[Objective] The UDP-D-glucuronate 4-epimerase (GAE) families of Gossypium hirsutum L. and G. barbadense were investigated from whole genomes to provide a theoretical basis for further studies regarding the GAE family’s function in cotton fiber development. [Methods] The GAE family was identified using bioinformatics analysis software, and the expression pattern during fiber development was analyzed using transcriptional data. [Results] In total, 21 and 22 GAE genes were systematically identified from G. hirsutum and G. barbadense, respectively. They were classified into three subfamilies. Most of the GhGAEs and GbGAEs had no introns. They co-distributed over 12 chromosomes and contained four conserved motifs. All of the GAE proteins were predicted to localize to the Golgi membrane. On the basis of changes in the GAEs’ expression levels at different stages of fiber development, GAE proteins were divided into four categories, high expression at the initial stage, high expression at the fiber elongation stage, high expression at the secondary wall thickening period and low expression during the whole period. GhGAE01, -02, -11 and -12 and GbGAE01, -02, -11 and -21 were highly expressed in G. hirsutum and G. barbadense, respectively. These genes might play important roles in fiber development. [Conclusion] These results provide useful references for studying the GAE gene family’s function in cotton fiber development.
[Objective] To improve the stress resistance of cotton (Gossypium hirsutum L.) under low-phosphorus (Pi) stress, the roles of related functional genes were investigated. [Methods] The structural characteristics of GhWRKY6 were analyzed using bioinformatics methods. To assess low Pi-stress resistance, an overexpression vector was constructed and transformed into Arabidopsis thaliana. The expression levels of Pi stress-related genes in A. thaliana were analyzed using real-time quantitative polymerase chain reaction. [Results] The GhWRKY6 gene was cloned from the cDNA of Upland cotton, and a bioinformatics analysis indicated that the gene contains a WRKY conserved domain and is a WRKY family transcription factor. Under low-Pi stress, the transgenic lines showed delayed germination, shorter primary root lengths, fewer lateral roots, and lower biomasses compared with wild-type, but there were no differences between wild-type and over-expression lines under normal growth conditions. The real-time quantitative polymerase chain reaction analysis indicated that GhWRKY6 can affect the expression of key phosphate transporter genes. [Conclusion] GhWRKY6 acts as a negative regulator in plant low-Pi response signaling pathways.
[Objective] Lint percentage is a critical factor in cotton (Gossypium hirsutum L.) yield; however, there is limited genetic researches available to dissect the genetic characteristics of cotton lint percentage or for illustrating the mechanism of how lint percentage contributes to yield formation.【Methods】This study used the major gene plus polygene genetic model to perform a comprehensive study on genetic variation among lint percentage characteristics. In total, a 250-recombinant inbred line population was constructed for cultivar CCRI 70, a national high-quality cotton, and this population and the cultivar’s parental lines were phenotyped in nine environments in the Yellow River Valley, the Yangtze River Valley and Northwest Inland Region. 【Results】The lint percentage of the female parent sGK Zhong 156 was greater than that of the male parent 901-001 when grown in the nine environments. The lint percentage range of the recombinant inbred lines was 33.91%-40.18%, with an average of 38.01%, and the average was lower than that of the parental values. Thus, the performance was heterotic. The absolute values of skewness and kurtosis were less than 1.0, indicating a normal distribution, and the coefficients of variation ranged from 5.36% to 8.17%. Lint percentage showed the following geographical trend: Northwest Inland Region>the Yellow River Valley>the Yangtze River Valley. The genetic model is as follows: in different environments, lint percentage is controlled by two to four pairs of main genes or two pairs of major genes plus polygenes. The heritability of major genes ranged from 1.26% to 83.13%, the multiple gene heritability ranged from 27.35% to 90.83%, and the heritability of major genes plus multiple gene ranged from 92.00% to 99.35%. In the current study, lint percentage was mainly controlled by the major genes model having two major genes plus polygenes and the major gene model having two to four major genes. Among 2015 in Anyang, Henan, 2016 in Anyang, Henan and 2016 in Linqing, Shandong, only the former had four pairs of major genes. 【Conclusion】When the main gene plus polygenic benefits on lint traits is greater than 90%, then a high quality cotton is produced. The results are helpful in elucidating the genetic rules regulating the yield components of CCRI 70, and they provide a theoretical basis for improving cotton yield.
