirmed by their zeta potential (chitosan, +43 mV and pectin, −36 to −42 mV) and Fourier transform infrared (FTIR) spectroscopy in the range of 1800–1600 cm‐1 indicating the strong interactions between chitosan and pectin. Chitosan (2% w/v) and pectin (0.25% w/v) had the lowest water vapour permeability (WVP) of 1.86 ± 0.02 × 10−9 in gday‐1 m‐1 Pa‐1 among all other formulations. The application of the coating on strawberries extended the shelf life (9 days) compared to the control (6 days) at room temperature (25 °C) while still retaining the colour, firmness and pH of strawberries. The results obtained illuminate the potential application of safer, ecofriendly and sustainable packaging materials in the food industry.

Analyses of Microstructure and Dynamic Deposition of Cell Wall Components in Xylem Provide Insights into Differences between Two Black Poplar Cultivars

The chemical composition of the cell wall varies between species and even within the same species, and impacts the properties of the cell wall. In this study, the dynamic chemical compositions of the xylem cell walls of two black poplar cultivars, Populus × euramericana ‘Zhonglin46’ and Populus × euramericana ‘Neva,’ were investigated in situ using stimulated Raman scattering microscopy (SRS). Meanwhile, the pectin structural features were examined using immunofluorescence methods. The results showed that Neva displayed faster thickening of the fiber cell walls than Zhonglin46 did, and it had a greater cell wall thickness in mature xylem. A faster deposition speed of lignin and cellulose during xylem maturation was revealed in Neva. Significantly higher lignin contents were found in the mature xylem of Neva compared with those of Zhonglin46, while no obvious differences in cellulose deposition in mature xylem were observed between the two cultivars. The patterns of pectin deposition during xylem maturation were similar in the two cultivars, but more pectin was found in the mature xylem of Neva than in that of Zhonglin46. The chemical deposition patterns account for the anatomical feature differences between the cultivars. These results provide valuable insights into the chemical deposition and anatomical differences between cultivars, and they might be helpful in understanding the wood growth processes and facilitating the utilization of different poplar cultivars.

A Golgi-localized manganese transporter functions in pollen tube tip growth to control male fertility in Arabidopsis

Manganese (Mn) serves as an essential cofactor for many enzymes in various compartments of a plant cell. Allocation of Mn among various organelles thus plays a central role in Mn homeostasis to support metabolic processes. We report the identification of a Golgi-localized Mn transporter (named PML3) that is essential for rapid cell elongation in young tissues such as emerging leaves and the pollen tube. In particular, the pollen tube defect in the pml3 loss-of-function mutant caused severe reduction in seed yield, a critical agronomic trait. Further analysis suggested that a loss of pectin deposition in the pollen tube might cause the pollen tube to burst and slow its elongation, leading to decreased male fertility. As the Golgi apparatus serves as the major hub for biosynthesis and modification of cell-wall components, PML3 may function in Mn homeostasis of this organelle, thereby controlling metabolic and/or trafficking processes required for pectin deposition in rapidly elongating cells.

Golgi-localized membrane protein AtTMN1/EMP12 functions in the deposition of rhamnogalacturonan II and I for cell growth in Arabidopsis.

Appropriate pectin deposition in cell walls is important for cell growth in plants. Rhamnogalacturonan II (RG-II) is a portion of pectic polysaccharides; its borate crosslinking is essential for maintenance of pectic networks. However, the overall process of RG-II synthesis is not fully understood. To identify a novel factor for RG-II deposition or dimerization in cell walls, we screened Arabidopsis mutants with altered boron (B)-dependent growth. The mutants exhibited alleviated disorders of primary root and stem elongation, and fertility under low B, but reduced primary root lengths under sufficient B conditions. Altered primary root elongation was associated with cell elongation changes caused by loss of function in AtTMN1 (Transmembrane Nine 1)/EMP12, which encodes a Golgi-localized membrane protein of unknown function that is conserved among eukaryotes. Mutant leaf and root dry weights were lower than those of wild-type plants, regardless of B conditions. In cell walls, AtTMN1 mutations reduced concentrations of B, RG-II specific 2-keto-3-deoxy monosaccharides, and rhamnose largely derived from rhamnogalacturonan I (RG-I), suggesting reduced RG-II and RG-I. Together, our findings demonstrate that AtTMN1 is required for the deposition of RG-II and RG-I for cell growth and suggest that pectin modulates plant growth under low B conditions.

