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Naturally colored cotton varieties attract investigators due to their eco-friendly and hypoallergenic properties. Genetic mechanisms, determining control of pigment biosynthesis pathway in cotton fiber, are being intensively studied nowadays. However, the knowledge, explaining control of proanthocyanidins accumulation in cotton fiber by the MBW complex (R2R3-Myb, bHLH-Myc and WD40), is insufficient. In this connection, we focused on the regulatory genes from a number of the most likely ones involved in proanthocyanidins biosynthesis. We used the Sanger sequencing approach to reveal the allelic diversity of the R2R3-Myb and bHLH-Myc genes among contrast genotype accessions including various fiber shades and hypocotyl color. Having used the number of bioinformatics tools, we concluded that the replacement of conserved tryptophan residue abolished the DNA-binding activity of the GhMYB10-A transcription factor and this, probably, can be associated with the light brown fiber phenotype. Deeper studies are required to definitely establish the GhMYB10-A function. However, our achievements can be practically applied in marker-assisted breeding of cotton varieties with naturally colored fiber.

Brown cotton is a major cultivar of naturally colored cotton, and brown cotton fibers (BCFs) are widely utilized as raw materials for textile industry production due to their advantages of being green and dyeing-pollution-free. However, the mechanisms underlying the pigmentation in fibers are still poorly understood, which significantly limits their extensive applications in related fields. In this study, we conducted a multidimensional comparative analysis of the transcriptomes and metabolomes between brown and white fibers at different developmental periods to identify the key genes and pathways regulating the pigment deposition. The transcriptomic results indicated that the pathways of flavonoid biosynthesis and phenylpropanoid biosynthesis were significantly enriched regulatory pathways, especially in the late development periods of fiber pigmentation; furthermore, the genes distributed in the pathways of PAL, CHS, F3H, DFR, ANR, and UFGT were identified as significantly up-regulated genes. The metabolic results showed that six metabolites, namely (−)-Epigallocatechin, Apiin, Cyanidin-3-O-glucoside, Gallocatechin, Myricetin, and Poncirin, were significantly accumulated in brown fibers but not in white fibers. Integrative analysis of the transcriptomic and metabolomic data demonstrated a possible regulatory network potentially regulating the pigment deposition, in which three MYB transcription factors promote the expression levels of flavonoid biosynthesis genes, thereby inducing the content increase in (−)-Epigallocatechin, Cyanidin-3-O-glucoside, Gallocatechin, and Myricetin in BCFs. Our findings provide new insights into the pigment deposition mechanism in BCFs and offer references for genetic engineering and breeding of colored cotton materials. [ABSTRACT FROM AUTHOR]

Naturally colored cotton (NCC) offers an environmentally friendly fiber for textile applications. Processing white cotton fiber into textiles requires extensive energy, water, and chemicals, whereas processing of NCC skips the most polluting activity, scouring-bleaching and dyeing; therefore, NCC provides an avenue to minimize the harmful impacts of textile production. NCC varieties are suitable for organic agriculture since they are naturally insect and disease-resistant, salt and drought-tolerant. Various fiber shades, ranging from light green to tan and brown, are available in the cultivated NCC (Gossypium hirsutum L.) species. The pigments responsible for the color of brown cotton fiber are proanthocyanidins or their derivatives synthesized by the flavonoid pathway. Due to pigments, the NCC has excellent ultraviolet protection properties. Some brown cotton varieties exhibited superior thermal resistance of fiber that can be used to make fabrics with enhanced flame retardancy. Here, we review molecular mechanisms involved in the pigment production of brown cotton and challenges in breeding NCC varieties with a wide range of colors but without penalty in fiber quality. Also, we discuss opportunities for NCC with flame-retarding properties in textile applications. [ABSTRACT FROM AUTHOR]

Naturally colored cotton (NCC) offers an environmentally friendly fiber for textile applications. Processing white cotton fiber into textiles requires extensive energy, water, and chemicals, whereas processing of NCC skips the most polluting activity, scouring-bleaching and dyeing; therefore, NCC provides an avenue to minimize the harmful impacts of textile production. NCC varieties are suitable for organic agriculture since they are naturally insect and disease-resistant, salt and drought-tolerant. Various fiber shades, ranging from light green to tan and brown, are available in the cultivated NCC (Gossypium hirsutum L.) species. The pigments responsible for the color of brown cotton fiber are proanthocyanidins or their derivatives synthesized by the flavonoid pathway. Due to pigments, the NCC has excellent ultraviolet protection properties. Some brown cotton varieties exhibited superior thermal resistance of fiber that can be used to make fabrics with enhanced flame retardancy. Here, we review molecular mechanisms involved in the pigment production of brown cotton and challenges in breeding NCC varieties with a wide range of colors but without penalty in fiber quality. Also, we discuss opportunities for NCC with flame-retarding properties in textile applications.

