Project description:Crop wild relatives are an important reservoir of natural biodiversity. However, incorporating wild genetic diversity into breeding programs is often hampered by reproductive barriers and a lack of accurate genomic information. We assembled a high-quality, accurately centromere-anchored genome of Gossypium anomalum, a stress-tolerant wild cotton species. We provided a strategy to discover and transfer agronomically valuable genes from wild diploid species to tetraploid cotton cultivars. With a (Gossypium hirsutum × G. anomalum)2 hexaploid as a bridge parent, we developed a set of 74 diploid chromosome segment substitution lines (CSSLs) of the wild cotton species G. anomalum in the G. hirsutum background. This set of CSSLs included 70 homozygous substitutions and four heterozygous substitutions, and it collectively contained about 72.22% of the G. anomalum genome. Twenty-four quantitative trait loci associated with plant height, yield, and fiber qualities were detected on 15 substitution segments. Integrating the reference genome with agronomic trait evaluation of the CSSLs enabled location and cloning of two G. anomalum genes that encode peroxiredoxin and putative callose synthase 8, respectively, conferring drought tolerance and improving fiber strength. We have demonstrated the power of a high-quality wild-species reference genome for identifying agronomically valuable alleles to facilitate interspecific introgression breeding in crops.
Project description:Cotton is an important crop that has been the beneficiary of multiple genome sequencing efforts, including diverse representatives of wild species for germplasm development. Gossypium anomalum is a wild African diploid species that harbors stress-resistance and fiber-related traits with potential application to modern breeding efforts. In addition, this species is a natural source of cytoplasmic male sterility and a resource for understanding hybrid lethality in the genus. Here, we report a high-quality de novo genome assembly for G. anomalum and characterize this genome relative to existing genome sequences in cotton. In addition, we use the synthetic allopolyploids 2(A2D1) and 2(A2D3) to discover regions in the G. anomalum genome potentially involved in hybrid lethality, a possibility enabled by introgression of regions homologous to the D3 (Gossypium davidsonii) lethality loci into the synthetic 2(A2D3) allopolyploid.
Project description:Some wild cotton species are remarkably tolerant to salt stress, and hence represent valuable resources for improving salt tolerance of the domesticated allotetraploid species Gossypium hirsutum L. Here, we first detected salt-induced stress changes in physiological and biochemical indexes of G. anomalum, a wild African diploid cotton species. Under 350 mmol/L NaCl treatment, the photosynthetic parameters declined significantly, whereas hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents increased. Catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) activity and proline (PRO) content also significantly increased, reaching peak values at different stages of salt stress. We used RNA-Seq to characterize 15,476 differentially expressed genes in G. anomalum roots after 6, 12, 24, 72, and 144 h of salt stress. Gene Ontology enrichment analysis revealed these genes to be related to sequence-specific DNA and iron ion binding and oxidoreductase, peroxidase, antioxidant, and transferase activity; meanwhile, the top enriched pathways from the Kyoto Encyclopedia of Genes and Genomes database were plant hormone signal transduction, phenylpropanoid biosynthesis, fatty acid degradation, carotenoid biosynthesis, zeatin biosynthesis, starch and sucrose metabolism, and MAPK signaling. A total of 1231 transcription factors were found to be expressed in response to salt stress, representing ERF, MYB, WRKY, NAC, C2H2, bZIP, and HD-ZIP families. Nine candidate genes were validated by quantitative real-time PCR and their expression patterns were found to be consistent with the RNA-Seq data. These data promise to significantly advance our understanding of the molecular response to salt stress in Gossypium spp., with potential value for breeding applications.
Project description:Gossypium anomalum (B1B1) is a valuable wild resource for the genetic improvement of G. hirsutum (A1A1D1D1) in terms of fiber quality and disease and pest resistance, but the inherent difficulties in distant hybridization hinder its utilization in breeding programs. Monosomic alien addition lines (MAALs) are powerful tools for interspecific gene transfer. First, to access useful genes from G. anomalum, a fertile hexaploid from G. hirsutum × G. anomalum was obtained and then additional chromosomes were selected using SSR markers in successive backcrosses and self-crossing from BC2F1 to BC4F4. Finally, a complete set of 13 MAALs were developed. All the MAALs were confirmed by chromosome-specific anchored SSRs and genome-wide resequencing. The MAALs demonstrated abundant variation in morphological, agronomic, yield-related, and fiber quality traits. MAAL_3B had excellent fiber strength and fineness, indicating that the transmitted chromosome may carry desirable genes for the observed phenotypes. This complete set of MAALs will provide important genetic bridge material for the identification and introgression of favorable genes from G. anomalum and lay an important foundation for the genetic improvement of cotton.
Project description:Drought stress is a key limiting factor for cotton (Gossypium spp.) growth, production, development, and production worldwide. Some wild diploid cotton species are remarkably tolerant of water deficit and constitute an important reservoir for understanding the molecular mechanisms of Gossypium spp. drought tolerance and improving cultivated upland cotton. Here, we utilized RNA-Seq technology to characterize the leaf transcriptomes of a wild African diploid cotton species, Gossypium anomalum, under drought stress. A total of 12,322 differentially expressed genes (DEGs) were identified after mapping valid clean reads to the reference genome of G. anomalum, of which 1243 were commonly differentially expressed at all stages of drought stress. These genes were significantly enriched for molecular functions Gene Ontology terms related to cytoskeleton, hydrolase activity, cellular redox, and binding. Additionally, a substantial proportion of enriched biological process terms concerned cell or subcellular processes, while most in the cellular components category concerned membrane function and photosynthesis. An enrichment analysis against the Kyoto Encyclopedia of Genes and Genomes showed the top significantly enriched pathways to be photosynthesis-antenna proteins, amino sugar and nucleotide sugar metabolism, starch and sucrose metabolism, MAPK signaling pathway, glutathione metabolism, and plant hormone signal transduction. The DEGs also exhibited interestingly significant enrichments for drought stress-induced tandemly repeated genes involved in iron ion binding, oxidoreductase activity, heme binding, and other biological processes. A large number of genes encoding transcription factors, such as MYB, bHLH, ERF, NAC, WRKY, and bZIP, were identified as playing key roles in acclimatizing to drought stress. These results will provide deeper insights into the molecular mechanisms of drought stress adaptation in Gossypium spp.