Early development of epiphytic roots: perspectives based on the composition of the velamen cell wall

ABSTRACT The velamen, a root structure of some epiphytic species for water uptake, usually is stratified epidermis consisting of dead cells. In general, its cell walls exhibit variation during development, including in thickness and amount and type of impregnated substances. These changes result in diverse physical and chemical properties that can serve in water and nutrient uptake, as well as in mechanical support and protection. On this basis, the main objective of the current study was to describe the composition of the cell walls of the velamen during the development of the roots of four species of Cattleya. Anatomical, histochemical and immunocytochemical analyses were performed with samples (n=3 individuals per species) of meristematic, developing, and mature regions of the root. The development of the primary wall led to the deposition of pectins as highly methylesterified homogalacturonans, which were demetihylesterified with maturation of the velamen. The deposition of lipids (and subsequently lignins) in velamen cells marked a transition stage to the formation of the secondary wall, which gives rigidity to the tissue. For the first time, we showed that the deposition of lipids and lignins began close to the exodermis in the direction of the epivelamen.

Sucrose starvation induces the degradation of proteins in trans-Golgi network and secretory vesicle cluster in tobacco BY-2 cells.

ER: endoplasmic reticulum; GI-TGN: Golgi-released independent TGN; GFP: green fluorescent protein; mRFP: monomeric red fluorescent protein; P4H1.1: prolyl 4-hydroxylase 1.1; PM: plasma membrane; SCAMP2: secretory carrier membrane protein 2; SUT2: sucrose transporter 2; SVC: secretory vesicle cluster; SYP41: syntaxin of plant 41; TGN: trans-Golgi network; YFP: yellow fluorescent protein.

The combined effects of light intensity, temperature, and water potential on wall deposition in regulating hypocotyl elongation of Brassica rapa.

Hypocotyl elongation is a critical sign of seed germination and seedling growth, and it is regulated by multi-environmental factors. Light, temperature, and water potential are the major environmental stimuli, and their regulatory mechanism on hypocotyl growth has been extensively studied at molecular level. However, the converged point in signaling process of light, temperature, and water potential on modulating hypocotyl elongation is still unclear. In the present study, we found cell wall was the co-target of the three environmental factors in regulating hypocotyl elongation by analyzing the extension kinetics of hypocotyl and the changes in hypocotyl cell wall of Brassica rapa under the combined effects of light intensity, temperature, and water potential. The three environmental factors regulated hypocotyl cell elongation both in isolation and in combination. Cell walls thickened, maintained, or thinned depending on growth conditions and developmental stages during hypocotyl elongation. Further analysis revealed that the imbalance in wall deposition and hypocotyl elongation led to dynamic changes in wall thickness. Low light repressed wall deposition by influencing the accumulation of cellulose, hemicellulose, and pectin; high temperature and high water potential had significant effects on pectin accumulation overall. It was concluded that wall deposition was tightly controlled during hypocotyl elongation, and low light, high temperature, and high water potential promoted hypocotyl elongation by repressing wall deposition, especially the deposition of pectin.

Characterization of the pectin methyl-esterase gene family and its function in controlling pollen tube growth in pear (Pyrus bretschneideri)

Pectin methyl-esterases (PMEs) play crucial roles in plant growth. In this study, we identified 81 PbrPMEs in pear. Whole-genome duplication and purifying selection drove the evolution of PbrPME gene family. The expression of 47 PbrPMEs was detected in pear pollen tube, which were assigned to 13 clusters by an expression tendency analysis. One of the 13 clusters presented opposite expression trends towards the changes of methyl-esterified pectins at the apical cell wall. PbrPMEs were localized in the cytoplasm and plasma membrane. Repression of PbrPME11, PbrPME44, and PbrPME59 resulted in the inhibition of pear pollen tube growth and abnormal deposition of methyl-esterified pectins at pollen tube tip. Pharmacological analysis confirmed that reduced PbrPME activities repressed the pollen tube growth. Overall, we have explored the evolutionary characteristics of PbrPME gene family and found the key PbrPME genes that control the growth of pollen tube, which deepened the understanding of pear fertility regulation.

