LncRNA improves cold resistance of winter wheat by interacting with miR398

Genome-wide characterization of drought-responsive long non-coding RNAs in sorghum (Sorghum bicolor)

Drought stress strongly affects crop yield. Although knowledge of long non-coding RNAs (lncRNAs) has been updated continuously and rapidly, information about lncRNAs in drought resistance regulation is extremely limited in sorghum. Here, lncRNA-sequencing was performed with seedlings of a sorghum cultivar (Jinza29) under three water control treatments to investigate the mechanism of lncRNAs responsible for drought resistance in sorghum. A total of 377 differentially expressed lncRNAs (DElncRNAs) were identified. We also predicted 4322 and 2827 transcripts as potential cis-target and trans-target genes for drought-responsive lncRNAs, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that those target genes exhibited marked enrichment into "oxidoreductase activity", "signal transducer activity", "DNA repair", "photosynthesis", "glutathione metabolism", and "phenylpropanoid biosynthesis" and other terms associated with abiotic stress resistance. Moreover, several lncRNAs were estimated to modulate the expression of other genes related to stress response and photosynthetic carbon metabolism. Additionally, we found 107 DElncRNAs that might be candidate target mimics for 56 miRNAs. LncRNAs play important roles in drought adaptation of sorghum through interacting with protein-encoding genes. The obtained results provided novel insights into the biological characteristics of lncRNAs and offered potential regulatory factors for genetically enhancing drought resistance in sorghum.

MiR398b Targets Superoxide Dismutase Genes in Soybean in Defense Against Heterodera glycines via Modulating Reactive Oxygen Species Homeostasis

MicroRNAs play crucial roles in plant defense responses. However, the underlying mechanism by which miR398b contributes to soybean responses to soybean cyst nematode (Heterodera glycines) remains elusive. In this study, by using Agrobacterium rhizogenes-mediated transformation of soybean hairy roots, we observed that miR398b and target genes GmCCS and GmCSD1b played vital functions in soybean-H. glycines interaction. The study revealed that the abundance of miR398b was downregulated by H. glycines infection, and overexpression of miR398b enhanced the susceptibility of soybean to H. glycines. Conversely, silencing of miR398b improved soybean resistance to H. glycines. Detection assays revealed that miR398b rapidly senses stress-induced reactive oxygen species, leading to the repression of target genes GmCCS and GmCSD1b and regulating the accumulation of plant defense genes against nematode infection. Moreover, exogenous synthetic ds-miR398b enhanced soybean sensitivity to H. glycines by modulating H2O2 and O2- levels. Functional analysis demonstrated that overexpression of GmCCS and GmCSD1b in soybean enhanced resistance to H. glycines. RNA interference-mediated repression of GmCCS and GmCSD1b in soybean increased susceptibility to H. glycines. RNA sequencing revealed that a majority of differentially expressed genes in overexpressed GmCCS were associated with oxidative stress. Overall, the results indicate that miR398b targets superoxide dismutase genes, which negatively regulate soybean resistance to H. glycines via modulating reactive oxygen species levels and defense signals.

Exploring the emerging role of long non-coding RNAs (lncRNAs) in plant biology: Functions, mechanisms of action, and future directions

Long non-coding RNAs (lncRNAs) are a class of RNA transcripts that surpass 200 nucleotides in length and lack discernible coding potential. LncRNAs that have been functionally characterized have pivotal functions in several plant processes, including the regulation of flowering, and development of lateral roots. It also plays a crucial role in the plant's response to abiotic stressors and exhibits vital activities in environmental adaptation. The progress in NGS (next-generation sequencing) and functional genomics technology has facilitated the discovery of lncRNA in plant species. This review is a brief explanation of lncRNA genomics, its molecular role, and the mechanism of action in plants. The review also addresses the challenges encountered in this field and highlights promising molecular and computational methodologies that can aid in the comparative and functional analysis of lncRNAs.

Update on functional analysis of long non-coding RNAs in common crops

With the rapid advances in next-generation sequencing technology, numerous non-protein-coding transcripts have been identified, including long noncoding RNAs (lncRNAs), which are functional RNAs comprising more than 200 nucleotides. Although lncRNA-mediated regulatory processes have been extensively investigated in animals, there has been considerably less research on plant lncRNAs. Nevertheless, multiple studies on major crops showed lncRNAs are involved in crucial processes, including growth and development, reproduction, and stress responses. This review summarizes the progress in the research on lncRNA roles in several major crops, presents key strategies for exploring lncRNAs in crops, and discusses current challenges and future prospects. The insights provided in this review will enhance our comprehension of lncRNA functions in crops, with potential implications for improving crop genetics and breeding.

