Screening of drought resistance indices and evaluation of drought resistance in cotton(Gossypium hirsutum L.)

Sixteen cotton cultivars widely planted in China were sowed under five different drought concentrations(0,2.5,5,7.5,and 10%)using PEG6000 to screen the indices of drought resistance identification and explore the drought resistance of different cotton cultivars.Eighteen physiological indices including root,stem,and leaf water contents(RWC,SWC,and LWC),net photosynthetic rate(Pn),the maximum photochemical quantum yield(Fv/Fm),the actual photochemical quantum yield(ΦPSII),non-photochemical quenching coefficient(NPQ),leaf water potential(LWP),osmotic potential(Ψs),leaf relative conductivity(REC),leaf proline content(Pro),leaf and root soluble protein contents(LSPC and RSPC),leaf and root malondialdehyde(MDA)contents(LMDA and RMDA),root superoxide dismutase,peroxidase,and catalase activities(RSOD,RPOD,and RCAT)were measured.Results indicated the 18 physiological indices can be converted into five or six independent comprehensive indices by principal component analysis,and nine typical indices(Fv/Fm,SWC,LWP,Pro,LMDA,RSPC,RMDA,RSOD,and RCAT)screened out by a stepwise regression method could be utilized to evaluate the drought resistance.Moreover,the 16 cotton cultivars were divided into four types:drought sensitive,drought weak sensitive,moderate drought resistant,and drought resistant types.The resistance ability of two selected cotton cultivars(drought resistant cultivar,Dexiamian 1;drought sensitive cultivar,Yuzaomian 9110)with contrasting drought sensitivities were further verified by pot experiment.Results showed that the responses of final cotton biomass,yield,and yield composition to drought were significantly different between the two cultivars.In conclusion,drought resistant cultivar Dexiamian 1 and drought sensitive cultivar Yuzaomian 9110 were screened through hydroponics experiment,which can be used as ideal experimental materials to study the mechanism of different cotton cultivars with contrasting drought sensitivities in response to drought stress.

Relationship between plant canopy characteristics and photosynthetic productivity in diverse cultivars of cotton(Gossypium hirsutum L.)

Genotype and plant type affect photosynthetic production by changing the canopy structure in crops.To analyze the mechanism of action of heterosis and plant type on canopy structure in cotton(Gossypium hirsutum L.),we had selected two cotton hybrids(Shiza 2,Xinluzao 43) and two conventional varieties(Xinluzao 13,Xinluzao 33) with different plant types in this experiment.We studied canopy characteristics and their correlation with photosynthesis in populations of different genotypes and plant types during yield formation in Xinjiang,China.Canopy characteristics including leaf area index(LAI),mean foliage tilt angle(MTA),canopy openness(DIFN),and chlorophyll relative content(SPAD).The results showed that LAI and SPAD peak values were higher and their peak values arrived later,and the adjustment capacity of MTA during the flowering and boll-forming stages was stronger in Xinluzao 43,with the normal-leaf,pagoda plant type,than these values in other varieties.DIFN of Xinluzao 43 remained between0.09 and 0.12 during the flowering and boll-forming stages,but was lower than that in the other varieties during the boll-opening stage.Thus,these characteristics of Xinluzao 43 were helpful for optimizing the light environment and maximizing light interception,thereby increasing photosynthetic capability.The photosynthetic rate and photosynthetic area were thus affected by cotton genotype as changes in the adjustment range of MTA,increases in peak values of LAI and SPAD,and extension of the functional stage of leaves.Available photosynthetic area and canopy light environment were affected by cotton plant type as changes in MTA and DIFN.Heterosis expression and plant type development were coordinated during different growth stages,the key to optimizing the canopy structure and further increasing yield.

Ameliorative effects of potassium on drought-induced decreases in fiber length of cotton(Gossypium hirsutum L.) are associated with osmolyte dynamics during fiber development

