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•Functional ABA biosynthesis genes show specific roles for ABA accumulation at different stages of seed development and seedling establishment.•De novo ABA biosynthesis during ...embryogenesis is required for late seed development, maturation, and induction of primary dormancy.•ABA plays multiple roles with the key LAFL hub to regulate various downstream signaling genes in seed and seedling development.•Key ABA signaling genes ABI3, ABI4, and ABI5 play important multiple functions with various cofactors during seed development such as de-greening, desiccation tolerance, maturation, dormancy, and seed vigor.•The crosstalk between ABA and other phytohormones are complicated and important for seed development and seedling establishment.
Seed is vital for plant survival and dispersion, however, its development and germination are influenced by various internal and external factors. Abscisic acid (ABA) is one of the most important phytohormones that influence seed development and germination. Until now, impressive progresses in ABA metabolism and signaling pathways during seed development and germination have been achieved. At the molecular level, ABA biosynthesis, degradation, and signaling genes were identified to play important roles in seed development and germination. Additionally, the crosstalk between ABA and other hormones such as gibberellins (GA), ethylene (ET), Brassinolide (BR), and auxin also play critical roles. Although these studies explored some actions and mechanisms by which ABA-related factors regulate seed morphogenesis, dormancy, and germination, the complete network of ABA in seed traits is still unclear.
Presently, seed faces challenges in survival and viability. Due to the vital positive roles in dormancy induction and maintenance, as well as a vibrant negative role in the seed germination of ABA, there is a need to understand the mechanisms of various ABA regulators that are involved in seed dormancy and germination with the updated knowledge and draw a better network for the underlying mechanisms of the ABA, which would advance the understanding and artificial modification of the seed vigor and longevity regulation.
Here, we review functions and mechanisms of ABA in different seed development stages and seed germination, discuss the current progresses especially on the crosstalk between ABA and other hormones and signaling molecules, address novel points and key challenges (e.g., exploring more regulators, more cofactors involved in the crosstalk between ABA and other phytohormones, and visualization of active ABA in the plant), and outline future perspectives for ABA regulating seed associated traits.
Summary
Trichomes are specialized epidermal cells and a vital plant organ that protect plants from various harms and provide valuable resources for plant development and use. Some key genes related ...to trichomes have been identified in the model plant Arabidopsis thaliana through glabrous mutants and gene cloning, and the hub MYB‐bHLH‐WD40, consisting of several factors including GLABRA1 (GL1), GL3, TRANSPARENT TESTA GLABRA1 (TTG1), and ENHANCER OF GLABRA3 (EGL3), has been established. Subsequently, some upstream transcription factors, phytohormones and epigenetic modification factors have also been studied in depth. In cotton, a very important fibre and oil crop globally, in addition to the key MYB‐like factors, more important regulators and potential molecular mechanisms (e.g. epigenetic modifiers, distinct metabolic pathways) are being exploited during different fibre developmental stages. This occurs due to increased cotton research, resulting in the discovery of more complex regulation mechanisms from the allotetraploid genome of cotton. In addition, some conservative as well as specific mediators are involved in trichome development in other species. This study summarizes molecular mechanisms in trichome development and provides a detailed comparison of the similarities and differences between Arabidopsis and cotton, analyses the possible reasons for the discrepancy in identification of regulators, and raises future questions and foci for understanding trichome development in more detail.
Multiple cotton genomes (diploid and tetraploid) have been assembled. However, genomic variations between cultivars of allotetraploid upland cotton (Gossypium hirsutum L.), the most widely planted ...cotton species in the world, remain unexplored. Here, we use single-molecule long read and Hi-C sequencing technologies to assemble genomes of the two upland cotton cultivars TM-1 and zhongmiansuo24 (ZM24). Comparisons among TM-1 and ZM24 assemblies and the genomes of the diploid ancestors reveal a large amount of genetic variations. Among them, the top three longest structural variations are located on chromosome A08 of the tetraploid upland cotton, which account for ~30% total length of this chromosome. Haplotype analyses of the mapping population derived from these two cultivars and the germplasm panel show suppressed recombination rates in this region. This study provides additional genomic resources for the community, and the identified genetic variations, especially the reduced meiotic recombination on chromosome A08, will help future breeding.