[Objective] Here, we examined the mechanism of the photosynthetic pathway in dwarfed upland cotton (Gossypium hirsutum L.). [Methods] The upland cotton dwarf line LA-1 and the near-isogenic line LH-1 were used as research materials. We screened for dwarf-related differentially expressed genes at protein and mRNA levels by applying the isobaric tags for relative and absolute quantitation method in combination with LC-MS/MS quantitative proteomic technology and quantitative reverse-polymerase chain reaction. The difference in the photosynthetic abilities between the two materials were detected using physiological and biochemical methods. [Results] An analysis on the differential expression of proteins encoded by photosynthetic system elements revealed that PsbO, PsaE, PsaH, PetF-1 and PetF-2 were down-regulated, while PetC and delta were up-regulated in LA-1. The expression trends of the mRNA levels were the same as at the protein levels, except for those of the delta gene. The net photosynthetic rate, stomatal conductance and transpiration rate in LA-1 were lower than those LH-1, but the intercellular CO2 concentration was not significantly different after budding. This indicated that the non-stomatal factor led to a decreased net photosynthetic rate in LA-1. Chlorophyll fluorescence detection revealed that the actual photosynthetic efficiency and potential photochemical activity of photosystem II in LA-1 were significantly decreased, while non-photochemical quenching was significantly increased. [Conclusion] The dwarfism of LA-1 is related to the photosynthetic pathway, and the results lay a foundation for exploring key dwarf-related genes and the molecular basis for dwarfism in upland cotton.
[Objective] Bacillus malacitensis Z-5 has a significant biocontrol effect on cotton Verticillium wilt mainly through its production of antifungal substances. This study aimed to optimize the culture medium’s composition. Additionally, it aimed to identify the genes that produce the antifungal substances and determine the components of these antifungal substances. [Methods] Single factor tests were used to determine the optimal carbon and nitrogen sources, as well as the inorganic salt level. The most rapid rise method was used to determine the carbon and nitrogen sources and the inorganic salt’s optimal content area. Box-Behnken response surface methodology was applied, and the composition of the medium that produced the optimum level of antifungal substances was determined using antifungal activity as the screening index. The composition of the antifungal substances and the related genes from the Z-5 strain were identified using liquid chromatography-mass spectrometry and polymerase chain reaction, respectively. [Results] The optimal medium for the generation of antifungal substances by the Z-5 strain consisted of 2.68% (mass fraction) corn flour, 1.45% yeast powder, 0.03% K2SO4, 0.8% Na2HPO4·12H2O, and 0.2% NaH2PO4·2H2O at pH 7.2-7.4. The antifungal zone was 1.34 cm in diameter, which was close to the predicted value, confirming that the model was reliable and effective. Antifungal substances were mainly lipopeptide antibiotics C14 surfactin B, C14-C17 iturin A, and C14, C15, and C17 iturin B. polymerase chain reaction revealed that srfAB, ituC, and ituD occur in the Z-5 genome. [Conclusion] This study optimized the culture medium for producing antifungal substances, which are composed of lipopeptide antibiotics, from the B. malacitensis Z-5 strain. The results provide a theoretical reference and material basis for the prevention of cotton Verticillium wilt using these antifungal substances.
[Objective] The yield and quality of fiber were investigated by fiber initiation on the surface of cotton ovules. Thus, it is necessary to investigate the small RNAs related to fiber initiation and their target genes to determine the mechanism of fiber initiation. [Methods] In this study, using the Gossypium hirsutum L. genome sequence as the reference, six small RNA libraries were constructed, and high-throughput sequencing was performed using 0 day post anthesis ovules of wild type and fuzzless mutant. [Results] A total of 459 miRNAs, 301 conserved and 158 novel ones, were identified. In total, 13 differentially expressed miRNAs were obtained, and their target genes were predicted and analyzed. A bioinformatics analysis of the target genes revealed that a majority of transcription factors encode homeodomain-leucine zippers, GRAS (Gibberellic acid insensitive, Repressor of GAI, Scarecrow) and APETALA2 families, and their functions were concentrated in the transcriptional and post-transcriptional regulatory stages. Gene ontology annotations of the target genes revealed that they are involved in cell differentiation, anther development and floral organ development. Four miRNAs were randomly selected for a fluorescence quantitative polymerase chain reaction analysis, and the results confirmed the reliability of the sequencing data. [Conclusion] miRNAs regulated the initiation and development of fiber cells by targeting transcription factors and phytohormone-related genes.
