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Verticillium wilt, caused by the soil-borne fungus Verticillium dahliae , is one of the most devastating diseases in cotton (Gossypium spp.). Lignin in the cell wall forms a physical barrier to inhibit pathogen invasion, and defense-induced lignification reinforces secondary cell wall to prevent pathogens from further spreading. Cinnamyl alcohol dehydrogenases (CADs) catalyze the production of three main monolignols, p -coumaryl- (H), coniferyl- (G), and sinapyl-alcohols (S), which are the fundamental blocks of lignin. Here, we identified CAD genes in G. hirsutum , analyzed their expression profiles in cotton leaf, stem, and root from different developmental stages, and selected GhCAD35 , GhCAD45 , and GhCAD43 , which were consistently induced by V. dahliae inoculation in G. hirsutum cultivars resistant or susceptible to V. dahliae. On the basis of confirmation of the in vitro enzymatic activity of the three proteins in generation of the three monolignols, we used virus-induced gene silencing (VIGS) to investigate the effects of silencing of GhCAD35 , GhCAD45 , or GhCAD43 on resistance to V. dahliae as well as on deposition and the composition of lignin. Silencing each of the three CAD s impaired the defense-induced lignification and salicylic acid biosynthesis in stem, and compromised resistance to V. dahliae. Moreover, our study showed that silencing the three GhCAD s severely affected the biosynthesis of S-lignin, leading to a decrease of the syringyl/guaiacyl (S/G) ratio. Heterogeneous overexpression of GhCAD35 , GhCAD45 , or GhCAD43 in Arabidopsis enhanced disease resistance. Taken together, our study demonstrates a role of the three GhCAD s in defense-induced lignin biosynthesis and resistance to V. dahliae in G. hirsutum. [ABSTRACT FROM AUTHOR]

Summary: Cotton seeds are typically covered by lint and fuzz fibres. Natural 'fuzzless' mutants are an ideal model system for identifying genes that regulate cell initiation and elongation. Here, using a genome‐wide association study (GWAS), we identified a ~ 6.2 kb insertion, larINDELFZ, located at the end of chromosome 8, composed of a ~ 5.0 kb repetitive sequence and a ~ 1.2 kb fragment translocated from chromosome 12 in fuzzless Gossypium arboreum. The presence of larINDELFZ was associated with a fuzzless seed and reduced trichome phenotypes in G. arboreum. This distant insertion was predicted to be an enhancer, located ~ 18 kb upstream of the dominant‐repressor GaFZ (Ga08G0121). Ectopic overexpression of GaFZ in Arabidopsis thaliana and G. hirsutum suggested that GaFZ negatively modulates fuzz and trichome development. Co‐expression and interaction analyses demonstrated that GaFZ might impact fuzz fibre/trichome development by repressing the expression of genes in the very‐long‐chain fatty acid elongation pathway. Thus, we identified a novel regulator of fibre/trichome development while providing insights into the importance of noncoding sequences in cotton. [ABSTRACT FROM AUTHOR]

Summary: Improving yield is a primary mission for cotton (Gossypium hirsutum) breeders; development of cultivars with suitable architecture for high planting density (HPDA) can increase yield per unit area.We characterized a natural cotton mutant, AiSheng98 (AS98), which exhibits shorter height, shorter branch length, and more acute branch angle than wild‐type.A copy number variant at the HPDA locus on Chromosome D12 (HPDA‐D12), encoding a dehydration‐responsive element‐binding (DREB) transcription factor, GhDREB1B, strongly affects plant architecture in the AS98 mutant. We found an association between a tandem duplication of a c. 13.5 kb segment in HPDA‐D12 and elevated GhDREB1B expression resulting in the AS98 mutant phenotype. GhDREB1B overexpression confers a significant decrease in plant height and branch length, and reduced branch angle.Our results suggest that fine‐tuning GhDREB1B expression may be a viable engineering strategy for modification of plant architecture favorable to high planting density in cotton. [ABSTRACT FROM AUTHOR]

