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N6‐methyladenosine (m6A) is the most prevalent internal modification of mRNA and plays an important role in regulating plant growth. However, there is still a lack of effective tools to precisely modify m6A sites of individual transcripts in plants. Here, programmable m6A editing tools are developed by combining CRISPR/dCas13(Rx) with the methyltransferase GhMTA (Targeted RNA Methylation Editor, TME) or the demethyltransferase GhALKBH10 (Targeted RNA Demethylation Editor, TDE). These editors enable efficient deposition or removal of m6A modifications at targeted sites of endo‐transcripts GhECA1 and GhDi19 within a broad editing window ranging from 0 to 46 nt. TDE editor significantly decreases m6A levels by 24%–76%, while the TME editor increases m6A enrichment, ranging from 1.37‐ to 2.51‐fold. Furthermore, installation and removal of m6A modifications play opposing roles in regulating GhECA1 and GhDi19 mRNA transcripts, which may be attributed to the fact that their m6A sites are located in different regions of the genes. Most importantly, targeting the GhDi19 transcript with TME editor plants results in a significant increase in root length and enhanced drought resistance. Collectively, these m6A editors can be applied to study the function of specific m6A modifications and have the potential for future applications in crop improvement. [ABSTRACT FROM AUTHOR]

Global water scarcity and extreme weather intensify drought stress, significantly reducing cotton yield and quality worldwide. Drought treatments are conducted using a population of chromosome segment substitution lines generated from E22 (G. hirsutum) and 3–79 (G. barbadense) as parental lines either show superior yields or fiber quality under both control and drought conditions. Fourteen datasets, covering 4 yields and 4 quality traits, are compiled and assessed for drought resistance using the drought resistance coefficient (DRC) and membership function value of drought resistance (MFVD). Genome‐wide association studies, linkage analysis, and bulked segregant analysis are combined to analyze the DR‐related QTL. A total of 121 significant QTL are identified by DRC and MFVD of the 8 traits. CRISPR/Cas9 and virus‐induced gene silencing techniques verified DRR1 and DRT1 as pivotal genes in regulating drought resistant of cotton, with hap3‐79 exhibiting greater drought resistance than hapE22 concerning DRR1 and DRT1. Moreover, 14 markers with superior yield and fiber quality are selected for drought treatment. This study offers valuable insights into yield and fiber quality variations between G. hirsutum and G. barbadense amid drought, providing crucial theoretical and technological backing for developing cotton varieties resilient to drought, with high yield and superior fiber quality. [ABSTRACT FROM AUTHOR]

Summary: N6‐methyladenosine (m6A) is the most prevalent internal modification present in mRNAs, and is considered to participate in a range of developmental and biological processes. Drought response is highly regulated at the genomic, transcriptional and post‐transcriptional levels. However, the biological function and regulatory mechanism of m6A modification in the drought stress response is still poorly understood. We generated a transcriptome‐wide m6A map using drought‐resistant and drought‐sensitive varieties of cotton under different water deficient conditions to uncover patterns of m6A methylation in cotton response to drought stress. The results reveal that m6A represents a common modification and exhibit dramatic changes in distribution during drought stress. More 5'UTR m6A was deposited in the drought‐resistant variety and was associated with a positive effect on drought resistance by regulating mRNA abundance. Interestingly, we observed that increased m6A abundance was associated with increased mRNA abundance under drought, contributing to drought resistance, and vice versa. The demethylase GhALKBH10B was found to decrease m6A levels, facilitating the mRNA decay of ABA signal‐related genes (GhZEP, GhNCED4 and GhPP2CA) and Ca2+ signal‐related genes (GhECA1, GhCNGC4, GhANN1 and GhCML13), and mutation of GhALKBH10B enhanced drought resistance at seedling stage in cotton. Virus‐induced gene silencing (VIGS) of two Ca2+‐related genes, GhECA1 and GhCNGC4, reduced drought resistance with the decreased m6A enrichment on silenced genes in cotton. Collectively, we reveal a novel mechanism of post‐transcriptional modification involved in affecting drought response in cotton, by mediating m6A methylation on targeted transcripts in the ABA and Ca2+ signalling transduction pathways. [ABSTRACT FROM AUTHOR]