Drechslerella dactyloides and Dactylaria brochopaga mediated structural defense in tomato plants pre-challenged with Meloidogyne incognita

The present study was undertaken with the objectives to study Drechslerella dactyloides NDAd-05 and Dactylaria brochopaga NDDb-15 mediated induction of structural defense responses leading to lower disease development and promoting growth in tomato pre-challenged with Meloidogyne incognita. The potential strains D. dactyloides NDAd-05 and D. brochopaga NDDb-15 were taken from Plant-Microbe Interaction and Rhizosphere Biology Lab, ICAR-National Bureau of Agriculturally Important Microorganisms, Kushmaur, Maunath Bhanjan, India. In vitro root colonization assay was performed using D. dactyloides NDAd-05 and D. brochopaga NDDb-15 in sand:soil culture (2:1) and significant tomato root colonization by NDAd-05 and NDDb-15 was recorded. The study elucidated multifarious effects of D. dactyloides NDAd-05 and D. brochopaga NDDb-15 when inoculated either individually or in combination in tomato plants pre-challenged with M. incognita. Additionally, D. dactyloides NDAd-05 and D. brochopaga NDDb-15 increased antioxidant as well as biocontrol activities significantly in tomato against M. incognita. Microscopic visualization of H2O2 and superoxide radicals in tomato leaves further corroborated the above findings. Further, inoculation of D. dactyloides NDAd-05 and D. brochopaga NDDb-15 activated the phenylpropanoid pathway in roots leading to increase cell wall lignifications and pectin deposition in tomato roots in addition to direct trapping and parasitizing of juveniles and adults of M. incognita. From the results it can be concluded that increased cell wall lignifications and pectin deposition probably restricted the entry of nematodes and ultimately decreased the M. incognita population in tomato roots. It was also observed that plants treated with bioagents individually or in combination modulated the phenotypical alterations and assisted plant growth promotion. This might be due to the interaction-dependent modulation of physio-biochemical pathways in the tomato plants which ultimately reduced the inoculum potential and disease intensity of M. incognita.

A mechanism for efficient cadmium phytoremediation and high bioethanol production by combined mild chemical pretreatments with desirable rapeseed stalks

Cadmium (Cd) is one of the most hazardous trace metals, and rapeseed is a major oil crop over the world with considerable lignocellulose residues applicable for trace metal phytoremediation and cellulosic ethanol co-production. In this study, we examined that two distinct rapeseed cultivars could accumulate Cd at 72.48 and 43.70 ug/g dry stalk, being the highest Cd accumulation among all major agricultural food crops as previously reported. The Cd accumulation significantly increased pectin deposition as a major factor for trace metal association with lignocellulose. Meanwhile, the Cd-accumulated rapeseed stalks contained much reduced wall polymers (hemicellulose, lignin) and cellulose degree of polymerization, leading to improved lignocellulose enzymatic hydrolysis. Notably, three optimal chemical pretreatments were performed for enhanced biomass enzymatic saccharification and bioethanol production by significantly increasing cellulose accessibility and lignocellulose porosity, along with a complete Cd release for collection and recycling. Hence, this study proposed a mechanism model interpreting why rapeseed stalks are able to accumulate much Cd and how the Cd-accumulated stalks are of enhanced biomass saccharification. It has also provided a powerful technology for both cost-effective Cd phytoremediation and value-added bioethanol co-production with minimum waste release.

CircRNA Expression Pattern and ceRNA and miRNA-mRNA Networks Involved in Anther Development in the CMS Line of Brassica campestris.

