GhPIPLC2D promotes cotton fiber elongation by enhancing ethylene biosynthesis

Transcriptional regulation of phospholipid transport in cotton fiber elongation by GhMYB30D04-GhHD1 interaction complex

Cotton fiber length is basically determined by well-coordinated gene expression and phosphatidylinositol phosphates (PIPs) accumulation during fiber elongation but the regulatory mechanism governing PIPs transport remains unknown. Here, we report a MYB transcription factor GhMYB30D04 in Gossypium hirsutum that promotes fiber elongation through modulating the expression of PIP transporter gene GhLTPG1. Knockout of GhMYB30D04 gene in cotton (KO) results in a reduction of GhLTPG1 transcripts with lower accumulation of PIPs, leading to shorter fibers and lower fiber yield. Conversely, GhMYB30D04 overexpression (GhMYB30D04-OE) causes richer PIPs and longer cotton fibers, mimicking the effects of exogenously applying PIPs on the ovules of GhMYB30D04-KO and wild type. Furthermore, GhMYB30D04 interacts with GhHD1, the crucial transcription factor of fiber initiation, to form an activation complex stabilized by PIPs, both of which upregulate GhLTPG1 expression. Comparative omics-analysis revealed that higher and extended expressions of LTPG1 in fiber elongation mainly correlate with the variations of the GhMYB30D04 gene between two cotton allotetraploids, contributing to longer fiber in G. babardense. Our work clarifies a mechanism by which GhHD1-GhMYB30D04 form a regulatory module of fiber elongation to tightly control PIP accumulation. Our work still has an implication that GhMYB30D04-GhHD1 associates with development transition from fiber initiation to elongation.

The 4Fs of cotton: genome editing of cotton for fiber, food, feed, and fuel to achieve zero hunger

Cotton is globally known for its high-priority cellulose-rich natural fiber. In addition to providing fiber for the textile industry, it is an important source material for edible oil, livestock feed, and fuel products. Global warming and the growing population are the major challenges to the world's agriculture and the potential risks to food security. In this context, improving output traits in cotton is necessary to achieve sustainable cotton production. During the last few years, high throughput omics techniques have aided in identifying crucial genes associated with traits of cotton fiber, seed, and plant architecture which could be targeted with more precision and efficiency through the CIRPSR/Cas-mediated genome editing technique. The various CRISPR/Cas systems such as CRISPR/Cas9, CRISPR/nCas9, and CRISPR/Cas12a have been employed to edit cotton genes associated with a wide range of traits including fiber length, flowering, leaf colour, rooting, seed oil, plant architecture, gossypol content, somatic embryogenesis, and biotic and abiotic stresses tolerance, highlighting its effectiveness in editing the cotton genome. Thus, CRISPR/Cas-mediated genome editing has emerged as a technique of choice to tailor crop phenotypes for better yield potential and environmental resilience. The review covers a comprehensive analysis of cotton phenotypic traits and their improvement with the help of the latest genome editing tools to improve fiber, food, feed, and fuel-associated genes of cotton to ensure food security.

GhFAD3-4 Promotes Fiber Cell Elongation and Cell Wall Thickness by Increasing PI and IP3 Accumulation in Cotton

The omega-3 fatty acid desaturase enzyme gene FAD3 is responsible for converting linoleic acid to linolenic acid in plant fatty acid synthesis. Despite limited knowledge of its role in cotton growth, our study focused on GhFAD3-4, a gene within the FAD3 family, which was found to promote fiber elongation and cell wall thickness in cotton. GhFAD3-4 was predominantly expressed in elongating fibers, and its suppression led to shorter fibers with reduced cell wall thickness and phosphoinositide (PI) and inositol triphosphate (IP3) levels. Transcriptome analysis of GhFAD3-4 knock-out mutants revealed significant impacts on genes involved in the phosphoinositol signaling pathway. Experimental evidence demonstrated that GhFAD3-4 positively regulated the expression of the GhBoGH3B and GhPIS genes, influencing cotton fiber development through the inositol signaling pathway. The application of PI and IP6 externally increased fiber length in GhFAD3-4 knock-out plants, while inhibiting PI led to a reduced fiber length in GhFAD3-4 overexpressing plants. These findings suggest that GhFAD3-4 plays a crucial role in enhancing fiber development by promoting PI and IP3 biosynthesis, offering the potential for breeding cotton varieties with superior fiber quality.