Summary: Cotton fibre is a unicellular seed trichome, and lint fibre initials per seed as a factor determines fibre yield. However, the mechanisms controlling fibre initiation from ovule epidermis are not understood well enough. Here, with single‐cell RNA sequencing (scRNA‐seq), a total of 14 535 cells were identified from cotton ovule outer integument of Xu142_LF line at four developmental stages (1.5, 1, 0.5 days before anthesis and the day of anthesis). Three major cell types, fibre, non‐fibre epidermis and outer pigment layer were identified and then verified by RNA in situ hybridization. A comparative analysis on scRNA‐seq data between Xu142 and its fibreless mutant Xu142 fl further confirmed fibre cluster definition. The developmental trajectory of fibre cell was reconstructed, and fibre cell was identified differentiated at 1 day before anthesis. Gene regulatory networks at four stages revealed the spatiotemporal pattern of core transcription factors, and MYB25‐like and HOX3 were demonstrated played key roles as commanders in fibre differentiation and tip‐biased diffuse growth respectively. A model for early development of a single fibre cell was proposed here, which sheds light on further deciphering mechanism of plant trichome and the improvement of cotton fibre yield. [ABSTRACT FROM AUTHOR]

Summary: Drought resistance (DR) is a complex trait that is regulated by a variety of genes. Without comprehensive profiling of DR‐related traits, the knowledge of the genetic architecture for DR in cotton remains limited. Thus, there is a need to bridge the gap between genomics and phenomics. In this study, an automatic phenotyping platform (APP) was systematically applied to examine 119 image‐based digital traits (i‐traits) during drought stress at the seedling stage, across a natural population of 200 representative upland cotton accessions. Some novel i‐traits, as well as some traditional i‐traits, were used to evaluate the DR in cotton. The phenomics data allowed us to identify 390 genetic loci by genome‐wide association study (GWAS) using 56 morphological and 63 texture i‐traits. DR‐related genes, including GhRD2, GhNAC4, GhHAT22 and GhDREB2, were identified as candidate genes by some digital traits. Further analysis of candidate genes showed that Gh_A04G0377 and Gh_A04G0378 functioned as negative regulators for cotton drought response. Based on the combined digital phenotyping, GWAS analysis and transcriptome data, we conclude that the phenomics dataset provides an excellent resource to characterize key genetic loci with an unprecedented resolution which can inform future genome‐based breeding for improved DR in cotton. [ABSTRACT FROM AUTHOR]

Introduction: Advanced age is the foremost risk factor for atrial fibrillation (AF). Telomere length is a surrogate for biological aging, but the association between shortened leukocyte telomere length (LTL) and recurrence of AF (RAF) after ablation remains inconclusive. Methods: In this prospective analysis, 282 patients underwent an initial catheter ablation for paroxysmal or persistent AF. The association between RAF and LTL was analyzed by univariate and multivariate Cox regression, as well as time‐dependent receiver operating characteristic (ROC) analysis and Kaplan‐Meier analysis. Results: After a mean follow‐up of 14.20 ± 5.04 months, RAF was documented in 78 of the 277 patients who completed the study (28.16%). In Cox proportional hazards models, LTL, age, diagnosis to ablation time (DTAT), N‐terminal pronatriuretic peptide, and CHA2DS2‐VASc score were significantly associated with RAF. After multivariable adjustment, LTL and DTAT were predicted as independent risk factors for RAF with hazard ratio (HR) of 3.17 (95% confidence interval [CI]: 1.23‐8.15, P = 0.017) and 1.43 (95% CI: 1.10‐1.86, P = 0.007), respectively. In addition, ROC analysis indicated the potential diagnostic value of LTL with an area under the curve of 0.64 (P < 0.001; sensitivity = 60.3%, specificity = 57.8%), and an optimum cut‐off value of 1.040. LTL less than or equal to 1.040 was defined as shortened LTL, while LTL greater than 1.040 nonshortened LTL. Kaplan‐Meier analysis showed RAF rate curve was separated significantly between two groups (21.2% vs 35.9%, log‐rank test result P = 0.007). Patients with shortened LTL might have a higher risk for RAF with HR = 1.84 (P = 0.008). Conclusions: Shortened LTL is an independent risk factor for AF recurrence. Shortened LTL could be a potential biomarker in predicting RAF after ablation. [ABSTRACT FROM AUTHOR]

