StoMYB41 positively regulates the Solanum torvum response to Verticillium dahliae in an ABA dependent manner.

MYB transcription factor despite their solid involvement in growth are potent regulator of plant stress response. Herein, we identified a MYB gene named as StoMYB41 in a wild eggplant species Solanum torvum. The expression level of StoMYB41 was higher in root than the tissues including stem, leaf, and seed. It induced significantly by Verticillium dahliae inoculation. StoMYB41 was localized in the nucleus and exhibited transcriptional activation activity. Silencing of StoMYB41 enhanced susceptibility of Solanum torvum against Verticillium dahliae, accompanied by higher disease index. The significant down-regulation of resistance marker gene StoABR1 comparing to the control plants was recorded in the silenced plants. Moreover, transient expression of StoMYB41 could trigger intense hypersensitive reaction mimic cell death, darker DAB and trypan blue staining, higher ion leakage, and induced the expression levels of StoABR1 and NbDEF1 in the leaves of Solanum torvum and Nicotiana benthamiana. Taken together, our data indicate that StoMYB41 acts as a positive regulator in Solanum torvum against Verticillium wilt.

Improvement of qualitative and quantitative traits in cotton under normal and stressed environments using genomics and biotechnological tools: A review.

Due to the increasing demand for high-quality and high fiber-yielding cotton (Gossypium spp.), research into the development of stress-resilient cotton cultivars has acquired greater significance. Various biotic and abiotic stressors greatly affect cotton production and productivity, posing challenges to the future of the textile industry. Moreover, the content and quality of cottonseed oil can also potentially be influenced by future environmental conditions. Apart from conventional methods, genetic engineering has emerged as a potential tool to improve cotton fiber quality and productivity. Identification and modification of genome sequences and the expression levels of yield-related genes using genetic engineering approaches have enabled to increase both the quality and yields of cotton fiber and cottonseed oil. Herein, we evaluate the significance and molecular mechanisms associated with the regulation of cotton agronomic traits under both normal and stressful environmental conditions. In addition, the importance of gossypol, a toxic phenolic compound in cottonseed that can limit consumption by animals and humans, is reviewed and discussed.

Hub Genes in Stable QTLs Orchestrate the Accumulation of Cottonseed Oil in Upland Cotton via Catalyzing Key Steps of Lipid-Related Pathways.

Upland cotton is the fifth-largest oil crop in the world, with an average supply of nearly 20% of vegetable oil production. Cottonseed oil is also an ideal alternative raw material to be efficiently converted into biodiesel. However, the improvement in kernel oil content (KOC) of cottonseed has not received sufficient attention from researchers for a long time, due to the fact that the main product of cotton planting is fiber. Previous studies have tagged QTLs and identified individual candidate genes that regulate KOC of cottonseed. The regulatory mechanism of oil metabolism and accumulation of cottonseed are still elusive. In the current study, two high-density genetic maps (HDGMs), which were constructed based on a recombinant inbred line (RIL) population consisting of 231 individuals, were used to identify KOC QTLs. A total of forty-three stable QTLs were detected via these two HDGM strategies. Bioinformatic analysis of all the genes harbored in the marker intervals of the stable QTLs revealed that a total of fifty-one genes were involved in the pathways related to lipid biosynthesis. Functional analysis via coexpression network and RNA-seq revealed that the hub genes in the co-expression network that also catalyze the key steps of fatty acid synthesis, lipid metabolism and oil body formation pathways (ACX4, LACS4, KCR1, and SQD1) could jointly orchestrate oil accumulation in cottonseed. This study will strengthen our understanding of oil metabolism and accumulation in cottonseed and contribute to KOC improvement in cottonseed in the future, enhancing the security and stability of worldwide food supply.

Comparative Transcriptome Analysis Revealed Key Genes Regulating Gossypol Synthesis in Tetraploid Cultivated Cotton.

Tetraploid cultivated cotton (Gossypium spp.) produces cottonseeds rich in protein and oil. Gossypol and related terpenoids, stored in the pigment glands of cottonseeds, are toxic to human beings and monogastric animals. However, a comprehensive understanding of the genetic basis of gossypol and gland formation is still lacking. We performed a comprehensive transcriptome analysis of four glanded versus two glandless tetraploid cultivars distributed in Gossypium hirsutum and Gossypium barbadense. A weighted gene co-expression network analysis (WGCNA) based on 431 common differentially expressed genes (DEGs) uncovered a candidate module that was strongly associated with the reduction in or disappearance of gossypol and pigment glands. Further, the co-expression network helped us to focus on 29 hub genes, which played key roles in the regulation of related genes in the candidate module. The present study contributes to our understanding of the genetic basis of gossypol and gland formation and serves as a rich potential source for breeding cotton cultivars with gossypol-rich plants and gossypol-free cottonseed, which is beneficial for improving food safety, environmental protection, and economic gains of tetraploid cultivated cotton.

