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Aluminum-activated malate transporters (ALMT) are widely involved in plant growth and metabolic processes, including adaptation to acid soils, guard cell regulation, anion homeostasis, and seed development. Although ALMT genes have been identified in Arabidopsis, wheat, barley, and Lotus japonicus, little is known about its presence in Gossypium hirsutum L. In this study, ALMT gene recognition in diploid and tetraploid cotton were done using bioinformatics analysis that examined correlation between homology and evolution. Differentially regulated ALMT genetic profile in G. hirsutum was examined, using RNA sequencing and qRT-PCR, during six fiber developmental time-points, namely 5 d, 7 d, 10 d, 15 d, 20 d, and 25 d. We detected 36 ALMT genes in G. hirsutum, which were subsequently annotated and divided into seven sub-categories. Among these ALMT genes, 34 had uneven distribution across 14/26 chromosomes. Conserved domains and gene structure analysis indicated that ALMT genes were highly conserved and composed of exons and introns. The GhALMT gene expression profile at different DPA (days post anthesis) in different varieties of G. hirsutum is indicative of a crucial role of ALMT genes in fiber development in G. hirsutum. This study provides basis for advancements in the cloning and functional enhancements of ALMT genes in enhancing fiber development and augmenting high quality crop production. [ABSTRACT FROM AUTHOR]

Background: Dissecting genome organization is indispensable for further functional and applied studies. As genome sequences data shown, cotton genomes contain more than 60% repetitive sequences, so study on repetitive sequences composition, structure, and distribution is the key step to dissect cotton genome. Results: In this study, a bacterial artificial chromosome (BAC) clone enriched in repetitive sequences, was discovered initiatively by fluorescence in situ hybridization (FISH). FISHing with allotetraploidy cotton as target DNA, dispersed signals on most regions of all A sub-genome chromosomes, and only middle regions of all D sub-genome chromosomes were detected. Further FISHing with other cotton species bearing A or D genome as target DNA, specific signals were viewed. After BAC sequencing and bioinformational analysis, 129 repeat elements, size about 57,172 bp were found, accounting for more than 62% of the BAC sequence (91,238 bp). Among them, a type of long terminal repeat-retrotransposon (LTR-RT), LTR/Gypsy was the key element causing the specific FISH results. Using the fragments of BAC matching with the identified Gypsy-like LTR as probes, the BAC-57I23-like FISH signals were reappeared. Running BLASTN, the fragments had good match with all chromosomes of G. arboreum (A2) genome and A sub-genome of G. hirsutum (AD1), and had relatively inferior match with all chromosomes of D sub-genome of AD1, but had little match with the chromosomes of G. raimondii (D5) genome, which was consistent with the FISH results. Conclusion: A repeats-enriched cytogenetic marker to identify A and D sub-genomes of Gossypium was discovered by FISH. Combined sequences analysis with FISH verification, the assembly quality of repetitive sequences in the allotetraploidy cotton draft genome was assessed, and better chromosome belonging was verified. We also found the genomic distribution of the identified Gypsy-LTR-RT was similar to the distribution of heterochromatin. The expansion of this type of Gypsy-LTR-RT in heterochromatic regions may be one of the major reasons for the size gap between A and D genome. The findings showed here will help to understand the composition, structure, and evolution of cotton genome, and contribute to the further perfection of the draft genomes of cotton. [ABSTRACT FROM AUTHOR]

Background: Cytogenetic map can provide not only information of the genome structure, but also can build a solid foundation for genetic research. With the developments of molecular and cytogenetic studies in cotton (Gossypium), the construction of cytogenetic map is becoming more and more imperative. Results: A cytogenetic map of chromosome 1 (A101) of Gossypium herbaceum (A1) which includes 10 bacterial artificial chromosome (BAC) clones was constructed by using fluorescent in situ hybridization (FISH). Meanwhile, comparison and analysis were made for the cytogenetic map of chromosome 1 (A101) of G. herbaceum with four genetic linkage maps of chromosome 1 (Ah01) of G. hirsutum ((AD)1) and one genetic linkage map of chromosome 1 of (A101) G. arboreum (A2). The 10 BAC clones were also used to be localized on G. raimondii (D5) chromosome 1 (D501), and 2 of them showed clear unique hybridized signals. Furthermore, these 2 BAC clones were also shown localized on chromosome 1 of both A sub-genome and D sub-genome of G. hirsutum. Conclusion: The comparison of the cytogenetic map with genetic linkage maps showed that most of the identified marker-tagged BAC clones appearing same orders in different maps except three markers showing different positions, which might indicate chromosomal segmental rearrangements. The positions of the 2 BAC clones which were localized on Ah01 and Dh01 chromosomes were almost the same as that on A101 and D501 chromosomes. The corresponding anchored SSR markers of these 2 BAC clones were firstly found to be localized on chromosome D501 (Dh01) as they were not seen mapped like this in any genetic map reported. [ABSTRACT FROM AUTHOR]

