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Background: Anthocyanins, a class of specialized metabolites that are ubiquitous among plant species, have attracted a great deal of attention from plant biologists due to their chemical diversity. They confer purple, pink, and blue colors that attract pollinators, protect plants from ultraviolet (UV) radiation, and scavenge reactive oxygen species (ROS) to facilitate plant survival during abiotic stress. In a previous study, we identified Beauty Mark (BM) in Gossypium barbadense as an activator of the anthocyanin biosynthesis pathway; this gene also directly led to the formation of a pollinator-attracting purple spot. Results: Here, we found that a single nucleotide polymorphism (SNP) (C/T) within the BM coding sequence was responsible for variations in this trait. Transient expression assays of BM from G. barbadense and G. hirsutum in Nicotiana benthamiana using luciferase reporter gene also suggested that SNPs in the coding sequence could be responsible for the absent beauty mark phenotype observed in G. hirsutum. We next demonstrated that the beauty mark and UV floral patterns are associated phenotypes and that UV exposure resulted in increased ROS generation in floral tissues; BM thus contributed to ROS scavenging in G. barbadense and wild cotton plants with flowers containing the beauty mark. Furthermore, a nucleotide diversity analysis and Tajima's D Test suggested that there have been strong selective sweeps in the GhBM locus during G. hirsutum domestication. Conclusions: Taken together, these results suggest that cotton species differ in their approaches to absorbing or reflecting UV light and thus exhibit variations in floral anthocyanin biosynthesis to scavenge reactive ROS; furthermore, these traits are related to the geographic distribution of cotton species. [ABSTRACT FROM AUTHOR]

Protoplasts, which lack cell walls, are ideal research materials for genetic engineering. They are commonly employed in fusion (they can be used for more distant somatic cell fusion to obtain somatic hybrids), genetic transformation, plant regeneration, and other applications. Cotton is grown throughout the world and is the most economically important crop globally. It is therefore critical to study successful extraction and transformation efficiency of cotton protoplasts. In the present study, a cotton callus protoplast extraction method was tested to optimize the ratio of enzymes (cellulase, pectinase, macerozyme R-10, and hemicellulase) used in the procedure. The optimized ratio significantly increased the quantity and activity of protoplasts extracted. We showed that when enzyme concentrations of 1.5% cellulase and 1.5% pectinase, and either 1.5% or 0.5% macerozyme and 0.5% hemicellulase were used, one can obtain increasingly stable protoplasts. We successfully obtained fluorescent protoplasts by transiently expressing fluorescent proteins in the isolated protoplasts. The protoplasts were determined to be suitable for use in further experimental studies. We also studied the influence of plasmid concentration and transformation time on protoplast transformation efficiency. When the plasmid concentration reaches 16 µg and the transformation time is controlled within 12–16 h, the best transformation efficiency can be obtained. In summary, this study presents efficient extraction and transformation techniques for cotton protoplasts. [ABSTRACT FROM AUTHOR]

Summary: Hybrid crop varieties have been repeatedly demonstrated to produce significantly higher yields than their parental lines; however, the low efficiency and high cost of hybrid seed production has limited the broad exploitation of heterosis for cotton production. One option for increasing the yield of hybrid seed is to improve pollination efficiency by insect pollinators. Here, we report the molecular cloning and characterization of a semidominant gene, Beauty Mark (BM), which controls purple spot formation at the base of flower petals in the cultivated tetraploid cotton species Gossypium barbadense. BM encodes an R2R3 MYB113 transcription factor, and we demonstrate that GbBM directly targets the promoter of four flavonoid biosynthesis genes to positively regulate petal spot development. Introgression of a GbBM allele into G. hirsutum by marker‐assisted selection restored petal spot formation, which significantly increased the frequency of honeybee visits in G. hirsutum. Moreover, field tests confirmed that cotton seed yield was significantly improved in a three‐line hybrid production system that incorporated the GbBM allele. Our study thus provides a basis for the potentially broad application of this gene in improving the long‐standing problem of low seed production in elite cotton hybrid lines. [ABSTRACT FROM AUTHOR]