Genome-Wide Analysis and Functional Characterization of LACS Gene Family Associated with Lipid Synthesis in Cotton (Gossypium spp.).

Cotton (Gossypium spp.) is the fifth largest oil crop in the world, and cottonseed provides abundant vegetable oil resources and industrial bioenergy fuels for people; therefore, it is of practical significance to increase the oil content of cotton seeds for improving the oil yield and economic benefits of planting cotton. Long-chain acyl-coenzyme A (CoA) synthetase (LACS) capable of catalyzing the formation of acyl-CoAs from free fatty acids has been proven to significantly participate in lipid metabolism, of which whole-genome identification and functional characterization of the gene family have not yet been comprehensively analyzed in cotton. In this study, a total of sixty-five LACS genes were confirmed in two diploid and two tetraploid Gossypium species, which were divided into six subgroups based on phylogenetic relationships with twenty-one other plants. An analysis of protein motif and genomic organizations displayed structural and functional conservation within the same group but diverged among the different group. Gene duplication relationship analysis illustrates the LACS gene family in large scale expansion through WGDs/segmental duplications. The overall Ka/Ks ratio indicated the intense purifying selection of LACS genes in four cotton species during evolution. The LACS genes promoter elements contain numerous light response cis-elements associated with fatty acids synthesis and catabolism. In addition, the expression of almost all GhLACS genes in high seed oil were higher compared to those in low seed oil. We proposed LACS gene models and shed light on their functional roles in lipid metabolism, demonstrating their engineering potential for modulating TAG synthesis in cotton, and the genetic engineering of cottonseed oil provides a theoretical basis.

Phosphorus-induced greater enhancement in carbon supply and storage for oil synthesis during the crucial period made cottonseed kernel oil yield have a higher increment than protein.

Cottonseed has a high utilization value due to its luxuriant oil and protein, but low phosphorus (P) in cropland reduces its yield and quality. A limited understanding of the physiological mechanism underlying these results restricted the exploration of P efficient management in cotton cultivation. A 3-year experiment was performed with Lu 54 (low-P sensitive) and Yuzaomian 9110 (low-P tolerant) under 0 (deficient-P), 100 (critical-P), and 200 (excessive-P) kg P2O5 ha-1 in a field having 16.9 mg kg-1 available P to explore the key pathway for P to regulate cottonseed oil and protein formation. P application markedly increased cottonseed oil and protein yields, with the enhanced acetyl-CoA and oxaloacetate contents during 20-26 days post anthesis being a vital reason. Notably, during the crucial period, decreased phosphoenolpyruvate carboxylase activity weakened the carbon allocation to protein, making malonyl-CoA content increase greater than free amino acid; Meanwhile, P application accelerated the carbon storage in oil but retarded that in protein. Consequently, cottonseed oil yield increased more than protein. Oil and protein synthesis in Lu 54 was more susceptible to P, resulting in greater increments in oil and protein yields than Yuzaomian 9110. Based on acetyl-CoA and oxaloacetate contents (the key substrates), the critical P content in the subtending leaf to cotton boll needed by oil and protein synthesis in Lu 54 (0.35%) was higher than Yuzaomian 9110 (0.31%). This study provided a new perception of the regulation of P on cottonseed oil and protein formation, contributing to the efficient P management in cotton cultivation.

Silicon modulate the non-enzymatic antioxidant defence system and oxidative stress in a similar way as boron in boron-deficient cotton flowers.