In environmental conditions, crop plants are extremely affected by multiple abiotic stresses including salinity, drought, heat, and cold, as well as several biotic stresses such as pests and ...pathogens. However, salinity, drought, and wilt diseases (e.g.,
and
) are considered the most destructive environmental stresses to cotton plants. These cause severe growth interruption and yield loss of cotton. Since cotton crops are central contributors to total worldwide fiber production, and also important for oilseed crops, it is essential to improve stress tolerant cultivars to secure future sustainable crop production under adverse environments. Plants have evolved complex mechanisms to respond and acclimate to adverse stress conditions at both physiological and molecular levels. Recent progresses in molecular genetics have delivered new insights into the regulatory network system of plant genes, which generally includes defense of cell membranes and proteins, signaling cascades and transcriptional control, and ion uptake and transport and their relevant biochemical pathways and signal factors. In this review, we mainly summarize recent progress concerning several resistance-related genes of cotton plants in response to abiotic (salt and drought) and biotic (
and
wilt) stresses and classify them according to their molecular functions to better understand the genetic network. Moreover, this review proposes that studies of stress related genes will advance the security of cotton yield and production under a changing climate and that these genes should be incorporated in the development of cotton tolerant to salt, drought, and fungal wilt diseases (
and
).
D‐2‐hydroxyglutarate dehydrogenase (D2HGDH) is a mitochondrial enzyme containing flavin adenine dinucleotide FAD, existing as a dimer, and it facilitates the specific oxidation of D‐2HG to ...2‐oxoglutarate (2‐OG), which is a key intermediate in the tricarboxylic acid (TCA) cycle. A Genome‐wide expression analysis (GWEA) has indicated an association between GhD2HGDH and flowering time. To further explore the role of GhD2HGDH, we performed a comprehensive investigation encompassing phenotyping, physiology, metabolomics, and transcriptomics in Arabidopsis thaliana plants overexpressing GhD2HGDH. Transcriptomic and qRT‐PCR data exhibited heightened expression of GhD2HGDH in upland cotton flowers. Additionally, early‐maturing cotton exhibited higher expression of GhD2HGDH across all tissues than delayed‐maturing cotton. Subcellular localization confirmed its presence in the mitochondria. Overexpression of GhD2HGDH in Arabidopsis resulted in early flowering. Using virus‐induced gene silencing (VIGS), we investigated the impact of GhD2HGDH on flowering in both early‐ and delayed‐maturing cotton plants. Manipulation of GhD2HGDH expression levels led to changes in photosynthetic pigment and gas exchange attributes. GhD2HGDH responded to gibberellin (GA3) hormone treatment, influencing the expression of GA biosynthesis genes and repressing DELLA genes. Protein interaction studies, including yeast two‐hybrid, luciferase complementation (LUC), and GST pull‐down assays, confirmed the interaction between GhD2HGDH and GhSOX (Sulfite oxidase). The metabolomics analysis demonstrated GhD2HGDH's modulation of the TCA cycle through alterations in various metabolite levels. Transcriptome data revealed that GhD2HGDH overexpression triggers early flowering by modulating the GA3 and photoperiodic pathways of the flowering core factor genes. Taken together, GhD2HGDH positively regulates the network of genes associated with early flowering pathways.
Dramatic shifts in global climate have intensified abiotic and biotic stress faced by plants. Plant microRNAs (miRNAs)-20-24 nucleotide non-coding RNA molecules-form a key regulatory system of plant ...gene expression; playing crucial roles in plant growth; development; and defense against abiotic and biotic stress. Moreover, they participate in cross-kingdom communication. This communication encompasses interactions with other plants, microorganisms, and insect species, collectively exerting a profound influence on the agronomic traits of crops. This article comprehensively reviews the biosynthesis of plant miRNAs and explores their impact on plant growth, development, and stress resistance through endogenous, non-transboundary mechanisms. Furthermore, this review delves into the cross-kingdom regulatory effects of plant miRNAs on plants, microorganisms, and pests. It proceeds to specifically discuss the design and modification strategies for artificial miRNAs (amiRNAs), as well as the protection and transport of miRNAs by exosome-like nanovesicles (ELNVs), expanding the potential applications of plant miRNAs in crop breeding. Finally, the current limitations associated with harnessing plant miRNAs are addressed, and the utilization of synthetic biology is proposed to facilitate the heterologous expression and large-scale production of miRNAs. This novel approach suggests a plant-based solution to address future biosafety concerns in agriculture.
Cotton is a paramount cash crop around the globe. Among all abiotic stresses, drought is a leading cause of cotton growth and yield loss. However, the molecular link between drought stress and ...vascular growth and development is relatively uncharted. Here, we validated a crucial role of GhWOX4, a transcription factor, modulating drought stress with that of vasculature growth in cotton. Knock-down of GhWOX4 decreased the stem width and severely compromised vascular growth and drought tolerance. Conversely, ectopic expression of GhWOX4 in
enhanced the tolerance to drought stress. Comparative RNAseq analysis revealed auxin responsive protein (AUX/IAA), abscisic acid (ABA), and ethylene were significantly induced. Additionally, MYC-bHLH, WRKY, MYB, homeodomain, and heat-shock transcription factors (HSF) were differentially expressed in control plants as compared to GhWOX4-silenced plants. The promotor zone of GhWOX4 was found congested with plant growth, light, and stress response related cis-elements. differentially expressed genes (DEGs) related to stress, water deprivation, and desiccation response were repressed in drought treated GhWOX4-virus-induced gene silencing (VIGS) plants as compared to control. Gene ontology (GO) functions related to cell proliferation, light response, fluid transport, and flavonoid biosynthesis were over-induced in TRV: 156-0 h/TRV: 156-1 h (control) in comparison to TRV: VIGS-0 h/TRV: VIGS-1 h (GhWOX4-silenced) plants. This study improves our context for elucidating the pivotal role of GhWOX4 transcription factors (TF), which mediates drought tolerance, plays a decisive role in plant growth and development, and is likely involved in different regulatory pathways in cotton.