Although genetic transformation has opened up a new era for cotton molecular breeding, it still suffers from the limitation problem of long transformation periods, which slows down the generation of new cotton germplasms. In this study, LT gene (SV40 large T antigen), which promotes the transformation efficiency of animal cells, was codon-optimized. Its overexpression vector was transformed into cotton. It was observed that EC (embryogenic callus) formation period was 33% shorter and transformation efficiency was slightly higher in the LT T0 generation than that of control. RNA-seq data of NEC (non-embryonic callus) and EC from LT and control revealed that more DEGs (differential expression genes) in NEC were identified than that of EC, indicating LT mainly functioned in NEC. Further KEGG, GO, and transcription factor analyses showed that DEGs were significantly enriched in brassinosteroid biosynthesis pathways and that bHLH, MYB, and AP2/ERF were the top three gene families, which are involved in EC formation. In addition, the key genes related to the auxin pathway were differentially expressed only in LT overexpression NEC, which caused early response, biosynthesis, and transportation of the hormone, resulting in EC earlier formation. In summary, the results demonstrated that LT can promote somatic embryogenesis in cotton, which provides a new strategy for improving cotton transformation and shortening EC formation time. [ABSTRACT FROM AUTHOR]

Plant trichomes are specialized epidermal cells that are widely distributed on plant aerial tissues. The initiation and progression of trichomes are controlled in a coordinated sequence of multiple molecular events. During the past decade, major breakthroughs in the molecular understanding of trichome development were achieved through the characterization of various trichomes defective mutants and trichome-associated genes, which revealed a highly complex molecular regulatory network underlying plant trichome development. This review focuses on the recent millstone in plant trichomes research obtained using genetic and molecular studies, as well as 'omics' analyses in model plant Arabidopsis and fiber crop cotton. In particular, we discuss the latest understanding and insights into the underlying molecular mechanisms of trichomes formation at multiple dimensions, including at the chromatin, transcriptional, post-transcriptional, and post-translational levels. We summarize that the integration of multi-dimensional trichome-associated genes will enable us to systematically understand the molecular regulation network that landscapes the development of the plant trichomes. These advances will enable us to address the unresolved questions regarding the molecular crosstalk that coordinate concurrent and ordered the changes in cotton fiber initiation and progression, together with their possible implications for genetic improvement of cotton fiber. [ABSTRACT FROM AUTHOR]

Background: Genome sequencing technologies have been improved at an exponential pace but precise chromosome-scale genome assembly still remains a great challenge. The draft genome of cultivated G. arboreum was sequenced and assembled with shotgun sequencing approach, however, it contains several misassemblies. To address this issue, we generated an improved reassembly of G. arboreum chromosome 12 using genetic mapping and reference-assisted approaches and evaluated this reconstruction by comparing with homologous chromosomes of G. raimondii and G. hirsutum. Results: In this study, we generated a high quality assembly of the 94.64 Mb length of G. arboreum chromosome 12 (A_A12) which comprised of 144 scaffolds and contained 3361 protein coding genes. Evaluation of results using syntenic and collinear analysis of reconstructed G. arboreum chromosome A_A12 with its homologous chromosomes of G. raimondii (D_D08) and G. hirsutum (AD_A12 and AD_D12) confirmed the significant improved quality of current reassembly as compared to previous one. We found major misassemblies in previously assembled chromosome 12 (A_Ca9) of G. arboreum particularly in anchoring and orienting of scaffolds into a pseudo-chromosome. Further, homologous chromosomes 12 of G. raimondii (D_D08) and G. arboreum (A_A12) contained almost equal number of transcription factor (TF) related genes, and showed good collinear relationship with each other. As well, a higher rate of gene loss was found in corresponding homologous chromosomes of tetraploid (AD_A12 and AD_D12) than diploid (A_A12 and D_D08) cotton, signifying that gene loss is likely a continuing process in chromosomal evolution of tetraploid cotton. Conclusion: This study offers a more accurate strategy to correct misassemblies in sequenced draft genomes of cotton which will provide further insights towards its genome organization. [ABSTRACT FROM AUTHOR]