Determining the genetic rearrangement and domestication footprints in Gossypium hirsutum cultivars and primitive race genotypes are essential for effective gene conservation efforts and the development of advanced breeding molecular markers for marker-assisted breeding. In this study, 94 accessions representing the 7 primitive races of G hirsutum, along with 9 G hirsutum and 12 Gossypium barbadense cultivated accessions were evaluated. The genotyping-by-sequencing (GBS) approach was employed and 146 558 single nucleotide polymorphisms (SNP) were generated. Distinct SNP signatures were identified through the combination of selection scans and association analyses. Phylogenetic analyses were also conducted, and we concluded that the Latifolium, Richmondi, and Marie-Galante race accessions were more genetically related to the G hirsutum cultivars and tend to cluster together. Fifty-four outlier SNP loci were identified by selection-scan analysis, and 3 SNPs were located in genes related to the processes of plant responding to stress conditions and confirmed through further genome-wide signals of marker-phenotype association analysis, which indicate a clear selection signature for such trait. These results identified useful candidate gene locus for cotton breeding programs. [ABSTRACT FROM AUTHOR]

Background: Genetically modified cotton accounts for 64% of the world's cotton growing area (22.3 million hectares). The genome sequencing of the diploid cotton progenitors Gossypium raimondii and Gossypium arboreum as well as the cultivated Gossypium hirsutum has provided a wealth of genetic information that could be exploited for crop improvement. Unfortunately, gene functional characterization in cotton is lagging behind other economically important crops due to the low efficiency, lengthiness and technical complexity of the available stable transformation methods. We present here a simple, fast and efficient method for the transient transformation of G. hirsutum that can be used for gene characterization studies. Results: We developed a transient transformation system for gene characterization in upland cotton. Using β-glucuronidase as a reporter for Agrobacterium-mediated transformation assays, we evaluated multiple transformation parameters such as Agrobacterium strain, bacterial density, length of co-cultivation, chemicals and surfactants, which can affect transformation efficiency. After the initial characterization, the Agrobacterium EHA105 strain was selected and a number of binary constructs used to perform gene characterization studies. 7-days-old cotton seedlings were co-cultivated with Agrobacterium and transient gene expression was observed 5 days after infection of the plants. Transcript levels of two different transgenes under the control of the cauliflower mosaic virus (CaMV) 35S promoter were quantified by real-time reverse transcription PCR (qRT-PCR) showing a 3–10 times increase over the levels observed in non-infected controls. The expression patterns driven by the promoters of two G. hirsutum genes as well as the subcellular localization of their corresponding proteins were studied using the new transient expression system and our observations were consistent with previously published results using Arabidopsis as a heterologous system. Conclusions: The Agrobacterium-mediated transient transformation method is a fast and easy transient expression system enabling high transient expression and transformation efficiency in upland cotton seedlings. Our method can be used for gene functional studies such as promoter characterization and protein subcellular localization in cotton, obviating the need to perform such studies in a heterologous system such as Arabidopsis. [ABSTRACT FROM AUTHOR]

Plants are frequently subjected to a range of environmental stresses, including drought, salinity, cold, pathogens, and herbivore attacks. To survive in such conditions, plants have evolved a novel adaptive mechanism known as 'stress memory'. The formation of stress memories necessitates coordinated responses at the cellular, genetic/genomic, and epigenetic levels, involving altered physiological responses, gene activation, hyper-induction and chromatin modification. Cotton (Gossypium spp.) is an important economic crop with numerous applications and high economic value. In this study, we establish G. hirsutum drought memory following cycles of mild drought and re-watering treatments and analyzed memory gene expression patterns. Our findings reveal the physiological, biochemical, and molecular mechanisms underlying drought stress memory formation in G. hirsutum. Specifically, H3K4me3, a histone modification, plays a crucial role in regulating [+ /+ ] transcriptional memory. Moreover, we investigated the intergenerational inheritance of drought stress memory in G. hirsutum. Collectively, our data provides theoretical guidance for cotton breeding. • We ensured that cotton drought memory was established after cycles of mild drought and re-watering treatment. In the process of repeated drought, the antioxidant capacity of seedlings was significantly enhanced. • H3K4me3 modification was involved in the formation of [+ /+ ] transcriptional memory, which only maintained 4 days. • The drought environment of the parents enhanced the ability of the progenies to resist adversity. However, the prolonged drought-induced H3K4me3 was not transmitted to the progenies, suggesting that different molecular mechanisms are involved in short- and long-term memory. [ABSTRACT FROM AUTHOR]