Transcriptomic Analysis Reveals the Key Role of Histone Deacetylation-mediated Phytohormones Interaction in Fiber Initiation of Cotton

Background: Histone deacetylation is one of the most important epigenetic modifications and plays diverse roles in plant development. However, the detailed functions and mechanisms of histone deacetylation in fiber development of cotton are still unclear. HDAC inhibitors (HDACi) have been used commonly to study the molecular mechanism underlying histone deacetylation or to facilitate disease therapy in humans through hindering the histone deacetylase catalytic activity. Trichostatin A (TSA) - the most widely used HDACi has been used to determine the role of histone deacetylation on different developmental stages of plants. Results: Here, exogenous TSA was applied in the fiber initiation and elongation in vitro, and the results demonstrated the crucial role of histone deacetylation in fiber initiation regulation. Therefore, we made a transcriptomic analysis to reveal the underlying mechanisms. Through RNA-Seq analysis, the differentially expressed genes were mostly enriched in plant hormone signal transduction,phenylpropanoid biosynthesis, photosynthesis, and carbon metabolism pathways, suggesting the potential role of phytohormone, phenylpropanoid metabolism, and energy metabolism downstream of histone deacetylation in fiber initiation. The phytohormone signal transduction pathways harbor the most differentially expressed genes. Deeper studies showed that some genes promoting auxin, Gibberellic Acid (GA), and Salicylic Acid (SA) signaling were down-regulated, while some genes facilitating Abscisic Acid (ABA) and inhibiting Jasmonic Acid (JA) singling were up-regulated after the TSA treatments. Conclusions: Collectively, we established a model, in which histone deacetylation can regulate some key genes involved in different phytohormone pathways, consequently, promoting the auxin, GA, JA and SA signaling, whereas, repressing the ABA signaling to improve the fiber cell initiation; besides that the genes associated with energy metabolism, phenylpropanoid, and glutathione metabolism were also involved in. The above results provided novel clues to illuminate the underlying mechanisms of epigenetic modifications as well as interactions of different phytohormones in fiber cell differentiation, which is also very valuable for molecular breeding of higher quality cotton.

Genome-Wide Analysis of AAT Genes and Their Expression Profiling during Fiber Development in Cotton

Amino acid transporters (AATs) are a kind of membrane proteins that mediate the transport of amino acids across cell membranes in higher plants. The AAT proteins are involved in regulating plant cell growth and various developmental processes. However, the biological function of this gene family in cotton fiber development is not clear. In this study, 190, 190, 101, and 94 full-length AAT genes were identified from Gossypiumhirsutum, G. barbadense, G. arboreum, and G. raimondii. A total of 575 AAT genes from the four cotton species were divided into two subfamilies and 12 clades based on phylogenetic analysis. The AAT genes in the four cotton species were distributed on all the chromosomes. All GhAAT genes contain multiple exons, and each GhAAT protein has multiple conserved motifs. Transcriptional profiling and RT qPCR analysis showed that four GhATT genes tend to express specifically at the fiber initiation stage. Eight genes tend to express specifically at the fiber elongation and maturity stage, and four genes tend to express specifically at the fiber initiation and elongation stages. Our results provide a solid basis for further elucidating the biological function of AAT genes related to cotton fiber development and offer valuable genetic resources for crop improvement in the future.

Comparative transcriptome analysis uncovers cell wall reorganization and repressed cell division during cotton fiber initiation

