Fiber Cell Development Research Articles

Sphingolipid Profile during Cotton Fiber Growth Revealed That a Phytoceramide Containing Hydroxylated and Saturated VLCFA Is Important for Fiber Cell Elongation.

Cotton fiber is a single-celled seed trichrome that arises from the epidermis of the ovule’s outer integument. The fiber cell displays high polar expansion and thickens but not is disrupted by cell division. Therefore, it is an ideal model for studying the growth and development of plant cells. Sphingolipids are important components of membranes and are also active molecules in cells. However, the sphingolipid profile during fiber growth and the differences in sphingolipid metabolism at different developmental stages are still unclear. In this study, we detected that there were 6 classes and 95 molecular species of sphingolipids in cotton fibers by ultrahigh performance liquid chromatography-MS/MS (UHPLC-MS/MS). Among these, the phytoceramides (PhytoCer) contained the most molecular species, and the PhytoCer content was highest, while that of sphingosine-1-phosphate (S1P) was the lowest. The content of PhytoCer, phytoceramides with hydroxylated fatty acyls (PhytoCer-OHFA), phyto-glucosylceramides (Phyto-GluCer), and glycosyl-inositol-phospho-ceramides (GIPC) was higher than that of other classes in fiber cells. With the development of fiber cells, phytosphingosine-1-phosphate (t-S1P) and PhytoCer changed greatly. The sphingolipid molecular species Ceramide (Cer) d18:1/26:1, PhytoCer t18:1/26:0, PhytoCer t18:0/26:0, PhytoCer t18:1/h20:0, PhytoCer t18:1/h26:0, PhytoCer t18:0/h26:0, and GIPC t18:0/h16:0 were significantly enriched in 10-DPA fiber cells while Cer d18:1/20:0, Cer d18:1/22:0, and GIPC t18:0/h18:0 were significantly enriched in 20-DPA fiber cells, indicating that unsaturated PhytoCer containing hydroxylated and saturated very long chain fatty acids (VLCFA) play some role in fiber cell elongation. Consistent with the content analysis results, the related genes involved in long chain base (LCB) hydroxylation and unsaturation as well as VLCFA synthesis and hydroxylation were highly expressed in rapidly elongating fiber cells. Furthermore, the exogenous application of a potent inhibitor of serine palmitoyltransferase, myriocin, severely blocked fiber cell elongation, and the exogenous application of sphingosine antagonized the inhibition of myriocin for fiber elongation. Taking these points together, we concluded that sphingolipids play crucial roles in fiber cell elongation and SCW deposition. This provides a new perspective for further studies on the regulatory mechanism of the growth and development of cotton fiber cells.

English

Cotton is the world's most important source of renewable fiber, and it is largely utilized in the textile industry to make clothes. In contrast to the ovule epidermis, cotton fibers are single cells that have differentiated from it, making them an attractive model system for the study of polyploidization, production of cell wall and elongation of cell. Plant hormones, that are present in very small low quantities in the plant, play essential roles in a variety of developmental processes, and new research has found that hormones play a critical role in controlling cotton fiber formation, as well as other developmental processes. For example, it has been demonstrated that the exogenous administration of hormones can stimulate the start and development of fiber cells. However, there is currently a lack of a thorough knowledge of phytohormones that regulate the formation of fiber. This paper focuses on latest developments in the understanding of the roles of different phytohormones involved in fiber development, including brassinosteroid, gibberellin, cytokinin, auxin, ethylene and abscisic acid. This paper reviews the discovery of genes associated in hormone biosynthesis and signaling pathways, as well as the methods by which these phytohormones control the commencement and elongation of fiber cells in cotton. All of the hormones involved in fiber formation are beneficial; however, cytokinin and abscisic acid are detrimental. Auxin, gibberellin, brassinosteroid, ethylene, jasmonate, and strigolactones are among the hormones involved in fiber development. A complete analysis of the function of phytohormones in cotton fiber development is our goal.

