[Objective] This study aims to characterize the GhROP6 and study its roles of resistance to Verticillium wiltin upland cotton (Gossypium hirsutum L.). [Method] The bioinformatics analysis was used to identify Rho-related guanosine triphosphatase from plants (ROP) genes in upland cotton. The chromosome distributions, expression pattern analysis of GhROP genes were investigated. The function of GhROP6 gene was studied by quantitative real-time polymerase chain reaction (qRT-PCR), virus-induced gene silencing (VIGS), plant genetic transformation and metabolism analysis. [Result] Totally, 28 ROP genes were identified in upland cotton. And the corresponding amino acid sequence contained the ROP protein specific structures, including four GTP/GDP binding domains, effector domain binding to downstream target proteins and variable C-terminal regions. Chromosomal mapping analysis showed that 24 ROP genes were symmetrically distributed in subgenome A and subgenome D, and 3 genes specifically distributed in subgenome D. qRT-PCR analysis showed that the transcript levels of GhROP6 varied in different organs, and showed higher expression level in petals, stigma, fiber of 10 days post anthesis. Meanwhile, the transcript level of GhROP6 was upregulated in cotton by methyl jasmonate (MeJA). Knock-down of GhROP6 through VIGS weakened the cotton resistance to Verticillium wilt, and reduced the expression of GhLOX1, GhOPR3-1, GhOPR3-3, GhAOC1, GhAOS involved in jasmonic acid (JA) synthesis, and the expression of GhMYC2 involved in JA signaling pathway, and the expression of GhCCR-1, GhF5H-1, GhCCoAOMT-2, and GhCCoAOMT-3 genes involved in lignin synthesis. However, constitutively activated GhROP6 in Arabidopsis enhanced the plants resistantce to V. dahliae. Further analysis showed that the contents of JA-isoleucine and lignin in transgenic Arabidopsis were higher than those of wild type. [Conclusion] GhROP6 may involve in the resistance of cotton to Verticillium wilt through JA synthesis and signaling pathway and lignin synthesis.
[Objective] The purpose of this study is to analyze the function of myo-inositol-1-phosphate synthase gene GhMIPS1A in fiber development and stress resistance of upland cotton (Gossypium hirsutum L.). [Method] Phylogenetic analysis, gene structure analysis, conserved motif analysis, quantitative real-time polymerase chain reaction (qRT-PCR), tobacco transient transformation over-expression in Arabidopsis, and virus-induced gene silencing (VIGS) were performed to study the functions of GhMIPS1A. [Result] GhMIPS1A gene was cloned from upland cotton TM-1. Bioinformatics analysis showed that there were four highly conserved motifs, which were GWGGNNG, LWTANTERY, NGSPQNTFVPGL, and SYNHLGNNDG. GhMIPS1A was localized to the cell membrane. Overexpression of GhMIPS1A gene in Arabidopsis thaliana resulted in elongation of root, and a more than 1-fold increase of inositol content. The temporospatial expression pattern analysis showed that GhMIPS1A gene was highly expressed in root, stem, leaf, and fiber, and the expression level in Xinluzao 18 with high lint percentage was significantly higher than that of in Delfos 531 with low lint percentage. And GhMIPS1A gene had a high expression level at the initial stage of fiber development. Compared with the wild type, the cotton fiber density of three GhMIPS1A-silenced lines significantly decreased, and the lint percentage decreased by 4.48, 4.93, and 3.95 percentage points, and the inositol content decreased by 31.83%, 32.90%, and 29.46%, respectively. Under drought treatment or salt treatment, the expression level of GhMIPS1A gene increased first and then decreased. [Conclusion] GhMIPS1A gene plays an positive role in cotton fiber development and can respond to drought stress and salt stress, which can provide genetic resources and genetic basis for the breeding of new cotton varieties with high yield, fine fiber, and salt and drought tolerance.
[Objective] SHI-related sequence (SRS) family is a group of plant-specific transcription factors that play important roles in regulating plant development and response to adversity stress. However, the function of SRS gene family in cotton has not been well characterized. [Method] Based on the published genomic data of Gossypium hirsutum, G. barbadense and Arabidopsis thaliana, the genome-wide identification and phylogenetic analysis of SRS genes in cotton were conducted. And the expression pattern of SRS genes in ovule and fiber at different developmental stages, in different organs and under different abiotic stress conditions were analyzed. [Result] In total, 27 and 26 SRS genes were identified in G. hirsutum and G. barbadense, respectively. According to the phylogenetic analysis, SRS genes in cotton could be divided into three groups, and different groups had similar conserved motifs. There were multiple pairs of homologous genes in each subgroup. Some SRS genes were highly expressed in ovules at different developmental stages, and were also responsive to various abiotic stresses. [Conclusion]The evolution and potential functions of SRS gene family were analyzed and predicted, which provided a theoretical basis for the functional analysis of SRS genes in cotton.
[Objective] This study aims to evaluate and validate SSR (simple sequence repeat) markers associated with traits of fiber quality, yield, and resistance to Verticillium wilt of upland cotton, and identify typical materials carrying elite alleles. [Method] Among the 26 SSR markers identified from previous studies, the two-tailed t-test was used to screen the mutation sites with significant effect on phenotypic variations of 474 upland cotton materials, and to identify typical materials. [Result] A total of 30 polymorphic loci were detected, and can be used to fully differentiate 420 upland cotton materials. Interestingly, 20 mutation sites were significantly associated with target traits (P<0.05), of which, 6 mutation sites were closely related to boll weight and fiber length, respectively. Moreover, there are 3, 3, 1, and 1 loci associated with micronaire value, breaking elongation, plant height and boll number, respectively. And, the marker combinations (JESPR220-160+BNL2440-240+BNL226-320) and (CM45-140+CGR6528-180+JESPR152-125) were associated with the boll weight and fiber length, with phenotypic effect of 0.27 g and 1.27 mm, respectively. Furthermore, 14 typical materials carrying elite alleles were obtained. [Conclusions] In this study, polymorphic sites with significant phenotypic effects and typical materials of elite alleles were obtained, which provided references for cotton molecular marker-assisted selection and material selection.