Background Tetraploid cotton plants serve as prime natural fiber source for the textile industry. Although various omics studies have revealed molecular basis for fiber development, a better understanding of transcriptional regulation mechanism regulating lint fiber initiation is necessary to meet global natural fiber demand. Results Here, we aimed to perform transcriptome sequencing to identify DEGs (differentially expressed genes) in ovules of the cotton variety Xu142 and its fibreless mutant Xu142fl during early lint fiber initiation period. Totally, 5516 DEGs including 1840 upregulated and 3676 downregulated were identified. GO enrichment analysis revealed that the downregulated DEGs were mainly associated with biological processes such as transcription related biosynthesis and metabolism, organic cyclic compound biosynthesis and metabolism, photosynthesis, and plant cell wall organization, with molecular functions involving transcription related binding, organic cyclic compound binding, and dioxygenase activity, while the upregulated DEGs were associated with DNA replication and phospholipid biosynthetic related processes. Among the 490 DEGs annotated as transcription factor genes, 86.5% were downregulated in the mutant including the Malvaceae-specific MMLs, expression patterns of which were confirmed during the central period of lint fiber initiation. Investigation of the 16 genes enriched in the cell wall organization revealed that 15 were EXPA coding genes. Conclusions Overall, our data indicate that lint fiber initiation is a complicated process involving cooperation of multiple transcription factor families, which might ultimately lead to the reorganization of the cell wall and terminated cell division of the differentiating fiber initials.

Genome-Wide Analysis of the Phospholipase D Family in Five Cotton Species, and Potential Role of GhPLD2 in Fiber Development and Anther Dehiscence

Phospholipase D (PLD) and its hydrolysis product phosphatidic acid play an important role in the regulation of several cellular processes, including root growth, pollen tube elongation, and microtubule reorganization. Here, we systematically identified and analyzed the membership, characterization, and evolutionary relationship of PLDs in five species of cotton. The results of the transcriptomic analysis suggested that the evaluated PLD genes showed high expression levels in anther tissue and during the fiber initiation and elongation periods. Quantitative real-time polymerase chain reaction showed differential expression of GhPLD genes in the anthers of photoperiod sensitive male sterility mutant 5 (psm5). Previous research on multiple stable quantitative trait loci also suggests the role of PLD genes in the fiber development. Further analyses showed that GhPLD2 protein is localized to the plasma membrane. The virus-induced gene silencing of GhPLD2 in cotton seedlings repressed its expression by 40–70%, which led to a reduction in reactive oxygen species (ROS) levels, 22% anther indehiscence, and disrupted fiber initiation and elongation. Thus, we inferred that GhPLD2 may promote ROS production, which, in turn, may regulate anther dehiscence and fiber development.

Co-expression network and comparative transcriptome analysis for fiber initiation and elongation reveal genetic differences in two lines from upland cotton CCRI70 RIL population

Upland cotton is the most widely planted for natural fiber around the world, and either lint percentage (LP) or fiber length (FL) is the crucial component tremendously affecting cotton yield and fiber quality, respectively. In this study, two lines MBZ70-053 and MBZ70-236 derived from G. hirsutum CCRI70 recombinant inbred line (RIL) population presenting different phenotypes in LP and FL traits were chosen to conduct RNA sequencing on ovule and fiber samples, aiming at exploring the differences of molecular and genetic mechanisms during cotton fiber initiation and elongation stages. As a result, 249/128, 369/206, 4296/1198 and 3547/2129 up-/down- regulated differentially expressed genes (DGEs) in L2 were obtained at −3, 0, 5 and 10 days post-anthesis (DPA), respectively. Seven gene expression profiles were discriminated using Short Time-series Expression Miner (STEM) analysis; seven modules and hub genes were identified using weighted gene co-expression network analysis. The DEGs were mainly enriched into energetic metabolism and accumulating as well as auxin signaling pathway in initiation and elongation stages, respectively. Meanwhile, 29 hub genes were identified as 14-3-3ω, TBL35, GhACS, PME3, GAMMA-TIP, PUM-7, etc., where the DEGs and hub genes revealed the genetic and molecular mechanisms and differences during cotton fiber development.