Mapping-by-sequencing the locus of EMS-induced mutation responsible for tufted-fuzzless seed phenotype in cotton.

Cotton fiber mutants are valuable resources for studying functions of altered genes and their roles in fiber development. The n4t is a recessive tufted-fuzzless seed mutant created through chemical mutagenesis with ethyl methanesulfonate. Genetic analysis indicated that the tufted-fuzzless phenotype is controlled by a single recessive locus. In this study, we developed an F2 population of 602 progeny plants and sequenced the genomes of the parents and two DNA bulks from F2 progenies showing the mutant phenotype. We identified DNA sequence variants between the tufted-fuzzless mutant and wild type by aligning the sequence reads to the reference TM-1 genome and designed subgenome-specific SNP markers. We mapped the n4t locus on chromosome D04 within a genomic interval of about 411kb. In this region, seven genes showed significant differential expression between the tufted-fuzzless mutant and wild type. Possible candidate genes are discussed in this study. The utilization of the n4t mutant along with other fiber mutants will facilitate our understanding of the molecular mechanisms of cotton fiber cell growth and development.

Genome-wide identification and expression analysis of the GhIQD gene family in upland cotton (Gossypium hirsutum L.)

BackgroundCalmodulin (CaM) is one of the most important Ca2+ signaling receptors because it regulates diverse physiological and biochemical reactions in plants. CaM functions by interacting with CaM-binding proteins (CaMBPs) to modulate Ca2+ signaling. IQ domain (IQD) proteins are plant-specific CaMBPs that bind to CaM by their specific CaM binding sites.ResultsIn this study, we identified 102 GhIQD genes in the Gossypium hirsutum L. genome. The GhIQD gene family was classified into four clusters (I, II, III, and IV), and we then mapped the GhIQD genes to the G. hirsutum L. chromosomes. Moreover, we found that 100 of the 102 GhIQD genes resulted from segmental duplication events, indicating that segmental duplication is the main force driving GhIQD gene expansion. Gene expression pattern analysis showed that a total of 89 GhIQD genes expressed in the elongation stage and second cell wall biosynthesis stage of the fiber cells, suggesting that GhIQD genes may contribute to fiber cell development in cotton. In addition, we found that 20 selected GhIQD genes were highly expressed in various tissues. Exogenous application of MeJA significantly enhanced the expression levels of GhIQD genes.ConclusionsOur study shows that GhIQD genes are involved in fiber cell development in cotton and are also widely induced by MeJA. Thw results provide bases to systematically characterize the evolution and biological functions of GhIQD genes, as well as clues to breed better cotton varieties in the future.

Genome-wide characterization of the WAK gene family and expression analysis under plant hormone treatment in cotton

BackgroundWall-associated kinases (WAK), one of the receptor-like kinases (RLK), function directly in the connection and communication between the plant cell wall and the cytoplasm. WAK genes are highly conserved and have been identified in plants, such as rice, but there is little research on the WAK gene family in cotton.ResultsIn the present study, we identified 29 GhWAK genes in Gossypium hirsutum. Phylogenetic analysis showed that cotton WAK proteins can be divided into five clades. The results of synteny and Ka/Ks analysis showed that the GhWAK genes mainly originated from whole genome duplication (WGD) and were then mainly under purifying selection. Transcriptome data and real-time PCR showed that 97% of GhWAK genes highly expressed in cotton fibers and ovules. β-glucuronidase (GUS) staining assays showed that GhWAK5 and GhWAK16 expressed in Arabidopsis leaf trichomes. Fourteen GhWAK genes were found to possess putative gibberellin (GA) response elements in the promoter regions, 13 of which were significantly induced by GA treatment. Ten GhWAK genes contained auxin (IAA) response elements and the expression level of nine GhWAKs significantly increased under auxin treatment.ConclusionsWe provide a preliminary analysis of the WAK gene family in G. hirsutum, which sheds light on the potantial roles of GhWAK genes in cotton fiber cell development. Our data also provides a useful resource for future studies on the functional roles of GhWAK genes.