Identification and Analysis of lncRNA and circRNA Related to Wheat Grain Development

The role of lncRNA and circRNA in wheat grain development is still unclear. The objectives of this study were to characterize the lncRNA and circRNA in the wheat grain development and to construct the interaction network among lncRNA, circRNA, and their target miRNA to propose a lncRNA-circRNA-miRNA module related to wheat grain development. Full transcriptome sequencing on two wheat varieties (Annong 0942 and Anke 2005) with significant differences in 1000-grain weight at 10 d (days after pollination), 20 d, and 30 d of grain development were conducted. We detected 650, 736, and 609 differentially expressed lncRNA genes, and 769, 1054, and 1062 differentially expressed circRNA genes in the grains of 10 days, 20 days and 30 days after pollination between Annong 0942 and Anke 2005, respectively. An analysis of the lncRNA-miRNA and circRNA-miRNA targeting networks reveals that circRNAs exhibit a more complex and extensive interaction network in the development of cereal grains and the formation of grain shape. Central to these interactions are tae-miR1177, tae-miR1128, and tae-miR1130b-3p. In contrast, lncRNA genes only form a singular network centered around tae-miR1133 and tae-miR5175-5p when comparing between varieties. Further analysis is conducted on the underlying genes of all target miRNAs, we identified TaNF-YB1 targeted by tae-miR1122a and TaTGW-7B targeted by miR1130a as two pivotal regulatory genes in the development of wheat grains. The quantitative real-time PCR (qRT-PCR) and dual-luciferase reporter assays confirmed the target regulatory relationships between miR1130a-TaTGW-7B and miR1122a-TaNF-YB1. We propose a network of circRNA and miRNA-mediated gene regulation in the development of wheat grains.

Maize miRNAs and their putative target genes involved in chilling stress response in 5-day old seedlings

BACKGROUND

In the context of early sowing of maize as a promising adaptation strategy that could significantly reduce the negative effects of climate change, an in-depth understanding of mechanisms underlying plant response to low-temperature stress is demanded. Although microRNAs (miRNAs) have been recognized as key regulators of plant stress response, research on their role in chilling tolerance of maize during early seedling stages is scarce. Therefore, it is of great significance to explore chilling-responsive miRNAs, reveal their expression patterns and associated target genes, as well as to examine the possible functions of the conserved and novel miRNAs. In this study, the role of miRNAs was examined in 5d-old maize seedlings of one tolerant and one sensitive inbred line exposed to chilling (10/8 °C) stress for 6 h and 24 h, by applying high throughput sequencing.

RESULTS

A total of 145 annotated known miRNAs belonging to 30 families and 876 potentially novel miRNAs were identified. Differential expression (DE) analysis between control and stress conditions identified 98 common miRNAs for both genotypes at one time point and eight miRNAs at both time points. Target prediction and enrichment analysis showed that the DE zma-miR396, zma-miR156, zma-miR319, and zma-miR159 miRNAs modulate growth and development. Furthermore, it was found that several other DE miRNAs were involved in abiotic stress response: antioxidative mechanisms (zma-miR398), signal transduction (zma-miR156, zma-miR167, zma-miR169) and regulation of water content (zma-miR164, zma-miR394, zma-miR396). The results underline the zma-miRNAs involvement in the modulation of their target genes expression as an important aspect of the plant's survival strategy and acclimation to chilling stress conditions.

CONCLUSIONS

To our understanding, this is the first study on miRNAs in 5-d old seedlings' response to chilling stress, providing data on the role of known and novel miRNAs post-transcriptional regulation of expressed genes and contributing a possible platform for further network and functional analysis.

Predicted roles of long non-coding RNAs in abiotic stress tolerance responses of plants

The plant genome exhibits a significant amount of transcriptional activity, with most of the resulting transcripts lacking protein-coding potential. Non-coding RNAs play a pivotal role in the development and regulatory processes in plants. Long non-coding RNAs (lncRNAs), which exceed 200 nucleotides, may play a significant role in enhancing plant resilience to various abiotic stresses, such as excessive heat, drought, cold, and salinity. In addition, the exogenous application of chemicals, such as abscisic acid and salicylic acid, can augment plant defense responses against abiotic stress. While how lncRNAs play a role in abiotic stress tolerance is relatively well-studied in model plants, this review provides a comprehensive overview of the current understanding of this function in horticultural crop plants. It also delves into the potential role of lncRNAs in chemical priming of plants in order to acquire abiotic stress tolerance, although many limitations exist in proving lncRNA functionality under such conditions.