Zinc (Zn) deficiency is often associated with calcareous soils throughout the world, whereas application of Zn not only enhances biological yield but exhibits significant interactions with nutrients. Hence, a two-year field experiment was performed in 2004 and 2005 to assess the crop Zn requirements as well as nutrient interactions in cotton. The present study followed a randomized complete block design with five Zn levels: 0.0, 5.0, 7.5, 10.0, and 12.5 kg Zn as ZnSO4.7H2O. The biological yield of cotton increased progressively with increasing Zn rates. In general, cotton yield was higher in 2005 over 2004. Interestingly, Zn fertilization resulted in increased accumulation of nitrogen (N), potassium (K), boron (B), and Zn, whereas decreased the phosphorus (P), calcium (Ca), magnesium (Mg), iron (Fe), copper (Cu), and manganese (Mn) (p ≤ 0.05) uptake by cotton. The enhanced macronutrients accumulation in cotton by Zn application improved the cotton yield. In conclusion, biological yield and nutrient composition of the cotton plant are greatly influenced by Zn supply under irrigated environments. [ABSTRACT FROM AUTHOR]

The current research was conducted to find out modification in mineral profiling of cotton after the attack of bacterial blight disease caused by Xanthomonas citri pv malvacearum. Leaves of three susceptible and resistant (un-inoculated and inoculated) cultivars were collected for the determination of alteration in ionic status. The remarkable variation (p = 5) in the ionic contents was observed across treatments, groups (un-inoculated and inoculated), types (susceptible and resistant) and varieties of cotton plants due to the infection by X. citri pv malvacearum. Nested random's effect analysis of variance revealed significant difference in ionic status (Ca, N, K, P, Mg, Zn, Cu and Fe) in leaves of cotton. Resistant type of plants expressed 2.40% and 0.19% while susceptible type showed 2.17% and 0.16% difference in concentrations of P and N respectively. Moreover, resistant type expressed 408.3, 310.2, 21.1, 2.9, 1.83 and 1.61 ppm while susceptible type showed 378.8, 270.2, 14.6, 2.4, 1.75 and 1.35 ppm difference in concentrations of Ca, K, Zn, Mg, Cu and Fe respectively. It was accomplished that resistant cultivars accumulated these ions at higher concentrations than susceptible varieties. These increased ionic contents in resistant plants strengthen the biochemical and physiological processes of the host plants which help to avoid the spread of pathogen. [ABSTRACT FROM AUTHOR]

The sensitivity to abscisic acid (ABA) by its receptors, pyrabactin resistance-like proteins (PYLs), is considered a most important factor in activating the ABA signal pathway in response to abiotic stress. However, it is still unknown which PYL is the crucial ABA receptor mediating response to drought stress in cotton (Gossypium hirsutum L.). Here, we reported the identification and characterization of highly induced ABA receptor GhPYL9-11A in response to drought in cotton. It is observed that GhPYL9-11A was highly induced by ABA treatment. GhPYL9-11A binds to protein phosphatase 2Cs (PP2Cs) in an ABA-independent manner. Moreover, the GhPYL-11A-PP2C interactions are partially disrupted by mutations, proline (P84) and histidine (H111), in the gate-latch region. Transgenic Arabidopsis overexpressing GhPYL9-11A plants were hypersensitive to ABA during seed germination and early seedling stage. Further, the increased in root growth and up regulation of drought stress-related genes in transgenic Arabidopsis as compared to wild type confirmed the potential role of GhPYL9-11A in abiotic stress tolerance. Consistently, the expression level of GhPYL9-11A is on average higher in drought-tolerant cotton cultivars than in drought-sensitive cottons under drought treatment. In conclusion, the manipulation of GhPYL9-11A expression could be a useful strategy for developing drought-tolerant cotton cultivars. [ABSTRACT FROM AUTHOR]

Zinc (Zn) deficiency is widespread in calcareous soils. Therefore, we conducted a 2-year field experiment to investigate the impact of graded Zn levels on growth, yield, and fiber and oil quality of cotton (Gossypium hirsutum L., cv. CIM-473) grown in a calcareous Aridisol having 0.54 mg diethylenetriaminepentaacetic acid (DTPA)-extractable Zn kg-1 soil. Zinc use increased boll bearing, boll weight, seed index, and seed cotton yield (P ≤ 0.05). Maximum yield increase was 15%, with 7.5 kg Zn ha-1; however, greater Zn levels depressed yield. Leaf chlorophyll, membrane permeability, seed protein, and oil content and quality improved (P ≤ 0.05), and fiber quality remained unaffected with Zn use. Critical Zn concentration in cotton leaves was 36 mg kg-1. Positive relationships of leaf Zn concentration were observed with boll weight, protein content, total unsaturated fatty acids, and fiber characteristics. Thus, Zn fertilization of low-Zn Aridisols is suggested for improving cotton productivity and seed quality. [ABSTRACT FROM AUTHOR]

