Detection of Favorable QTL Alleles and Candidate Genes for Lint Percentage by GWAS in Chinese Upland Cotton

Improving cotton yield is a major breeding goal for Chinese upland cotton. Lint percentage is an important yield component and a critical economic index for cotton cultivars, and raising the lint percentage has a close relationship to improving cotton lint yield. To investigate the genetic architecture of lint percentage, a diversity panel consisting of 355 upland cotton accessions was grown, and the lint percentage was measured in four different environments. Genotyping was performed with specific-locus amplified fragment sequencing (SLAF-seq). Twelve single-nucleotide polymorphisms (SNPs) associated with lint percentage were detected via a genome-wide association study (GWAS), in which five SNP loci distributed on chromosomes At3 (A02) and At4 (A08) and contained two major-effect QTLs, which were detected in the best linear unbiased predictions (BLUPs) and in more than three environments simultaneously. Furthermore, favorable haplotypes (FHs) of two major-effect QTLs and 47 putative candidate genes in the two linkage disequilibrium (LD) blocks of these associated loci were identified. The expression levels of these putative candidate genes were estimated using RNA-seq data from ten upland cotton tissues. We found that Gh_A02G1268 was very highly expressed during the early fiber development stage, whereas the gene was poorly expressed in the seed. These results implied that Gh_A02G1268 may determine the lint percentage by regulating seed and fiber development. The favorable QTL alleles and candidate genes for lint percentage identified in this study will have high potential for improving lint yield in future Chinese cotton breeding programs

Identification, Expression, and Functional Analysis of the Group IId WRKY Subfamily in Upland Cotton (Gossypium hirsutum L.)

WRKY transcription factors have diverse functions in regulating stress response, leaf senescence, and plant growth and development. However, knowledge of the group IId WRKY subfamily in cotton is largely absent. This study identified 34 group IId WRKY genes in the Gossypium hirsutum genome, and their genomic loci were investigated. Members clustered together in the phylogenetic tree had similar motif compositions and gene structural features, revealing similarity and conservation within group IId WRKY genes. During the evolutionary process, 14 duplicated genes appeared to undergo purification selection. Public RNA-seq data were used to examine the expression patterns of group IId WRKY genes in various tissues and under drought and salt stress conditions. Ten highly expressed genes were identified, and the ten candidate genes revealed distinct expression patterns under drought and salt treatments by qRT-PCR analysis. Among them, Gh_A11G1801 was used for functional characterization. GUS activity was differentially induced by various stresses in Gh_A11G1801p::GUS transgenic Arabidopsis plants. The virus-induced gene silencing (VIGS) of Gh_A11G1801 resulted in drought sensitivity in cotton plants, which was accompanied by elevated malondialdehyde (MDA) content and reduced catalase (CAT) content. Taken together, these findings obtained in this study provide valuable resources for further studying group IId WRKY genes in cotton. Our results also enrich the gene resources for the genetic improvements of cotton varieties that are suitable for growth in stressful conditions

Corrigendum to: The TianQin project: current progress on science and technology

In the originally published version, this manuscript included an error related to indicating the corresponding author within the author list. This has now been corrected online to reflect the fact that author Jun Luo is the corresponding author of the article

The cytochrome P450 gene GhCYP94C1 is involved in drought stress in upland cotton (Gossypium hirsutum L.)

Cytochrome P450 proteins belong to one of the largest families of enzyme proteins in plants and play important roles in plant growth and development and the stress response. In our previous studies, a cytochrome P450 gene, GhCYP94C1 (cytochrome P450 94C1), was functionally characterized as a positive regulator of seed germination, main root elongation and early flowering. However, whether the gene has other potential functions remains to be further explored. In our study, expression analysis showed that GhCYP94C1 was highly expressed in roots and was suppressed by drought treatment. Endogenous silencing of GhCYP94C1 via virus-induced gene silencing (VIGS) increased drought resistance in cotton plants, which was accompanied by the upregulated expression of the abscisic acid (ABA) biosynthesis gene nine-cis-epoxycarotenoid dioxygenase 9 (GhNCED9) during drought stress. Our findings suggested that GhCYP94C1 may play an important role in drought resistance. Combined with previous research results, the present results provide a theoretical basis for future breeding of new cotton varieties with early maturation and drought resistance

Characterization and functional analysis of GhWRKY42, a group IId WRKY gene, in upland cotton (Gossypium hirsutum L.)

