Abstract
To understand the mechanism of fiber development and pigmentation formation, the mRNAs of two cotton lines were sequenced: line Z128 (light brown fiber) was a selected mutant from line Z263 (dark brown fiber). The primary walls of the fiber cell in both Z263 and Z128 contain pigments; more pigments were laid in the lumen of the fiber cell in Z263 compared with that in Z128. However, Z263 contained less cellulose than Z128. A total of 71,895 unigenes were generated: 13,278 (20.26%) unigenes were defined as differentially expressed genes (DEGs) by comparing the library of Z128 with that of Z263; 5,345 (8.16%) unigenes were up-regulated and 7,933 (12.10%) unigenes were down-regulated. qRT-PCR and comparative transcriptional analysis demonstrated that the pigmentation formation in brown cotton fiber was possibly the consequence of an interaction between oxidized tannins and glycosylated anthocyanins. Furthermore, our results showed the pigmentation related genes not only regulated the fiber color but also influenced the fiber quality at the fiber elongation stage (10 DPA). The highly expressed flavonoid gene in the fiber elongation stage could be related to the fiber quality. DEGs analyses also revealed that transcript levels of some fiber development genes (Ca2+/CaM, reactive oxygen, ethylene and sucrose phosphate synthase) varied dramatically between these two cotton lines.
Highlights
Upland cotton (Gossypium hirsutum L.) is the largest natural fiber producer of the plants
Though the primary walls of the fiber cell in both Z263 and Z128 contain pigments (Fig. 1), more pigments were laid in the lumen of the fiber cell in Z263 compared with that Z128
The RNA-seq approach based on generation sequencing technology provided us with a new method to study the transcriptome of developing cotton fibers
Summary
Upland cotton (Gossypium hirsutum L.) is the largest natural fiber producer of the plants. Interest in naturally colored cotton has grown because it may reduce pollution, making it preferable to white fiber which requires a dyeing process [1,2,3]. Its commercial application is very limited due to the lack of fiber color diversity and low fiber quality [2]. Limited brown (different color depth) and green fiber lines, among other varieties, have been used in the textile industry. A previous study demonstrated that there was a significant negative correlation between the degree of fiber color and lint percentage and fiber quality traits in cotton [4]. Subsequent studies should focus on improving the fiber quality and revealing the underlying mechanisms for pigmentation formation in naturally colored cotton
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