Fiber length of cotton(Gossypium hirsutum L.)decreases under drought stress,potassium(K)could diminish the decreased caused by drought,but the mechanism associated with this alleviation effect is not clear.We evaluated the effect of K on fiber elongation using two cotton cultivars,Simian 3 and Siza 3,grown in well-watered and drought-stressed conditions.Potassium fertilizer(K2O)was applied 0,150,or 300 kg ha?1 in each growing condition.Drought stress reduced the final fiber length due to a decline in the maximum rate of rapid elongation(Vmax,mmday?1).The application of K alleviated the droughtinduced fiber length reduction by increasing Vmax.At 10 and 15 days post-anthesis(DPA),drought significantly reduced osmotic potential(OP)and increased K+and malate contents at all K rates,relative to well-watered conditions,which was associated with increased activities of phosphoenolpyruvate carboxylase(PEPC),V-ATPase,PPase,and PM H+-ATPase in cotton fiber.However,the relative contribution of K+and malate to OP declined under drought in comparison with well-watered condition.Compared with control without K,K application decreased OP and increased the accumulation of osmolytes(K+,malate and soluble sugar)as well as the activities of related enzymes in fiber irrespective of water treatments.Moreover,K application increased osmotic adjustment during drought,and improved the contribution of K+and malate to OP,especially under drought stress.This study showed that drought decreased fiber length by reducing Vmax,and K application ameliorates the decline in fiber elongation due to drought by enhancing osmolytes accumulation and their contribution to OP in fiber cells.

Cloning and Characterization of a Somatic Embryogenesis Receptor-Like Kinase Gene in Cotton (Gossypium hirsutum)

A novel gene, GhSERK1, was identified in cotton. It encoded a protein belonging to the somatic embryogenesis receptor-like kinase (SERK) family. The genomic sequence of GhSERK1 was 6 920 bp in length, containing a predicted transcriptional start site (TSS). Its full-length cDNA was 2 502 bp, encoding a protein of 627 amino acids. Sequence analysis of GhSERK1 revealed high levels of similarity to other reported SERKs, as well as a conserved intron/exon structure that was unique to members of the SERK family. Expression analysis showed that GhSERK1 mRNA was present in all organs of cotton plants and at different developmental stages, but its transcripts were most abundant in reproductive organs. Compared with that of the male-fertile line, the level of GhSERK1 mRNA was lower in the anther of the male-sterile cotton line, in which the pollen development was defected. Taken together, these findings illustrated that the GhSERK1 play a critical role during the anther formation, and may also have a broad role in other aspects of plant development.

Genetic variation in LBL1 contributes to depth of leaf blades lobes between cotton subspecies, Gossypium barbadense and Gossypium hirsutum

Leaf is a essential part of the plants for photosynthetic activities which mainly economize the resources for boll heath. Significant variations of leaf shapes across the Gossypium sp. considerably influence the infiltration of sunlight for photosynthesis. To understand the genetic variants and molecular processes underlying for cotton leaf shape, we used F_2 population derived from upland cotton genotype P30 A(shallow-lobed leaf) and sea-island cotton genotype ISR(deeplobed leaf) to map leaf deep lobed phenotype controlling genes LBL1 and LBL2. Genetic analysis and localization results have unmasked the position and interaction between both loci of LBL1 and LBL2, and revealed the co-dominance impact of the genes in regulating depth of leaf blades lobes in cotton. LBL1 had been described as a main gene and member of transcription factor family leucine zipper(HD-ZIPI) from a class I homologous domain factor Gorai.002 G244000. The qRT-PCR results elaborated the continuous change in expression level of LBL1 at different growth stages and leaf parts of cotton. Higher expression level was observed in mature large leaves followed by medium and young leaves respectively. For further confirmation, plants were tested from hormonal induction treatments, which explained that LBL1 expression was influenced by hormonal signaling. Moreover, the highest expression level was detected in brassinolides(BR) treatment as compared to other hormones, and this hormone plays an important role in the process of leaf blade lobed formation.

Comparative Analysis of Salinity-Induced Proteomic Changes in Cotton (Gossypium hirsutum L.)

Salt stress on cotton varieties of distinct salinity tolerance can induce expression of different proteins. Zhong 07, a salt-tolerant variety and Zhong s9612, a salt-sensitive variety, were utilized as experimental materials. The leaves of trefoil seedlings treated with or without 0.4% NaCl for 24 h were harvested for whole-protein extraction. Two-dimensional technology, combined with mass spectroscopy (MS) analysis and protein database searching, was employed to detect differentially expressed proteins and determine their identities and biological functions. Compared with the control, Zhong 07 showed 10 differentially expressed proteins under salt stress, of which 6 were upregulated and 4 were downregulated. Meanwhile, 12 differentially expressed proteins were detected in Zhong s9612 under salt stress, of which 10 were upregulated and 2 were downregulated. In the matrix-assisted laser desorption-ionization/time of flight-time of flight/MS analysis, 14 differentially expressed proteins were successfully identified, including the ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisco) large subunit-binding protein subunit alpha (RuBisco α), luminal binding protein (LBP), heat shock protein 70 (Hsp1, 2, 3), pathogenesis-related protein class 10 (PR-10), quinoneoxidoreductase-like protein (QOR), S-adenosylmethioninesyn-thetase (SAMS), enolase (EN), and RuBisco large subunit-binding protein subunit beta (RuBisco β). Cellular function is ultimately executed by proteins, and cotton varieties with different salt tolerance can be influenced by salt stress to various degrees, which can provide certain theoretical foundation for the identification of salt tolerance of cotton varieties. The findings also provide some proteins, such as the RuBisco large subunit binding proteins α and β subunits, OEE2 protein, HSP70, and S-adenosylmethionine synthetase, which can be used as protein markers of salt-to-lerance before- and post-treatment, making a big difference in salt-tolerance identification in cotton.