Allotetraploid cotton (Gossypium hirsutum and Gossypium barbadense) are cultivated worldwide for its white fiber. For centuries, conventional breeding approaches increase cotton yield at the cost of extensive erosion of natural genetic variability. Sea Island cotton (G. barbadense) is known for its superior fiber quality, but show poor adaptability as compared to Upland cotton. Here, in this study, we use ethylmethanesulfonate (EMS) as a mutagenic agent to induce genome-wide point mutations to improve the current germplasm resources of Sea Island cotton and develop diverse breeding lines with improved adaptability and excellent economic traits. We determined the optimal EMS experimental procedure suitable for construction of cotton mutant library. At M6 generation, mutant library comprised of lines with distinguished phenotypes of the plant architecture, leaf, flower, boll, and fiber. Genome-wide analysis of SNP distribution and density in yellow leaf mutant reflected the better quality of mutant library. Reduced photosynthetic efficiency and transmission electron microscopy of yellow leaf mutants revealed the effect of induced mutations at physiological and cellular level. Our mutant collection will serve as the valuable resource for basic research on cotton functional genomics, as well as cotton breeding. [ABSTRACT FROM AUTHOR]

Cotton is an important economic crop affected by different abiotic stresses at different developmental stages. Salinity limits the growth and productivity of crops worldwide. Na+/H+ antiporters play a key role during the plant development and in its tolerance to salt stress. The aim of the present study was a genome-wide characterization and expression pattern analysis under the salinity stress of the sodium-proton antiporter (NHX) of Gossypium barbadense in comparison with Gossypium hirsutum. In G. barbadense, 25 NHX genes were identified on the basis of the Na+_H+ exchanger domain. All except one of the G. barbadenseNHX transporters have an Amiloride motif that is a known inhibitor of Na+ ions in plants. A phylogenetic analysis inferred three classes of GbNHX genes—viz., Vac (GbNHX1, 2 and 4), Endo (GbNHX6), and PM (GbNHX7). A high number of the stress-related cis-acting elements observed in promoters show their role in tolerance against abiotic stresses. The Ka/Ks values show that the majority of GbNHX genes are subjected to strong purifying selection under the course of evolution. To study the functional divergence of G. barbadenseNHX transporters, the real-time gene expression was analyzed under salt stress in the root, stem, and leaf tissues. In G. barbadense, the expression was higher in the stem, while in G. hirsutum the leaf and root showed a high expression. Moreover, our results revealed that NHX2 homologues in both species have a high expression under salinity stress at higher time intervals, followed by NHX7. The protein-protein prediction study revealed that GbNHX7 is involved in the CBL-CIPK protein interaction pathway. Our study also provided valuable information explaining the molecular mechanism of Na+ transport for the further functional study of Gossypium NHX genes. [ABSTRACT FROM AUTHOR]