ZmmiR398b negatively regulates maize resistance to sugarcane mosaic virus infection by targeting ZmCSD2/4/9

MicroRNAs (miRNAs) are widely involved in various biological processes of plants and contribute to plant resistance against various pathogens. In this study, upon sugarcane mosaic virus (SCMV) infection, the accumulation of maize (Zea mays) miR398b (ZmmiR398b) was significantly reduced in resistant inbred line Chang7-2, while it was increased in susceptible inbred line Mo17. Degradome sequencing analysis coupled with transient co-expression assays revealed that ZmmiR398b can target Cu/Zn-superoxidase dismutase2 (ZmCSD2), ZmCSD4, and ZmCSD9 in vivo, of which the expression levels were all upregulated by SCMV infection in Chang7-2 and Mo17. Moreover, overexpressing ZmmiR398b (OE398b) exhibited increased susceptibility to SCMV infection, probably by increasing reactive oxygen species (ROS) accumulation, which were consistent with ZmCSD2/4/9-silenced maize plants. By contrast, silencing ZmmiR398b (STTM398b) through short tandem target mimic (STTM) technology enhanced maize resistance to SCMV infection and decreased ROS levels. Interestingly, copper (Cu)-gradient hydroponic experiments demonstrated that Cu deficiency promoted SCMV infection while Cu sufficiency inhibited SCMV infection by regulating accumulations of ZmmiR398b and ZmCSD2/4/9 in maize. These results revealed that manipulating the ZmmiR398b-ZmCSD2/4/9-ROS module provides a prospective strategy for developing SCMV-tolerant maize varieties.

A long non-coding RNA functions as a competitive endogenous RNA to modulate TaNAC018 by acting as a decoy for tae-miR6206

Increasing evidence indicates a strong correlation between the deposition of cuticular waxes and drought tolerance. However, the precise regulatory mechanism remains elusive. Here, we conducted a comprehensive transcriptome analysis of two wheat (Triticum aestivum) near-isogenic lines, the glaucous line G-JM38 rich in cuticular waxes and the non-glaucous line NG-JM31. We identified 85,143 protein-coding mRNAs, 4,485 lncRNAs, and 1,130 miRNAs. Using the lncRNA-miRNA-mRNA network and endogenous target mimic (eTM) prediction, we discovered that lncRNA35557 acted as an eTM for the miRNA tae-miR6206, effectively preventing tae-miR6206 from cleaving the NAC transcription factor gene TaNAC018. This lncRNA-miRNA interaction led to higher transcript abundance for TaNAC018 and enhanced drought-stress tolerance. Additionally, treatment with mannitol and abscisic acid (ABA) each influenced the levels of tae-miR6206, lncRNA35557, and TaNAC018 transcript. The ectopic expression of TaNAC018 in Arabidopsis also improved tolerance toward mannitol and ABA treatment, whereas knocking down TaNAC018 transcript levels via virus-induced gene silencing in wheat rendered seedlings more sensitive to mannitol stress. Our results indicate that lncRNA35557 functions as a competing endogenous RNA to modulate TaNAC018 expression by acting as a decoy target for tae-miR6206 in glaucous wheat, suggesting that non-coding RNA has important roles in the regulatory mechanisms responsible for wheat stress tolerance.

Plant non-coding RNAs: The new frontier for the regulation of plant development and adaptation to stress

Most plant transcriptomes constitute functional non-coding RNAs (ncRNAs) that lack the ability to encode proteins. In recent years, more research has demonstrated that ncRNAs play important regulatory roles in almost all plant biological processes by modulating gene expression. Thus, it is important to study the biogenesis and function of ncRNAs, particularly in plant growth and development and stress tolerance. In this review, we systematically explore the process of formation and regulatory mechanisms of ncRNAs, particularly those of microRNAs (miRNAs), small interfering RNAs (siRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). Additionally, we provide a comprehensive overview of the recent advancements in ncRNAs research, including their regulation of plant growth and development (seed germination, root growth, leaf morphogenesis, floral development, and fruit and seed development) and responses to abiotic and biotic stress (drought, heat, cold, salinity, pathogens and insects). We also discuss research challenges and provide recommendations to advance the understanding of the roles of ncRNAs in agronomic applications.