Investigation of GhFAT Genes Related to Seed Oil Content and Fatty Acid Composition in Gossypium hirsutum L.

Fatty Acyl-ACP thioesterase(FAT)is a key enzyme controlling oil biosynthesis in plant seeds.FATs can be divided into two subfamilies,FATA and FATB according to their amino acid sequences and substrate specificity.The Upland cotton genome contains 20 GhFAT genes,amongst which 6 genes were of the GhFATA subfamily and 14 of the GhFATB subfamily.The 20 GhFAT genes are unevenly distributed on 14 chromosomes.The GhFATA genes have 5 or 7 exons and the GhFATB genes have 6 or 7 exons.All GhFAT proteins have the conserved Acyl-ACP_TE domain and PLN02370 super family,the typical characteristics of plant thioesterases.Analyses of the expression level of GhFATs and the compositions of fatty acid in 5-60 days-post-anthesis seeds showed that the ratio of saturated fatty acids to unsaturated fatty acids was consistent with the expression profile of GhFATB12,GhFATB3,and GhFATB10;the ratio of monounsaturated fatty acid to polyunsaturated fatty acids was consistent with the expression profile of GhFATA3.The oil contents of mature cottonseeds were positively correlated with the contents of palmitic acid and linolenic acid as well as seed vigor.These results provide essential information for further exploring the role(s)of the specific GhFATs in determining oil biosynthesis and cottonseed compositions.

Isolation and Expression Analysis of Two Genes Encoding Cinnamate 4-Hydroxylase from Cotton(Gossypium hirsutum)

Two genes(GhC4H1 and GhC4H2) that encode putative cotton cinnamate 4-hydroxylases that catalyze the second step in the phenylpropanoid pathway were isolated from developing cotton fibers. GhC4H1 and GhC4H2 each contain open reading frames of 1 518 base pairs(bp) in length and both encode proteins consisting of 505 amino acid residues. They are 90.89% identical to each other at the amino acid sequence level and belong to class I of plant C4 Hs. GhC4H1 and GhC4H2 genomic DNA are 2 247 and 2 161 bp long, respectively, and contain two introns located at conserved positions relative to the coding sequence. GhC4H1 and GhC4H2 promoters were isolated and found to contain many cis-elements(boxes P, L and AC-I element) previously identified in the promoters of other phenylpropanoid pathway genes. Histochemical staining showed GUS expression driven by the GhC4H1 and GhC4H2 promoters in ovules and fibers tissues. GhC4H1 and GhC4H2 were also widely expressed in other cotton tissues. GhC4H2 expression reached its highest level during the elongation stage of fiber development, whereas GhC4H1 expression increased during the secondary wall development period in cotton fibers. Our results contribute to a better understanding of the biochemical role of GhC4H1 and GhC4H2 in cotton fiber development.

Molecular Marker-assisted Selection for Verticillium Wilt Resistance in Upland Cotton (Gossypium hirsutum)

Verticillium wilt is a global important disease ofcotton,which threatens the development ofcotton production seriously.Recent years,because of the change in climate and croppingpattern,Verticillium wilt was broke out incotton production areas in China,which

Selection and Characterization of a Novel Glyphosate Tolerant Upland Cotton(Gossypium hirsutum L.) Mutant(R1098)

Stepwise selection approach was adopted to obtain glyphosate-tolerant upland cotton mutant(R1098) from the embryogenic calli of Coker 312(Gossypium hirsutum L.).The calli were transferred to selection medium and multi-step selection pressure process was carried out until the

An Integrated Genetic,Physical and Transcript Map of Homoeologous Chromosomes 12 and 26 in Upland Cotton(Gossypium hirsutum L.)