Multiple transporters and channels mediate cation transport across the plasma membrane and tonoplast to regulate ionic homeostasis in plant cells. However, much less is known about the molecular function of transporters that facilitate cation transport in other organelles such as Golgi. We report here that Arabidopsis KEA4, KEA5, and KEA6, members of cation/proton antiporters‐2 (CPA2) superfamily were colocalized with the known Golgi marker, SYP32‐mCherry. Although single kea4,5,6 mutants showed similar phenotype as the wild type under various conditions, kea4/5/6 triple mutants showed hypersensitivity to low pH, high K+, and high Na+ and displayed growth defects in darkness, suggesting that these three KEA‐type transporters function redundantly in controlling etiolated seedling growth and ion homeostasis. Detailed analysis indicated that the kea4/5/6 triple mutant exhibited cell wall biosynthesis defect during the rapid etiolated seedling growth and under high K+/Na+ condition. The cell wall‐derived pectin homogalacturonan (GalA)3 partially suppressed the growth defects and ionic toxicity in the kea4/5/6 triple mutants when grown in the dark but not in the light conditions. Together, these data support the hypothesis that the Golgi‐localized KEAs play key roles in the maintenance of ionic and pH homeostasis, thereby facilitating Golgi function in cell wall biosynthesis during rapid etiolated seedling growth and in coping with high K+/Na+ stress. Plastidial K+ transporters KEA1, KEA2, and KEA3 have been reported to play important roles in chloroplast osmoregulation, integrity, and pH regulation in Arabidopsis. However, much less is known about the molecular identity and function of KEA4, KEA5, and KEA6. In our report, we demonstrate that the Golgi‐localized KEA4, KEA5, and KEA6 play key roles in the maintenance of ionic and pH homeostasis, thereby facilitating Golgi function in cell wall biosynthesis during rapid cell growth of etiolated seedlings and in coping with high K+/Na+ stress. This study represents the first functional analysis of these three transporters in any plant species. [ABSTRACT FROM AUTHOR]

Summary: Auxin is as an efficient initiator and regulator of cell fate during somatic embryogenesis (SE), but the molecular mechanisms and regulating networks of this process are not well understood. In this report, we analysed SE process induced by Leafy cotyledon1‐like 1 (GhL1L1), a NF‐YB subfamily gene specifically expressed in embryonic tissues in cotton. We also identified the target gene of GhL1L1, and its role in auxin distribution and cell fate specification during embryonic development was analysed. Overexpression of GhL1L1 accelerated embryonic cell formation, associated with an increased concentration of IAA in embryogenic calluses (ECs) and in the shoot apical meristem, corresponding to altered expression of the auxin transport gene GhPIN1. By contrast, GhL1L1‐deficient explants showed retarded embryonic cell formation, and the concentration of IAA was decreased in GhL1L1‐deficient ECs. Disruption of auxin distribution accelerated the specification of embryonic cell fate together with regulation of GhPIN1. Furthermore, we showed that PHOSPHATASE 2AA2 (GhPP2AA2) was activated by GhL1L1 through targeting the G‐box of its promoter, hence regulating the activity of GhPIN1 protein. Our results indicate that GhL1L1 functions as a key regulator in auxin distribution to regulate cell fate specification in cotton and contribute to the understanding of the complex process of SE in plant species. [ABSTRACT FROM AUTHOR]

The growth and yield of many crops, including cotton, are affected by water deficit. Cotton has evolved drought specific as well as general morpho-physiological, biochemical and molecular responses to drought stress, which are discussed in this review. The key physiological responses against drought stress in cotton, including stomata closing, root development, cellular adaptations, photosynthesis, abscisic acid ( ABA) and jasmonic acid ( JA) production and reactive oxygen species ( ROS) scavenging, have been identified by researchers. Drought stress induces the expression of stress-related transcription factors and genes, such as ROS scavenging, ABA or mitogen-activated protein kinases ( MAPK) signalling genes, which activate various drought-related pathways to induce tolerance in the plant. It is crucial to elucidate and induce drought-tolerant traits via quantitative trait loci ( QTL) analysis, transgenic approaches and exogenous application of substances. The current review article highlights the natural as well as engineered drought tolerance strategies in cotton. [ABSTRACT FROM AUTHOR]