Macrophage Recruitment in Immune-Privileged Lens During Capsule Repair, Necrotic Fiber Removal and Fibrosis

Emerging evidence of the presence of immune cells challenges the concept of the lens as an immune privileged organ, however, the underlying mechanism remains elusive. Here, we provide a direct mechanism supporting a role of macrophage recruitment in immuno-privileged lens during capsule rupture repair, fiber cell removal and fibrosis. Posterior lens capsule rupture was observed in a connexin (Cx) 50 and aquaporin 0 (AQP0) double knockout (dKO) mouse model. A ruptured posterior lens capsule resulted in lens fiber tissue extrusion into the vitreous cavity, forming a disorganized “tail-like” tissue at postnatal age of 15 days (P15). This “tail-like” tissue also contained hyaloid vessels, fibrotic tissue and macrophages. The regression of the hyaloid vessel system that contains macrophages was delayed. Moreover, fiber cell debris were detected inside the macrophages, suggesting phagocytic engulfment by macrophages. Additionally, necrotic fiber cells were surrounded by macrophages in the “tail-like” lens tissue. These macrophages were reduced after P30, and phenotypically distinct M2 macrophages were detected inside the lens, which coincided with an increase in necrotic fiber cells. By P90, the “tail-like” tissue completely disappeared, and the posterior capsule rupture was healed and replaced with thick fibrotic tissue. Furthermore, administration of colony stimulating factor 1 (CSF-1) activated polarization of macrophages to M2 and accelerated capsule repair, while inhibition of the CSF-1 receptor delayed the repair process. Taken together, these results suggest that necrotic fiber cells associated with lens posterior rupture lead to the recruitment of macrophages, which are delivered by the regression delayed hyaloid vessel system. M2 macrophages activated by CSF-1 mediate capsule rupture repair, fiber cell removal and development of fibrosis.

Jute CDPK genes and their role in stress tolerance and fiber development: A genome-wide bioinformatic investigation of Chorchorus capsularis and C. olitorius

Calcium-dependent protein kinases (CDPKs) are plant-specific calcium sensors, which regulate plant growth and development and induce protective responses to environmental stresses. To date, no information on jute CDPKs is available and their uses in the genetic improvement program is underutilized. In this study, we exploited recently available genome sequence information of two jute species: Corchorus olitorius and C. capsularis to identify, characterise, and functional analysis. Using bioinformatics tools, 16 and 18 CDPK genes with serine/threonine protein kinase along with EF-hand calcium-binding domain were identified from the genomes of C. olitorius and C. capsularis, respectively. Different chromosomes harboured different CDPK genes. Four distinct clades of CDPK genes were identified by phylogenetic analysis. Protein of each clade showed higher conservation in length, structure, and presence of motif. The most prominent transcriptional responses were detected in saline and drought conditions where more than half of the CDPKs were upregulated, suggesting their important roles in abiotic stress responses of jute. Specifically, CoCDPK6, 11, 12, and their corresponding homologs CcCDPK18, 10, 8 were highly expressed in saline and drought conditions. On the other hand, CoCDPK6, 7, 11, 12, and their homologs CcCDPK18, 17, 10, 8 were highly expressed in fiber cell indicating their involvement in fiber cell development. Our results provide an important foundation for further functional dissection of CDPKs of C. olitorius and C. capsularis for salinity and drought stress adaptation and fiber quality improvement.