Silicon (Si) application, especially via foliar application, may be promising to attenuate oxidative damage, as Si can improve the non-enzymatic antioxidant system of cotton flowers. However, studies that address the relationship between boron (B) and Si in cotton flowers are still scarce. Therefore, this paper aimed to evaluate the effect of silicon alone and added to the borate solution applied via foliar spray on the oxidative stress; proline, carotenoid, and phenol contents; and biomass production of cotton flowers grown under moderate B deficiency. The experiment was arranged in a completely randomized design with ten replicates and the following five treatments: control (cotton plants under boron deficiency); water application (without B and Si); boron application; silicon application; and B + Si. The application of B, Si, and B + Si reduced the malondialdehyde content in cotton petals by 45%, 48%, and 59%, respectively, and in cotton anthers by57%, 64%, and 67%, respectively. The dry matter of cotton petals in the respective treatments increased by 20%, 16%, 35%, and 44%, while the dry matter of cotton anthers increased by 40%, 24%, 48%, and 53%, respectively, compared to the treatment with water only. There was a strong relationship between B content and dry matter; Si content and the contents of phenols and proline; and carotenoid content and the contents of MDA and H2O2. B deficiency can induce oxidative stress specifically in the petals and anthers of cotton, with carotenoids being the main defense mechanism in flowers, while Si is capable of strongly activating defense mechanisms from phenol and proline. In conclusion, the development of organs related to reproduction is impaired by B deficiency. In addition, the foliar application of Si and B attenuates the effects of oxidative stress on the sepals and anthers of cotton, mainly favoring the development of cotton anthers.

Biodegradation of monocrotophos by Brucella intermedia Msd2 isolated from cotton plant.

Widespread and inadequate use of Monocrotophos has led to several environmental issues. Biodegradation is an ecofriendly method used for detoxification of toxic monocrotophos. In the present study, Msd2 bacterial strain was isolated from the cotton plant growing in contaminated sites of Sahiwal, Pakistan. Msd2 is capable of utilizing the monocrotophos (MCP) organophosphate pesticide as its sole carbon source for growth. Msd2 was identified as Brucella intermedia on the basis of morphology, biochemical characterization and 16S rRNA sequencing. B. intermedia showed tolerance of MCP up to 100 ppm. The presence of opd candidate gene for pesticide degradation, gives credence to B. intermedia as an effective bacterium to degrade MCP. Screening of the B. intermedia strain Msd2 for plant growth promoting activities revealed its ability to produce ammonia, exopolysaccharides, catalase, amylase and ACC-deaminase, and phosphorus, zinc and potassium solubilization. The optimization of the growth parameters (temperatures, shaking rpm, and pH level) of the MCP-degrading isolate was carried out in minimal salt broth supplemented with MCP. The optimal pH, temperature, and rpm for Msd2 growth were observed as pH 6, 35 °C, and 120 rpm, respectively. Based on optimization results, batch degradation experiment was performed. Biodegradation of MCP by B. intermedia was monitored using HPLC and recorded 78% degradation of MCP at 100 ppm concentration within 7 days of incubation. Degradation of MCP by Msd2 followed the first order reaction kinetics. Plant growth promoting and multi-stress tolerance ability of Msd2 was confirmed by molecular analysis. It is concluded that Brucella intermedia strain Msd2 could be beneficial as potential biological agent for an effective bioremediation for polluted environments.

The cotton pectin methyl esterase gene GhPME21 functions in microspore development and fertility in Gossypium hirsutum L.

Pectin widely exists in higher plants' cell walls and intercellular space of higher plants and plays an indispensable role in plant growth and development. We identified 55 differentially expressed genes related to pectin degradation by transcriptomic analysis in the male sterile mutant, ms1. A gene encoding pectin methylesterase (GhPME21) was found to be predominantly expressed in the developing stamens of cotton but was significantly down-regulated in ms1 stamens. The tapetal layer of GhPME21 interfered lines (GhPME21i) was significantly thickened compared to that of WT at the early stage; anther compartment morphology of GhPME21i lines was abnormal, and the microspore wall was broken at the middle stage; Alexander staining showed that the pollen grains of GhPME21i lines differed greatly in volume at the late stage. The mature pollen surfaces of GhPME21i lines were deposited with discontinuous and broken sheets and prickles viewed under SEM. Fewer pollen tubes were observed to germinate in vitro in GhPME21i lines, while tiny of those in vivo were found to elongate to the ovary. The seeds harvested from GhPME21i lines as pollination donors were dry and hollow. The changes of phenotypes in GhPME21i lines at various stages illustrated that the GhPME21 gene played a vital role in the development of cotton stamens and controlled plant fertility by affecting stamen development, pollen germination, and pollen tube elongation. The findings of this study laid the groundwork for further research into the molecular mechanisms of PMEs involved in microspore formation and the creation of cotton male sterility materials.

