Gossypium Klotzschianum Research Articles

Genetic map construction and functional characterization of genes within the segregation distortion regions (SDRs) in the F2:3 populations derived from wild cotton species of the D genome

BackgroundSegregation distortion (SD) is a common phenomenon among stable or segregating populations, and the principle behind it still puzzles many researchers. The F2:3 progenies developed from the wild cotton species of the D genomes were used to investigate the possible plant transcription factors within the segregation distortion regions (SDRs). A consensus map was developed between two maps from the four D genomes, map A derived from F2:3 progenies of Gossypium klotzschianum and G. davidsonii while Map B from G. thurberi and G. trilobum F2:3 generations. In each map, 188 individual plants were used.ResultsThe consensus linkage map had 1 492 markers across the 13 linkage groups with a map size of 1 467.445 cM and an average marker distance of 1.037 0 cM. Chromosome D502 had the highest percentage of SD with 58.6%, followed by Chromosome D507 with 47.9%. Six thousand and thirty-eight genes were mined within the SDRs on chromosome D502 and D507 of the consensus map. Within chromosome D502 and D507, 2 308 and 3 730 genes were mined, respectively, and were found to belong to 1 117 gourp out of which 622 groups were common across the two chromosomes. Moreover, genes within the top 9 groups related to plant resistance genes (R genes), whereas 188 genes encoding protein kinase domain (PF00069) comprised the largest group. Further analysis of the dominant gene group revealed that 287 miRNAs were found to target various genes, such as the gra-miR398, gra-miR5207, miR164a, miR164b, miR164c among others, which have been found to target top-ranked stress-responsive transcription factors such as NAC genes. Moreover, some of the stress- responsive cis-regulatory elements were also detected. Furthermore, RNA profiling of the genes from the dominant family showed that higher numbers of genes were highly upregulated under salt and osmotic stress conditions, and also they were highly expressed at different stages of fiber development.ConclusionThe results indicated the critical role of the SDRs in the evolution of the key regulatory genes in plants.

Salt-tolerance diversity in diploid and polyploid cotton (Gossypium) species.

The development of salt-tolerant genotypes is pivotal for the effective utilization of salinized land and to increase global crop productivity. Several cotton species comprise the most important source of textile fibers globally, and these are increasingly grown on marginal or increasingly saline agroecosystems. The allopolyploid cotton species also provide a model system for polyploid research, of relevance here because polyploidy was suggested to be associated with increased adaptation to stress. To evaluate the genetic variation of salt tolerance among cotton species, 17 diverse accessions of allopolyploid (AD-genome) and diploid (A- and D-genome) Gossypium were evaluated for a total of 29 morphological and physiological traits associated with salt tolerance. For most morphological and physiological traits, cotton accessions showed highly variable responses to 2weeks of exposure to moderate (50mm NaCl) and high (100mm NaCl) hydroponic salinity treatments. Our results showed that the most salt-tolerant species were the allopolyploid Gossypium mustelinum from north-east Brazil, the D-genome diploid Gossypium klotzschianum from the Galapagos Islands, followed by the A-genome diploids of Africa and Asia. Generally, A-genome accessions outperformed D-genome cottons under salinity conditions. Allopolyploid accessions from either diploid genomic group did not show significant differences in salt tolerance, but they were more similar to one of the two progenitor lineages. Our findings demonstrate that allopolyploidy in itself need not be associated with increased salinity stress tolerance and provide information for using the secondary Gossypium gene pool to breed for improved salt tolerance.

Simple Sequence Repeat (SSR) Genetic Linkage Map of D Genome Diploid Cotton Derived from an Interspecific Cross between Gossypium davidsonii and Gossypium klotzschianum.

The challenge in tetraploid cotton cultivars is the narrow genetic base and therefore, the bottleneck is how to obtain interspecific hybrids and introduce the germplasm directly from wild cotton to elite cultivars. Construction of genetic maps has provided insight into understanding the genome structure, interrelationships between organisms in relation to evolution, and discovery of genes that carry important agronomic traits in plants. In this study, we generated an interspecific hybrid between two wild diploid cottons, Gossypium davidsonii and Gossypium klotzschianum, and genotyped 188 F2:3 populations in order to develop a genetic map. We screened 12,560 SWU Simple Sequence Repeat (SSR) primers and obtained 1000 polymorphic markers which accounted for only 8%. A total of 928 polymorphic primers were successfully scored and only 728 were effectively linked across the 13 chromosomes, but with an asymmetrical distribution. The map length was 1480.23 cM, with an average length of 2.182 cM between adjacent markers. A high percentage of the markers on the map developed, and for the physical map of G. raimondii, exhibited highly significant collinearity, with two types of duplication. High level of segregation distortion was observed. A total of 27 key genes were identified with diverse roles in plant hormone signaling, development, and defense reactions. The achievement of developing the F2:3 population and its genetic map constructions may be a landmark in establishing a new tool for the genetic improvement of cultivars from wild plants in cotton. Our map had an increased recombination length compared to other maps developed from other D genome cotton species.

Salt stress responsiveness of a wild cotton species (Gossypium klotzschianum) based on transcriptomic analysis.

