Temperature impacts on cotton yield superposed by effects on plant growth and verticillium wilt infection in China.

China produces and consumes the largest amount of cotton, playing a critical role in the world's fiber and textile industries. Theoretically, an increase in temperature poses a complex set of impacts on both cotton and pathogen diseases. However, empirical evidence regarding the overall effect on regional cotton yield in China is currently lacking. In this study, we employ county-level cotton statistics and degree-day indices (n = 30,502) to demonstrate a temperature effect on cotton yield, influenced by both direct temperature effects and indirect effects on verticillium wilt infection in China. Our findings indicate that temperatures between the base growing temperature (15 °C) and the optimal infection threshold for cotton wilt disease (25 °C) reduce cotton yield. However, beyond this threshold, when disease infection is significantly limited, higher temperatures become beneficial. Temperatures exceeding 32 °C causes heat stress, which dominates and drives a decline in yield. Furthermore, we provide a risk assessment of warming on cotton in future climate scenarios. Our model projections reveal an overall decrease in cotton yield ranging from 6.2 to 30.6%, accompanied by amplified heat stress (resulting in a yield decrease of 11.6 to 48.7%) but a reduced threat of verticillium wilt (yield increase of 8.2 to 23.6%) in future. Particularly, the Northwest Region, currently responsible for 80% of cotton production, is expected to be particularly vulnerable. This study emphasizes the importance of investing in long-term technological advancements such as cotton heat-tolerance breeding and redistributing cotton growing areas.

Oil candidate genes in seeds of cotton (Gossypium hirsutum L.) and functional validation of GhPXN1.

BACKGROUND: Cottonseed oil is a promising edible plant oil with abundant unsaturated fatty acids. However, few studies have been conducted to explore the characteristics of cottonseed oil. The molecular mechanism of cottonseed oil accumulation remains unclear. RESULTS: In the present study, we conducted comparative transcriptome and weighted gene co-expression network (WGCNA) analysis for two G. hirsutum materials with significant difference in cottonseed oil content. Results showed that, between the high oil genotype 6053 (H6053) and the low oil genotype 2052 (L2052), a total of 412, 507, 1,121, 1,953, and 2,019 differentially expressed genes (DEGs) were detected at 10, 15, 20, 25, and 30 DPA, respectively. Remarkably, a large number of the down-regulated DEGs were enriched in the phenylalanine metabolic processes. Investigation into the dynamic changes of expression profiling of genes associated with both phenylalanine metabolism and oil biosynthesis has shed light on a significant competitive relationship in substrate allocation during cottonseed development. Additionally, the WGCNA analysis of all DEGs identified eight distinct modules, one of which includes GhPXN1, a gene closely associated with oil accumulation. Through phylogenetic analysis, we hypothesized that GhPXN1 in G. hirsutum might have been introgressed from G. arboreum. Overexpression of the GhPXN1 gene in tobacco leaf suggested a significant reduction in oil content compared to the empty-vector transformants. Furthermore, ten other crucial oil candidate genes identified in this study were also validated using quantitative real-time PCR (qRT-PCR). CONCLUSIONS: Overall, this study enhances our comprehension of the molecular mechanisms underlying cottonseed oil accumulation.

Overexpression of the cotton trihelix transcription factor GhGT23 in Arabidopsis mediates salt and drought stress tolerance by binding to GT and MYB promoter elements in stress-related genes.