Current perspectives of lncRNAs in abiotic and biotic stress tolerance in plants

Abiotic/biotic stresses pose a major threat to agriculture and food security by impacting plant growth, productivity and quality. The discovery of extensive transcription of large RNA transcripts that do not code for proteins, termed long non-coding RNAs (lncRNAs) with sizes larger than 200 nucleotides in length, provides an important new perspective on the centrality of RNA in gene regulation. In plants, lncRNAs are widespread and fulfill multiple biological functions in stress response. In this paper, the research advances on the biological function of lncRNA in plant stress response were summarized, like as Natural Antisense Transcripts (NATs), Competing Endogenous RNAs (ceRNAs) and Chromatin Modification etc. And in plants, lncRNAs act as a key regulatory hub of several phytohormone pathways, integrating abscisic acid (ABA), jasmonate (JA), salicylic acid (SA) and redox signaling in response to many abiotic/biotic stresses. Moreover, conserved sequence motifs and structural motifs enriched within stress-responsive lncRNAs may also be responsible for the stress-responsive functions of lncRNAs, it will provide a new focus and strategy for lncRNA research. Taken together, we highlight the unique role of lncRNAs in integrating plant response to adverse environmental conditions with different aspects of plant growth and development. We envisage that an improved understanding of the mechanisms by which lncRNAs regulate plant stress response may further promote the development of unconventional approaches for breeding stress-resistant crops.

The ncRNAs Involved in the Regulation of Abiotic Stress-Induced Anthocyanin Biosynthesis in Plants

Plants have evolved complicated defense and adaptive systems to grow in various abiotic stress environments such as drought, cold, and salinity. Anthocyanins belong to the secondary metabolites of flavonoids with strong antioxidant activity in response to various abiotic stress and enhance stress tolerance. Anthocyanin accumulation often accompanies the resistance to abiotic stress in plants to scavenge reactive oxygen species (ROS). Recent research evidence showed that many regulatory pathways such as osmoregulation, antioxidant response, plant hormone response, photosynthesis, and respiration regulation are involved in plant adaption to stress. However, the molecular regulatory mechanisms involved in controlling anthocyanin biosynthesis in relation to abiotic stress response have remained obscure. Here, we summarize the current research progress of specific regulators including small RNAs, and lncRNAs involved in the molecular regulation of abiotic stress-induced anthocyanin biosynthesis. In addition, an integrated regulatory network of anthocyanin biosynthesis controlled by microRNAs (miRNAs), long non-coding RNAs (lncRNAs), transcription factors, and stress response factors is also discussed. Understanding molecular mechanisms of anthocyanin biosynthesis for ROS scavenging in various abiotic stress responses will benefit us for resistance breeding in crop plants.

Genome-Wide Identification of the CBF Gene Family and ICE Transcription Factors in Walnuts and Expression Profiles under Cold Conditions

Cold stress impacts woody tree growth and perennial production, especially when the temperature rapidly changes in late spring. To address this issue, we conducted the genome-wide identification of two important transcription factors (TFs), CBF (C-repeat binding factors) and ICE (inducers of CBF expression), in three walnut (Juglans) genomes. Although the CBF and ICE gene families have been identified in many crops, very little systematic analysis of these genes has been carried out in J. regia and J. sigillata. In this study, we identified a total of 16 CBF and 12 ICE genes in three Juglans genomes using bioinformatics analysis. Both CBF and ICE had conserved domains, motifs, and gene structures, which suggests that these two TFs were evolutionarily conserved. Most ICE genes are located at both ends of the chromosomes. The promoter cis-regulatory elements of CBF and ICE genes are largely involved in light and phytohormone responses. Based on 36 RNA sequencing of leaves from four walnut cultivars ('Zijing', 'Lvling', 'Hongren', and 'Liao1') under three temperature conditions (8 °C, 22 °C, and 5 °C) conditions in late spring, we found that the ICE genes were expressed more highly than CBFs. Both CBF and ICE proteins interacted with cold-related proteins, and many putative miRNAs had interactions with these two TFs. These results determined that CBF1 and ICE1 play important roles in the tolerance of walnut leaves to rapid temperature changes. Our results provide a useful resource on the function of the CBF and ICE genes related to cold tolerance in walnuts.

Non-coding RNAs (ncRNAs) in plant: Master regulators for adapting to extreme temperature conditions

Unusual daily temperature fluctuations caused by climate change and climate variability adversely impact agricultural crop production. Since plants are immobile and constantly receive external environmental signals, such as extreme high (heat) and low (cold) temperatures, they have developed complex molecular regulatory mechanisms to cope with stressful situations to sustain their natural growth and development. Among these mechanisms, non-coding RNAs (ncRNAs), particularly microRNAs (miRNAs), small-interfering RNAs (siRNAs), and long-non-coding RNAs (lncRNAs), play a significant role in enhancing heat and cold stress tolerance. This review explores the pivotal findings related to miRNAs, siRNAs, and lncRNAs, elucidating how they functionally regulate plant adaptation to extreme temperatures. In addition, this review addresses the challenges associated with uncovering these non-coding RNAs and understanding their roles in orchestrating heat and cold tolerance in plants.