[Objective] This study aimed to clarify the effects of chemical fertilizers reduction and stalk returning on soil nutrients content, nutrient absorption and yield of cotton. [Method] A three-year field experiment was conducted from 2016 to 2018. Six treatments were included: traditional chemical fertilizer (NPK) as control, stalk returning (S), traditional chemical fertilizer plus stalk returning (NPKS), chemical fertilizer reduction of 25% plus stalk returning (0.75NPKS), controlled-release fertilizer plus stalk returning (CRFS), and controlled-release fertilizer reduction of 25% plus stalk returning (0.75CRFS). [Result] Within the three-year experiment, the organic matter content, alkaline nitrogen content, available phosphorus content, and potassium content in soil were increased in NPKS and CRFS. Both 0.75NPKS and 0.75CRFS treatments increased the soil organic matter content, and reduced available phosphorus content year by year, and had no significant effect on alkaline nitrogen and available potassium content compared with NPK. From 2016 to 2018, nitrogen absorption and phosphorus absorption and apparent recovery efficiency in the treatments of NPKS, CRFS, 0.75NPKS and 0.75CRFS were increased year by year,while there was no significant difference in potassium absorption compared with NPK. In 2018, phosphorus absorptions in these four fertilizer plus stalk returning treatments were 6.17%, 8.01%, 8.88% and 7.94% significantly higher than that of NPK, respectively. At initial boll opening stage, the SPAD values and net photosynthetic rates of the second leaf from the top in NPKS and CRFS treatments showed a rising trend year by year, that those of 0.75NPKS and 0.75CRFS treatments had no significant differences compared with NPK. Within 3 years, the seed cotton yield of NPKS and CRFS were not significantly higher than that of NPK, and the seed cotton yield of 0.75NPKS and 0.75CRFS were slightly fewer compared with NPK without significant differences. The boll number per unit area, boll weight and lint percentage in the treatments of NPK, NPKS, 0.75NPKS, CRFS and 0.75CRFS were approximately the same in every year. [Conclusion] Chemical fertilizer reduction of 25% and stalk returning can increase the fertilizer apparent recovery efficiency without influence on the cotton yield in the three-year experiment, but it is necessary to supply phosphorus fertilizer properly in long-term fertilizer reduction application.
[Objective] The purpose of this study is to clarify the differences in the bacteria of different wing morphic cotton aphids, and to explore the relationship between the bacteria and the wing dimorphic in cotton aphids. [Method] The V3-V4 region of 16S rRNA gene of alate and apterous Aphis gossypii was sequenced by Illumina MiSeq high-throughput sequencing technology. Then, operational taxonomic unit (OTU) clustering, α diversity, species composition and classification were analyzed according to the sequencing results. [Result] A total of 234 bacteria OTUs, belonging to 16 phyla, 32 classes, 64 orders, 107 families, 148 genera, and 187 species, were identified from all samples. Among them, Buchnera was the dominant genus. Bacteria diversity between these two wing morphs was different, and the bacteria diversity in apterous morph (belonging to 12 phyla, 23 classes, 50 orders, 82 families, 106 genera, and 136 species) was slightly higher than that of alate morph (belonging to 14 phyla, 26 classes, 45 orders, 72 families, 97 genera, and 120 species). There were significant differences in the relative abundance of many bacteria between the two morphs of cotton aphid. The relative abundance of Rhodococcus in the alate aphid was relatively higher (0.136%), but that in the apterous aphid was relatively lower (0.078%). Besides, the relative abundance of norank-cyanobacteria was lower (0.005%) in the alate aphid but higher (0.024%) in the apterous aphid. [Conclusion] There were differences in bacteria composition and community structure between alate and apterous cotton aphid. This study expanded the understanding about wing dimorphism in cotton aphids.
[Objective] A quantitative detection technique for biocontrol Bacillus subtilis NCD-2 was developed and used to evaluate the colonization of strain NCD-2 in cotton rhizosphere. [Method] Specific primers for strain NCD-2 were designed based on the whole genome sequences of strain NCD-2. The colonization dynamics of strain NCD-2 in cotton rhizosphere soil were quantified by real-time polymerase chain reaction (PCR). [Result] The real-time PCR detection technique for strain NCD-2 was successfully developed. Real-time PCR detection result showed that the population contents of strain NCD-2 in cotton rhizosphere soil were 1.14×105 g-1 and 9.5×104 g-1 on the 8th day and 16th day after sowing, respectively. Comparatively, 2.15×105 g-1 and 2.45×105 g-1 of strain NCD-2 in soil at the 8th day and the 16th day after sowing were obtained by traditional colony counting method. The correlation coefficients between the two methods were 0.99 at the 8th day and 0.95 at the 16th day. The control effect of NCD-2 strains against cotton rhizoctonia damping-off was 67.9% at 16 days after seed treatment. At that time the population content of strain NCD-2 was 7.6×105 g-1 in soil with real-time PCR detection. [Conclusion] The established real-time PCR detection technique in this study can accurately reflect the colonization of NCD-2 strain in cotton rhizosphere, and lays a foundation for using the strain to effectively control diseases.