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Using naturally colored cotton (NCC) can eliminate dyeing, printing and industrial processing, and reduce sewage discharge and energy consumption. Proanthocyanidins (PAs), the primary coloration components in brown fibers, are polyphenols formed by oligomers or polymers of flavan-3-ol units derived from anthocyanidins. Three essential structural genes for flavanone and flavonoid hydroxylation encoding flavanone-3-hydroxylase (F3H), flavonoid 3′-hydroxylase (F3′H) and flavonoid 3′5′-hydroxylase (F3′5′H) are initially committed in the flavonoid biosynthesis pathway to produce common precursors. The three genes were all expressed predominantly in developing fibers of NCCs, and their expression patterns varied temporally and spatially among NCC varieties. In GhF3Hi, GhF3′Hi and GhF3′5′Hi silenced lines of NCC varieties XC20 and ZX1, the expression level of the three genes decreased in developing cotton fiber, negatively correlated with anthocyanidin content and fiber color depth. Fiber color depth and type in RNAi lines changed with endogenous gene silencing efficiency and expression pattern,the three hydroxylase genes functioned in fiber color formation. GhF3H showed functional differentiation among NCC varieties and GhF3′H acted in the accumulation of anthocyanin in fiber. Compared with GhF3′H, GhF3′5′H was expressed more highly in brown fiber with a longer duration of expression and caused lighter color of fibers in GhF3′5′H silenced lines. These three genes regulating fiber color depth and type could be used to improve these traits by genetic manipulation.

Brown cotton is a major cultivar of naturally colored cotton, and brown cotton fibers (BCFs) are widely utilized as raw materials for textile industry production due to their advantages of being green and dyeing-pollution-free. However, the mechanisms underlying the pigmentation in fibers are still poorly understood, which significantly limits their extensive applications in related fields. In this study, we conducted a multidimensional comparative analysis of the transcriptomes and metabolomes between brown and white fibers at different developmental periods to identify the key genes and pathways regulating the pigment deposition. The transcriptomic results indicated that the pathways of flavonoid biosynthesis and phenylpropanoid biosynthesis were significantly enriched regulatory pathways, especially in the late development periods of fiber pigmentation; furthermore, the genes distributed in the pathways of PAL, CHS, F3H, DFR, ANR, and UFGT were identified as significantly up-regulated genes. The metabolic results showed that six metabolites, namely (−)-Epigallocatechin, Apiin, Cyanidin-3-O-glucoside, Gallocatechin, Myricetin, and Poncirin, were significantly accumulated in brown fibers but not in white fibers. Integrative analysis of the transcriptomic and metabolomic data demonstrated a possible regulatory network potentially regulating the pigment deposition, in which three MYB transcription factors promote the expression levels of flavonoid biosynthesis genes, thereby inducing the content increase in (−)-Epigallocatechin, Cyanidin-3-O-glucoside, Gallocatechin, and Myricetin in BCFs. Our findings provide new insights into the pigment deposition mechanism in BCFs and offer references for genetic engineering and breeding of colored cotton materials.

Leucoanthocyanidin reductase (LAR) is the critical enzyme in the synthesis pathway of proanthocyanidins, which are the primary pigments in brown cotton fibers. Our previous study has revealed significant differences in the expression levels of GhLAR1 between white and brown cotton fibers at 10 DPA. In this work, the expression pattern of the GhLAR1 gene was further studied, and the promoter of GhLAR1 (1780 bp) was isolated and characterized. Bioinformatic analysis indicated that GhLAR1 promoter contained many known light response elements and several defenses related to transcriptional factor-binding boxes, which may partially explain the response of the GhLAR1 to temperature, NaCl, and PEG treatments. Furthermore, GhLAR1 was preferentially and strongly expressed in fibers and flowers of cotton, and the expression levels in all tested tissues (especially fibers) of brown cotton were significantly higher than those in white cotton. Consistent with the expression analysis, the GhLAR1 promoter mainly drove GUS expression in epidermal trichomes and floral organs. [ABSTRACT FROM AUTHOR]