Deciphering shared attributes of plant long non-coding RNAs through a comparative computational approach

Over the past decade, long non-coding RNA (lncRNA), which lacks protein-coding potential, has emerged as an essential regulator of the genome. The present study examined 13,599 lncRNAs in Arabidopsis thaliana, 11,565 in Oryza sativa, and 32,397 in Zea mays for their characteristic features and explored the associated genomic and epigenomic features. We found lncRNAs were distributed throughout the chromosomes and the Helitron family of transposable elements (TEs) enriched, while the terminal inverted repeat depleted in lncRNA transcribing regions. Our analyses determined that lncRNA transcribing regions show rare or weak signals for most epigenetic marks except for H3K9me2 and cytosine methylation in all three plant species. LncRNAs showed preferential localization in the nucleus and cytoplasm; however, the distribution ratio in the cytoplasm and nucleus varies among the studied plant species. We identified several conserved endogenous target mimic sites in the lncRNAs among the studied plants. We found 233, 301, and 273 unique miRNAs, potentially targeting the lncRNAs of A. thaliana, O. sativa, and Z. mays, respectively. Our study has revealed that miRNAs, which interact with lncRNAs, target genes that are involved in a diverse array of biological and molecular processes. The miRNA-targeted lncRNAs displayed a strong affinity for several transcription factors, including ERF and BBR-BPC, mutually present in all three plants, advocating their conserved functions. Overall, the present study showed that plant lncRNAs exhibit conserved genomic and epigenomic characteristics and potentially govern the growth and development of plants.

A Survey of Computational Methods and Databases for lncRNA-MiRNA Interaction Prediction

Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are two prevalent non-coding RNAs in current research. They play critical regulatory roles in the life processes of animals and plants. Studies have shown that lncRNAs can interact with miRNAs to participate in post-transcriptional regulatory processes, mainly involved in regulating cancer development, metastatic progression, and drug resistance. Additionally, these interactions have significant effects on plant growth, development, and responses to biotic and abiotic stresses. Deciphering the potential relationships between lncRNAs and miRNAs may provide new insights into our understanding of the biological functions of lncRNAs and miRNAs, and the pathogenesis of complex diseases. In contrast, gathering information on lncRNA-miRNA interactions (LMIs) through biological experiments is expensive and time-consuming. With the accumulation of multi-omics data, computational models are extremely attractive in systematically exploring potential LMIs. To the best of our knowledge, this is the first comprehensive review of computational methods for identifying LMIs. Specifically, we first summarized the available public databases for predicting animal and plant LMIs. Second, we comprehensively reviewed the computational methods for predicting LMIs and classified them into two categories, including network-based methods and sequence-based methods. Third, we analyzed the standard evaluation methods and metrics used in LMI prediction. Finally, we pointed out some problems in the current study and discuss future research directions. Relevant databases and the latest advances in LMI prediction are summarized in a GitHub repository https://github.com/sheng-n/lncRNA-miRNA-interaction-methods, and we'll keep it updated.

Comprehensive insights into the regulatory mechanisms of lncRNA in alkaline-salt stress tolerance in rice

BACKGROUND

Alkaline-salt is one of the abiotic stresses that slows plant growth and developmental processes and threatens crop yield. Long non-coding RNAs (lncRNAs) are endogenous RNA found in plants that engage in a variety of cellular functions and stress responses.

METHOD

lncRNAs act as competing endogenous RNAs (ceRNA) and constitute a new set of gene control. The precise regulatory mechanism by which lncRNAs function as ceRNAs in response to alkaline-salt stress remains unclear. We identified alkaline-salt responsive lncRNAs using transcriptome-wide analysis of two varieties including alkaline-salt tolerant [WD20342 (WD)] and alkaline-salt sensitive [Caidao (CD)] rice cultivar under control and alkaline-salt stress treated [WD20342 (WDT, and Caidao (CDT)] conditions.

RESULTS

Investigating the competitive relationships between mRNAs and lncRNAs, we next built a ceRNA network involving lncRNAs based on the ceRNA hypothesis. Expression profiles revealed that a total of 65, 34, and 1549 differentially expressed (DE) lncRNAs, miRNAs, and mRNAs were identified in alkaline-salt tolerant WD (Control) vs. WDT (Treated). Similarly, 75 DE-lncRNAs, 34 DE-miRNAs, and 1725 DE-mRNAs (including up-regulated and down-regulated) were identified in alkaline-salt sensitive CD (Control) vs. CDT (Treated), respectively. An alkaline-salt stress ceRNA network discovered 321 lncRNA-miRNA-mRNA triplets in CD and CDT, with 32 lncRNAs, 121 miRNAs, and 111 mRNAs. Likewise, 217 lncRNA-miRNA-mRNA triplets in WD and WDT revealed the NONOSAT000455-osa_miR5809b-LOC_Os11g01210 triplet with the highest degree as a hub node with the most significant positive correlation in alkaline-salt stress response.

