Cotton is a potential and excellent candidate to balance both agricultural production and reme-diation of mercury-contained soil, as its main production fiber hardly involve into food chains. However, there is known rarely about the tolerance and response to Hg environments in cotton. In this study, The biochemical and physiological damages, in response to mercury (Hg), were investigated in upland cotton seedlings. The results on cottonseeds germination, indicated the germination rate were suppressed by high Hg levels, as the decrease of percentage was more than 10% at 1000 µM Hg. Shoots and roots’ growth were significantly inhibited above 10 µM Hg. The inhibitor rates (IR) in fresh weight were close between shoots and roots, whereas that in dry weight the root growth was more obviously influenced by Hg. In comparison of organs, the growth inhibition ranked as root > leaf > stem. The declining of translocation factor (TF) op-posed the Hg level even as low to 0.05 at 50 µM Hg. The assimilation of cotton plants was af-fected negatively by Hg toxicity, as evidenced from the performances on photosynthesis pig-ments (chlorophyll a and b) and gas exchange (Intercellular CO2 concentration (Ci), CO2 assimila-tion rate (Pn) and stomatal conductance (Gs)). Sick phenotypes on leaf surface included small white zone, shrinking and necrosis. Membrane lipid peroxidation and leakage were Hg dose-dependent as indicated by malondialdehyde (MDA) content and relative conductivity (RC) values in leaves and roots. More than 10 µM Hg damaged antioxidant enzyme system in both leaves and roots (P<0.05). Concludingly, 10 µM Hg post negative consequences to upland cotton plants in growth, physiology and biochemistry, whereas high phytotoxicity and damage ap-peared at more than 50 µM Hg concentration.

This study was carried out to evaluate the impact of Amegilla calens bee on fruit and seed yields of G. hirsutum in an experimental field, in September 2018 and 2019. The experiments were carried out on 540 flowers divided in four treatments: 120 flowers accessible to all visitors; 120 flowers bagged to avoid all visits; 200 flowers protected and uncovered when they were opened, to allow A. calens visits; 100 flowers bagged then uncovered and rebagged without the visit of insects or any other organism. Bees daily rhythm of activity, its foraging behaviour on flowers, its pollination efficiency, the fruiting rate, the number of seeds per fruit and the percentage of normal seeds were evaluated. Results indicate that among 11 insect species recorded on flowers, X. olivacea ranked second and harvested nectar. Throughout the pollination efficiency of a single flower visit, X. olivacea provoked a significant increase of the podding rate, the mean number of seeds per pod, the percentage of normal seeds and the mean weight of a seed by 39.48 %, 18.19 %, 49.62 % and 31.53 % respectively. The conservation and installation of X. olivacea nests close to P. vulgaris fields is recommended to improve its pod production and seed quality.

Magnesium (Mg) is a vital element, which involves in various key cellular processes in plants. Mg transporter (MGT) genes play an important role in magnesium distribution and ionic balance maintenance. Here, MGT family members were identified and characterized in three species of the plant family Malvaceae, including Theobroma cacao, Corchorus capsularis, and Gossypium hirsutum to improve our understanding of their structure, regulatory systems, functions, and possible interactions. We identified 18, 41, and 16 putative non-redundant MGT genes from the genome of T. cacao, G. hirsutum, and C. capsularis, respectively, which were clustered into five groups within maximum likelihood tree. Several segmental/tandem duplication events were determined between MGTs genes. It seems that MGTs were slowly evolving and have been evolved under a purifying selection. Analysis of gene promoter regions showed that MGTs have a high potential to respond to biotic/abiotic stresses as well as hormones. The expression patterns of MGT genes revealed their possible T. cacaorole in response to P. megakarya fungi in T. cacao, whereas MGT genes showed differential expression in various tissues and respond to several abiotic stresses, including cold, salt, drought, and heat stress in G. hirsutum. Besides, the co-expressions network of MGTs indicated that genes involved in auxin responsive, lipid metabolism, cell wall organization, and photoprotection can interact with MGTs.

Cotton (Gossypium L.) is a major source of natural fibre for the world's textile industry and is also an important oil plant. Cotton fibre is the main source of textiles, the seeds are used for oil and the rest of the bagasse is a high-protein animal feed. In addition, more than 50 industries use cotton's so-called short fibre. Breeding studies in cotton are generally based on crosses between the best genotypes in terms of yield and fibre quality. However, the narrow genetic diversity of cultivars has a negative impact on cotton breeding programmes. For this reason, the identification of genetic resources and the disclosure of genetic diversity are important. Herein, high-resolution capillary gel electrophoresis was used to determine the genetic diversity of G. hirsutum and G. barbadense genotypes. Using 19 EST-SSR markers, a total of 47 genotypes were screened. The PIC values of the markers used ranged from 0.268 to 0.889. The mean PIC value was calculated to be 0.603. Concerning the clustering, PCoA and population structure analyses gave similar results, and the genotypes could be divided into 3 main groups. Genetic admixture with G. hirsutum was found in some genotypes of G. barbadense species. We can conclude that i) the EST-SSR markers used in this study are effective in the determination of genetic diversity, ii) The genetic diversity should be increased through the collection of genetic resources iii) genic EST-SSR markers in this study should be considered in breeding programmes by using them in QTL studies.