High quality naturally colored cotton fibers, coupled with rich colors, have become essentially desirable in current textile market to meet demands on the increasing standard of living and ecological textile industry. Both proanthocyanidins (PAs) and lignin originate from phenylpropanoid metabolism, our findings demonstrated that these two secondary metabolites synchronously regulate the color and quality of brown cotton fibers. From the fibers with different color types, the color depth of brown fiber was darkening with PAs accumulated more in a certain rang. When the PAs content in brown cotton fiber reached a certain threshold, the fiber color remained unchanged despite an increase in PAs content. Simultaneously, the cellulose content in the secondary cell wall (SCW) decreased when the lignin content synchronously increased, and the ratio of different types of lignin monomers changed. The changes of SCW compositions resulted in the reduced quality of mature brown cotton fibers that characterized with thin secondary cell walls, shorter length, lower micronaire values, and lower maturity. This discovery helps us understand the biochemical and molecular mechanisms of coloration and quality composition in brown cotton fibers, and will provide insights for genetic manipulation on NCCs in order to produce high quality multi-colored fibers. ● The changes of cellulose and lignin content in SCW resulted in the reduced quality of mature brown cotton fibers. ● PAs in BCF reached a certain threshold, the fiber color remained unchanged, accompanied lignin increase in SCW and fiber quality deteriorated. ● PAs and lignin are parallel originated from phenylpropanoid metabolism, synchronously regulated BCF color and quality. [ABSTRACT FROM AUTHOR]

Cotton, one of the indispensable raw materials of the textile industry, is a natural fiber that can be produced in various shades of brown and green beyond the white color. Naturally colored cotton offers an important opportunity to develop innovative products with high added value for the textile industry with its various properties. In today's conditions, where environmentally friendly production is of great importance, the development of new processes and production methods that do not create waste has gained great importance. One way to eliminate dyeing process that creates the largest waste load among finishing processes and thus gain significant environmental advantages is to grow colored natural fiber. Although the production of colored cotton is a subject that has been accomplished many years ago, when the literature is examined, it is understood that the fact that colored cotton is behind white cotton in terms of physical-technological properties poses a significant obstacle to the widespread use of these fibers. In this study, after giving brief information about the cultivation and types of colored cotton; a literature survey on the general fiber characteristics, advantages and disadvantages of colored cotton and previous studies in textile field on colored cotton is presented. [ABSTRACT FROM AUTHOR]

White and naturally colored organic cotton fiber usage and its production as textile end-products have been one of the new considerable efforts to reduce the waste generated during wet textile processing stages. This paper has focused on evaluation of the mechanical and air permeability properties of plain, twill and ribs fabrics made of unique white and naturally colored Turkish organic cotton types. Statistical evaluation of yarn and fabric properties was conducted using ANOVA statistical approach. According to statistical test results of two-factor ANOVA, cotton type and fabric weave structure parameters were generally significant factors on some mechanical and air permeability properties of fabric samples made of white and naturally colored cotton at significance level of 0.05. As a general result, white and naturally colored organic Turkish cotton utilized textile fabrics have given satisfying mechanical and air permeability property levels which reveal that those samples may be used for apparel garments. [ABSTRACT FROM AUTHOR]

Cotton is the world's most important fiber crop, and naturally colored cotton (NCC) is an important kind of environmental friendly material. The NCC described here refers to that the cotton fiber itself can synthesize pigments and present colors. NCC has gone through domestication and traditional breeding era in history. Due to the bottlenecks faced by NCC such as low fiber yield, poor quality, narrow color spectrum and unstable color, coupled with the advent of the industrialization era, the practical application of NCC has entered into a trough period. However, NCC has the advantages of environmentally friendly, antimicrobial and flame retardant, and researchers gradually resume the study of colored cotton from the breeding and physiological and biochemical perspectives. Especially with the arrival of the era of cotton functional genome, important research progresses have been made in the genetic study and genetic engineering of NCC. This study was focused on the metabolic pathways, genetic regulatory models and research highlights of NCC, which will provide new ideas for molecular design breeding of NCC, and realize the creation of high-yield, fine-quality and color-diverse NCC. • Molecular design breeding is feasible to breed the high-yield, fine-quality and color-diverse naturally colored cotton (NCC). • Anthocyanin metabolic pathway can produce diverse metabolites and break through the narrow spectrum of NCC. • The color genes within cotton species or exogenous species is practical to create new variety of NCC. [ABSTRACT FROM AUTHOR]