Membrane lipid raft organization during cotton fiber development

BackgroundCotton fiber is a single-celled seed trichome that originates from the ovule epidermis. It is an excellent model for studying cell elongation. Along with the elongation of cotton fiber cell, the plasma membrane is also extremely expanded. Despite progress in understanding cotton fiber cell elongation, knowledge regarding the relationship of plasma membrane in cotton fiber cell development remains elusive.MethodsThe plasma membrane of cotton fiber cells was marked with a low toxic fluorescent dye, di-4-ANEPPDHQ, at different stages of development. Fluorescence images were obtained using a confocal laser scanning microscopy. Subsequently, we investigated the relationship between lipid raft activity and cotton fiber development by calculating generalized polarization (GP values) and dual-channel ratio imaging.ResultsWe demonstrated that the optimum dyeing conditions were treatment with 3 μmol·L− 1 di-4-ANEPPDHQ for 5 min at room temperature, and the optimal fluorescence images were obtained with 488 nm excitation and 500–580 nm and 620–720 nm dual channel emission. First, we examined lipid raft organization in the course of fiber development. The GP values were high in the fiber elongation stage (5–10 DPA, days past anthesis) and relatively low in the initial (0 DPA), secondary cell wall synthesis (20 DPA), and stable synthesis (30 DPA) stages. The GP value peaked in the 10 DPA fiber, and the value in 30 DPA fiber was the lowest. Furthermore, we examined the differences in lipid raft activity in fiber cells between the short fiber cotton mutant, Li-1, and its wild-type. The GP values of the Li-1 mutant fiber were lower than those of the wild type fiber at the elongation stage, and the GP values of 10 DPA fibers were lower than those of 5 DPA fibers in the Li-1 mutant.ConclusionsWe established a system for examining membrane lipid raft activity in cotton fiber cells. We verified that lipid raft activity exhibited a low-high-low change regularity during the development of cotton fiber cell, and the pattern was disrupted in the short lint fiber Li-1 mutant, suggesting that membrane lipid order and lipid raft activity are closely linked to fiber cell development.

Modification of phytosterol composition influences cotton fiber cell elongation and secondary cell wall deposition

BackgroundCotton fiber is a single cell that arises from the epidermis of ovule. It is not only a main economic product of cotton, but an ideal material for studying on the growth and development of plant cell. Our previous study indicated that phytosterol content and the ratio of campesterol to sitosterol fluctuated regularly in cotton fiber development. However, what effects of modified phytosterol content and composition on the growth and development of cotton fiber cell is unknown. In this study, we overexpressed the GhSMT2–1, a cotton homologue of sterol C-24 methyltransferase 2 gene in transgenic upland cotton plants to modify phytosterol content and composition in fiber cells and investigated the changes on fiber elongation and secondary cell wall deposition.ResultsGhSMT2–1 overexpression led to changes of phytosterol content and the ratio of campesterol to sitosterol in fiber cell. At the rapid elongation stage of fiber cell, total phytosterol and sitosterol contents were increased while campesterol content was decreased in transgenic fibers when compared to control fibers. Accordingly, the ratio of campesterol to sitosterol declined strikingly. Simultaneously, the transgenic fibers were shorter and thicker than control fibers. Exogenous application of sitosterol or campesterol separately inhibited control fiber cell elongation in cotton ovule culture system in vitro. In addition, campesterol treatment partially rescued transgenic fiber elongation.ConclusionThese results elucidated that modification of phytosterol content and composition influenced fiber cell elongation and secondary cell wall formation. High sitosterol or low ratio of campesterol to sitosterol suppresses fiber elongation and/or promote secondary cell wall deposition. The roles of sitosterol and campesterol were discussed in fiber cell development. There might be a specific ratio of campesterol to sitosterol in different developmental stage of cotton fibers, in which GhSMT2–1 play an important role. Our study, at a certain degree, provides novel insights into the regulatory mechanisms of fiber cell development.