Comparative transcriptome analysis uncovers cell wall reorganization and repressed cell division during cotton fiber initiation

Background Tetraploid cotton plants serve as prime natural fiber source for the textile industry. Although various omics studies have revealed molecular basis for fiber development, a better understanding of transcriptional regulation mechanism regulating lint fiber initiation is necessary to meet global natural fiber demand. Conclusions Here, we aimed to perform transcriptome sequencing to identify DEGs (differentially expressed genes) in ovules of the cotton variety Xu142 and its fibreless mutant Xu142fl during early lint fiber initiation period. Totally, 5516 DEGs including 1840 upregulated and 3676 downregulated were identified. GO enrichment analysis revealed that the downregulated DEGs mainly associated with biological processes such as transcription related biosynthesis and metabolism, organic cyclic compound biosynthesis and metabolism, photosynthesis, and plant cell wall organization, with molecular functions involving transcription related binding, organic cyclic compound binding, and dioxygenase activity, while the upregulated DEGs were associated with DNA replication and phospholipid biosynthetic related processes. Among the 490 DEGs annotated as transcription factor genes 86.5% were downregulated in the mutant including the Malvaceae-specific MMLs, expression patterns of which were confirmed during the central period of lint fiber initiation. Investigation of the 20 genes enriched in the cell wall organization revealed that 17 were EXPA coding genes. Overall, we suggest that lint fiber initiation is a complicated process involving cooperation of multiple transcription factor families, which might ultimately lead to the reorganization of the cell wall and terminated cell division of the differentiating fiber initials.

Identification of potential key genes and pathways associated with the Pashmina fiber initiation using RNA-Seq and integrated bioinformatics analysis

Pashmina goat (Capra hircus) is an economically important livestock species, which habitats the cold arid desert of the Ladakh region (India), and produces a princely animal fiber called Pashmina. The Pashmina goat has a double coat fleece as an adaptation to the very harsh cold winters the outer long coarse hair (guard hair) produced from primary hair follicles and the inner fine Pashmina fiber produced from secondary hair follicles. Pashmina fiber undergoes a circannual and synchronized growth cycle. In the present study, we analyzed transcriptome profiles from 10 different Pashmina goats during anagen and telogen to delineate genes and signaling pathways regulating active (anagen) and regressive (telogen) phases of the follicle growth. During anagen, 150 genes were expressed at significantly higher levels with log (FC) > 2 and padj < 0.05. The RNA seq results were subjected to qRT-PCR validation. Among the nine genes selected, the expression of HAS1, TRIB2, P2RX1. PRG4, CNR2, and MMP25 were significantly higher (p < 0.05) in the anagen phase, whereas MC4R, GIPC2, and CDO1 were significantly expressed (p < 0.05) in the telogen phase which supports and validates the gene expression pattern from the RNA-sequencing. Differentially expressed genes revealed that Pashmina fiber initiation is largely controlled by signaling pathways like Wnt, NF-Kappa, JAK-STAT, Hippo, MAPK, Calcium, and PI3K-Akt. Expression of genes from the Integrin family, Cell adhesion molecules, and ECM-receptors were observed to be at much higher levels during anagen. We identified key genes (IL36RN, IGF2, ITGAV, ITGA5, ITCCR7, CXCL5, C3, CCL19, and CXCR3) and a collagen cluster which might be tightly correlated with anagen-induction. The regulatory network suggests the potential role of RUNX3, NR2F1/2, and GATA family transcription factors in anagen-initiation and maintaining fiber quality in Pashmina goats.

Trajectories of Cotton Fiber Initiation: A Regulatory Perspective

The epidermal cells on the surface of the cotton ovules undergo differentiation to produce fibers, which are single-celled hair-like protrusions resembling the plant trichomes. The initiation of these unicellular fibers from the cotton ovule surface is a complex and tightly regulated process. The initiation step is the cell fate-determining stage, which leads to the commitment of cells that eventually developed into fibers, thus becomes the most crucial phase in fiber development. The in-depth knowledge of molecular regulation is a prerequisite to get a clear view of the fiber initiation process's genetic and epigenetic control. The identification and functional validation of cotton fiber initiation-related genes, few fibreless mutants, transcription factors, microRNAs, epigenetic regulators, as well as the elucidation of the role of phytohormones as signaling molecules, has played a significant role in understanding the cotton fiber initiation process at the molecular level. This review focuses on the comprehensive information regarding the genetic and epigenetic regulation of cotton fiber initiation. Thus, the review will provide readers insight into mechanistic details that operate during cotton fiber initiation.