We have sequenced and assembled a draft genome of G. raimondii, whose progenitor is the putative contributor of the D subgenome to the economically important fiber-producing cotton species Gossypium ...hirsutum and Gossypium barbadense. Over 73% of the assembled sequences were anchored on 13 G. raimondii chromosomes. The genome contains 40,976 protein-coding genes, with 92.2% of these further confirmed by transcriptome data. Evidence of the hexaploidization event shared by the eudicots as well as of a cotton-specific whole-genome duplication approximately 13-20 million years ago was observed. We identified 2,355 syntenic blocks in the G. raimondii genome, and we found that approximately 40% of the paralogous genes were present in more than 1 block, which suggests that this genome has undergone substantial chromosome rearrangement during its evolution. Cotton, and probably Theobroma cacao, are the only sequenced plant species that possess an authentic CDN1 gene family for gossypol biosynthesis, as revealed by phylogenetic analysis.
ABSTRACT
Cotton (Gossypium spp.) is one of the most important fiber crops worldwide. In the last two decades, transgenesis and genome editing have played important roles in cotton improvement. ...However, genotype dependence is one of the key bottlenecks in generating transgenic and gene‐edited cotton plants through either particle bombardment or Agrobacterium‐mediated transformation. Here, we developed a shoot apical meristem (SAM) cell‐mediated transformation system (SAMT) that allowed the transformation of recalcitrant cotton genotypes including widely grown upland cotton (Gossypium hirsutum), Sea island cotton (Gossypium barbadense), and Asiatic cotton (Gossypium arboreum). Through SAMT, we successfully introduced two foreign genes, GFP and RUBY, into SAM cells of some recalcitrant cotton genotypes. Within 2–3 months, transgenic adventitious shoots generated from the axillary meristem zone could be recovered and grown into whole cotton plants. The GFP fluorescent signal and betalain accumulation could be observed in various tissues in GFP‐ and RUBY‐positive plants, as well as in their progenies, indicating that the transgenes were stably integrated into the genome and transmitted to the next generation. Furthermore, using SAMT, we successfully generated edited cotton plants with inheritable targeted mutagenesis in the GhPGF and GhRCD1 genes through CRISPR/Cas9‐mediated genome editing. In summary, the established SAMT transformation system here in this study bypasses the embryogenesis process during tissue culture in a conventional transformation procedure and significantly accelerates the generation of transgenic and gene‐edited plants for genetic improvement of recalcitrant cotton varieties.
The shoot apical meristem cell‐mediated transformation system SAMT, an efficient genotype‐independent genetic transformation system for cotton, sidesteps the need for somatic embryogenesis and paves an effective alternative way to generate transgenic and gene‐edited plants in cotton and other recalcitrant dicot plant species for genetic improvement.
Cotton (Gossypium hirsutum) is the major source of natural textile fibers. Brassinosteroids (BRs) play crucial roles in regulating fiber development. The molecular mechanisms of BRs in regulating ...fiber elongation, however, are poorly understood. pagoda1 (pag1) was identified via an activation tagging genetic screen and characterized by genome walking and brassinolide (BL) supplementation. RNA‐Seq analysis was employed to elucidate the mechanisms of PAG1 in regulating fiber development. pag1 exhibited dwarfism and reduced fiber length due to significant inhibition of cell elongation and expansion. BL treatment rescued its growth and fiber elongation. PAG1 encodes a homolog of Arabidopsis CYP734A1 that inactivates BRs via C‐26 hydroxylation. RNA‐Seq analyses showed that the constitutive expression of PAG1 downregulated the expression of genes involved in very‐long‐chain fatty acids (VLCFA) biosynthesis, ethylene‐mediated signaling, response to cadmium, cell wall development, cytoskeleton organization and cell growth. Our results demonstrate that PAG1 plays crucial roles in regulating fiber development via controlling the level of endogenous bioactive BRs, which may affect ethylene signaling cascade by mediating VLCFA. Therefore, BR may be a critical regulator of fiber elongation, a role which may in turn be linked to effects on VLCFA biosynthesis, ethylene and cadmium signaling, cell wall‐ and cytoskeleton‐related gene expression.
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