The difference between upland cotton and sea-island cotton, high yield and adaptability of upland cotton; low yield of sea-island cotton and superior fiber quality. For a long time, people have been trying to analyze the reasons for the differences in yield, adaptability and quality of upland cotton and sea-island cotton, and tried to cultivate a new cotton variety with high yield, good fiber and strong adaptability, but it has not been successful.
Recently, Zhang Tianzhen, a professor at the College of Agriculture and Biotechnology of Zhejiang University, published a research paper on "Nature-Genetics", which reported the origin of high-quality tetraploid upland cotton and sea-island cotton and the genetic mechanism of interspecific differentiation, revealing the wide adaptability of upland cotton. The high quality genetic basis of island cotton.
Achieving a more complete genome assembly According to Zhang Tianzhen, the cotton genus includes 46 diploid cotton species and five tetraploid cotton species. All diploid cotton species may be advanced from a common ancestor. It is then differentiated into 8 genomes, including A, B, C, D, E, F, G, and K.
"All tetraploid cotton species are formed by the interspecific hybridization of A genome Asian cotton and D genome Raymond cotton, which is a heterotetraploid cotton species." Zhang Tianzhen told the Journal of Chinese Academy of Sciences.
The team performed ultra-high-deep sequencing of two heterotetraploid cotton species, Upland CottonTM-1 and Sea Island Cotton Hai7124, followed by genome sequencing using the sequenced cotton genome sequence using DeNovoMAGIC3 software.
It is worth mentioning that the continuity of the newly assembled seaweed Hai7124 genome has increased by 47-fold and 90-fold, respectively, compared to the two published old versions, and the continuity of the upland cotton TM-1 genome has also increased by 10-20 fold. The integrity of the genome, especially in the assembly of the centromere region of the repetitive sequence enrichment, is greatly enhanced.
Zhang Tianzhen said that the study combines the most advanced assembly and optical mapping technologies in the genome field to significantly improve the accuracy, completeness and continuity of the newly assembled two cotton genomic sequences, which is four times more. The research on cotton breeding has laid a solid foundation.
“Reference genomic sequences are a very important foundation work for functional genomics research.” Hua Jinping, a professor at the Agricultural College of China Agricultural University, told the Journal of Chinese Academy of Sciences that “the assembly of the upland cotton TM-1 is the third and also At present, the most complete version reflects the scientific spirit of the excellence and perseverance of Chinese scientists. The release of Hai7124 from the island cotton also represents the latest development of Chinese scientists in this field, providing an important basis for the study of functional genomics of the island cotton."
![The difference between upland cotton and sea island cotton]()
The reason for the formation and evolution of cotton seeds was discovered. Next, the researchers used these two well-assembled genomic cotton varieties to find out the gene-specific, structural variation and species-specific changes in the extended gene family through genome-wide comparative analysis. The reason for the formation and evolution of cotton.
"By comparing the genomic differences between upland cotton and sea-island cotton, we found that there are many amplified specific genes in each of the two cotton varieties, and speculated that some of the specific genes may be related to the specificity of cotton." Introduction, in the genome of two cotton species, differences in chromosome structure were also found.
The researchers found that during fiber development, the membrane transport, sugar synthesis, and carbohydrate metabolism pathways of upland cotton and sea island cotton were differentially enriched.
The expression of genes involved in cell elongation, such as sucrose transport, ion transport, and vacuolar invertase, is much longer in terrestrial cotton fiber development than in upland cotton. "This is the main reason for the superior quality of the island cotton fiber." Zhang Tianzhen said.
In addition, more genes in the upland cotton, such as ethylene and ABA signaling, are activated, and these genes can regulate the response of cotton to cold and hot environments. Therefore, these genes may be closely related to the wide adaptability of upland cotton.
Helping cotton varieties to improve domesticated cotton Zhang Tianzhen said that although China's cotton production ranks in the forefront of the world, China's cotton production is also facing a major crisis, such as single cotton type, poor fiber quality, and low fiber strength.
"Therefore, fully studying the function of cotton genome is of great significance for accelerating the selection of high-quality cotton varieties and ensuring the sustainable development of China's cotton industry."
The researchers said the findings will help clarify the history of cotton domestication and the evolution of the cotton genome. In addition, the differential genes in the cotton genome of the upland cotton and the island cotton can be further studied for the next step of cotton breeding, improving the quality of cotton fiber and enhancing the adaptability of cotton to the external environment.
“This research method can also be extended to other crops in order to better understand the history of crop domestication and improve the quality of crops,” Zhang said.