Quantitative trait locus mapping of Populus bark features and stem diameter

BackgroundBark plays important roles in photosynthate transport and storage, along with physical and chemical protection. Bark texture varies extensively among species, from smooth to fissured to deeply furrowed, but its genetic control is unknown. This study sought to determine the main genomic regions associated with natural variation in bark features and stem diameter. Quantitative trait loci (QTL) were mapped using an interspecific pseudo-backcross pedigree (Populus trichocarpa x P. deltoides and P. deltoides) for bark texture, bark thickness and diameter collected across three years, two sites and three biological replicates per site.ResultsQTL specific to bark texture were highly reproducible in shared intervals across sites, years and replicates. Significant positive correlations and co-localization between trait QTL suggest pleiotropic regulators or closely linked genes. A list of candidate genes with related putative function, location close to QTL maxima and with the highest expression level in the phloem, xylem and cambium was identified.ConclusionCandidate genes for bark texture included an ortholog of Arabidopsis ANAC104 (PopNAC128), which plays a role in lignified fiber cell and ray development, as well as Pinin and Fasciclin (PopFLA) genes with a role in cell adhesion, cell shape and migration. The results presented in this study provide a basis for future genomic characterization of genes found within the QTL for bark texture, bark thickness and diameter in order to better understand stem and bark development in Populus and other woody perennial plants. The QTL mapping approach identified a list of prime candidate genes for further validation using functional genomics or forward genetics approaches.

Interaction between calcium and potassium modulates elongation rate in cotton fiber cells

Calcium (Ca2+) is necessary for fiber cell development in cotton (Gossypium hirsutum), both as a cell wall structural component and for environmental signaling responses. It is also known that potassium (K+) plays a critical role in cotton fiber cell elongation. However, it is unclear whether Ca2+ integrates its activities with K+ to regulate fiber elongation. Here, we report the novel discovery that Ca2+ deficiency, when integrated with K+ signaling, promotes fiber elongation. Using inductively coupled plasma-mass spectrometry (ICP-MS), we determined dynamic profiles of the ionome in ovules and fibers at different developmental stages, and found that a high accumulation of macro-elements, but not Ca2+, was associated with longer fibers. Using an in vitro ovule culture system, we found that under Ca2+-deficient conditions, sufficient K+ (52 mM) rapidly induced ovule and fiber browning, while reduced K+ (2 or 27 mM) not only suppressed tissue browning but also altered fiber elongation. Reduced K+ also enhanced reactive oxygen species scavenging ability and maintained abscisic acid and jasmonic acid levels, which in turn compensated for Ca2+ deficiency. Ca2+ deficiency combined with reduced K+ (0 mM Ca2+ and 27 mM K+) produced longer fibers in cultured ovules, due to cell wall loosening by phytosulfokine (PSK), expansin (EXP), and xyloglucan endotransglycosylase/hydrolase (XTH), and an increase of the K+ content of fiber cells. Using transgenic cotton, we showed that the CBL-INTERACTING PROTEIN KINASE 6 (GhCIPK6) gene mediates the uptake of K+ under Ca2+-deficient conditions. This study establishes a new link between Ca2+, K+, and fiber elongation.

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The cotton β-galactosyltransferase 1 (GalT1) that galactosylates arabinogalactan proteins participates in controlling fiber development.

Arabinogalactan proteins (AGPs) are highly glycosylated proteins that play pivotal roles in diverse developmental processes in plants. Type-II AG glycans, mostly O-linked to the hydroxyproline residues of the protein backbone, account for up to 95% w/w of the AGP, but their functions are still largely unclear. Cotton fibers are extremely elongated single-cell trichomes on the seed epidermis; however, little is known of the molecular basis governing the regulation of fiber cell development. Here, we characterized the role of a CAZy glycosyltransferase 31 (GT31) family member, GhGalT1, in cotton fiber development. The fiber length of the transgenic cotton overexpressing GhGalT1 was shorter than that of the wild type, whereas in the GhGalT1-silenced lines there was a notable increase in fiber length compared with wild type. The carbohydrate moieties of AGPs were altered in fibers of GhGalT1 transgenic cotton. The galactose: arabinose ratio of AG glycans was higher in GhGalT1 overexpression fibers, but was lower in GhGalT1-silenced lines, compared with that in the wild type. Overexpression of GhGalT1 upregulates transcript levels of a broad range of cell wall-related genes, especially the fasciclin-like AGP (FLA) backbone genes. An enzyme activity assay demonstrated that GhGalT1 is a β-1,3-galactosyltransferase (β-1,3-GalT) involved in biosynthesis of the β-1,3-galactan backbone of the type-II AG glycans of AGPs. We also show that GhGalT1 can form homo- and heterodimers with other cotton GT31 family members to facilitate AG glycan assembly of AGPs. Thus, our data demonstrate that GhGalT1 influences cotton fiber development via controlling the glycosylation of AGPs, especially FLAs.