To evaluate the role of potassium (K) in maintaining nitrogen metabolism and osmotic adjustment development of cotton functional leaves to sustain growth under soil drought and rewatering conditions, the plants of two cotton cultivars Siza 3 (low-K sensitive) and Simian 3 (low-K tolerant), were grown under three different K rates (K0, K1, and K2; 0, 150, and 300 kg K 2 O ha −1 , respectively) and exposed to drought stress with 40 ± 5% soil relative water content (SRWC). The drought stress was applied at flowering stage by withholding water for eight days followed by rewatering to a well-watered level (75 ± 5% SRWC). The results showed that drought-stressed plants of both cultivars showed a decrease in leaf relative water content (RWC) and osmotic potential in the functional leaves and developed osmotic adjustment with an increase in the contents of free amino acids, soluble sugars, inorganic K, and nitrate as compared to well-watered plants. In drought-stressed plants, nitrogen-metabolizing enzyme activities of nitrogen reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT) were diminished significantly (P ≤ 0.05) along with decreased chlorophyll content and soluble proteins. However, drought-stressed plants under K application not only exhibited higher osmotic adjustment with greater accumulation of osmolytes but also regulated nitrogen metabolism by maintaining higher enzyme activities, soluble proteins, and chlorophyll content in functional leaves as compared to the plants without K application. Siza 3 showed better stability in enzyme activities and resulted in 89% higher seed cotton yield under K2 as compared to K0 in drought-stressed plants, whereas this increase was 53% in the case of Simian 3. The results of the study suggested that K application enhances cotton plants’ potential for sustaining high nitrogen-metabolizing enzyme activities and related components to supplement osmotic adjustment under soil drought conditions. [ABSTRACT FROM AUTHOR]

Under drought, limited photo-assimilates synthesis and their poor partitioning is a main constraint to final yield production in cotton ( Gossypium hirsutum L.). To study the potassium (K) role in photo-assimilation and carbohydrate metabolism in cotton under soil drought stress during flowering and boll formation stage, a two-year pot experiment was conducted in 2015 and 2016. Two cotton cultivars namely Simian 3 (low-K tolerant) and Siza 3 (low-K sensitive) were grown under three K rates (0, 150 and 300 kg K 2 O ha −1 ). Plants were exposed to well-watered [(75 ± 5%) soil relative water content (SRWC)] and water stress (35–40% SRWC) for 7 days followed by re-watering to SRWC (75 ± 5%). The results showed that water-stressed plants under K0 application exhibited significant decline in net photosynthesis, stomatal conductance, intercellular CO 2 concentration and ribulose-1,5-bisphosphate carboxylase (Rubisco) activity and resulting in reduced photo-assimilates synthesis and partitioning towards reproductive organs in both cultivars. Conversely, K application decreased the decline in photosynthesis, Rubisco activity and biomass accumulation and partitioning. The positive effects of K application increased as increasing K rates, and that was more pronounced in Siza 3 than Simian 3. Drought stress decreased starch content but increased sucrose content; whereas, K application maintained higher concentration of sucrose in leaves of water-stressed plants through the regulation of higher sucrose phosphate synthase (SPS), sucrose synthase (SuSy) and lower soluble acid invertase (SAI) activities. The results of the study concluded that K application regulated the photo-assimilation and translocation process along with the related enzymes activities in cotton. The study suggests that K nutrient management strategy has the potential to minimize the impacts of drought stress in cotton. [ABSTRACT FROM AUTHOR]

Cotton is not only a raw material for the textile industry, but also an important strategic material. However, traditional breeding methods have narrowed the genetic diversity of current cotton cultivars. Abundant germplasm resources is a solid foundation for breeding, the use of chemical mutagenesis to create abundant mutation is of great significance to cotton breeding. This study used ethyl methanesulfonate (EMS) to mutagenize upland cotton material TM-1. First, we obtained a mutant library with abundant mutations and abundant phenotypes of the leaf, boll, locules numbers and plant architecture,. Second, based on the genome-wide analysis of the leaf and plant structure mutant., it showed that the library had a saturated genome mutations. Further GO and KEGG analysis showed SNPs were significantly enriched in DNA repair and response to hormone, non-homologous end joining (NHEJ) and homologous recombination (HR) pathways, which explained the mutated trait. In addition, we screened candidate gene (Gh_D05G364200) for crumpled leaf by BSA and transcriptome sequencing. Above all, the mutant library we obtained provides abundant resources for cotton functional genomics and breeding. • An upland cotton saturated mutant library was obtained. • SNPs of mutant plants were significantly enriched in DNA repair, NHEJ and HR pathways, which explained the mutated trait. • Gene (Gh_D05G364200) was screened as a candidate gene for crumpled leaf traits. [ABSTRACT FROM AUTHOR]

