The Zinc finger-homeodomain (ZF-HD) protein family of homeobox genes plays a vital role during the development processes of plants and animals. The number, subcellular localization, chromosome distribution, motif, evolutionary relationships and tissue-expression patterns of the ZF-HD protein family were studied in the genome of Gossypium hirsutum L. acc. 'TM-1' using bioinformatics methods. In total, 35 GhZHD genes were identified in the 'TM-1' genome, and a majority of the members are located in nucleus. The family members were distributed on 20 chromosomes and two scaffolds, and 11 pairs were orthologous genes. The family could be divided into six groups based on the phylogenetic analysis, and there were similar motif types and arrangements in each group. Most GhZHD genes were expressed in ovules and fibers, some were expressed in roots, stems, buds and flowers, and a fraction were expressed in leaves and calli.
Cotton is an important economic crop, and fatty acids account for 25%-40% of cottonseeds. A positive correlation exists between the unsaturated fatty acid content and cold tolerance. GhKAR and GhENR are two reductase genes that are responsible for carbon-chain extension, which is related to fatty acid synthesis in cotton. Here, we built two vectors that over-expressed GhKAR and GhENR independently, and then separately transferred the vectors into upland cotton by means of the pollen tube channel. The positive transformants containing single vector copies were obtained after being identified by PCR and Southern hybridization. The objectives of this research were to explore the gene functions and to provide candidate genes for high-oil and abiotic stress-resistance breeding in cotton. The oil contents in transgenic T4 lines were 10.2%-14.1% higher than that of the control (wild type). The fatty acidcompositions of transgenic lines were analyzed by gas chromatography and revealed that the unsaturated fatty acidcontent increased by 4.04%-6.02% compared with the control. Additionally, the cold tolerance of the transgenic lines was investigated under low-temperature (4 ℃) stress. The changes in the physiological indexes were evaluated. The relative electric conductivity and proline contents of the transgenic lines were remarkably or extremely higher than those of the control, but the malonaldehyde contents were remarkablylower in all periods of stress treatment. The results indicated that the transgenic lines could potentially be used in improving cotton's cold tolerance.
Allene oxide synthase (AOS) is the key enzyme in the jasmonic acid (JA) biosynthesis pathway. As a class of plant hormones, JA plays an important role in the regulation of plant growth and development, but studies on JAs regulatory role in somatic embryo development are lacking. Here, we identified AOS family members during cotton somatic embryo development. The opening read frames of the six genes are all ~1500 bp, but only two genes contain introns, and the genes are dispersed across five different chromosomes. Based on the expression profile clusters, these genes are mainly divided into three subgroups: the high expression levels of GhAOS1 and GhAOS6 in cotton somatic embryos, the high expression levels of GhAOS2 and GhAOS3 in calli and embryogenetic calli, and the high expression levels of GhAOS4 and GhAOS5 in cotton stems and leaves.The groupings suggest that the genes play different roles during somatic embryo development. Most AOS genes were located in the peroxisome, which may be involved in photorespiration, and somatic embryo germination and maturation. The identification and bioinformatics analyses laid the foundation for the function analysis of the AOS gene family in cotton somatic embryos.
Verticillium wilt is a major limiting factor in cotton production, and the key of breeding resistant varieties by genetic engineering is to clone resistance genes. In this study, based on the cotton genomic sequence and previous Verticillium wilt-resistance gene predictions, we extracted the target sequence and predicted that it contained 63 genes. The gene Ontology showed that 63 genes participated in a variety of biological processes, and 6 of them were involved in plant stress responses. According to the results of the Gene Ontology analysis and previous studies, we selected 15 genes as research subjects. A promoter sequence analysis showed that the promoter regions of 15 genes contained a variety of cis-acting elements, and 6 genes contained W-box components. Using the root of Gossypium barbadense L. cv. Hai7124 and Gossypium hirsutum L. cv. Sumian 8 seedlings treated with Verticillium dahliae for different times, we analyzed the expression profiles of 14 genes. The expression levels of eight genes were induced and changed after treatment with V. dahliae, and the expression differences of transmembrane protein 214-a isoform 1, Cytochrome P450 and Udp-glycosyl transferase 89a2-like were the most significant between G. barbadense L. cv. Hai7124 and G. hirsutum L. cv. Sumian 8. The study provides candidate Verticillium wilt-resistance genes for cloning in the future.
