'Pink cotton candy'-A new dye-free cotton
新型无染料棉“粉红棉花糖”
- 关键词：
- 来源：
- PLANT BIOTECHNOLOGY JOURNAL
- 类型：
- 学术文献
- 语种：
- 英语
- 原文发布日期：
- 2022-12-28
- 摘要：
- White cotton is the dominant natural fibre, accounting for a $USD 36 billion share of the $USD 1.5 trillion global textile industry and, for many decades, has been dyed post-production. Modern cotton ginning and spinning processes require longer and stronger fibres, favouring superior white cotton varieties, which are more amenable to post-harvest dyeing. However, large quantities of synthetic dyes from textile dyeing released into the environment/waterways are harming the health of humans and other organisms. Eco-friendly alternatives are urgently needed to reduce pollution and save water; coloured dye-free cotton could be a solution. While naturally coloured cotton has been known for more than 5000 years and occurs in all four species of cultivated cotton, that is Gossypium (G.) hirsutum, G. barbadense, G. herbaceum and G. arboretum, these coloured varieties generally have low yield, poor fibre quality and variable and unstable colours. Although conventional breeding has improved the properties of some coloured cotton, quality and yield remain low compared with white cotton and colour range is limited.Betalains are tyrosine-derived pigments found naturally in the order Caryophyllales of flowering plants, and fungi and bacteria. Betalains comprise two classes of compounds, that is yellow-orange betaxanthins and red-violet betacyanins. These compounds are synthesized through a series of enzymatic steps including hydroxylases, dioxygenases and glucosyl transferases that produce visible colours. As the Malvaceae typically do not produce betalains, we embarked on genetically engineering the betalain pathway in G. hirsutum, the world's largest plant-based fibre commodity.We designed constructs that included the coding sequences (CDS) of BvDODA1 (Beta vulgaris, GeneBank ID HQ656027.1), BvCYP76AD1 (HQ656023.1) and MjcDOPA5GT (Mirabilis jalapa, AB182643.1; Polturak et al., 2017; Timoneda et al., 2019). The CDSs were optimized for Arabidopsis and synthesized by GeneArt . Constructs (pAGM4723 vector) were assembled via Golden Gate cloning with a 2 × 35 S-driven kanamycin resistance gene. The betalain genes were driven by either a 2 × 35 S constitutive promoter or a ltp3/8K12 (LTP) mid-late-stage cotton fibre-specific promoter. Transgenic plants were generated through tissue culture transformation (Murray et al., 1999). Coker 315-11 was used as the recipient of transformation by infection with Agrobacterium tumefaciens strain AGL1 containing different constructs. Transgenic and wild-type (controls) cotton plants were grown in a greenhouse at 28°C/20°C (day/night) with natural light.Despite strong betalain accumulation during fibre development in the fibre-specific lines, the colour faded to light brown/pink in the final days of boll maturation, when the bolls dried and opened (transgenic lines: 55–60 DPA vs wild type: 55 DPA). This suggests that vacuole-located betalain was degraded during the final maturation stage. Cotton bolls were collected at around 10, 15, 20, 25, 30, 40, 50 and 60 DPA, and boll coats were either cut open or removed entirely followed by 48 h of freeze-drying, and the pink colour was retained.Mature fibre or freeze-dried immature fibre (>46 DPA) from controls and five independent T0 plants with the fibre-specific betalain expression were measured by Cottonscope for fibre quality. The results suggested the transgenic lines have the potential to present similar maturity ratio and fineness as the wild type (Line 44). The seed numbers and fibre yield were less in the T0 compared with wild type, which is common to see in T0 generation. Subsequent generations of transgenic plants could potentially retain wild-type-like yield and fibre quality alongside strong pigment accumulation, noting that Coker 315 can be introgressed into modern elite varieties for yield and quality. New colours may be generated by crossing the betalain lines with existing naturally coloured genotypes (Ke et al., 2022).In conclusion, we present a novel example of introducing the exogenous multi-gene betalain pathway to generate a plant-made pink cotton fibre which remains pink until the very late stages of fibre development. Using the betalain pathway is advantageous because the pigment is stable over a wide pH range (Jackman and Smith, 1996), potentially improving colour stability and consistency. Future research could investigate reducing pigment degradation (potentially via cross-linking) and introducing new colours.
- 所属专题：
- 171