The cultivation of naturally colored cotton has captured the attention lately due to the increasing environmental concerns and problems. The green color in cotton fibers is owing to a lipid biopolymer (suberin) sandwiched between the lamellae of cellulose microfibrils in the secondary wall. Naturally colored green cotton fiber does not need dyeing or coloration process due to their inherent color characteristics leading to more ecological and sustainable textile production. Naturally colored cotton growers and producers have less requirement for the pesticides, insecticides since these varieties have already insect and diseaseresistant qualities as well as they exhibit property for drought and salt tolerant leading to more environmental friendly cotton fiber production. The colorimetric (CIE L*, a*, b*, C*, ho, K/S etc.) properties of studied naturally green colored Turkish cotton fiber were explored before and after scouring (with NaOH), and oxidizing processes with hydrogen peroxide and sodium hypochlorite (with different sodium hypochlorite concentrations and different oxidizing treatment periods and at different pH levels, with or without scouring process as a precursor treatment etc.) in comparison with their greige (un-treated) counterpart. The application of scouring process with NaOH to naturally green colored cotton fiber increases the color yield levels leading to darker appearance. Similarly, hydrogen peroxide and sodium hypochlorite oxidizing processes resulted in an increase in the color yield levels of naturally green colored cotton fibers leading to darker appearance. Even at high sodium hypochlorite concentrations such as 200 ml/l at pH 12 and room temperature for 48 hours, the naturally green colored cotton fibers maintain their color. [ABSTRACT FROM AUTHOR]

The existence of only natural brown and green cotton fibers (BCF and GCF, respectively), as well as poor fiber quality, limits the use of naturally colored cotton (Gossypium hirsutum L.). A better understanding of fiber pigment regulation is needed to surmount these obstacles. In this work, transcriptome analysis and quantitative reverse transcription PCR revealed that 13 and 9 phenylpropanoid (metabolic) pathway genes were enriched during pigment synthesis, while the differential expression of phenylpropanoid (metabolic) and flavonoid metabolic pathway genes occurred among BCF, GCF, and white cotton fibers (WCF). Silencing the chalcone flavanone isomerase gene in a BCF line resulted in three fiber phenotypes among offspring of the RNAi lines: BCF, almost WCF, and GCF. The lines with almost WCF suppressed chalcone flavanone isomerase, while the lines with GCF highly expressed the glucosyl transferase (3GT) gene. Overexpression of the Gh3GT or Arabidopsis thaliana 3GT gene in BCF lines resulted in GCF. Additionally, the phenylpropanoid and flavonoid metabolites of BCF and GCF were significantly higher than those of WCF as assessed by a metabolomics analysis. Thus, the flavonoid biosynthetic pathway controls both brown and green pigmentation processes. Like natural colored fibers, the transgenic colored fibers were weaker and shorter than WCF. This study shows the potential of flavonoid pathway modifications to alter cotton fibers’ color and quality.

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The purpose of this study was to examine the effects of repeated treatments of perspiration, weathering, and laundering as well as their interactions on the ultraviolet radiation (UVR) protection of a naturally colored cotton lightweight fabric suitable for summer clothing. The research design was a 2 (perspiration) × 3 (weathering) repeated measures (measured before and after each laundering cycle, up to 15 cycles) experimental design. Complicated interactions were found among these three treatment factors. Laundering alone (without weathering) increased the UVR protection, whereas weathering significantly reduced the protection. The conditions in a hot and humid climate facilitated the decline of protection, but perspiration played a role in slowing down the reduction. [ABSTRACT FROM AUTHOR]

Naturally brown-colored cotton (NBCC) fibers have been reported as having excellent antibacterial properties. In this study, the antioxidant properties of NBCC fibers were investigated. The results demonstrate that the antioxidant capacity of NBCC is significantly higher than that of white cotton. An NBCC variety with a darker color has a much higher capacity in which the 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging activities are 6.9 and 6.1 times those of white cotton, respectively. The antioxidant properties of NBCC were durable after scouring and laundering. The phenolic pigment composition in the fibers was found to contribute to their antioxidant properties. The results presented have furthered the understanding of the polyfunctional properties of NBCC fibers and their pigment components. [ABSTRACT FROM AUTHOR]