A mutant cotton fatty acid desaturase 2-1d allele causes protein mistargeting and altered seed oil composition.

BACKGROUND: Cotton (Gossypium sp.) has been cultivated for centuries for its spinnable fibers, but its seed oil also possesses untapped economic potential if, improvements could be made to its oleic acid content. RESULTS: Previous studies, including those from our laboratory, identified pima accessions containing approximately doubled levels of seed oil oleic acid, compared to standard upland cottonseed oil. Here, the molecular properties of a fatty acid desaturase encoded by a mutant allele identified by genome sequencing in an earlier analysis were analyzed. The mutant sequence is predicted to encode a C-terminally truncated protein lacking nine residues, including a predicted endoplasmic reticulum membrane retrieval motif. We determined that the mutation was caused by a relatively recent movement of a Ty1/copia type retrotransposon that is not found associated with this desaturase gene in other sequenced cotton genomes. The mutant desaturase, along with its repaired isozyme and the wild-type A-subgenome homoeologous protein were expressed in transgenic yeast and stably transformed Arabidopsis plants. All full-length enzymes efficiently converted oleic acid to linoleic acid. The mutant desaturase protein produced only trace amounts of linoleic acid, and only when strongly overexpressed in yeast cells, indicating that the missing C-terminal amino acid residues are not strictly required for enzyme activity, yet are necessary for proper subcellular targeting to the endoplasmic reticulum membrane. CONCLUSION: These results provide the biochemical underpinning that links a genetic lesion present in a limited group of South American pima cotton accessions and their rare seed oil oleic acid traits. Markers developed to the mutant desaturase allele are currently being used in breeding programs designed to introduce this trait into agronomic upland cotton varieties.

Effects of soil drought on cottonseed kernel carbohydrate metabolism and kernel biomass accumulation.

Cottonseed is the main coproduct of cotton production. The carbohydrate metabolism provides carbon substrate for the accumulation of cottonseed kernel biomass which was the basis of cottonseed kernel development. However, the responses of drought stress on carbohydrate metabolism in kernels are still unclear. To address this, two cotton cultivars (Dexiamian 1 and Yuzaomian 9110) were cultivated under three water treatments including soil relative water content (SRWC) at (75 ± 5)% (control), (60 ± 5)% (mild drought) and (45 ± 5)% (severe drought) to investigate the effects of soil drought on cottonseed kernel carbohydrate metabolism and kernel biomass accumulation. Results suggested that drought restrained the accumulation of cottonseed kernel biomass which eventually decreased cottonseed kernel biomass at maturity. In detail, the down-regulation of sucrose phosphate synthase (SPS) activity led to the inhibition of sucrose synthesis, while the up-regulation of invertase (INV) promoted the sucrose decomposite, which reduced the sucrose content eventually under drought. Though hexose content was increased, phosphoenolpyruvic acid (PEP) content was decreased under drought by downregulating 6-phosphofructokinase (PFK) and pyruvate kinase (PK) activities, which hindered the conversion of hexose to PEP. The large decrease of sucrose and PEP contents hindered the accumulation of kernel biomass. The related substances contents and enzyme activities in carbohydrate metabolism of Yuzaomian 9110 were more susceptible to drought stress than Dexiamian 1.

Gossypol and related compounds are produced and accumulate in the aboveground parts of the cotton plant, independent of roots as the source.

MAIN CONCLUSION: Use of Ultra-low gossypol cottonseed event as a scion in a graft combination confirmed that roots are not a source of terpenoids in the aboveground parts of a cotton plant. Gossypol and related terpenoids, derived from the same basic biosynthetic pathway, are present in the numerous lysigenous glands in the aboveground parts of a cotton plant. Roots, with sparse presence of such glands, do produce significant amount of gossypol and a different set of terpenoids. These compounds serve a defensive function against various pests and pathogens. This investigation was undertaken to examine whether gossypol produced in the roots can replenish the gossypol content of the cottonseed-glands that are largely devoid of this terpenoid in a genetically engineered event. Graft unions between a scion derived from the RNAi-based, Ultra-low gossypol cottonseed (ULGCS) event, TAM66274, and a rootstock derived from wild-type parental genotype, Coker 312 (Coker), were compared with various other grafts that served as controls. The results showed that the seeds developing within the scion of test grafts (ULGCS/Coker) continued to maintain the ultra-low gossypol levels found in the TAM66274 seeds. Molecular analyses confirmed that while the key gene involved in gland development showed normal activity in the developing embryos in the scion, two genes encoding the enzymes involved in gossypol biosynthesis were suppressed. Thus, the gene expression data confirmed the results obtained from biochemical measurements and collectively demonstrated that roots are not a source of gossypol for the aboveground parts of the cotton plant. These findings, combined with the results from previous investigations, support the assertion that gossypol and related terpenoids are produced in a highly localized manner in various organs of the cotton plant and are retained therein.