Cotton is a pioneer of saline land crop, while salt stress still causes its growth inhibition and fiber production decrease. Phenotype identification showed better salt tolerance of a wild diploid cotton species Gossypium klotzschianum. To elucidate the salt-tolerant mechanisms in G. klotzschianum, we firstly detected the changes in hormones, H2O2 and glutathione (GSSH and GSH), then investigated the gene expression pattern of roots and leaves treated with 300 mM NaCl for 0, 3, 12, 48 h, and each time control by RNA-seq on the Illumina-Solexa platform. Physiological determination proved that the significant increase in hormone ABA at 48 h, while that in H2O2 was at 12 h, likewise, the GSH content decrease at 48 h and the GSSH content increase at 48 h, under salt stress. In total, 37,278 unigenes were identified from the transcriptome data, 8,312 and 6,732 differentially expressed genes (DEGs) were discovered to be involved in salt stress tolerance in roots and leaves, respectively. Gene function annotation and expression analysis elucidated hormone biosynthesis and signal transduction, reactive oxygen species (ROS), and salt overly sensitive (SOS) signal transduction related genes revealed the important roles of them in signal transmission, oxidation balance and ion homeostasis in response to salinity stress. This is a report which focuses on primary response to highly salty stress (upto 300 mM NaCl) in cotton using a wild diploid Gossypium species, broadening our understanding of the salt tolerance mechanism in cotton and laying a solid foundation of salt resistant for the genetic improvement of upland cotton with the resistance to salt stress.

Molecular Mapping and Identification of QTLs for Fiber Micronaire on Chromosome 7 from Gossypium klotzschianum

Gossypium klotzschianum, carrying the elite alleles, is a diploid species of D genome originated from Galapagos Island, harboring the lethal genes to cause inconsistency of apical bud growth. In this research, we overcame the obstacle and established a BC1F2 population derived from (Simian 2 × G. klotzschianum) × Simian 2 (G. hirsutum). The SSR marker NAU1362 on chro-mosome 7 showed significant correlation with micronaire value by single marker analysis. The BC2F3 and BC2F4 populations were developed from the cross between BC1F2 individuals containing target segments of chromosome 7 from G. klotzschianum and recurrent parent Simian 2. The software Cartographer (V2.5) and the composite interval mapping were further employed to identify quantitative trait loci (QTL) associated with fiber micronaire in two generations. The fiber micronaire QTL qFMIC-7-1 identified in BC1F2 population was confirmed in BC2F3 and BC2F4, which explained 9.0% and 8.8% of the phenotypic variances, respectively. The G. klotzschianum allele decreased the fiber micronaire value. Another micronaire QTL, qFMIC-7-2, on chromo-some 7 was also detected in BC2F3 and BC2F4 generations with phenotypic variance of 3.7% and 4.7%, respectively. Simian 2 was genotyped as decreased micronaire value. These results provide valuable resources for effectively utilization of potential elite genes from G. klotzschianum.

Somatic embryogenesis and plant regeneration in wild cotton ( Gossypium klotzschianum )

A simple and efficient method for high frequency somatic embryogenesis and plant regeneration from hypocotyl-derived cultures and suspension cultures of Gossypium klotzschianum Anderss, a wild, diploid species of cotton is described here. Embryogenic cultures were induced from hypocotyl sections on MSB medium with 0.9 μM 2,4-D and 2.32 μM kinetin. MSB medium containing 0.045 μM 2,4-D, 0.93 μM kinetin, 2.46 μM IBA promoted embryogenic culture proliferation and embryo development. Suspension cultures with 0.23 μM 2,4-D and 0.93 μM kinetin also produced many embryos. Somatic embryos cultured on MSB medium with PGRs produced secondary embryos, and embryos developed into normal plantlets on PGR-free MSB medium. Regenerated plantlets were transferred onto the quarter-strength MSB medium with 0.5% active charcoal to avoid recallusing. Hypocotyls were better than cotyledons for culture induction and plant regeneration. 2,4-D and kinetin were essential for culture induction and maintenance.

Anther culture and plant regeneration of cotton (Gossypium klotzschianum Anderss)

Gossypium klotzschianum Anderss is an important wild species of cotton with great po-tential to be used in cotton breeding. Although study on its tissue culture was initiated inthe middle of the 1970s, regenerative plants have not been obtained until now, and an-ther has not been used for tissue culture as explants. In order to utilize effectively the

Establishment of embryogenic suspension cultures of a wild relative of cotton (Gossypium klotzschianum Anderss.)

Maintainable, highly embryogenic suspension cultures of a wild relative of cotton (Gossypium klotzschianum Anderss.) have been obtained. Callus with no apparent organization was used to establish the liquid culture. Callus growth conditions as well as suspension medium composition were optimized. A visual selection scheme was beneficial for the maintenance of the embryogenic suspension. These liquid cultures have been maintained for over 10 mo. with no loss in embryogenic capacity. The somatic embryos developed after transfer of the embryogenic tissues to a hormone-free liquid medium.

Initiation of callus and somatic embryos from explants of mature cotton (Gossypium klotzschianum Anderss)

Stem and petiole sections from a diploid species of cotton (Gossypium klotzschianum Anderss.) were longitudinally sliced and placed on a callus induction medium. Explants with the cut surface in contact with the medium either browned or produced a slow growing red callus which could not be subcultured. Explants oriented with the epidermis in contact with the medium produced a rapidly growing, friable, green callus which could be subcultured biweekly and has been maintained for 12 months. Globular and torpedo embryos were obtained 2 weeks after transfer of the callus to a liquid medium containing the auxin, 2,4-dichlorophenoxyacetic acid. Following subculture to an auxin-free medium, the embryos underwent additional development but plantlets were not obtained. Attempts to consistently regenerate plants from embryos are currently under way.

Isolation and culture of protoplasts from cotton ( Gossypium klotzschianum Anderss.) callus cultures

Protoplasts were enzymatically isolated from callus of Gossypium klotzschianum Anderss. with a 20.5% yield. Isolation efficiency was influenced by age of callus, incubation time, concentration of osmoticum and agitation speed. The enzyme incubation mixture consisted of 1% Cellulysin, 0.5% Macerase and 0.7 M mannitol at pH 4.7. Divisions of protoplasts were first observed 3 days after isolation and multicellular colonies were formed by 2 weeks.