Development of Fiber and Textile-Shaped Organic Solar Cells for Smart Textiles

Photovoltaic textiles consisting of fiber-shaped organic photovoltaic cells provide power for diverse electronic devices including flexible and wearable devices. In the present study, fiber-shaped organic photovoltaic cells with an inverted polymer-fullerene bulk-heterojunction structure were successfully fabricated by solution processing of all functional layers under ambient conditions. The transparent resin coating greatly enhanced the photovoltaic performance and the sealed photovoltaic fibers showed an electrical power output up to 4.6 and 0.14 mW/cm2 under the sunlight and indoor light irradiation conditions. In addition,the coated fibers were stably woven into textiles. The obtained photovoltaic textiles showed excellent flexibility and foldability in addition to power generation characteristics. These results have opened up the possibility of development of flexible, lightweight, low-cost, and scalable fiber-based organic photovoltaic textiles.

Cloning and Functional Analysis of the Promoter of an Ascorbate Oxidase Gene from Gossypium hirsutum.

Apoplastic ascorbate oxidase (AO) plays significant roles in plant cell growth. However, the mechanism of underlying the transcriptional regulation of AO in Gossypium hirsutum remains unclear. Here, we obtained a 1,920-bp promoter sequence from the Gossypium hirsutum ascorbate oxidase (GhAO1) gene, and this GhAO1 promoter included a number of known cis-elements. Promoter activity analysis in overexpressing pGhAO1::GFP-GUS tobacco (Nicotiana benthamiana) showed that the GhAO1 promoter exhibited high activity, driving strong reporter gene expression in tobacco trichomes, leaves and roots. Promoter 5’-deletion analysis demonstrated that truncated GhAO1 promoters with serial 5’-end deletions had different GUS activities. A 360-bp fragment was sufficient to activate GUS expression. The P-1040 region had less GUS activity than the P-720 region, suggesting that the 320-bp region from nucleotide -720 to -1040 might include a cis-element acting as a silencer. Interestingly, an auxin-responsive cis-acting element (TGA-element) was uncovered in the promoter. To analyze the function of the TGA-element, tobacco leaves transformed with promoters with different 5’ truncations were treated with indole-3-acetic acid (IAA). Tobacco leaves transformed with the promoter regions containing the TGA-element showed significantly increased GUS activity after IAA treatment, implying that the fragment spanning nucleotides -1760 to -1600 (which includes the TGA-element) might be a key component for IAA responsiveness. Analyses of the AO promoter region and AO expression pattern in Gossypium arboreum (Ga, diploid cotton with an AA genome), Gossypium raimondii (Gr, diploid cotton with a DD genome) and Gossypium hirsutum (Gh, tetraploid cotton with an AADD genome) indicated that AO promoter activation and AO transcription were detected together only in D genome/sub-genome (Gr and Gh) cotton. Taken together, these results suggest that the 1,920-bp GhAO1 promoter is a functional sequence with a potential effect on fiber cell development, mediated by TGA-element containing sequences, via the auxin-signaling pathway.

Small interfering RNAs from bidirectional transcripts of GhMML3_A12 regulate cotton fiber development.