The study was conducted on the individual chromosome identification in Gossypium darwinii (AdDd), G. klotzschianum (D3k), G. davidsonii (D3d), G. armourianum (D2-1) and G. aridum (D4) using a multi-probe fluorescence of in situ hybridization (FISH) system. Comparative analysis on their genetic maps with that of physical maps was made as well. The FISH probes used contained two sets of bacterial artificial chromosome (BAC) clones [one is specific to 26 individual chromosomes from A and D subgenomes of G. hirsutum (Ah and Dh) while the other is a D genome centromere- specific BAC clone 150D24], 45S and 5S rDNA clones. The results showed that all Ad chromosomes were marked with the 13 Ah chromosome-specific BAC clones, whilst all Dd, D3k, D3d, D2-1 and D4 chromosomes and chromosomal arms were identified with the 13 Dh chromosome-specific BAC clones and the D genome centromere-specific BAC. According to the homology within D subgenomes which are between A (D) genome and A (D) subgenome, the systematic nomenclature for individual chromo- some in the five species was established. The chromosomes of A (D) subgenomes in G. darwinii were named as Ad01-Ad13 (Dd01-Dd13). The chromosomes in D3k, D3d, D2-1 and D4 were named as D3k01-D3k13, D3d01-D3d13, D2-101-D2-113 and D401-D413, respectively. Based on the successful identification for individual chromosomes, 45S and 5S rDNA were located to the special chromosomes and chromosomal arms for all five species. And there appeared chromosomal collinearity from the BAC clones among different species by comparing BACs positions, which suggested that the majority of chromosome segment homology may exist between D genomes and D subgenome. Moreover, as the genetic map and physical map were integrated, the orientations of genetic maps for Dd and D genomes of diploid cotton were established. The orientations of some of chromosomes in genetic maps (Dd03, Dd04, Dd06, Dd09, Dd10 and Dd12) were found switched. The SSR marker in the middle of linkage group 04 was corrected at nearby the end of chromosome 04 by FISH. The study will be helpful to establish a theoretical basis using the wild gene bank to exploit more genes aiming for cotton breeding and will provide powerful evidences both for the evolution of Gossypium and assembling the sequences of the obtained and as well the on-going whole genome sequencing projects of cotton. [ABSTRACT FROM AUTHOR]

The experiment on individual chromosome assignments and chromosomal diversity was conducted using a multi-probe fluorescence in situ hybridization (FISH) system in D subgenome of tetraploid Gossypium barbadense (Db), G. thurberi (D1) and G. trilobum (D8), which the later two were the possible subgenome donors of tetraploid cottons. The FISH probes contained a set of bacterial artificial chromosome (BAC) clones specific to 13 individual chromosomes from D subgenome of G. hirsutum (Dh), a D genome centromere-specific BAC clone 150D24, 45S and 5S ribosomal DNA (rDNA) clones, respectively. All tested chromosome orientations were confirmed by the centromere-specific BAC probe. In D1 and D8, four 45S rDNA loci were found assigning at the end of the short arm of chromosomes 03, 07, 09 and 11, while one 5S rDNA locus was successfully marked at pericentromeric region of the short arm of chromosome 09. In Db, three 45S rDNA loci and two 5S rDNA loci were found out. Among them, two 45S rDNA loci were located at the terminal of the short arm of chromosomes Db07 and Db09, whilst one 5S rDNA locus was found situating near centromeric region of the short arm of chromosome Db09. The positions of the BAC clones specific to the 13 individual chromosomes from Dh were compared between D1, D8 and Db. The result showed the existence of chromosomal collinearity within D1 and D8, and as well between them and Db. The results will serve as a base for understanding chromosome structure of cotton and polyploidy evolution of cotton genome and will provide bio-information for assembling the sequences of finished and the on-going cotton whole genome sequencing projects. [ABSTRACT FROM AUTHOR]

As high-strength cotton fibers are critical components of high quality cotton, developing cotton cultivars with high-strength fibers as well as high yield is a top priority for cotton development. Recently, chromosome segment substitution lines (CSSLs) have been developed from high-yield Upland cotton (Gossypium hirsutum) crossed with high-quality Sea Island cotton (G. barbadense). Here, we constructed a CSSL population by crossing CCRI45, a high-yield Upland cotton cultivar, with Hai1, a Sea Island cotton cultivar with superior fiber quality. We then selected two CSSLs with significantly higher fiber strength than CCRI45 (MBI7747 and MBI7561), and one CSSL with lower fiber strength than CCRI45 (MBI7285), for further analysis.We sequenced all four transcriptomes at four different time points postanthesis, and clustered the 44,678 identified genes by function. We identified 2200 common differentially-expressed genes (DEGs): those that were found in both high quality CSSLs (MBI7747 and MBI7561), but not in the low quality CSSL (MBI7285). Many of these genes were associated with various metabolic pathways that affect fiber strength. Upregulated DEGs were associated with polysaccharide metabolic regulation, single-organism localization, cell wall organization, and biogenesis, while the downregulated DEGs were associated with microtubule regulation, the cellular response to stress, and the cell cycle. Further analyses indicated that three genes, XLOC_036333 [mannosyl-oligosaccharide-a-mannosidase (MNS1)], XLOC_029945 (FLA8), and XLOC_075372 (snakin-1), were potentially important for the regulation of cotton fiber strength. Our results suggest that these genes may be good candidates for future investigation of the molecular mechanisms of fiber strength formation and for the improvement of cotton fiber quality through molecular breeding. [ABSTRACT FROM AUTHOR]