Cyclic AMP (cAMP) is a pivotal signaling molecule existing in almost all living organisms. It is an intracellular non-protein small molecule that regulates the activity of intracellular enzymes and non-enzyme proteins when its concentration changes in response to the binding of extracellular signals to cell surface receptors. As such, cAMP is referred to as a second messenger with an important role in cell signaling and modulation a variety of cellular responses. cAMP can help plants cope with abiotic stress, but the mechanism by which it improves salt tolerance has not been elucidated. In our study, we treated cotton with Forskolin (a cAMP activator) to increase cAMP levels, and found that it improved cotton seed tolerance to salt stress, thereby improving the germination rate of seeds in saline soil. Through transcriptome analysis, we characterized the responses of ABA, proteins, and pathways to salt stress after cAMP signaling, and four genes related to salt tolerance and signal transduction were identified. Three of them, GhLTI65 , GhGOLS2 , and GhNAC002 were silenced by virus induced gene silencing (VIGs), and the plant tolerance to salt stress was significantly reduced as compared with the control plants. Among these, we found that GhLTI65 (RD29B) was not only involved in the salt stress response, but played a role in the cAMP signaling cascade. We further performed yeast two-hybrid assays and bimolecular fluorescence complementation (BiFC) to determine that GhLTI65 interacts with the SNF1-related protein kinase GhPV42A in the cytoplasm, and that their co-expression is regulated by ABA-related signaling. We propose that ABA and cAMP signaling increase the expression of GhPV42A by integrating related mitogen-activated protein kinase (MAPK)cascade signaling, and that GhPV42A further interacts with GhLTI65 to increase its expression, thereby helping plants to receive signals and to respond to salt stress. [ABSTRACT FROM AUTHOR]

• AhCMO -transgenic cotton showed significant resistance to chilling stress and contribute to the improvement of cotton fiber yield. • AhCMO transgenic cotton mainly improved the concentration of cellular osmoprotectants which enhanced chilling resistance in cotton. • AhCMO is an ideal candidate for genetic engineering, which may greatly contribute to enhancing cotton low temperature resistance. Low temperature is a major factor limiting seedling growth and the production of cotton (Gossypium hirsutum L.). However, enhancing chilling tolerance is typically negatively correlated with yield in agricultural production. Here, we demonstrate that transgenic cotton expressing Atriplex hortensis choline monooxygenase (AhCMO) greatly enhanced resistance to chilling stress. The promotion of chilling tolerance is mainly due to an increase in the content of osmoprotectants, especially glycine betaine and proline. The increased chilling tolerance was further verified at the molecular level using genome-wide expression profiling by RNA-sequencing. Further detailed analysis showed that the number of genes involved in scavenging of reactive oxygen species (ROS) was down-regulated and the activity of superoxide dismutase (SOD) and catalase (CAT) were decreased in AhCMO transgenic cotton compared with wild type after low temperture treatment. More importantly, overexpression of AhCMO in cotton moderately improved cotton fiber yield in normal growth condition. These data show that AhCMO transgenic cotton enhances low temperature tolerance via directly accumulating cellular osmoprotectants. Manipulating the expression of AhCMO by biotechnological tools could be a powerful method to enhance chilling tolerance in cotton. [ABSTRACT FROM AUTHOR]

To investigate whether potassium (K) application enhances the potential of cotton ( Gossypium hirsutum L.) plants to maintain physiological functions during drought and recovery, low K-sensitive (Siza 3) and -tolerant (Simian 3) cotton cultivars were exposed to three K rates (0, 150, and 300 K 2 O kg ha −1 ) and either well-watered conditions or severe drought stress followed by a recovery period. Under drought stress, cotton plants showed a substantial decline in leaf water potential, stomatal conductance, photosynthetic rate, and the maximum and actual quantum yield of PSII, resulting in greater non-photochemical quenching and lipid peroxidation as compared to well-watered plants. However, plants under K application not only showed less of a decline in these traits but also displayed greater potential to recover after rewatering as compared to the plants without K application. Plants receiving K application showed lower lipid peroxidation, higher antioxidant enzyme activities, and increased proline accumulation as compared to plants without K application. Significant relationships between rates of photosynthetic recovery and K application were observed. The cultivar Siza 3 exhibited a more positive response to K application than Simian 3. The results suggest that K application enhances the cotton plant's potential to maintain functionality under drought and facilitates recovery after rewatering. [ABSTRACT FROM AUTHOR]