C2H2 zinc finger proteins play key roles in plant growth, development and abiotic stress-response processes. Based on a previous study of the suppression subtractive hybridization libraries of upland cotton (G. hirsutum L.) roots under salt stress, a salt stress-response gene, GhC2H2, was selected. By combining rapid amplification of cDNA ends and reverse transcription-polymerase chain reaction methods, the full length of GhC2H2 (GenBank Accession No. HM002632) was isolated. It had an open reading frame region of 819 bp that encoded 272 aa. The GhC2H2 protein contains two C2H2 zinc finger domains. A transient expression analysis indicated that the transcription factor was localized in the nucleus. An expression profile analysis showed that the gene was up-regulated in different tissues (root, stem and leaf) of upland cotton under salt stress, and we hypothesized that GhC2H2 may be involved in the early stage of the salt-stress response. A phenotypic trait analysis of transgenic cotton lines in two environments (normal and saline-alkali soil) showed that overexpressed GhC2H2 could improve the lint percentage as well as the fiber quality. Thus, we hypothesized that GhC2H2 participates in both the salt-stress responsive process and fiber development.
Gossypol enantiomers of pure gossypol and cotton samples were analyzed by high-performance liquid chromatography, with a C18 chromatographic column and an acetonitrile mobile phase, using 2% D-aminopropanol, 10% acetic acid and 88% acetonitrile as gossypol extraction and derivatization reagents at 75 ℃ for 45 min. This method distinguished(-)-gossypol and (+)-gossypol in cotton seeds and other plant parts. The chromatographic target peaks were very clear and there were few impurity-associated peaks. The first peak was (+)-gossypol, and the(-)-gossypol peak appeared after 7 min. The (-)- and (+)-gossypol contents in the seeds, roots, stems and leaves of the 25 genotypes belonging to 4 cultivated cotton species were systematically determined. The total gossypol content, (-)- and (+)-gossypol, in the seeds and roots of Gossypium barbadense was the highest, followed by that of Gossypium hirsutum. The total gossypol contents in the seeds and roots of the two diploid cotton species, Gossypium arboreum and Gossypium herbaceum, were significantly lower than those of the two tetraploid cotton species. However, the contentsin the leaves of the two diploid cotton species were much higher than those of the two tetraploid cotton species.There were some differences between the (-)-gossypol and (+)-gossypol content in almost every plant part from all of the genotypes in the experiment. Among the four cultivated cotton species, the (-)-gossypol content in G. barbadense was slightly higher than that of (+)-gossypol, while the opposite was true in G. hirsutum. However, the (+)-gossypol content was much higher, being 2/3 of the total gossypol, than the(-)-gossypol content in most G. arboreum and G. herbaceum plant parts. The total gossypol contents, which contained mostly (-)-gossypol, in the seeds and leaves of glandless cotton were very low. There was no (+)-gossypol in the glandless cotton seeds at all. The total gossypol content and the ratio of the (-)/(+)-gossypols in the stems of glandless cotton were almost the same as those of glanded cotton, but the total gossypol contents and (+)-gossypol proportion in the glandless cotton roots were much greater than those of glanded cotton.
To understand the effects of the sowing date and planting density on cotton nitrogen metabolism under late and direct seeding, a field split-plot design with sowing date (S1: 30th May and S2: 14th June) as the main plot and density (plants·m-2) (D1: 7.5, D2: 9.0 and D3: 10.5) as the subplot, was used to measure the nitrate content dynamics in petioles and roots. The results showed the following: 1) the cotton nitrate contents in petioles and roots were first bloom period>peak bloom period>squaring period; 2) the cotton petiole nitrate content decreased in leaf sites from the top (with the highest value at the 1st leaf) to the bottom during the squaring and first bloom periods, increased gradually in the central leaf sites (with the highest values at the 1st and 4th leaf) during the peak bloom period, and then declined from the top to second leaf site as the sowing date was delayed. The contents also initially rose and then dropped as the planting density increased; and 3) although significant interaction effects were observed on the average nitrate contents in petioles and roots during different periods, the main effects of sowing time and density differed. Before the first flower's fertilization (squaring), the average nitrate content in cotton petioles from top to bottom decreased by 42.9%, while the content in cotton roots significantly increased by 12.1% as the result of late sowing. Density had no significant effects on the average nitrate contents in cotton petioles and roots. After the first flower's fertileization (first bloom and peak bloom), due to the delay in the sowing date, no significant differences were observed between the average petiole nitrate contents of 5.05 mg·g-1 and 2.62 mg·g-1 at first and peak bloom, respectively. However, the average root nitrate content in S1 plants was significantly higher than that in S2 plants during first bloom period, which was opposite of the peak bloom results. Compared with first bloom period at D1, the average petioles and root nitrate contents significantly decreased up to 14.3% and 30.8%, respectively, at D2 and up to 16.6% and 29.2%, respectively, at D3 as the planting density increased. However, during peak bloom period, the average nitrate content in the petioles at D2 was significantly higher than those at D1(11.1%) and D3 (23.3%), whereas the trend in the average nitrate content in roots was contrary to that in first bloom period. In conclusion, under late sowing and higher density conditions, after fertilizer application at the first flower period, delayed sowing did not alter the average nitrate content in the main leaf petioles, while the optimum planting density resulted in a higher than average nitrate content being stored in the main leaf petioles, contributing to the sufficient supply of substrate for leaf nitrate metabolism.