Cotton (Gossypium hirsutum L.) is the world's most economically valuable textile crop. However, cotton plants are often subjected to numerous abiotic stresses that can dramatically limit yield. Trihelix transcription factors (TTFs) play important roles in abiotic stress responses in many plant species, and efforts to better understand their roles in cotton abiotic stress responses are ongoing. In this study, a member of the cotton TTF family (GhGT23) was functionally characterized. This protein contains a SANT domain and is a member of the SIP subfamily of TTF proteins. GhGT23 was significantly (p < 0.05) and highly expressed in cotton fiber compared to relatively low expression in other tissues. A significant (p < 0.05) increase in GhGT23 expression occurred in cotton seedlings within 12 hours of drought, salt, and ABA exposure. The GhGT23 protein localized in the nucleus but exhibited no signs of transactivation activity. GhGT23 overexpression in Arabidopsis conferred enhanced drought and salt stress tolerance. The expression of stress-related genes was higher in transgenic Arabidopsis expressing GhGT23 than in wild-type plants subjected to salt stress. The results of electrophoretic mobility shift assay revealed that GhGT23 could bind to the GT cis-elements GT-1Box (Box II), GT2-Box, GT3-Box, GT-3a (Site1-type), GT-3b, and Box as well as the MYB cis-elements MBS1 and MRE4. Our results demonstrate that GhGT23 positively regulates salt and drought stress responses, possibly by enhancing the expression of stress-related genes.

Analysis of PAT1 subfamily members in the GRAS family of upland cotton and functional characterization of GhSCL13-2A in Verticillium dahliae resistance.

KEY MESSAGE: GhSCL13-2A, a member of the PAT1 subfamily in the GRAS family, positively regulates cotton resistance to Verticillium dahliae by mediating the jasmonic acid and salicylic acid signaling pathways and accumulation of reactive oxygen species. Verticillium wilt (VW) is a devastating disease of upland cotton (Gossypium hirsutum) that is primarily caused by the soil-borne fungus Verticillium dahliae. Scarecrow-like (SCL) proteins are known to be involved in plant abiotic and biotic stress responses, but their roles in cotton defense responses are still unclear. In this study, a total of 25 GhPAT1 subfamily members in the GRAS family were identified in upland cotton. Gene organization and protein domain analysis showed that GhPAT1 members were highly conserved. GhPAT1 genes were widely expressed in various tissues and at multiple developmental stages, and they were responsive to jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) signals. Furthermore, GhSCL13-2A was induced by V. dahliae infection. V. dahliae resistance was enhanced in Arabidopsis thaliana by ectopic overexpression of GhSCL13-2A, whereas cotton GhSCL13-2A knockdowns showed increased susceptibility. Levels of reactive oxygen species (ROS) and JA were also increased and SA content was decreased in GhSCL13-2A knockdowns. At the gene expression level, PR genes and SA signaling marker genes were down-regulated and JA signaling marker genes were upregulated in GhSCL13-2A knockdowns. GhSCL13-2A was shown to be localized to the cell membrane and the nucleus. Yeast two-hybrid and luciferase complementation assays indicated that GhSCL13-2A interacted with GhERF5. In Arabidopsis, V. dahliae resistance was enhanced by GhERF5 overexpression; in cotton, resistance was reduced in GhERF5 knockdowns. This study revealed a positive role of GhSCL13-2A in V. dahliae resistance, establishing it as a strong candidate gene for future breeding of V. dahliae-resistant cotton cultivars.

Trihelix Transcriptional Factor GhGT26 of Cotton Enhances Salinity Tolerance in Arabidopsis.

Cotton (Gossypium hirsutum L.), the most important textile crop worldwide, often encounters abiotic stress during its growing season and its productivity is significantly limited by adverse factors. Trihelix transcription factors (also known as GT factors) are important proteins involved in the morphological development and responses to abiotic stress in plants. However, their functions and molecular mechanisms in the cotton toward abiotic stress response remain unclear. In this study, a member (GhGT26) of the cotton Trihelix family was functionally characterized in the model plant Arabidopsis. This protein containing a SANT domain belongs to the GT-1 subgroup of trihelix proteins. GhGT26 was widely expressed in tissues (with the highest level in flower) and responded to high salt and ABA treatments at the transcriptional level. Using the Arabidopsis protoplast assay system, we found that the GhGT26 protein was located in the cell nuclei. The EMSA assay revealed that the GhGT26 protein could bind to the Site1-type GT cis elements (GT-3a) and MYB elements MRE3 and MRE4. The overexpression of GhGT26 improved plant tolerance to salt stress in transgenic Arabidopsis plants. Although ABA inhibits root elongation, the statistical analysis revealed that the root lengths of GhGT26-overexpressing Arabidopsis were the same as the wild plants after ABA treatment. Our results demonstrate that GhGT26 positively regulates salt stress via ABA-independent pathways. This evidence suggests that the GhGT26 may participate in the regulation of stress tolerance in cotton.