While Upland cotton(Gossypium hirsutum L.) represents 95% of the world production,its genetic improvement is hindered by the shortage of effective genomic tools and resources.The

Isolate a Gene for Velvet Hairiness in Cotton (Gossypium hirsutum L. ) by Map-based Cloning

Cotton crop is prone to many insect pests.Finely dense pubescence（pilose/velvet hairy）,one of the important elements of defenseumbrella confers in built resistance againstseveral insect pests.The present research wasconducted to isolate DNA markers for velvethairiness,which would be useful to launch map-basedcloning.An F2 population developed

The BEL1-like transcription factor GhBLH5-A05 participates in cotton response to drought stress

Drought stress impairs crop growth and development.BEL1-like family transcription factors may be involved in plant response to drought stress,but little is known of the molecular mechanism by which these proteins regulate plant response and defense to drought stress.Here we show that the BEL1-like transcription factor GhBLH5-A05 functions in cotton(Gossypium hirsutum)response and defense to drought stress.Expression of GhBLH5-A05 in cotton was induced by drought stress.Overexpression of GhBLH5-A05 in both Arabidopsis and cotton increased drought tolerance,whereas silencing GhBLH5-A05 in cotton resulted in elevated sensitivity to drought stress.GhBLH5-A05 binds to cis elements in the promoters of GhRD20-A09 and GhDREB2C-D05 to activate the expression of these genes.GhBLH5-A05 interacted with the KNOX transcription factor GhKNAT6-A03.Co-expression of GhBLH5-A05 and GhKNAT6-A03 increased the transcription of GhRD20-A09 and GhDREB2C-D05.We conclude that GhBLH5-A05 acts as a regulatory factor with GhKNAT6-A03 functioning in cotton response to drought stress by activating the expression of the drought-responsive genes GhRD20-A09 and GhDREB2C-D05.

Introgression of Gossypium klotzschianum Genome into Cultivated Cotton,G.hirsutum

Exotic Gossypium germplasm is a rich source of useful agronomic traits for improvement programs of cultivated cotton.Efficient use of genetic variation available in the wild relatives depends

Down-regulation of GhADF1 in cotton(Gossypium hirsutum)improves plant drought tolerance and increases fiber yield

Fiber productivity and quality of cotton are severely affected by abiotic stresses.In this study,we identified the role of GhADF1,an actin depolymerizing factor,in cotton response to drought stress.GhADF1 expression in cotton could be induced by PEG6000.GhADF1-RNAi transgenic cotton showed increased tolerance to drought stress during seed germination and seedling development as well as at the reproductive stage.In contrast,overexpression of GhADF1 led to a drought-sensitive phenotype in transgenic plants.GhADF1-RNAi plants produced an enlarged root system with longer primary roots,more lateral roots,increased root dry biomass,and increased cell size.In leaves of GhADF1-RNAi cotton,proline content and activities of reactive oxygen species-scavenging enzymes were increased following drought stress compared with those in wild type.GhADF1-RNAi lines showed higher water-use efficiency than the wild type,accompanied by reduced leaf stomatal density and conductance.GhADF1-RNAi cotton produced higher fiber yield in the field under both normal and drought conditions.Transcriptomic analyses identified 124 differentially expressed genes in leaves of GhADF1-RNAi lines compared with the wild type following drought treatment.Upregulated genes included those encoding transcription factors,protein kinases,heat shock proteins,and other proteins known to be involved in stress responses.We conclude that GhADF1 reduces the expression of abiotic stress-associated genes in cotton response to drought stress and may be a promising candidate gene for crop improvement by genetic manipulation.

Suppressing a mitochondrial calcium uniporter activates the calcium signaling pathway and promotes cell elongation in cotton