Male-sterile plants provide an important breeding tool for the heterosis of hybrid crops, such as Brassicaceae. In the last decade, circular RNAs (circRNAs), as a novel class of covalently closed and single-stranded endogenous non-coding RNAs (ncRNAs), have received much attention because of their functions as “microRNA (miRNA) sponges” and “competing endogenous RNAs” (ceRNAs). However, the information about circRNAs in the regulation of male-sterility and anther development is limited. In this study, we established the Polima cytoplasm male sterility (CMS) line “Bcpol97-05A”, and the fertile line, “Bcajh97-01B”, in Brassica campestris L. ssp. chinensis Makino, syn. B. rapa ssp. chinensis, and performed RNA expression profiling comparisons between the flower buds of the sterile line and fertile line by whole-transcriptome sequencing. A total of 31 differentially expressed (DE) circRNAs, 47 DE miRNAs, and 4779 DE mRNAs were identified. By using Cytoscape, the miRNA-mediated regulatory network and ceRNA network were constructed, and the circRNA A02:23507399|23531438 was hypothesized to be an important circRNA regulating anther development at the post-transcriptional level. The gene ontology (GO) analysis demonstrated that miRNAs and circRNAs could regulate the orderly secretion and deposition of cellulose, sporopollenin, pectin, and tryphine; the timely degradation of lipids; and the programmed cell death (PCD) of tapetum cells, which play key roles in anther development. Our study revealed a new circRNA–miRNA–mRNA network, which is involved in the anther development of B. campestris, which enriched the understanding of CMS in flowering plants, and laid a foundation for further study on the functions of circRNAs and miRNAs during anther development.

Plant AP180 N-Terminal Homolog Proteins Are Involved in Clathrin-Dependent Endocytosis during Pollen Tube Growth in Arabidopsis thaliana.

Polarized cell growth in plants is maintained under the strict control and exquisitely choreographed balance of exocytic and endocytic membrane trafficking. The pollen tube has become a model system for rapid polar growth in which delivery of cell wall material and membrane recycling are controlled by membrane trafficking. Endocytosis plays an important role that is poorly understood. The plant AP180 N-Terminal Homolog (ANTH) proteins are putative homologs of Epsin 1 that recruits clathrin to phosphatidylinositol 4, 5-bisphosphate (PIP2) containing membranes to facilitate vesicle budding during endocytosis. Two Arabidopsis ANTH encoded by the genes AtAP180 and AtECA2 are highly expressed in pollen tubes. Pollen tubes from T-DNA inserted knockout mutant lines display significant morphological defects and unique pectin deposition. Fluorescent tagging reveals organization into dynamic foci located at the lateral flanks of the pollen tube. This precisely defined subapical domain coincides which clathrin-mediated endocytosis (CME) and PIP2 localization. Using a liposome-protein binding test, we showed that AtECA2 protein and ANTH domain recombinant proteins have strong affinity to PIP2 and phosphatidic acid containing liposomes in vitro. Taken together these data suggest that Arabidopsis ANTH proteins may play an important role in CME, proper cell wall assembly and morphogenesis.

Deficiency of AtGFAT1 activity impairs growth, pollen germination and tolerance to tunicamycin in Arabidopsis.

The hexosamine biosynthetic pathway (HBP) plays essential roles in growth and development in plants. However, insight into the biological function of glutamine:fructose-6-phosphate amidotransferase 1 (GFAT1), mediating the first regulatory step of the HBP, remains unclear in plants. Here, we report the molecular characterization of Arabidopsis AtGFAT1 gene. AtGFAT1 was highly expressed in mature pollen grains, but its expression was not detectable in the rest of the organs. Pollen grains bearing the gfat1-2 knockout allele displayed defects in a polar deposition of pectin and callose in the pollen cell wall, leading to no genetic transmission of the gfat1-2 allele through the male gametophyte. AtGFAT1 overexpression increased glucosamine (GlcN) content and enhanced resistance to tunicamycin (Tm) treatment, while RNAi-mediated suppression reduced GlcN content and resistance to Tm treatment. However, the decrease in Tm resistance by RNAi suppression of AtGFAT1 was recovered by a GlcN supplement. The exogenous GlcN supplement also rescued gfat1-2/gaft1-2 mutant plants, which were otherwise not viable. The gfat1-2/gfat1-2 plants stopped growing at the germination stage on GlcN-free medium, but GlcN supplement allowed wild-type growth of gfat1-2/gfat1-2 plants. In addition, reactive oxygen species production, cell death and a decrease in protein N-glycosylation were observed in gfat1-2/gaft1-2 mutant plants grown on GlcN-free medium, whereas these aberrant defects were not detectable on GlcN-sufficient medium. Taken together, these results show that the reduction of protein N-glycosylation was at least partially responsible for many aberrant phenotypes in growth and development as well as the response to Tm treatment caused by AtGFAT1 deficiency in Arabidopsis.