Comparative transcriptome analysis of melon (Cucumis melo L.) reveals candidate genes and pathways involved in powdery mildew resistance.

Powdery mildew is a major disease in melon, primarily caused by Podosphaera xanthii (Px). Some melon varieties were resistant to powdery mildew, while others were susceptible. However, the candidate genes associated with resistance and the mechanism of resistance/susceptibility to powdery mildew in melon remain unclear. In this study, disease-resistant melon cultivar TG-1 and disease-susceptible melon cultivar TG-5 were selected for comparative transcriptome analysis. The results suggested that the numbers of differentially expressed genes (DEGs) in TG-5 was always more than that in TG-1 at each of the four time points after Px infection, indicating that their responses to Px infection may be different and that the active response of TG-5 to Px infection may be earlier than that of TG-1. Transcription factors (TFs) analysis among the DEGs revealed that the bHLH, ERF, and MYB families in TG-1 may play a vital role in the interaction between melon and powdery mildew pathogens. GO enrichment analysis of these DEGs in TG-5 showed that the SBP, HSF, and ERF gene families may play important roles in the early stage of melon development after Px infection. Finally, we speculated on the regulatory pathways of melon powdery mildew and found PTI and ABA signaling genes may be associated with the response to Px infection in melon.

Identification of BR biosynthesis genes in cotton reveals that GhCPD-3 restores BR biosynthesis and mediates plant growth and development.

MAIN CONCLUSION: Brassinosteroid (BR) synthesis genes in different cotton species was comprehensively identified, and the participation of GhCPD-3 in the BR synthesis signaling pathway for regulating plant development was verified. Brassinosteroid is a natural steroidal phytohormone that plays fundamental roles in plant growth and development. In cotton, detailed characterization and functional validation of BR biosynthesis genes remain rare. Here, 16, 8 and 9 BR biosynthesis genes were identified in Gossypium hirsutum, Gossypium raimondii and Gossypium arboreum, respectively, and their phylogenetic relationships, gene structures, conserved motifs of the encoded proteins, chromosomal locations were determined and a synteny analysis was performed. Gossypium hirsutum and Arabidopsis BR biosynthesis genes closely clustered in the phylogenetic tree and fragment duplication was likely the primary cause promoting gene family expansion in G. hirsutum. Gene Ontology (GO) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis showed their relevance as BR biosynthesis genes. GhCPD-3 was highly expressed in roots and stems and the loci of single nucleotide polymorphisms (SNPs) were significantly associated with these traits.Ectopic overexpression of GhCPD-3 in the cpd91 Arabidopsis mutant rescued the mutant phenotype by increasing plant height and leaf size in comparison to those of cpd91 and WT plants. Moreover, overexpressed GhCPD-3 in cpd91 mutants showed greater hypocotyl and root lengths than those of cpd91 and WT plants under light and dark conditions, respectively, indicating that BR actively promotes hypocotyl and root growth. Similar to CPD (CONSTITUTIVE PHOTOMORPHOGENIC DWARF), GhCPD-3 restores BR biosynthesis thereby mediating plant growth and development.

The genomic basis of geographic differentiation and fiber improvement in cultivated cotton.