CONCLUSION

The results of our investigation indicate that osa-miR5809b is dysregulated and plays a part in regulating the defense response of rice against alkaline-salt stress. Our study highlights the regulatory functions of lncRNAs acting as ceRNAs in the mechanisms underlying alkaline-salt resistance in rice.

Role of non-coding RNAs against salinity stress in Oryza species: Strategies and challenges in analyzing miRNAs, tRFs and circRNAs

Salinity is an imbalanced concentration of mineral salts in the soil or water that causes yield loss in salt-sensitive crops. Rice plant is vulnerable to soil salinity stress at seedling and reproductive stages. Different non-coding RNAs (ncRNAs) post-transcriptionally regulate different sets of genes during different developmental stages under varying salinity tolerance levels. While microRNAs (miRNAs) are well known small endogenous ncRNAs, tRNA-derived RNA fragments (tRFs) are an emerging class of small ncRNAs derived from tRNA genes with a demonstrated regulatory role, like miRNAs, in humans but unexplored in plants. Circular RNA (circRNA), another ncRNA produced by back-splicing events, acts as target mimics by preventing miRNAs from binding with their target mRNAs, thereby reducing the miRNA's action upon its target. Same may hold true between circRNAs and tRFs. Hence, the work done on these ncRNAs was reviewed and no reports were found for circRNAs and tRFs under salinity stress in rice, either at seedling or reproductive stages. Even the reports on miRNAs are restricted to seedling stage only, in spite of severe effects on rice crop production due to salt stress during reproductive stage. Moreover, this review sheds light on strategies to predict and analyze these ncRNAs in an effective manner.

Effects of differentially expressed microRNAs induced by rootstocks and silicon on improving chilling tolerance of cucumber seedlings (Cucumis sativus L.)

BACKGROUND

Rootstocks can improve the chilling tolerance of grafted cucumbers, but their effectiveness varies. Rootstocks with strong de-blooming capacity may result in lower chilling tolerance of grafted cucumbers compared to those with weak de-blooming capacity, while also reducing the silicon absorption. However, it remains unclear whether this reduction in chilling tolerance is due to differences in rootstock genotypes or the reduction in silicon absorption.

RESULTS

The chilling tolerance of cucumber seedlings was improved by using rootstocks and silicon nutrition. Rootstocks had a more significant effect than silicon nutrition, and the weak de-blooming rootstock 'Yunnan figleaf gourd' was superior to the strong de-blooming rootstock 'Huangchenggen No. 2'. Compared to self-rooted cucumber, twelve miRNAs were regulated by two rootstocks, including seven identical miRNAs (novel-mir23, novel-mir26, novel-mir30, novel-mir37, novel-mir46, miR395a and miR398a-3p) and five different miRNAs (novel-mir32, novel-mir38, novel-mir65, novel-mir78 and miR397a). Notably, four of these miRNAs (novel-mir38, novel-mir65, novel-mir78 and miR397a) were only identified in 'Yunnan figleaf gourd'-grafted cucumbers. Furthermore, six miRNAs (miR168a-5p, miR390a-5p, novel-mir26, novel-mir55, novel-mir67 and novel-mir70) were found to be responsive to exogenous silicon. Target gene prediction for 20 miRNAs resulted in 520 genes. Functional analysis of these target genes showed that 'Yunnan figleaf gourd' improves the chilling tolerance of cucumber by regulating laccase synthesis and sulfate metabolism, while 'Huangchenggen No. 2' and exogenous silicon reduced chilling stress damage to cucumber by regulating ROS scavenging and protein protection, respectively.

CONCLUSION

Among the identified miRNAs, novel-mir46 and miR398a-3p were found in cucumbers in response to chilling stress and two types of rootstocks. However, no identical miRNAs were identified in response to chilling stress and silicon. In addition, the differential expression of novel-mir38, novel-mir65, novel-mir78 and miR397a may be one of the important reasons for the differences in chilling tolerance of grafted cucumbers caused by two types of rootstocks.