Mitochondrial calcium uniporter(MCU)is a conserved calcium ion(Ca^(2+))transporter in the mitochondrial inner membrane of eukaryotic cells.How MCU proteins regulate Ca^(2+)flow and modulate plant cell development remain largely unclear.Here,we identified the gene GhMCU4 encoding a MCU protein that negatively regulates plant development and fiber elongation in cotton(Gossypium hirsutum).GhMCU4expressed constitutively in various tissues with the higher transcripts in elongating fiber cells.Knockdown of GhMCU4 in cotton significantly elevated the plant height and root length.The calcium signaling pathway was significantly activated and calcium sensor genes,including Ca^(2+)dependent modulator of interactor of constitutively active ROP(GhCMI1),calmodulin like protein(GhCML46),calciumdependent protein kinases(GhCPKs),calcineurin B-like protein(GhCBLs),and CBL-interacting protein kinases(GhCIPKs),were dramatically upregulated in GhMCU4-silenced plants.Metabolic processes were preferentially enriched,and genes related to regulation of transcription were upregulated in GhMCU4-silenced plants.The contents of Ca^(2+)and H_(2)O_(2)were significantly increased in roots and leaves of GhMCU4-silenced plants.Fiber length and Ca^(2+)and H_(2)O_(2)contents in fibers were significantly increased in GhMCU4-silenced plants.This study indicated that GhMCU4 plays a negative role in regulating cell elongation in cotton,thus expanding understanding in the role of MCU proteins in plant growth and development.

Introduction of Bacillus thuringiensis(Bt)gene does not reduce potassium use efficiency of Bt transgenic cotton(Gossypium hirsutum L.)

Background:Potassium(K)deficiency has become a common field production problem following the widespread adoption of Bacillus thuringiensis(Bt)transgenic cotton(Gossypium hirsutum L.)worldwide.The purpose of this study was to clarify whether the introduction of Bt gene directly reduces the K-use efficiency of cotton to induce K deficiency.Results:The cotton variety,Jihe 321(wild type,WT)and its two Bt(Cry1Ac)-transgenic overexpression lines(OE-29317,OE-29312)were studied in field with low soil-test K+(47.8 mg·kg^(−1)).In the field with low soil-test K+,only OE-29317 had less biomass and K+accumulation than the WT at some growth stages.Both Bt lines produced similar or even greater seed cotton yield than WT in the field.When the Bt gene(~70%)in OE-29317 and OE-29312 plants was silenced by virus-induced gene silencing(VIGS),the VIGS-Bt plants did not produce more biomass than VIGSgreen fluorescent protein(control)plants.Conclusions:The introduction of Bt gene did not necessarily hinder the K use efficiency of the cotton lines under this study.

Genome-wide association study of micronaire using a natural population of representative upland cotton(Gossypium hirsutum L.)

Background: Micronaire is a comprehensive index reflecting the fineness and maturity of cotton fiber.Micronaire is one of the important internal quality indicators of the cotton fiber and is closely related to the value of the cotton fiber.Understanding the genetic basis of micronaire is required for the genetic improvement of the trait.However,the genetic architecture of micronaire at the genomic level is unclear.The present genome-wide association study(GWAS)aimed to identify the genetic mechanism of the micronaire trait in 83 representa:tive upland cotton lines grown in multiple environments.Results GWAS of micronaire used 83 upland cotton accessions assayed by a Cotton 63 K Illumina Infinium single nucleotide polymorphism(SNP)array.A total of 11 quantitative trait loci(QTLs)for micronaire were detected on 10 chromosomes.These 11 QTLs included 27 identified genes with specific expression patterns.A novel QTL,qFM-A12–1,included 12 significant SNPs,and GhFLA9 was identified as a candidate gene based on haplotype block analysis and on strong and direct linkage disequilibrium between the significantly related SNPs and gene.GhFLA9 was expressed at a high level during secondary wall thickening at 20∼25 days post-anthesis.The expression level of GhFLA9 was significantly higher in the low micronaire line(Msco-12)than that in the high micronaire line(Chuangyou-9).Conclusions: This study provides a genetic reference for genetic improvement of cotton fiber micronaire and a foundation for verification of the functions of GhFLA9.

Development of SSR Markers towards Genetic Mapping in Cotton(Gossypium hirsutum L. )

Availability of informative molecular markers isa prerequisite for genetic mapping and marker-assisted selection projects.Micro-satellites orSimple Sequence Repeat(SSR)markers arePCR-based and currently the most widely usedmarker system in the plant molecular geneticscommunity due to their high degree ofpolymorphism,random distribution throughoutthe genome and their suitability for highthroughput genotyping formats.Despite itsglobal economic importance,cotton has

Development and Application of a Transformation-competent Artificial chromosome (TAG) Genomic DNA Library in Allotetrapolid Cotton (Gossypium hirsutum L. )

The technology of cloning and transferring oflarge DNA fragments in plants is important forhigh-efficient identification of new genes andstudy of gene functions.Tranformation-competent artificial chromosome(TAC)vectorsystem has been shown to be very useful forefficient gene isolation in Arobidopsis thaliana.In order to develop an efficient platform for