Cotton fiber development transition from elongation to secondary cell wall biosynthesis is a critical growth shifting phase that affects cotton fiber final length, strength and other properties. Morphological dynamic analysis indicates that an asynchronous fiber developmental pattern between two cotton species. The critical time point for Gh and Gb fiber elongation termination is, respectively, 23 and 27 days post-anthesis (dpa). The temporal changes of protein expression at three representative development periods (15–19, 19–23, 23–27 dpa) were examined in both species with iTRAQ technics. Strikingly, a large proportion of differentially expressed proteins (DEPs) was identified at 19–23 dpa in Gh or at 23–27 dpa in Gb, corresponding to their fiber developmental transition timing from elongation to secondary cell wall biosynthesis. To better understand fibers transitional development, we comparatively analyzed those DEPs in 19–23 dpa of Gh vs. in 23–27 dpa of Gb, and noted that these cotton species indeed share fundamentally similar fiber development features under the biological processes. It also showed that there have limited overlaps in both specific upregulated and downregulated proteins between the two species, suggesting specie-specific protein regulations in development. Proteomic profiling revealed dynamic changes of several key proteins and biological processes that potentially correlate with fiber development transition. During the transition, upregulated proteins mainly involved in carbohydrate/energy metabolism, oxidation-reduction, cytoskeleton, protein turnover, Ca²⁺ signaling etc, whereas important downregulated proteins mostly concentrated in phenylpropanoid and flavonoid secondary metabolism pathways. Several changed proteins in this key stage were also validated by qRT-PCR. Overall, the present study provides accurate pictures of the regulatory networks of functional proteins during the fiber developmental transition.

Palmer amaranth (Amaranthus palmeri) is a problematic common weed species, especially in cotton (Gossypium hirsutum). With the wide use of chemical herbicide and herbicide-tolerant transgenic cotton lines, Palmer amaranth populations have developed tolerance to commonly used herbicides. It is imperative to develop alternative weed control methods to slow the evolution of herbicide-resistant weed populations and provide new sources for weed management. Eleven chromosome substitution (CS) cotton lines CS-B26lo, CS-T17, CS-B16-15, CS-B17-11, CS-B12, CS-T05sh, CS-T26lo, CS-T11sh, CS-M11sh, CS-B22sh, and CS-B22lo were screened for weed-suppressing abilities in this study. The cotton lines were tested using the established stair-step structure methodology, which provided scope to study the effect of individual CS lines on the growth and development of Palmer amaranth weed without any interference of other external factors in the greenhouse. Height (cm) and chlorophyll concentration (cci) were measured for each plant in the system. The data were analyzed as a randomized complete block design using LSD mean comparisons of the genotypes at the P≤ .05 level. The 14th day after establishment resulted in the most significant variation in Palmer amaranth height reduction among the CS lines. Results indicated that CS-B22sh had the highest effect in reducing Palmer amaranth height and chlorophyll concentration with the most heightened susceptibility for Palmer amaranth. The cluster analysis revealed that Enlist® cotton, CS-CS-B22sh, and CS-T26lo were clustered in one group suggesting similar genetic potential with reference to Palmer amaranth growth and development. CS-B22sh showed novel genetic potential to control the growth and development of Palmer amaranth, a major weed in cotton fields. In the future, it will be interesting to investigate if CS-B22sh exudates from its root contain allelochemicals able to impede the growth and development of Palmer amaranth.

Cotton fiber is the leading natural textile material, and fiber elongation plays an essential role in the formation of cotton yield and quality. Although a wealth of components in the molecular network controlling cotton fiber elongation have been reported, a lot of players still need to be functionally dissected to understand the regulatory mechanism of fiber elongation comprehensively. In the present study, an R2R3-MYB transcription factor gene, GhMYB201, was characterized and functionally verified via CRISPR/Cas9 mediated gene editing. GhMYB201 was homologous to Arabidopsis AtMYB60, and both coding genes (GhMYB201At and Dt) were preferentially expressed in elongating cotton fibers. Knocking-out of GhMYB201 significantly reduced the rate and duration of fiber elongation, resulting in shorter and coarser mature fibers. It was found that GhMYB201 could bind and activate the transcription of cell wall loosening genes (GhRDLs), and also β-ketoacyl-CoA synthase (GhKCSs) genes to enhance very-long-chain fatty acid (VLCFA) levels in elongating fibers. Taken together, our data demonstrated that the transcription factor GhMYB201s play essential roles in promoting fiber elongation via activating genes related to cell wall loosening and VLCFA biosynthesis.

