Upland cotton is the most economically important fibre crop. The human-mediated selection has resulted in modern upland cultivars with higher yield and better fibre quality. However, changes in genome structure resulted from human-mediated selection are poorly understood. Comparative population genomics offers us tools to dissect the genetic history of domestication and helps to understand the genome-wide effects of human-mediated selection. Hereby, we report a comprehensive assessment of Gossypium hirsutum landraces, obsolete cultivars and modern cultivars based on high throughput genome-wide sequencing of the core set of genotypes. As a result of the genome-wide scan, we identified 93 differential regions and 311 selection sweeps associated with domestication and improvement. Furthermore, we performed genome-wide association studies to identify traits associated with the differential regions and selection sweeps. Our study provides a genetic basis to understand the domestication process in Chinese cotton cultivars. It also provides a comprehensive insight into changes in genome structure due to selection and improvement during the last century. We also identified multiple genome-wide associations (GWAS associations) for fibre yield, quality and other morphological characteristics.

Phytocyanins (PCs) are a class of plant-specific blue copper proteins that have been demonstrated to play a role in electron transport and plant development. Through analysis of the copper ligand residues, spectroscopic properties, and domain architecture of the protein, PCs have been grouped into four subfamilies: uclacyanins (UCs), stellacyanins (SCs), plantacyanins (PLCs), and early nodulin-like proteins (ENODLs). The present study aimed to identify and characterise the PCs present in three distinct cotton species (Gossypium hirsutum, Gossyium arboreum, and Gossypium raimondii) through the identification of 98, 63, and 69 genes respectively. We grouped PCs into four clades by using bioinformatics analysis and sequence alignment, which exhibit variations in gene structure and motif distribution. PCs are distributed across all chromosomes in each of the three species, with varying numbers of exons per gene and multiple conserved motifs, and with a minimum of 1 and maximum of 11 exons found on one gene. Transcriptomic data and qRT-PCR analysis revealed that two highly differentiated PC genes were expressed at the fibre initiation stage, while three highly differentiated PCs were expressed at the fibre elongation stage. These findings serve as a foundation for further investigations aimed at understanding the contribution of this gene family in cotton fibre production.

Cotton is one of the major industrial crops that supply natural fibers and oil for industries. This study was conducted to understand the mechanism of delayed gland morphogenesis in seeds of Gossypium bickii. In this study, we compared glandless seeds of G. bickii with glanded seeds of Gossypium arboreum. High-throughput sequencing technology was used to explore and classify the expression patterns of gland-related genes in seeds and seedlings of cotton plants. Approximately 131.33 Gigabases of raw data from 12 RNA sequencing samples with three biological replicates were generated. A total of 7196 differentially-expressed genes (DEGs) were identified in all transcriptome data. Among them, 3396 genes were found up-regulated and 3480 genes were down-regulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations were performed to identify different functions between genes unique to glandless imbibed seeds and glanded seedlings. Co-expression network analysis revealed four modules that were identified as highly associated with the development of glandless seeds. Here the hub genes in each module were identified by weighted gene co-expression network analysis (WGCNA). In total, we have selected 13 genes involved in transcription factors, protein and MYB-related functions, that were differentially expressed in transcriptomic data and validated by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). These selected genes may play an important role for delayed gland morphogenesis. Our study provides comprehensive insight into the key genes related to glandless traits of seeds and plants, and can be further exploited by functional and molecular studies.