A new method was discussed to quantitatively analyze the blend ratio of naturally colored cotton (NCC) and white cotton (WC) by UV-vis diffuse reflectance spectroscopy (UV-vis DRS). Three kinds of spectroscopy parameters, diffuse reflectance, reflection absorbance, and the K-M function, were used to correlate them with the blend ratio of NCC/ WC fibers. The results showed that diffuse reflectance and blending ratio had the highest correlation coefficients. Therefore this method can be widely used to quantify the blending ratio of NCC/WC fibers as a result of its greater accuracy and simplicity compared to traditional detection methods. [ABSTRACT FROM AUTHOR]

Copyright of Fibres & Textiles in Eastern Europe is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The moisture sorption behavior of white and naturally colored cotton fibers is studied by dynamic vapor sorption. Dark brown and brown fibers show a higher sorption capacity compared to beige and white fibers. The differences in sorption capacity are found to be related to the maturity and crystallinity index of the fibers. All fibers exhibited sorption hysteresis to varying degrees throughout the full relative humidity range. The variations in hysteresis behavior are mainly attributed to the differences in crystallinity index of the fibers. In addition the monolayer and polylayer moisture content is analyzed using the Hailwood Horrobin model. Monolayer sorption is most closely related to the crystallinity index and, to a lower extent, maturity of the fibers. For beige and white fibers monolayer sorption remains almost constant, whereas for darker fibers it shows a substantial increase with increasing color difference. In contrast, polylayer sorption shows a general increasing trend over the whole studied color spectrum. Also a noticeable relationship was found between the total hysteresis and the monolayer sorption. Yet such relation was less evident for polylayer sorption. This study contributes to the better understanding of the dynamic moisture sorption behavior of white and naturally colored cotton fibers. This improved understanding is important for optimal application of naturally colored cotton fibers in novel materials. [ABSTRACT FROM AUTHOR]

The antibacterial activity of naturally colored cottons (NCCs) is evaluated. Compared to the conventional white cotton, brown NCC was found to exhibit excellent antibacterial activity with a reduction rate of 89.1% and 96.7%, when in contact with two species of bacteria, Staphylococcus aureus and Klebsiella pneumoniae, respectively, while the antibacterial effect of green NCC was faint. To investigate the antibacterial mechanism of NCCs, pigments have been extracted from NCC fibers for further determination of their antibacterial activity using the disk diffusion method, and the chemical nature of extracted pigments was also analyzed. The results are as follows: the pigment from brown cotton fibers showed significant inhibition against the two challenge bacteria, while the resistance capacity of the pigment from green cotton fiber was insignificant, indicating that the antibacterial efficacy of NCC fibers was highly related to the chemical nature of the pigment. Diagnostic results indicated that the pigment from brown cotton belonged to condensed tannins, and the pigment from green cotton fiber was identified as flavonoids. The effect of high-temperature treatment on antibacterial activity of the pigment extracted from brown cotton was also examined. It showed that the general textile high-temperature curing conditions decrease its antibacterial activity, but the antibacterial activity still has a satisfactory retention, indicating a durable natural antibacterial performance of brown NCC to the high-temperature curing technology. [ABSTRACT FROM PUBLISHER]

Abstract: A comparative proteomic analysis was performed to identify the differences between brown cotton fiber and a white near-isogenic line, and 78 differential spots were identified at three time points (12-, 18-, and 24-day post-anthesis [DPA]) using MALDI-TOF/TOF. Our data illustrate several aspects of pigment synthesis and fiber development in brown color fiber (BCF). First, 21 spots were associated with secondary metabolism; 15 of these with high abundance in BCF were involved in flavonoid biosynthesis. Second, several spots with lower abundance in BCF were found. Thirteen spots were related to energy/carbohydrate metabolism; in particular, spots related to the glycolytic pathway exhibited lower abundance in 12DPA BCF. Several spots related to redox homeostasis, cytoskeleton, and protein metabolism also showed lower abundance in BCF, including proteins that are critical for fiber development, such as ascorbate peroxidase, superoxide dismutase, actin, annexin and heat shock protein. Third, several proteins such as leucine aminopeptidase preprotein and progesterone-5-beta-reductase were newly identified proteins in cotton fibers. These findings demonstrated the presence of a complicated metabolic network in BCF and advanced our understanding of the molecular mechanisms of pigment biosynthesis in colored cotton, which will provide new insight for the development of new color types by genetic manipulation. [Copyright &y& Elsevier]