Large-scale genomic surveys of crop germplasm are important for understanding the genetic architecture of favorable traits. The genomic basis of geographic differentiation and fiber improvement in cultivated cotton is poorly understood. Here, we analyzed 3,248 tetraploid cotton genomes and confirmed that the extensive chromosome inversions on chromosomes A06 and A08 underlies the geographic differentiation in cultivated Gossypium hirsutum. We further revealed that the haplotypic diversity originated from landraces, which might be essential for understanding adaptative evolution in cultivated cotton. Introgression and association analyses identified new fiber quality-related loci and demonstrated that the introgressed alleles from two diploid cottons had a large effect on fiber quality improvement. These loci provided the potential power to overcome the bottleneck in fiber quality improvement. Our study uncovered several critical genomic signatures generated by historical breeding effects in cotton and a wealth of data that enrich genomic resources for the research community.

[Cloning and functional analysis of the cotton Trihelix transcription factor GhGT29].

Trihelix transcription factors are important proteins involved in response to abiotic stresses in plants. Understanding the molecular mechanisms of Trihelix in cottons will lay the foundation to improve stress tolerance by gene engineering. In this study, a gene encoding Trihelix transcription factor was isolated in upland cottons using reverse transcription PCR according to bioinformatic analysis. The gene was named as GhGT29 (GenBank accession No. JQ013097), which was 1 092 bp, contained a 1 089 bp open reading frame and encoded a protein of 363 amino acids with a predicted molecular weight of 40.9 kDa and a isoelectric point of 5.45. SMART analysis showed GhGT29 contained one typical SANT motif. Phylogenetic analysis showed that GhGT29 belonged to the SH4 subfamily of the Trihelix family and was most closely related to AtSH4-like1 and AtSH4-like2. Quantitative real-time PCR (qRT-PCR) analysis revealed that GhGT29 was induced by high salt, drought, cold and abscisic acid. The expression profile also revealed that GhGT29 was constitutively expressed in all tested tissues, such as roots, stems, leaves, flowers, ovules (0 DPA) and fibers (12 DPA). The expression level of GhGT29 was the highest in flowers and the lowest in stems. Using the Arabidopsis protoplasts assay system, we found that the GhGT29 protein was located in cell nuclei and had trans-activation activity. These results revealed that GhGT29 might be involved in the regulation of stress resistance-related genes in stress signaling pathways in upland cottons.

Soybean Trihelix transcription factors GmGT-2A and GmGT-2B improve plant tolerance to abiotic stresses in transgenic Arabidopsis.

BACKGROUND: Trihelix transcription factors play important roles in light-regulated responses and other developmental processes. However, their functions in abiotic stress response are largely unclear. In this study, we identified two trihelix transcription factor genes GmGT-2A and GmGT-2B from soybean and further characterized their roles in abiotic stress tolerance. FINDINGS: Both genes can be induced by various abiotic stresses, and the encoded proteins were localized in nuclear region. In yeast assay, GmGT-2B but not GmGT-2A exhibits ability of transcriptional activation and dimerization. The N-terminal peptide of 153 residues in GmGT-2B was the minimal activation domain and the middle region between the two trihelices mediated the dimerization of the GmGT-2B. Transactivation activity of the GmGT-2B was also confirmed in plant cells. DNA binding analysis using yeast one-hybrid assay revealed that GmGT-2A could bind to GT-1bx, GT-2bx, mGT-2bx-2 and D1 whereas GmGT-2B could bind to the latter three elements. Overexpression of the GmGT-2A and GmGT-2B improved plant tolerance to salt, freezing and drought stress in transgenic Arabidopsis plants. Moreover, GmGT-2B-transgenic plants had more green seedlings compared to Col-0 under ABA treatment. Many stress-responsive genes were altered in GmGT-2A- and GmGT-2B-transgenic plants. CONCLUSION: These results indicate that GmGT-2A and GmGT-2B confer stress tolerance through regulation of a common set of genes and specific sets of genes. GmGT-2B also affects ABA sensitivity.

Ectopic expression of soybean GmKNT1 in Arabidopsis results in altered leaf morphology and flower identity.

