Genome wide identification and functional characterization of the cotton C-repeat binding factor (CBF) under cold stress condition

Background Low temperature is a common biological abiotic stress in major cotton growing areas. Cold stress significantly affects the growth, yield and yield quality of cotton. Therefore, it is important to develop a more robust and cold stress tolerant cotton germplasms. In response to climate change and erratic conditions, plants have evolved various survival mechanisms, one of which induction of various stress responsive transcription factors, such as the C-repeat binding factors (CBFs), which have been found to enhance cold tolerance in various plants. Results In this study detailed evaluation of the cotton CBF has been carried out. A total of 29, 28, 25, 21, 30, 26 and 15 proteins encoded by the CBF genes were identified in Gossypium herbaceum, Gossypium arboreum, Gossypium thurberi, Gossypium raimondii, Gossypium turneri, Gossypium longicalyx and Gossypium australe, respectively. Phylogenetic evaluation revealed that the proteins were grouped into seven clades, with clade 1 and 6 being the largest. Moreover, majority of the proteins encoded by the genes were predicted to be located within the nucleus, while some were distributed in other parts of the cell. Based on the transcriptome and RT-qPCR analysis, Gthu17439 (GthCBF4) was highly upregulated under cold stress, and was further validated through forward genetics. The Gthu17439 (GthCBF4) overexpressed plants showed a significantly tolerance to cold stress, with higher germination rate, higher root growth and high induction levels of stress responsive genes. The over-expressed plants exhibited low level of oxidative damage, due to significant reduction in the H2O2 production. Conclusion The results showed that the Gthu17439 (GthCBF4) could be playing a significant role in enhancing cold stress tolerance in cotton and can be further exploited in developing cotton germplasm with an improved cold-stress tolerance

The Gossypium longicalyx Genome as a Resource for Cotton Breeding and Evolution

Cotton is an important crop that has made significant gains in production over the last century. Emerging pests such as the reniform nematode have threatened cotton production. The rare African diploid species Gossypium longicalyx is a wild species that has been used as an important source of reniform nematode immunity. While mapping and breeding efforts have made some strides in transferring this immunity to the cultivated polyploid species, the complexities of interploidal transfer combined with substantial linkage drag have inhibited progress in this area. Moreover, this species shares its most recent common ancestor with the cultivated A-genome diploid cottons, thereby providing insight into the evolution of long, spinnable fiber. Here we report a newly generated de novo genome assembly of G. longicalyx. This high-quality genome leveraged a combination of PacBio long-read technology, Hi-C chromatin conformation capture, and BioNano optical mapping to achieve a chromosome level assembly. The utility of the G. longicalyx genome for understanding reniform immunity and fiber evolution is discussed.

The Gossypium longicalyx genome as a resource for cotton breeding and evolution

Cotton is an important crop that has made significant gains in production over the last century. Emerging pests such as the reniform nematode have threatened cotton production. The rare African diploid species Gossypium longicalyx is a wild species that has been used as an important source of reniform nematode immunity. While mapping and breeding efforts have made some strides in transferring this immunity to the cultivated polyploid species, the complexities of interploidal transfer combined with substantial linkage drag have inhibited progress in this area. Moreover, this species shares its most recent common ancestor with the cultivated A-genome diploid cottons, thereby providing insight into the evolution of long, spinnable fiber. Here we report a newly generated de novo genome assembly of G. longicalyx. This high-quality genome leveraged a combination of PacBio long-read technology, Hi-C chromatin conformation capture, and BioNano optical mapping to achieve a chromosome level assembly. The utility of the G. longicalyx genome for understanding reniform immunity and fiber evolution is discussed.

Production of New Cotton Interspecific Hybrids with Enhanced Fiber Fineness

<p>To improve cotton fiber fineness, the (<em>Gossypium hirsutum</em> L. × <em>Gossypium longicalyx </em>Hutch. &amp; Lee)² allohexaploid and the [(<em>Gossypium hirsutum</em> L. × <em>Gossypium thurberi </em>Tod.)² × <em>G. longicalyx</em>] allotetraploid were backcrossed to <em>G. hirsutum</em> to produce introgressed genetic stocks. The ribbon width (RW) of 600 swelled fibers produced by the hybrids, their parents, and their backcross progeny were analyzed for each compared genotype using an optical microscope. The RWs varied between 6.41±2.15 µm for <em>G. longicalyx</em> to 17.45±2.98 µm for the <em>G. hirsutum</em> parent cultivar C2. Fibers produced by the trispecific hybrids and their progeny were finer than the bispecific hybrid material. For the introgressed stocks, the lowest RWs were observed for the trispecific hybrid (10.79±2.14 µm) and certain backcross progenies (between 11.98±1.27 µm to 12.71±1.61 µm). The allohexaploid RW was 13.58±1.41 µm. One of its tetraploid progeny produced approximately the same value (13.94±2.48 µm). These results show that <em>G. longicalyx </em>is a potential genetic stock for cotton fiber fineness improvement. The genetic stocks produced are valuable materials for improve the fineness of cotton fiber.</p>