Natural antisense transcripts (NATs) are commonly observed in eukaryotic genomes, but only a limited number of such genes have been identified as being involved in gene regulation in plants. In this research, we investigated the function of small RNA derived from a NAT in fiber cell development. Using a map-based cloning strategy for the first time in tetraploid cotton, we cloned a naked seed mutant gene (N1 ) encoding a MYBMIXTA-like transcription factor 3 (MML3)/GhMYB25-like in chromosome A12, GhMML3_A12, that is associated with fuzz fiber development. The extremely low expression of GhMML3_A12 in N1 is associated with NAT production, driven by its 3' antisense promoter, as indicated by the promoter-driven histochemical staining assay. In addition, small RNA deep sequencing analysis suggested that the bidirectional transcriptions of GhMML3_A12 form double-stranded RNAs and generate 21-22nt small RNAs. Therefore, in a fiber-specific manner, small RNA derived from the GhMML3_A12 locus can mediate GhMML3_A12 mRNA self-cleavage and result in the production of naked seeds followed by lint fiber inhibition in N1 plants. The present research reports the first observation of gene-mediated NATs and siRNA directly controlling fiber development in cotton.

Functional divergence of GhCFE5 homoeologs revealed in cotton fiber and Arabidopsis root cell development

In GhCFE5 homoeologs, GhCFE5D interacted with more actin homologs and stronger interaction activity than GhCFE5A. GhCFE5D - but not GhCFE5A -overexpression severely disrupted actin cytoskeleton organization and significantly suppressed cell elongation. Homoeologous genes are common in polyploid plants; however, their functional divergence is poorly elucidated. Allotetraploid Upland cotton (Gossypium hirsutum, AADD) is the most widely cultivated cotton; accounting for more than 90% of the world's cotton production. Here, we characterized GhCFE5A and GhCFE5D homoeologs from G. hirsutum acc TM-1. GhCFE5 homoeologs are expressed preferentially in fiber cells; and a significantly greater accumulation of GhCFE5A mRNA than GhCFE5D mRNA was found in all tested tissues. Overexpression of GhCFE5D but not GhCFE5A seriously inhibits the Arabidopsis hypocotyl and root cell elongation. Yeast two-hybrid assay and bimolecular fluorescence complementation (BiFC) analysis showed that compared with GhCFE5A, GhCFE5D interacts with more actin homologs and has a stronger interaction activity both from Arabidopsis and Upland cotton. Interestingly, subcellular localization showed that GhCFE5 resides on the cortical endoplasmic reticulum (ER) network and is colocalized with actin cables. The interaction activities between GhCFE5 homoeologs and actin differ in their effects on F-actin structure in transgenic Arabidopsis root cells. The F-actin changed direction from vertical to lateral, and the actin cytoskeleton organization was severely disrupted in GhCFE5D-overexpressing root cells. These data support the functional divergence of GhCFE5 homoeologs in the actin cytoskeleton structure and cell elongation, implying an important role for GhCFE5 in the evolution and selection of cotton fiber.

An Epha4/Sipa1l3/Wnt pathway regulates eye development and lens maturation.

The signal-induced proliferation-associated family of proteins comprises four members, SIPA1 and SIPA1L1-3. Mutations of the human SIPA1L3 gene result in congenital cataracts. In Xenopus, loss of Sipa1l3 function led to a severe eye phenotype that was distinguished by smaller eyes and lenses including lens fiber cell maturation defects. We found a direct interaction between Sipa1l3 and Epha4, building a functional platform for proper ocular development. Epha4 deficiency phenocopied loss of Sipa1l3 and rescue experiments demonstrated that Epha4 acts upstream of Sipa1l3 during eye development, with both Sipa1l3 and Epha4 required for early eye specification. The ocular phenotype, upon loss of either Epha4 or Sipa1l3, was partially mediated by rax We demonstrate that canonical Wnt signaling is inhibited downstream of Epha4 and Sipa1l3 during normal eye development. Depletion of either Sipa1l3 or Epha4 resulted in an upregulation of axin2 expression, a direct Wnt/β-catenin target gene. In line with this, Sipa1l3 or Epha4 depletion could be rescued by blocking Wnt/β-catenin or activating non-canonical Wnt signaling. We therefore conclude that this pathomechanism prevents proper eye development and maturation of lens fiber cells, resulting in congenital cataracts.