Plant morphology is specified by leaves and flowers, and the shoot apical meristem (SAM) defines the architecture of plant leaves and flowers. Here, we reported the characterization of a soybean KNOX gene GmKNT1, which was highly homologous to Arabidopsis STM. The GmKNT1 was strongly expressed in roots, flowers and developing seeds. Its expression could be induced by IAA, ABA and JA, but inhibited by GA or cytokinin. Staining of the transgenic plants overexpressing GmKNT1-GUS fusion protein revealed that the GmKNT1 was mainly expressed at lobe region, SAM of young leaves, sepal and carpel, not in seed and mature leaves. Scanning electron microscopy (SEM) disclosed multiple changes in morphology of the epidermal cells and stigma. The transgenic Arabidopsis plants overexpressing the GmKNT1 showed small and lobed leaves, shortened internodes and small clustered inflorescence. The lobed leaves might result from the function of the meristems located at the boundary of the leaf. Compared with wild type plants, transgenic plants had higher expression of the SAM-related genes including the CUP, WUS, CUC1, KNAT2 and KNAT6. These results indicated that the GmKNT1 could affect multiple aspects of plant growth and development by regulation of downstream genes expression.

Soybean WRKY-type transcription factor genes, GmWRKY13, GmWRKY21, and GmWRKY54, confer differential tolerance to abiotic stresses in transgenic Arabidopsis plants.

WRKY-type transcription factors have multiple roles in the plant defence response and developmental processes. Their roles in the abiotic stress response remain obscure. In this study, 64 GmWRKY genes from soybean were identified, and were found to be differentially expressed under abiotic stresses. Nine GmWRKY proteins were tested for their transcription activation in the yeast assay system, and five showed such ability. In a DNA-binding assay, three proteins (GmWRKY13, GmWRKY27 and GmWRKY54) with a conserved WRKYGQK sequence in their DNA-binding domain could bind to the W-box (TTGAC). However, GmWRKY6 and GmWRKY21, with an altered sequence WRKYGKK, lost the ability to bind to the W-box. The function of three stress-induced genes, GmWRKY13, GmWRKY21 and GmWRKY54, was further investigated using a transgenic approach. GmWRKY21-transgenic Arabidopsis plants were tolerant to cold stress, whereas GmWRKY54 conferred salt and drought tolerance, possibly through the regulation of DREB2A and STZ/Zat10. Transgenic plants over-expressing GmWRKY13 showed increased sensitivity to salt and mannitol stress, but decreased sensitivity to abscisic acid, when compared with wild-type plants. In addition, GmWRKY13-transgenic plants showed an increase in lateral roots. These results indicate that the three GmWRKY genes play differential roles in abiotic stress tolerance, and that GmWRKY13 may function in both lateral root development and the abiotic stress response.

Characterization of a novel cell cycle-related gene from Arabidopsis.

Cell division is a fundamental biological process sharing conserved features and controls in all eukaryotes. The cell cycle is usually divided into four phases: G1, S, G2, and M. Regulated gene expression is an important mechanism for controlling cell cycle progression and genes involved in cell division-related processes often show transcriptional regulation dependent on cell cycle position. In the present report, a novel cell cycle-related gene (AtCPR) from Arabidopsis thaliana was isolated and characterized. Sequence analysis revealed that the deduced amino acid sequence of AtCPR showed 53.2% identity with p38-2G4, a mouse G1-to-S cell cycle specifically modulated and proliferation-associated nuclear protein. Assay of expression of AtCPR in partially synchronized cells suggested that AtCPR mRNA was expressed in the G1-to-S phase. In the AtCPR transgenic plants, no apparent phenotypic change was observed. By fusing a GFP tag to the AtCPR protein, it was found that AtCPR was mainly located in the nucleus. However, AtCPR does not have any transcriptional activation ability. cDNA microarray analysis showed that a total of 17 and 30 genes were identified as up-regulated and down-regulated, respectively.