Verticillium wilt (VW) is an important and widespread disease of cotton and once established is long lived and difficult to manage. In Australia, the non-defoliating pathotype of Verticillium dahliae is the most common, and extremely virulent. Breeding cotton varieties with increased VW resistance is the most economical and effective method of controlling this disease and is greatly aided by understanding the genetics of resistance. In this study, VW resistance was investigated in 240 F7 recombinant inbred lines (RIL) derived from a cross between MCU-5 that has good resistance and Siokra 1-4 which is susceptible. Using a controlled environment bioassay, we found that resistance based on plant survival or shoot biomass was complex but with major contributions from chromosomes D03 and D09, with genomic prediction analysis estimating a prediction accuracy of 0.73 based on survival scores compared to 0.36 for shoot biomass. Transcriptome analysis of MCU-5 and Siokra 1-4 roots uninfected or infected with V. dahliae revealed that the two cultivars displayed very different root transcriptomes and responded differently to V. dahliae infection. Ninety-nine differentially expressed genes were located in the two mapped resistance regions and so are potential candidates for further identifying the genes responsible for VW resistance.

Leucine-rich repeat receptor-like kinases (LRR-RLKs) have been reported to play important roles in plant growth, development and stress responses. However, no comprehensive analysis of this family has been performed in Gossypium, which are important economic crop and suffer various stresses in growth and development. Here we conducted a comprehensive analysis of LRR-RLK family in four Gossypium species (G. arboreum, G. barbadense, G. hirsutum and G. raimondii). A total of 1641 LRR-RLK genes were identified in the four Gossypium species involved in our study. Maximum-likelihood phylogenetic tree revealed that all the LRR-RLK genes were divided into 21 subgroups. Exon-intron organization structure of LRR-RLK genes kept relative conserved in subfamilies and between Arabidopsis and Gossypium. Subfamilies XI and XII were found dramatically expanded in Gossypium. Tandem duplication acted as an important mechanism in expansion of Gossypium LRR-RLK gene family. Function analysis suggested that plant hormone signaling and plant-pathogen interaction pathway were enriched in Gossypium LRR-RLK genes. Promoters analysis and expression profiles analysis revealed that Gossypium LRR-RLK genes were extensively regulated by TFs, phytohormone and various environmental stimuli, and play key roles in stress defense and diverse development processes. Our study provided valuable information for further function study of Gossypium LRR-RLK genes.

Three carbon-chain extension genes associated with fatty acid synthesis in cotton, namely GhKAR, GhHAD, and GhENR, play important roles in oil accumulation in cotton seeds. In the present study, these three genes were cloned and characterized. The expression patterns of GhKAR, GhHAD and GhENR in the high seed oil content cultivars 10H1007, 10H1014, and 10H1041 differed somewhat compared with those of 2074B with low seed oil content at different stages of seed development. GhKAR showed all three cultivars showed higher transcript levels than that of 2074B at 10, 40 and 45 DPA. The expression pattern of GhHAD showed a lower transcript level than that of 2074B at both 10 and 30 DPA but higher transcript level than that of 2074B at 40 DPA. GhENR showed a lower transcript level than that of 2074B at both 15 and 30 DPA. The highest transcript levels of GhKAR and GhENR were detected at 15 DPA in 10H1007, 10H1014, and 10H1041 compared with 2074B. From 5 to 45 days post anthesis (DPA) cotton seed, the oil content accumulated continuously in the developing seed. Oil accumulation reached the peak at 40 DPA to 45 DPA and slightly decreased in mature seed. In addition, GhKAR and GhENR showed different expression patterns in fiber and ovule development processes, in which they showed high expression levels at 20 DPA during fiber elongation stage, but their expression level peaked at 15 DPA during ovule development processes. These two genes showed the lowest expression levels at the late seed maturation stage, while GhHAD showed peak at 10 DPA of fiber development. Compared to 2074B, the oil contents of GhKAR and GhENR overexpression lines increased 1.05~1.08 folds. These results indicated that GhHAD, GhENR and GhKAR were involved in both seed oil synthesis and fiber elongation with dual biological functions in cotton.

Cotton (Gossypium hirsutum Linn.) is widely cultivated in China. The polyphagous insect Adelphocoris suturalis (Jakovlev) is a serious insect pest in cotton growing regions. Plants have evolved sophisticated systems to cope with herbivore attacks. However, the cotton defense mechanisms induced by A. suturalis feeding have lagged behind. We carried out untargeted proteomic analysis using the iTARQ technique and metabolomics based on LC-MS/MS analysis of cotton leaves fed upon by A. suturalis. Proteomic analysis identified 775 upregulated proteins and 477 downregulated proteins in plants that were infested by A. sututralis compared to the controls. Metabolomic analysis identified 50 differentially expressed metabolites in the positive ion mode and 14 in the negative ion mode compared to the controls. The tryptophan metabolism pathway was significantly changed in both the positive and negative ion mode in the metabolomics analysis. The alpha-linolenic acid pathway was significantly changed in both the proteomic and metabolomics analyses. Furthermore, the result was validated by RT-qPCR analysis of 5 related genes involved in alpha-linolenic acid pathway. These results indicate that tryptophan metabolism and the alpha-linolenic acid pathway may be important in cotton defense against herbivores and would enhance our understanding of plant defenses induced by A. sututrali feeding.