Changes in Fruit Firmness, Cell Wall Composition, and Transcriptional Profile in the yellow fruit tomato 1 ( yft1) Mutant.

Fruit firmness is an important trait in tomato ( Solanum lycopersicum), associated with shelf life and economic value; however, the precise mechanism determining fruit softening remains elusive. A yellow fruit tomato 1 ( yft1) mutant harbors a genetic lesion in the YFT1 gene and has significantly firmer fruit than those of the cv. M82 wild type at a red ripe stage, 54 days post-anthesis (dpa). When softening was further dissected, it was found that the yft1 firm fruit phenotype correlated with a difference in cellulose, hemicellulose, and pectin deposition in the primary cell wall (PCW) compared to cv. M82. Alterations in the structure of the pericarp cells, chemical components, hydrolase activities, and expression of genes encoding these hydrolases were all hypothesized to be a result of the loss of YFT1 function. This was further affirmed by RNA-seq analysis, where a total of 183 differentially expressed genes (DEGs, 50/133 down-/upregulated) were identified between yft1 and cv. M82. These DEGs were mainly annotated as participating in ethylene- and auxin-related signal transduction, sugar metabolism, and photosynthesis. This study provides new insights into the mechanism underlying the control of fruit softening.

Golgi-localized LOT regulates trans-Golgi network biogenesis and pollen tube growth

The trans-Golgi network (TGN) is an essential tubular-vesicular organelle derived from the Golgi and functions as an independent sorting and trafficking hub within the cell. However, the molecular regulation of TGN biogenesis remains enigmatic. Here we identified an Arabidopsis mutant loss of TGN (lot) that is defective in TGN formation and sterile due to impaired pollen tube growth in the style. The mutation leads to overstacking of the Golgi cisternae and significant reduction in the number of TGNs and vesicles surrounding the Golgi in pollen, which is corroborated by the dispersed cytosolic distribution of TGN-localized proteins. Consistently, deposition of extracellular pectin and plasma membrane localization of kinases and phosphoinositide species are also impaired. Subcellular localization analysis suggests that LOT is localized on the periphery of the Golgi cisternae, but the mutation does not affect the localization of Golgi-resident proteins. Furthermore, the yeast complementation result suggests that LOT could functionally act as a component of the guanine nucleotide exchange factor (GEF) complex of small Rab GTPase Ypt6. Taken together, these findings suggest that LOT is a critical player for TGN biogenesis in the plant lineage.

Soybean oleosomes studied by small angle neutron scattering (SANS)

HypothesisOleosomes are stabilized by a complex outer phospholipid-protein-layer. To improve understanding of its structure and stabilization mechanism, this shell has to be studied in extracellular native conditions. This should be possible by SANS using contrast variation. Oleosomes are expected to be highly temperature stable, with molecular changes occurring first in the protein shell. Direct measurements of changes in the shell structure are also important for processing methods, e.g. encapsulation. ExperimentsExtracted soybean oleosomes were studied directly and after encapsulation with pectin by SANS using contrast variation. In order to determine structure and size, a shell model of oleosomes was developed. The method was tested against a simple phospholipid-stabilized emulsion. The oleosomes’ temperature stability was investigated by performing SANS at elevated temperatures. FindingsSize (Rg = 1380 Å) and shell thickness of native and encapsulated oleosomes have been determined. This is the first report measuring the shell thickness of oleosomes directly. For native oleosomes, a shell of 9 nm thickness surrounds the oil core, corresponding to a layer of phospholipids and proteins. Up to 90 °C, no structural change was observed, confirming the oleosomes’ high temperature stability. Successful coavervation of oleosomes was shown by an increase in shell thickness of 10 nm after electrostatic deposition of pectin.