Identification of candidate genes in cotton associated with specific seed traits and their initial functional characterization in Arabidopsis.

Oilseed crops are used to produce vegetable oil to satisfy the requirements of humans and livestock. Cotton (Gossypium spp.) is of great economic value because it is used as both an important textile commodity and a nutrient-rich resource. Cottonseed oil is rich in polyunsaturated fatty acids and does not contain trans fatty acids; hence, it is considered a healthy vegetable oil. However, research on the genetic basis for cottonseed protein content, oil production, and fatty acid composition is lacking. Here, we investigated the protein content, oil content, and fatty acid composition in terms of oleic acid (C18:1) and linoleic acid (C18:2) in mature cottonseeds from 318 Gossypium hirsutum accessions. Moreover, we examined the dynamic change of protein content and lipid composition including palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3) in developing seeds from 258 accessions at 10 and 20 days post-anthesis. Then, we conducted a genome-wide association study and identified 152 trait-associated loci and 64 candidate genes responsible for protein and oil-related contents in mature cottonseeds and ovules. Finally, six candidate genes were experimentally validated to be involved in the regulation of fatty acid biosynthesis through heterologous expression in Arabidopsis. These results comprise a solid foundation for expanding our understanding of lipid biosynthesis in cotton, which will help breeders manipulate protein and oil contents to make it a fully developed 'fiber, food, and oil crop'.

GhMYC2 activates cytochrome P450 gene CYP71BE79 to regulate gossypol biosynthesis in cotton.

MAIN CONCLUSION: GhMYC2 regulates the gossypol biosynthesis pathway in cotton through activation of the expression of gossypol synthesis gene CYP71BE79, CDNC, CYP706B1, DH1, and CYP82D113. Cotton is one of the main cash crops globally. Cottonseed contains fiber, fat, protein, and starch, and has important economic value. However, gossypol in cottonseed seriously affects the development and utilization of cottonseed. Nonetheless, gossypol has great application potential in agriculture, medicine, and industry. Therefore, it is very important to study gossypol biosynthesis and its upstream regulatory pathways. It has been reported that the content of gossypol in hairy roots of cotton is regulated through jasmonic acid signaling; however, the specific molecular mechanism has not been revealed yet. We found that the expression of basic helix-loop-helix family transcription factor GhMYC2 was significantly upregulated after exogenous administration of methyl jasmonate to cotton seedlings, and the content of gossypol changed significantly with the variation of GhMYC2 expression. Further studies revealed that GhMYC2 could specifically bind to the G-Box in the promoter region of CDNC, CYP706B1, DH1, CYP82D113, CYP71BE79 to activate its expression and regulate gossypol synthesis, and its activation of CYP71BE79 promoter was inhibited by GhJAZ2. Not only that GhMYC2 could also interact with GoPGF. In this work, the molecular mechanisms of gossypol biosynthesis regulated by GhMYC2 were analyzed. The results provide a theoretical basis for cultivating new varieties of low-gossypol or high-gossypol cotton and creating excellent germplasm resources.

Thiamine functions as a key activator for modulating plant health and broad-spectrum tolerance in cotton.

Global climate changes cause an increase of abiotic and biotic stresses that tremendously threaten the world's crop security. However, studies on broad-spectrum response pathways involved in biotic and abiotic stresses are relatively rare. Here, by comparing the time-dependent transcriptional changes and co-expression analysis of cotton (Gossypium hirsutum) root tissues under abiotic and biotic stress conditions, we discovered the common stress-responsive genes and stress metabolism pathways under different stresses, which included the circadian rhythm, thiamine and galactose metabolism, carotenoid, phenylpropanoid, flavonoid, and zeatin biosynthesis, and the mitogen-activated protein kinase signaling pathway. We found that thiamine metabolism was an important intersection between abiotic and biotic stresses; the key thiamine synthesis genes, GhTHIC and GhTHI1, were highly induced at the early stage of stresses. We confirmed that thiamine was crucial and necessary for cotton growth and development, and its deficiency could be recovered by exogenous thiamine supplement. Furthermore, we revealed that exogenous thiamine enhanced stress tolerance in cotton via increasing calcium signal transduction and activating downstream stress-responsive genes. Overall, our studies demonstrated that thiamine played a crucial role in the tradeoff between plant health and stress resistance. The thiamine deficiency caused by stresses could transiently induce upregulation of thiamine biosynthetic genes in vivo, while it could be totally salvaged by exogenous thiamine application, which could significantly improve cotton broad-spectrum stress tolerance and enhance plant growth and development.