Abstract Background WRKY transcription factors (TFs) participate in various physiological processes of plants. Although WRKY genes have been well studied in model plants, knowledge of the functional roles of these genes is still extremely limited in cotton. Results In this study, a group IId WRKY gene from cotton, GhWRKY42, was isolated and characterized. Our data showed that GhWRKY42 localized to the nucleus. A transactivation assay in yeast demonstrated that GhWRKY42 was not a transcriptional activator. A β-glucuronidase (GUS) activity assay revealed that the promoter of GhWRKY42 showed fragment deletion activity in Nicotiana tabacum and was mainly expressed in the roots, stems and leaves of ProGhWRKY42::GUS transgenic Arabidopsis plants. Quantitative real-time PCR (qRT-PCR) analysis indicated that GhWRKY42 was up-regulated during leaf senescence and was induced after exposure to abiotic stresses. Constitutive expression of GhWRKY42 in Arabidopsis led to a premature aging phenotype, which was correlated with an increased number of senescent leaves, reduced chlorophyll content and elevated expression of senescence-associated genes (SAGs). In addition, virus-induced gene silencing (VIGS) was used to silence the endogenous GhWRKY42 gene in cotton, and this silencing reduced plant height. Conclusions Our findings indicate that GhWRKY42 is involved in abiotic stress responses, premature leaf senescence and stem development. This work establishes a solid foundation for further functional analysis of the GhWRKY42 gene in cotton

Genome-wide identification and expression analysis of PtJAZ gene family in poplar (Populus trichocarpa)

Abstract Background The jasmonate ZIM domain (JAZ) protein is a key repressor of the jasmonate signal transduction pathway, which plays an important role in plant growth and development and defense responses. In this study, based on the published whole-genome data, we identified members of the JAZ gene family in Populus trichocarpa. Through a series of bioinformatic approaches, their expression patterns under various stress conditions have been analyzed to explore and excavate the endogenous resistance genes of poplar and provide a theoretical basis for breeding new varieties of poplar resistance. Results A total of 13 PtJAZ genes have been identified in P. trichocarpa and designated as PtJAZ1–PtJAZ13. Those 13 PtJAZ genes were unevenly distributed on nine chromosomes, and they could be divided into four subfamilies. The gene structures and motif composition of the members derived from the same subfamily were similar. Collinearity analysis demonstrated that, compared with Arabidopsis thaliana and Oryza sativa, the most collinear pairs (13) were found in P. trichocarpa and Eucalyptus robusta. Cis-acting element analysis suggested that the promoter regions of PtJAZs contained a large number of hormones and stress response elements, of which abscisic acid (ABA) and methyl jasmonate (MeJA) hormone response elements were the most abundant. The PtJAZ genes not only had diverse expression patterns in different tissues, but they also responded to various abiotic and biotic stress conditions. The co-expression network and GO and KEGG analyses showed that JAZ genes were closely related to insect resistance. Conclusions In this study, applying bioinformatic methods, 13 PtJAZ gene family members from P. trichocarpa were identified and comprehensively analyzed. By further studying the function of the poplar JAZ gene family, the aim is to select genes with better insect resistance and stress resistance so as to lay a solid foundation for the subsequent breeding of new poplar varieties

Additional file 2: of Characterization and functional analysis of GhWRKY42, a group IId WRKY gene, in upland cotton (Gossypium hirsutum L.)

Table S2. Primers used in this study. (DOCX 32 kb

The WRKY transcription factor GhWRKY27 coordinates the senescence regulatory pathway in upland cotton (Gossypium hirsutum L.)

Abstract Background Premature senescence can reduce the yield and quality of crops. WRKY transcription factors (TFs) play important roles during leaf senescence, but little is known about their ageing mechanisms in cotton. Results In this study, a group III WRKY TF, GhWRKY27, was isolated and characterized. The expression of GhWRKY27 was induced by leaf senescence and was higher in an early-ageing cotton variety than in a non-early-ageing cotton variety. Overexpression of GhWRKY27 in Arabidopsis promoted leaf senescence, as determined by reduced chlorophyll content and elevated expression of senescence-associated genes (SAGs). Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays showed that GhWRKY27 interacted with an MYB TF, GhTT2. Putative target genes of GhWRKY27 were identified via chromatin immunoprecipitation followed by sequencing (ChIP-seq). Yeast one-hybrid (Y1H) assay and electrophoretic mobility shift assay (EMSA) revealed that GhWRKY27 binds directly to the promoters of cytochrome P450 94C1 (GhCYP94C1) and ripening-related protein 2 (GhRipen2–2). In addition, the expression patterns of GhTT2, GhCYP94C1 and GhRipen2–2 were identified during leaf senescence. Transient dual-luciferase reporter assay indicated that GhWRKY27 could activate the expression of GhCYP94C1 and GhRipen2–2. Conclusions Our work lays the foundation for further study of the functional roles of WRKY genes during leaf senescence in cotton. In addition, our data provide new insights into the senescence-associated mechanisms of WRKY genes in cotton