A conserved brassinosteroid-mediated BES1-CERP-EXPA3 signaling cascade controls plant cell elongation

Continuous plant growth is achieved by cell division and cell elongation. Brassinosteroids control cell elongation and differentiation throughout plant life. However, signaling cascades underlying BR-mediated cell elongation are unknown. In this study, we introduce cotton fiber, one of the most representative single-celled tissues, to decipher cell-specific BR signaling. We find that gain of function of GhBES1, a key transcriptional activator in BR signaling, enhances fiber elongation. The chromatin immunoprecipitation sequencing analysis identifies a cell-elongation-related protein, GhCERP, whose transcription is directly activated by GhBES1. GhCERP, a downstream target of GhBES1, transmits the GhBES1-mediated BR signaling to its target gene, GhEXPA3-1. Ultimately, GhEXPA3-1 promotes fiber cell elongation. In addition, inter-species functional analysis of the BR-mediated BES1-CERP-EXPA3 signaling cascade also promotes Arabidopsis root and hypocotyl growth. We propose that the BES1-CERP-EXPA3 module may be a broad-spectrum pathway that is universally exploited by diverse plant species to regulate BR-promoted cell elongation.

Molecular Regulation of Cotton Fiber Development: A Review

Cotton (Gossypium spp.) is an economically important natural fiber crop. The quality of cotton fiber has a substantial effect on the quality of cotton textiles. The identification of cotton fiber development-related genes and exploration of their biological functions will not only enhance our understanding of the elongation and developmental mechanisms of cotton fibers but also provide insights that could aid the cultivation of new cotton varieties with improved fiber quality. Cotton fibers are single cells that have been differentiated from the ovule epidermis and serve as a model system for research on single-cell differentiation, growth, and fiber production. Genes and fiber formation mechanisms are examined in this review to shed new light on how important phytohormones, transcription factors, proteins, and genes linked to fiber development work together. Plant hormones, which occur in low quantities, play a critically important role in regulating cotton fiber development. Here, we review recent research that has greatly contributed to our understanding of the roles of different phytohormones in fiber development and regulation. We discuss the mechanisms by which phytohormones regulate the initiation and elongation of fiber cells in cotton, as well as the identification of genes involved in hormone biosynthetic and signaling pathways that regulate the initiation, elongation, and development of cotton fibers.

Identification of key proteins related to high-quality fiber in Upland cotton via proteomics analysis

The dynamics of cotton fiber elongation and microfibirl deposition orientation were delineated; advanced ethylene synthesis and redox reaction homeostasis may be crucial for high-quality fiber formation. Fiber length, strength, and fineness determine the use and commercial value of cotton fiber, but their underlying molecular mechanisms remain obscure. We compared the dynamic change trajectories of length, diameter and microfibril orientation angle of the fibers produced by an introgression line SY6167 which generates high-quality fibers even better than Sea island cotton with those of the common-quality fibers from TM-1 across 5 to 30 days post anthesis (DPA). The proteomes were profiled and compared at six representative time points using 2-DE and MS/MS. 14 proteins differentially expressed inside each of cotton line temporally and significantly different tween the two lines were identified. The dynamic change trajectories of fiber length and microfibril angle are close to "s" and reverse "s" growth curves, respectively. SY6167 and TM-1 fibers entered the logarithmic elongation phase simultaneously at 10 DPA, and SY6167 kept elongating logarithmically for 2 more days than TM-1. In parallel to logarithmic elongation, microfibril orientation angles dived sharply, and SY6167 declined faster for a shorter duration than TM-1. 53% of the identified proteins are related to redox homeostasis, and most of them are expressed at higher levels in SY6167 during logarithmic elongation. 1-Aminocyclopropane-1-Carboxylic Acid Oxidase (ACO) started to accumulate at 16 DPA in SY6167, and its encoding genes were highly expressed at this stage, with a much higher level than TM-1. These findings suggest high-quality fibers are associated with high expression of the proteins related to stress and redox homeostasis, the continuously elevated expression of ethylene synthesis ACO gene may play an essential role.

Phosphatidic Acid in Plant Hormonal Signaling: From Target Proteins to Membrane Conformations

Cells sense a variety of extracellular signals balancing their metabolism and physiology according to changing growth conditions. Plasma membranes are the outermost informational barriers that render cells sensitive to regulatory inputs. Membranes are composed of different types of lipids that play not only structural but also informational roles. Hormones and other regulators are sensed by specific receptors leading to the activation of lipid metabolizing enzymes. These enzymes generate lipid second messengers. Among them, phosphatidic acid (PA) is a well-known intracellular messenger that regulates various cellular processes. This lipid affects the functional properties of cell membranes and binds to specific target proteins leading to either genomic (affecting transcriptome) or non-genomic responses. The subsequent biochemical, cellular and physiological reactions regulate plant growth, development and stress tolerance. In the present review, we focus on primary (genome-independent) signaling events triggered by rapid PA accumulation in plant cells and describe the functional role of PA in mediating response to hormones and hormone-like regulators. The contributions of individual lipid signaling enzymes to the formation of PA by specific stimuli are also discussed. We provide an overview of the current state of knowledge and future perspectives needed to decipher the mode of action of PA in the regulation of cell functions.