Two cotton varieties (CCRI 45 and CCRI 60) with different drought tolerances were screened to study the effects and duration of drought stress after re-watering on cotton root dry weight, yield and quality during the flowering and boll-forming stages using an artificial water-control method. Cotton root dry weight increased, and CCRI 45 had the greatest cotton lint yield, which was significant (P<0.05), under the 45%±5%-soil relative water content (SRWC)-induced drought stress for 6 d after re-watering. The cotton root dry weight increased, and CCRI 60 had the greatest cotton lint yield, which was significant (P<0.05), under the 60%±5%-SRWC-induced drought stress for 6 d after re-watering. However, CCRI 45 and CCRI 60 were significantly lower in root dry weights and lint yields under the 45±5%-SRWC-induced drought stress for 9 d after re-watering than the control. CCRI 45 had higher fiber length values, uniformity indexes, elongation rates and fiber strengths under the 60%±5%- and 45±5%-SRWC-induced drought stresses for 6 d after re-watering than the control. CCRI 60 had higher fiber length values, uniformity indexes, elongation rates and fiber strengths under the 45%±5%-SRWC-induced drought stress for 3 d and the 60%±5%- SRWC-induced drought stress for 6 d after re-watering than the control, but did not reach significant levels(P<0.05). CCRI 45 and CCRI 60 had significantly lower fiber-quality indexes under the 45%±5%-SRWC-induced drought stress for 9 d after re-watering than the control. The increases in the root dry weight and lint yield under the 45%±5%-SRWC-induced drought stress for 6 d after re-watering was greater in CCRI 45 than that in CCRI 60, which indicated that CCRI 45 had a greater drought resistance and ability to compensate than CCRI 60. Additionally, there was a positive correlation between the increases in lint yield and root dry weight. This study provides a theory basis for drought-resistant cultivation measures, and water-saving and high-yield cultivation technologies in cotton.
Based on farmer's production survey data from Hebei Province, the carbon footprint of cotton production in Hebei Province was estimated using a life-cycle assessment method in the agricultural sector. The proportions of different agricultural inputs in the carbon footprint of cotton production was explored. In addition, the relationships between fertilizer and irrigation inputs and the cotton yield output was analyzed. The results were as follows: 1) the carbon footprint per unit sown area, carbon footprint per unit yield, carbon footprint per unit biomass and carbon footprint per unit production value for cotton production in Hebei Province were 3272.71 kg·hm-2, 1.04 kg·kg-1, 0.40 kg·kg-1 and 0.34 kg·￥-1, respectively. The carbon footprint of cotton production was lower than that of winter wheat; 2) the main components of the carbon footprint were fertilizer(34.53%), electricity for irrigation (25.98%) and plastic film (18.44%); and 3) in this study, 25.63% of a field exposed to excessive fertilizer and 21.11% of a field exposed to excessive irrigation showed low yields. Thus, there were large energy savings and emission reduction potentials. Gradually expanding the cotton planting area and developing technology that limits water and fertilizer consumption, as well as eliminating plastic film during mulching, could help to mitigate greenhouse gas emissions from agricultural production of Hebei Province.
