Search

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] more...

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. more...

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. more...

The flavonoid pigments provide cotton cultivars with various shades of the naturally colored fiber. Despite of the deep knowledge about the flavonoids biosynthesis pathway in cotton, the genetic features underlying its control are not fully understood. Particularly, data on regulatory genes for the proanthocyanidins (PAs) branch are incomplete for the genus Gossypium L. Here we report results of comprehensive in silico analysis of the R2R3-Myb, bHLH-Myc and WD40 regulatory gene families, involved in the biosynthesis of flavonoid pigment PAs in cotton. For the first time, we identified regulatory genes R2R3-Myb, bHLH-Myc and WD40, including paralogous and homoeologous copies, among all sequenced diploid and allotetraploid cotton species: G. hirsutum L., G. barbadence L., G. raimondii L. and G. arboreum L. All duplication events occurred in the genome of the common diploid ancestor of the genus Gossypium and were supported by a negative evolution (Ka/Ks < 1). However, the GhTTG1/GhTTG3 genes are proved to be the most conservative and predominantly supported by selection, while GhTT2/GhMYB10 and GhTT8 are more variable and suitable for further analysis. The thorough study has suggested that all genes, with the exception of GhTT8-A2, possibly involved in the PAs biosynthesis. Therefore, information about structural organization and functionality of the all MBW genes in cotton genome is represented here. Revealing of the allelic diversities among identified genes, associating with contrast phenotype, may be useful for marker-assisted selection or genome editing for creation of naturally colored cotton cultivars with agriculturally valuable traits. [ABSTRACT FROM AUTHOR] more...

Brown cotton fibers (SA-1 and MC-BL) studied were inferior to a white cotton fiber (Sure-Grow 747) in fiber quality, i.e., a shorter length, fewer twists, and lower crystallinity, but showed superior thermal resistance in thermogravimetric, differential thermogravimetric, and microscale combustion calorimetric (MCC) analyses. Brown cotton fibers yielded 11-23 % smaller total heat release and 20-40 % greater char. Washing fibers in water and a 1 % NaOH solution showed that rich natural inorganic components and the condensed tannins present in brown cotton are responsible for the unusual thermal property. The loss of inorganics from white cotton during a water wash increased the thermal decomposition temperature of cellulose, resulting in no char yield. However, the stronger binding of metal ions for brown cotton as well as its dominant adsorption of sodium ions after a 1 % NaOH wash facilitated the low-temperature thermal-reaction route; the sodium content showed a significant negative correlation with the heat release capacity of the fiber. Condensed tannins greatly enhanced the adsorption of sodium ions to the fiber and exhibited inherent thermal stability. The limiting oxygen indices (LOI) calculated from the MCC parameters indicated the slower burning characteristic of brown cotton, and its LOI was further increased upon adsorption of sodium ions. [ABSTRACT FROM AUTHOR] more...