[Objective] This study aimed to investigate the effects of six plant growth promoters on the growth and development of cotton (Gossypium hirsutum L.), and to determine which is most beneficial for enhancing cotton yield in northern Jiangxi Province, China. [Methods] Foliar treatments of naphthalene acetic acid, gibberellin, cytokinin, brassinolide, sodium polyphenol sodium and amine fresh ester were applied at the three-leaf, squaring, first flowering and peak flowering stages of transplanted cotton in the northern Jiangxi region. Cotton growth and development in response to these promoters were investigated, and a pure water spray served as the control. Yield, yield component and agronomic trait data were collected during various growth periods. [Results] Cytokinin and sodium nitrate significantly facilitated the growth of cotton during the early and middle seasons. A more rapid boll setting was achieved by sodium nitrophenolate during the peak flowering stage. Amines promoted cotton growth throughout the plant’s lifecycle, and the plant leaf area and biomass values were the greatest among all the treatments. The brassinolide treatment resulted in a stronger resistance to adverse environmental stresses, and it produced larger bolls and higher cotton yields. Although naphthalene acetic acid had little effects on the growth and development of cotton during the early and middle seasons, a final yield increase was evident. Gibberellin negatively affected the late growth of cotton and led to smaller plant architectural structures and boll weights. The combination of brassinolide and amine fresh ester did not present any advantage over their independent applications. [Conclusion] The growth and development of cotton were significantly increased by the independent foliar applications of six plant promoters at the seedling, squaring, first flowering and peak flowering stages, resulting in seed cotton yield increases of 2.43%-10.4% under seedling transplanting conditions in northern Jiangxi Province. Therefore, we suggest that cytokinin or sodium nitrophenolate can be applied at the cotton seedling and squaring stages and that brassinolide or amine ester can be applied at the flowering and fruiting stages.
[Objective] The effects of nitrogen (N) application rates on cotton yield, nutrient uptake and utilization rate, soil available N and urease activity were investigated in low-fertility cotton fields of the Yellow River Basin. [Methods] Six N application rate treatments, 0, 90, 180, 270, 360 and 450 kg·hm-2 (N0, N90, N180, N270, N360 and N450, respectively), were established using cotton CCRI 79 in the field during 2016 and 2017. The cotton yield, dry matter quality, N, phosphorus and potassium accumulation levels, N use efficiency, 0-100-cm soil layer ammonium and nitrate N contents, 0-100-cm soil layer urease activity and other indicators were investigated. [Results] (1) Compared with N0, the N treatments significantly increased seed cotton yield, except the N90 treatment in 2016. Two years of N360 treatments significantly increased the number of bolls per cotton plant, while no significant differences were found among the seed cotton yields with other N treatments. The N application rates had no significant effect on lint percentage. (2) Compared with N0, N applications significantly increased the cotton dry matter accumulation. The accumulation of N, phosphorus and potassium in cotton increased along with the N application rates in the 90-360 kg·hm-2 range. The levels of N, phosphorus and potassium in N450-treated cotton decreased compared with N360-treated cotton. As the N application rates increased, the N agronomic efficiency and N fertilizer partial productivity of cotton decreased. When the N application rates exceeded 360 kg·hm-2, the N physiological efficiency began to decrease, but there were no significant differences among treatments. (3) The nitrate N contents in the 41-80-cm soil layers of the treatments, except for N90, significantly increased compared with N0. The nitrate N contents in the 41-80-cm soil layers of N270-, N360- and N450-treated cotton were significantly increased compared with those of N0, N90 and N180. However, N applications had no significant effects on the ammonium N contents in the soil. (4) The soil urease activities increased when N application rates were less than 360 kg·hm-2, and then decreased when the N application rates were greater than 360 kg·hm-2. [Conclusion] The optimum N application rate was 277.0 kg·hm-2. When the N application rates were greater than 360 kg·hm-2, the nitrate N contents in the soil increased. However, the nutrient accumulation levels and the N fertilization efficiencies decreased, and the soil urease activities were inhibited. No obvious increase in cotton yield was observed.
[Objective] The objective of this study was to identify the stable quantitative trait loci (QTLs) related to Verticillium wilt resistance in cotton. [Method] In this study, a population of 111 recombinant inbred lines (RILs) strains was developed by crossing a highly resistant parental line "Changkangmian" to Verticillium wilt and the susceptible parent TM-1. The complete composite interval mapping method was adopted to detect QTLs by Verticillium wilt disease index in multiple environmental conditions and periods in Anyang and Verticillium wilt affected areas of Xinjiang. Simple sequence repeat (SSR) markers of polymorphism were screened for genetic mapping. [Result] The genetic map was constructed by 40 simple sequence repeat (SSR) markers, consisted of 12 linkage groups with total length of 212.5 centimorgan (cM). A total of six QTLs related to the resistance to Verticillium wilt were obtained. The likelihood of odd (LOD) values ranged from 2.51 to 5.55. The maximum phenotypic variation explained (PVE) 20.34%, and the minimum PVE 6.93% were recorded. Among detected QTLs, qVR-D05-1 was detected in both Verticillium wilt affected fields in Anyang and Xinjiang in July 2015 and July 2016 with PVE of 12.96% and 20.34%, respectively. [Conclusion] This study can provide a potential reference for mapping stable QTLs related to resistance to Verticillium wilt.