Naturally colored cottons contain significantly higher amounts of wax and have a different wax constitution and connectivity with cellulose than conventional cotton. Researchers have proposed that this wax content, together with the natural pigmentation, may serve as a defense against soil-borne pathogens. The purpose of this research is to study the biodegradation and mildew resistance characteristics of naturally colored cotton compared to conventional white and dyed cotton under field soil burial and laboratory mildew culture conditions. Laboratory culture results show that naturally brown and green colored cotton fabrics resist the growth of Aspergillius niger. However, after soil burial, both naturally brown and green cotton specimens showed severe degradation, manifested by significant loss of fabric strength as well as fiber structural damage. This suggests that naturally colored cottons are biodegradable. However, the rate of biodegradation of naturally colored cottons, especially green cotton, is much lower than that of white cotton or conventional dyed cotton. [ABSTRACT FROM PUBLISHER]

The objective of this study was to determine whether enzymatic treatment can improve low moisture regain of three naturally colored cottons. There was an increase in weight of colored cottons after enzyme treatment. Moisture regain test was implemented to determine the cause of this increase. The result showed that moisture regain of three naturally colored cottons increased after scouring and increased further after enzyme treatment. Statistical results indicated that lipase was the least effective enzyme for brown cottons and the most effective enzyme for green cotton. For multiple enzyme treatment, treatments including amylase were most effective for brown cottons and for treatments including lipase were most effective for green cotton. Treatments with all four enzymes resulted in the lowest increase in moisture regain for all colored cottons. [ABSTRACT FROM AUTHOR]

Naturally colored cotton (NCC) based wovens are finished with 1,2,3,4-butanetetracarboxylic acid (BTCA), which is an environmentally friendly durable press (DP) finish. The colors of the NCC wovens before and after DP finishing are examined. The color fastnesses to home laundering and light irradiation are compared and evaluated. The DP finishing of BTCA has a negative effect on the color of NCC based fabrics. About 1/3 of the shade depth of the NCCs are decreased after a BTCA finishing. For both the fabrics with and without a DP finishing, home laundering results in evident color changes with decrease of shade depth. However, for probable crosslinking to pigments, a DP finishing could significantly improve the home laundering color fastness of NCCs. The performance of the color fastness to light after a BTCA finishing depends on the cotton breed. The BTCA finishing of the green NCC minimally improves the light fastness, while for the brown NCC, the color fastness to light decreases after the BTCA finishing. [ABSTRACT FROM AUTHOR]

Green-colored fiber (GCF) is the unique raw material for naturally colored cotton textile but we know little about the pigmentation process in GCF. Here we compared transcriptomes and metabolomes of 12, 18 and 24 days post-anthesis (DPA) fibers from a green fiber cotton accession and its white-colored fiber (WCF) near-isogenic line. We found a total of 2047 non-redundant metabolites in GCF and WCF that were enriched in 80 pathways, including those of biosynthesis of phenylpropanoid, cutin, suberin, and wax. Most metabolites, particularly sinapaldehyde, of the phenylpropanoid pathway had a higher level in GCF than in WCF, consistent with the significant up-regulation of the genes responsible for biosynthesis of those metabolites. Weighted gene co-expression network analysis (WGCNA) of genes differentially expressed between GCF and WCF was used to uncover gene-modules co-expressed or associated with the accumulation of green pigments. Of the 16 gene-modules co-expressed with fiber color or time points, the blue module associated with G24 (i.e., GCF at 24 DPA) was of particular importance because a large proportion of its genes were significantly up-regulated at 24 DPA when fiber color was visually distinguishable between GCF and WCF. A total of 56 hub genes, including the two homoeologous Gh4CL4 that could act in green pigment biosynthesis, were identified among the genes of the blue module that are mainly involved in lipid metabolism, phenylpropanoid biosynthesis, RNA transcription, signaling, and transport. Our results provide novel insights into the mechanisms underlying pigmentation of green fibers and clues for developing cottons with stable green colored fibers. [ABSTRACT FROM AUTHOR]