Rapid Identification of Pollen- and Anther-Specific Genes in Response to High-Temperature Stress Based on Transcriptome Profiling Analysis in Cotton.

Anther indehiscence and pollen sterility caused by high temperature (HT) stress have become a major problem that decreases the yield of cotton. Pollen- and anther-specific genes play a critical role in the process of male reproduction and the response to HT stress. In order to identify pollen-specific genes that respond to HT stress, a comparative transcriptome profiling analysis was performed in the pollen and anthers of Gossypium hirsutum HT-sensitive Line H05 against other tissue types under normal temperature (NT) conditions, and the analysis of a differentially expressed gene was conducted in the pollen of H05 under NT and HT conditions. In total, we identified 1111 pollen-specific genes (PSGs), 1066 anther-specific genes (ASGs), and 833 pollen differentially expressed genes (DEGs). Moreover, we found that the late stage of anther included more anther- and pollen-specific genes (APSGs). Stress-related cis-regulatory elements (CREs) and hormone-responsive CREs are enriched in the promoters of APSGs, suggesting that APSGs may respond to HT stress. However, 833 pollen DEGs had only 10 common genes with 1111 PSGs, indicating that PSGs are mainly involved in the processes of pollen development and do not respond to HT stress. Promoters of these 10 common genes are enriched for stress-related CREs and MeJA-responsive CREs, suggesting that these 10 common genes are involved in the process of pollen development while responding to HT stress. This study provides a pathway for rapidly identifying cotton pollen-specific genes that respond to HT stress.

lncRNA7 and lncRNA2 modulate cell wall defense genes to regulate cotton resistance to Verticillium wilt.

In plants, long noncoding RNAs (lncRNAs) regulate disease resistance against fungi and other pathogens. However, the specific mechanism behind this regulation remains unclear. In this study, we identified disease resistance-related lncRNAs as well as their regulating genes and assessed their functions by infection of cotton (Gossypium) chromosome segment substitution lines with Verticillium dahliae. Our results demonstrated that lncRNA7 and its regulating gene Pectin methylesterase inhibitor 13 (GbPMEI13) positively regulated disease resistance via the silencing approach, while ectopic overexpression of GbPMEI13 in Arabidopsis (Arabidopsis thaliana) promoted growth and enhanced resistance to V. dahliae. In contrast, lncRNA2 and its regulating gene Polygalacturonase 12 (GbPG12) negatively regulated resistance to V. dahliae. We further found that fungal disease-related agents, including the pectin-derived oligogalacturonide (OG), could downregulate the expression of lncRNA2 and GbPG12, leading to pectin accumulation. Conversely, OG upregulated the expression of lncRNA7, which encodes a plant peptide phytosulfokine (PSK-α), which was confirmed by lncRNA7 overexpression and Ultra Performance Liquid Chromatography Tandem Mass Spectrometry (UPLC-MS) experiments. We showed that PSK-α promoted 3-Indoleacetic acid (IAA) accumulation and activated GbPMEI13 expression through Auxin Response Factor 5. Since it is an inhibitor of pectin methylesterase (PME), GbPMEI13 promotes pectin methylation and therefore increases the resistance to V. dahliae. Consistently, we also demonstrated that GbPMEI13 inhibits the mycelial growth and spore germination of V. dahliae in vitro. In this study, we demonstrated that lncRNA7, lncRNA2, and their regulating genes modulate cell wall defense against V. dahliae via auxin-mediated signaling, providing a strategy for cotton breeding.

Identification and analysis of oil candidate genes reveals the molecular basis of cottonseed oil accumulation in Gossypium hirsutum L.