Fiber elongation is the key determinant of fiber quality and output in cotton ( Gossypium hirsutum). Although expression profiling and functional genomics provide some data, the mechanism of fiber development is still not well understood., Here, a gene encoding a calcium sensor, Gh Ca M7, was isolated based on its high expression level relative to other Gh Ca Ms in fiber cells at the fast elongation stage. The level of expression of Gh Ca M7 in the wild-type and the fuzzless/lintless mutant correspond to the presence and absence, respectively, of fiber initials., Overexpressing Gh Ca M7 promotes early fiber elongation, whereas Gh Ca M7 suppression by RNAi delays fiber initiation and inhibits fiber elongation. Reactive oxygen species ( ROS) play important roles in early fiber development. ROS induced by exogenous hydrogen peroxide ( H2 O2) and Ca2+ starvation promotes early fiber elongation. Gh Ca M7 overexpression fiber cells show increased ROS concentrations compared with the wild-type, while Gh Ca M7 RNAi fiber cells have reduced concentrations. Furthermore, we show that H2 O2 enhances Ca2+ influx into the fiber and feedback-regulates the expression of GhCaM7., We conclude that Gh Ca M7, Ca2+ and ROS are three important regulators involved in early fiber elongation. Gh Ca M7 might modulate ROS production and act as a molecular link between Ca2+ and ROS signal pathways in early fiber development. [ABSTRACT FROM AUTHOR]

As a product of asexual reproduction in plants, the somatic embryo ( SE) differentiates into a new plantlet via a zygotic embryogenesis-like process. Here, we present the phenotypic and cellular differences between SEs and zygotic embryos ( ZEs) revealed by histological section scanning using three parallel development stages of the two types of embryos of cotton ( Gossypium hirsutum cv. YZ1), including globular, torpedo and cotyledonary-stages. To identify the molecular characteristics of SE development in cotton, the digital gene expression system was used to profile the genes active during SE and ZE development. A total of 4242 differentially expressed genes ( DEGs) were identified in at least one developmental stage. Expression pattern and functional classification analysis based on these DEGs reveals that SE development exhibits a transcriptional activation of stress responses. RT- PCR analysis further confirmed enhanced expression levels of stress-related genes in SEs than in ZEs. Experimental stress treatment, induced by Na Cl and ABA, accelerated SE development and increased the transcription of genes related to stress response, in parallel with decelerated proliferation of embryogenic calluses under stress treatment. Our data reveal that SE development involves the activation of stress responses, which we suggest may regulate the balance between cell proliferation and differentiation. These results provide new insight into the molecular mechanisms of SE development and suggest strategies that can be used for regulating the developmental processes of somatic embryogenesis. [ABSTRACT FROM AUTHOR]

Summary The proteins of high-mobility group box (HmgB) family were involved in the regulation of transcription and other DNA-dependent processes. To investigate the function of HmgB proteins during cotton somatic embryogenesis (SE), four Gossypium hirsutum HmgB genes were characterized. The gene GhHmgB3 preferentially expressed in embryonic tissues and was studied in detail. RNA interference and over-expression was used to regulate the expression of GhHmgB3 during cotton SE by transforming both hypocotyl and embryogenic calli (ECs) via Agrobacterium tumefaciens. The GhHmgB3-deficient somatic cells of hypocotyls dedifferentiated more vigorously than the control cells, but they failed to differentiate to ECs. In another case, the proliferation and differentiation of GhHmgB3-deficient ECs were significantly improved, but failed to form plantlets. Over-expression of GhHmgB3 had no significant differences in callus initiation and differentiation compared with the control cell lines. The different expression genes between the control and GhHmgB3-deficient ECs were identified by Solexa sequencing technology. The bioinformatics analysis and experimental verification revealed series of abnormal mechanism associated with β-catenin signalling. These results in response to the down-regulation of GhHmgB3 revealed series of β-catenin-related mechanisms might be responsible for the deregulation of proliferation and differentiation of cells in cotton SE. [ABSTRACT FROM AUTHOR]