Whole-Transcriptome Sequencing Reveals a ceRNA Regulatory Network Associated with the Process of Periodic Albinism under Low Temperature in Baiye No. 1 (Camellia sinensis)

The young shoots of the tea plant Baiye No. 1 display an albino phenotype in the early spring under low environmental temperatures, and the leaves re-green like those of common tea cultivars during the warm season. Periodic albinism is precisely regulated by a complex gene network that leads to metabolic differences and enhances the nutritional value of tea leaves. Here, we identified messenger RNAs (mRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and microRNAs (miRNAs) to construct competing endogenous RNA (ceRNA) regulatory networks. We performed whole-transcriptome sequencing of 12 samples from four periods (Bud, leaves not expanded; Alb, albino leaves; Med, re-greening leaves; and Gre, green leaves) and identified a total of 6325 differentially expressed mRNAs (DEmRNAs), 667 differentially expressed miRNAs (DEmiRNAs), 1702 differentially expressed lncRNAs (DElncRNAs), and 122 differentially expressed circRNAs (DEcircRNAs). Furthermore, we constructed ceRNA networks on the basis of co-differential expression analyses which comprised 112, 35, 38, and 15 DEmRNAs, DEmiRNAs, DElncRNAs, and DEcircRNAs, respectively. Based on the regulatory networks, we identified important genes and their interactions with lncRNAs, circRNAs, and miRNAs during periodic albinism, including the ceRNA regulatory network centered on miR5021x, the GAMYB-miR159-lncRNA regulatory network, and the NAC035-miR319x-circRNA regulatory network. These regulatory networks might be involved in the response to cold stress, photosynthesis, chlorophyll synthesis, amino acid synthesis, and flavonoid accumulation. Our findings provide novel insights into ceRNA regulatory mechanisms involved in Baiye No. 1 during periodic albinism and will aid future studies of the molecular mechanisms underlying albinism mutants.

Combined lncRNA and mRNA Expression Profiles Identified the lncRNA–miRNA–mRNA Modules Regulating the Cold Stress Response in Ammopiptanthus nanus

Long non-coding RNAs (lncRNAs) have been shown to play critical regulatory roles in plants. Ammopiptanthus nanus can survive under severe low-temperature stress, and lncRNAs may play crucial roles in the gene regulation network underlying the cold stress response in A. nanus. To investigate the roles of lncRNAs in the cold stress response of A. nanus, a combined lncRNA and mRNA expression profiling under cold stress was conducted. Up to 4890 novel lncRNAs were identified in A. nanus and 1322 of them were differentially expressed under cold stress, including 543 up-regulated and 779 down-regulated lncRNAs. A total of 421 lncRNAs were found to participate in the cold stress response by forming lncRNA–mRNA modules and regulating the genes encoding the stress-related transcription factors and enzymes in a cis-acting manner. We found that 31 lncRNAs acting as miRNA precursors and 8 lncRNAs acting as endogenous competitive targets of miRNAs participated in the cold stress response by forming lncRNA–miRNA–mRNA regulatory modules. In particular, a cold stress-responsive lncRNA, TCONS00065739, which was experimentally proven to be an endogenous competitive target of miR530, contributed to the cold stress adaptation by regulating TZP in A. nanus. These results provide new data for understanding the biological roles of lncRNAs in response to cold stress in plants.

Genome-wide identification and characterization of tissue-specific non-coding RNAs in black pepper (Piper nigrum L.)

Long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) are the two classes of non-coding RNAs (ncRNAs) present predominantly in plant cells and have various gene regulatory functions at pre- and post-transcriptional levels. Previously deemed as "junk", these ncRNAs have now been reported to be an important player in gene expression regulation, especially in stress conditions in many plant species. Black pepper, scientifically known as Piper nigrum L., despite being one of the most economically important spice crops, lacks studies related to these ncRNAs. From a panel of 53 RNA-Seq datasets of black pepper from six tissues, namely, flower, fruit, leaf, panicle, root, and stem of six black pepper cultivars, covering eight BioProjects across four countries, we identified and characterized a total of 6406 lncRNAs. Further downstream analysis inferred that these lncRNAs regulated 781 black pepper genes/gene products via miRNA-lncRNA-mRNA network interactions, thus working as competitive endogenous RNAs (ceRNAs). The interactions may be various mechanisms like miRNA-mediated gene silencing or lncRNAs acting as endogenous target mimics (eTMs) of the miRNAs. A total of 35 lncRNAs were also identified to be potential precursors of 94 miRNAs after being acted upon by endonucleases like Drosha and Dicer. Tissue-wise transcriptome analysis revealed 4621 circRNAs. Further, miRNA-circRNA-mRNA network analysis showed 432 circRNAs combining with 619 miRNAs and competing for the binding sites on 744 mRNAs in different black pepper tissues. These findings can help researchers to get a better insight to the yield regulation and responses to stress in black pepper in endeavor of higher production and improved breeding programs in black pepper varieties.