Transposable elements play an important role during cotton genome evolution and fiber cell development.

Transposable elements (TEs) usually occupy largest fractions of plant genome and are also the most variable part of the structure. Although traditionally it is hallmarked as "junk and selfish DNA", today more and more evidence points out TE's participation in gene regulations including gene mutation, duplication, movement and novel gene creation via genetic and epigenetic mechanisms. The recently sequenced genomes of diploid cottons Gossypium arboreum (AA) and Gossypium raimondii (DD) together with their allotetraploid progeny Gossypium hirsutum (AtAtDtDt) provides a unique opportunity to compare genome variations in the Gossypium genus and to analyze the functions of TEs during its evolution. TEs accounted for 57%, 68.5% and 67.2%, respectively in DD, AA and AtAtDtDt genomes. The 1,694 Mb A-genome was found to harbor more LTR(long terminal repeat)-type retrotransposons that made cardinal contributions to the twofold increase in its genome size after evolution from the 775.2 Mb D-genome. Although the 2,173 Mb AtAtDtDt genome showed similar TE content to the A-genome, the total numbers of LTR-gypsy and LTR-copia type TEs varied significantly between these two genomes. Considering their roles on rewiring gene regulatory networks, we believe that TEs may somehow be involved in cotton fiber cell development. Indeed, the insertion or deletion of different TEs in the upstream region of two important transcription factor genes in At or Dt subgenomes resulted in qualitative differences in target gene expression. We suggest that our findings may open a window for improving cotton agronomic traits by editing TE activities.

Fiber cell development and fiber yield of flax (Linum usitatissimum L.) affected by the seasonal temperature pattern

Du, G.-H., Liu, F.-H. and Rowland, G. 2015. Fiber cell development and fiber yield of flax (Linum usitatissimum L.) affected by the seasonal temperature pattern. Can. J. Plant Sci. 95: 1215–1220. Three fiber flax cultivars ‘Ariane’, ‘Argos’ and ‘Viking’ were cultured in growth chambers under three seasonal temperature patterns (STPs) [parabolic (P), anti-parabolic (AP) and quasi-horizontal (QH) configurations]. The effect of STP was studied on fiber cell development and on fiber yield. The results indicated that, compared with the quasi-horizontal seasonal temperature pattern (QH-STP), the size of fiber cell cavity (SFCC) and fiber content (FC) decreased under parabolic seasonal temperature pattern (P-STP). However, the size of fiber cell (SFC) and SFCC decreased, but the number of fiber cells per bundle (NFCB) increased under anti-parabolic seasonal temperature pattern (AP-STP). Moreover, there was a significant positive correlation between fiber weight (FW) and width of fiber bundle (WFB), also between FC and NFCB. Considering the response of fiber flax cultivars to the different STPs, ‘Ariane’ had smaller SFC and SFCC, thinner thickness of fiber cell wall (TFCW) under AP-STP, and smaller SFCC and thicker TFCW under P-STP than under QH-STP, while ‘Argos’ had smaller SFC and SFCC, and higher NFCB under AP-STP, and smaller SFC under P-STP than under QH-STP. However, STPs had little effect on the fiber cell development of ‘Viking’. All three cultivars had high FC under AP-STP than under P-STP. These observations indicate that the fiber cell development and fiber yield of flax were related to the STP and suggest that AP-STP are the most favorable temperature conditions for fiber flax growth.