KEY MESSAGE: Based on the integration of QTL-mapping and regulatory network analyses, five high-confidence stable QTL regions, six candidate genes and two microRNAs that potentially affect the cottonseed oil content were discovered. Cottonseed oil is increasingly becoming a promising target for edible oil with its high content of unsaturated fatty acids. In this study, a recombinant inbred line (RIL) cotton population was constructed to detect quantitative trait loci (QTLs) for the cottonseed oil content. A total of 39 QTLs were detected across eight different environments, of which five QTLs were stable. Forty-three candidate genes potentially involved in carbon metabolism, fatty acid synthesis and triacylglycerol biosynthesis processes were further obtained in the stable QTL regions. Transcriptome analysis showed that nineteen of these candidate genes expressed during  the developing cottonseed ovules and may affect the cottonseed oil content. Besides, transcription factor (TF) and microRNA (miRNA) co-regulatory network analyses based on the nineteen candidate genes suggested that six genes, two core miRNAs (ghr-miR2949b and ghr-miR2949c), and one TF GhHSL1 were considered to be closely associated with the cottonseed oil content. Moreover, four vital genes were validated by quantitative real-time PCR (qRT-PCR). These results provide insights into the oil accumulation mechanism in developing cottonseed ovules through the construction of a detailed oil accumulation model.

Patterns of gene expression in pollen of cotton (Gossypium hirsutum) indicate downregulation as a feature of thermotolerance.

Reproductive performance in plants is impaired as maximum temperatures consistently approach 40°C. However, the timing of heatwaves critically affects their impact. We studied the molecular responses during pollen maturation in cotton to investigate the vulnerability to high temperature. Tetrads (TEs), uninucleate and binucleate microspores, and mature pollen were subjected to SWATH-MS and RNA-seq analyses after exposure to 38/28°C (day/night) for 5 days. The results indicated that molecular signatures were downregulated progressively in response to heat during pollen development. This was even more evident in leaves, where three-quarters of differentially changed proteins decreased in abundance during heat. Functional analysis showed that translation of genes increased in TEs after exposure to heat; however, the reverse pattern was observed in mature pollen and leaves. For example, proteins involved in transport were highly abundant in TEs whereas in later stages of pollen formation and leaves, heat suppressed synthesis of proteins involved in cell-to-cell communication. Moreover, a large number of heat shock proteins were identified in heat-affected TEs, but these proteins were less abundant in mature pollen and leaves. We speculate that the sensitivity of TE cells to heat is related to high rates of translation targeted to pathways that might not be essential for thermotolerance. Molecular signatures during stages of pollen development after heatwaves could provide markers for future genetic improvement.

Explore the gene network regulating the composition of fatty acids in cottonseed.

BACKGROUND: Cottonseed is one of the major sources of vegetable oil. Analysis of the dynamic changes of fatty acid components and the genes regulating the composition of fatty acids of cottonseed oil is of great significance for understanding the biological processes underlying biosynthesis of fatty acids and for genetic improving the oil nutritional qualities. RESULTS: In this study, we investigated the dynamic relationship of 13 fatty acid components at 12 developmental time points of cottonseed (Gossypium hirsutum L.) and generated cottonseed transcriptome of the 12 time points. At 5-15 day post anthesis (DPA), the contents of polyunsaturated linolenic acid (C18:3n-3) and saturated stearic acid (C18:0) were higher, while linoleic acid (C18:2n-6) was mainly synthesized after 15 DPA. Using 5 DPA as a reference, 15,647 non-redundant differentially expressed genes were identified in 10-60 DPA cottonseed. Co-expression gene network analysis identified six modules containing 3275 genes significantly associated with middle-late seed developmental stages and enriched with genes related to the linoleic acid metabolic pathway and α-linolenic acid metabolism. Genes (Gh_D03G0588 and Gh_A02G1788) encoding stearoyl-ACP desaturase were identified as hub genes and significantly up-regulated at 25 DPA. They seemed to play a decisive role in determining the ratio of saturated fatty acids to unsaturated fatty acids. FAD2 genes (Gh_A13G1850 and Gh_D13G2238) were highly expressed at 25-50 DPA, eventually leading to the high content of C18:2n-6 in cottonseed. The content of C18:3n-3 was significantly decreased from 5 DPA (7.44%) to 25 DPA (0.11%) and correlated with the expression characteristics of Gh_A09G0848 and Gh_D09G0870. CONCLUSIONS: These results contribute to our understanding on the relationship between the accumulation pattern of fatty acid components and the expression characteristics of key genes involved in fatty acid biosynthesis during the entire period of cottonseed development.