Because of farmland soil pollution resulting from ordinary agricultural mulch film that is used in the production of cotton, we conducted an experiment to study the degradation properties of ordinary plastic mulch film and different formulae of oxo-biodegradable mulch films, and their influences on soil moisture, soil temperature and cotton growth. The degradation levels of the oxo-biodegradable mulch films were greater than that of the control, and the maximum degradation weight loss of "degradable mulch film No.1" reached up to 74.5%. Oxo-biodegradable mulch films with different formulae showed different rates and intensities of degradation, and were somewhat controllable. Remnants of oxo-biodegradable film debris became thin and brittle, and settled close to the ground surface, thus continuing to increase the soil temperature and moisture. With a reasonable degradation induction period, the effects of oxo-biodegradable mulch film on soil moisture, soil temperature and cotton growth were equal to those of ordinary mulch film and no significant influence on the cotton yield was observed. This study showed that oxo-biodegradable mulch films can be used in agricultural production to replace ordinary ones.
The seedling stage is a sensitive period when cotton plants absorb phosphorus (P) from the soil. However, the suitable Olsen-P level during this period, and the effects of soil Olsen-P levels on the dry matter accumulation, and the carbon and nitrogen metabolism of cotton plants, were not clear. Thus, we conducted a pot experiment to explore the effects of soil Olsen-P levels on the growth of cotton (CCRI 79) plants and their physiological mechanisms in 2014 and 2015. The dry matter of the cotton seedling increased as the available soil P concentration increased in the treatments, but the root to shoot ratio decreased. There was no significant effect on the cotton plant's growth in soils with higher Olsen-P levels. However, the dry matter accumulation was highest in the 9.0 mg·kg-1 Olsen-P treatment, but it had the lowest root to shoot ratio of 0.3. The total chlorophyll content of the functional leaves significantly increased and then decreased as the available soil P concentration increased in the treatments. It was highest in the 7.2 mg·kg-1 Olsen-P treatment, which influenced the concentrations of chlorophyll a more strongly than chlorophyll b. The sucrose, soluble sugar, starch and total amino acid contents significantly increased as the available P concentration increased, but did not steadily increase at concentrations greater than 9.0 mg·kg-1. As the available soil P concentration increased, the P absorption significantly improved, but the root P efficiency ratio significantly decreased in the cotton seedlings. Thus, the lower soil Olsen-P level affected cotton leaf chlorophyll and sugar contents, as well as the total amount of amino acids to restrain cotton growth, and the critical Olsen-P level was 9 mg·kg-1 for cotton plant growth at the seedling stage in our experiment.
Excessive fertilization causes negative externalities and presents cotton farmers with the dual challenge of increasing cotton production and protecting the environment. We conducted a survey at the household level in Xinjiang to determine the amount of fertilization and analyzed, using an econometric model, the main factors affecting the farmers' behaviors regarding applying excessive amounts of fertilizers. Based on the farmers' behavior, the average amount of fertilizer applied was 610.20 kg·hm-2, which is 59.6% higher than the cotton requirement. The model's analysis indicated that the major causes for excessive fertilization were the lack of rational fertilization training and the desire to avoid the loss of revenue. The research provides a useful methodology for understanding the farmers' behaviors and helpful knowledge for guiding fertilization at the household level.
To explore the physiological mechanisms in the key stages of lint yield development in transgenic cotton, we conducted two years of field experiments to evaluate the cotton canopy and physiological properties. We compared growth, yield and yield components of new genotypes of transgenic RRM2 and ACO2-E6 cottons with those of their conventional parental materials, CCRI 12 (CK1) and CCRI 24 (CK2), respectively, in 2014 and 2015. The boll weight, seed cotton yield, lint yield, upper-half mean length and breaking tenacity of transgenic RRM2 cotton exceeded or significantly exceeded those of CCRI 12. The lint percent, seed cotton yield, lint yield, upper-half mean length and fiber strength of transgenic ACO2-E6 cotton exceeded or significantly exceeded those of CCRI 24. The seed cotton yields of different transgenic cottons showed significant linear correlations with leaf area indexes, photosystem II quantum yields, photosystem II maximum photochemical efficiencies and total soluble sugar contents. Leaf area indexes and total soluble contents of transgenic cottons in the key stages of yield development exceeded or significantly exceeded those of CCRI 12 and CCRI 24, respectively. Transgenic cotton presented stronger, more vigorous growth, better canopy structures and more reasonable 'source-link' ratios.