Genome-wide analysis of long non-coding RNAs in sugar beet (Beta vulgaris L.) under drought stress

Drought stress is one of the most severe abiotic stresses that restrict global crop production. Long non-coding RNAs (lncRNAs) have been proved to play a key role in response to drought stress. However, genome-wide identification and characterization of drought-responsive lncRNAs in sugar beet is still lacking. Thus, the present study focused on analyzing lncRNAs in sugar beet under drought stress. We identified 32017 reliable lncRNAs in sugar beet by strand-specific high-throughput sequencing. A total of 386 differentially expressed lncRNAs (DElncRNAs) were found under drought stress. The most significantly upregulated and downregulated lncRNAs were TCONS_00055787 (upregulated by more than 6000 fold) and TCONS_00038334 (downregulated by more than 18000 fold), respectively. Quantitative real-time PCR results exhibited a high concordance with RNA sequencing data, which conformed that the expression patterns of lncRNAs based on RNA sequencing were highly reliable. In addition, we predicted 2353 and 9041 transcripts that were estimated to be the cis- and trans-target genes of the drought-responsive lncRNAs. As revealed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, the target genes of DElncRNAs were significantly enriched in organelle subcompartment, thylakoid, endopeptidase activity, catalytic activity, developmental process, lipid metabolic process, RNA polymerase activity, transferase activity, flavonoid biosynthesis and several other terms associated with abiotic stress tolerance. Moreover, 42 DElncRNAs were predicted as potential miRNA target mimics. LncRNAs have important effects on plant adaptation to drought conditions through the interaction with protein-encoding genes. The present study leads to greater insights into lncRNA biology and offers candidate regulators for improving the drought tolerance of sugar beet cultivars at the genetic level.

Wheat Long Noncoding RNAs from Organelle and Nuclear Genomes Carry Conserved microRNA Precursors Which May Together Comprise Intricate Networks in Insect Responses

Long noncoding RNAs (lncRNAs) are a diverse class of noncoding RNAs that are typically longer than 200 nucleotides but lack coding potentials. Advances in deep sequencing technologies enabled a better exploration of this type of noncoding transcripts. The poor sequence conservation, however, complicates the identification and annotation of lncRNAs at a large scale. Wheat is among the leading food staples worldwide whose production is threatened by both biotic and abiotic stressors. Here, we identified putative lncRNAs from durum wheat varieties that differ in stem solidness, a major source of defense against wheat stem sawfly, a devastating insect pest. We also analyzed and annotated lncRNAs from two bread wheat varieties, resistant and susceptible to another destructive pest, orange wheat blossom midge, with and without infestation. Several putative lncRNAs contained potential precursor sequences and/or target regions for microRNAs, another type of regulatory noncoding RNAs, which may indicate functional networks. Interestingly, in contrast to lncRNAs themselves, microRNAs with potential precursors within the lncRNA sequences appeared to be highly conserved at the sequence and family levels. We also observed a few putative lncRNAs that have perfect to near-perfect matches to organellar genomes, supporting the recent observations that organellar genomes may contribute to the noncoding transcript pool of the cell.

Transcriptomics integrated with widely targeted metabolomics reveals the cold resistance mechanism in Hevea brasiliensis

The rubber tree is the primary source of natural rubber and is mainly cultivated in Southeast Asian countries. Low temperature is the major abiotic stress affecting the yield of the rubber tree. Therefore, uncovering the cold resistance mechanism in the rubber tree is necessary. The present study used RNA-sequencing technology and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to analyze the transcriptomic and metabolomic changes in two rubber tree clones with different cold resistance capacities (temperature-sensitive Reyan 8-79 and cold-resistant Yunyan 77-4) at 0 h, 2 h, 6 h, and 20 h of exposure to 4°C. Independent analysis of the transcriptome and metabolitome showed that under prolonged low-temperature treatment, Yunyan 77-4 expressed more genes involved in regulating enzyme activity, changing cell permeability, and synthesizing significant metabolites, such as flavonoids and amino acids, than Reyan 8-79. The KEGG annotation and enrichment analysis identified arginine metabolism and biosynthesis of flavonoids as the major pathway associated with cold resistance. Integrated transcriptome and metabolome analysis showed that the increase in the expression of genes modulated flavonoid biosynthesis, arginine biosynthesis, and anthocyanins biosynthesis, resulting in higher levels of metabolites, such as naringenin chalcone, apigenin, dihydroquercetin, cyanidin 3-glucoside, L-arginosuccinate, N-acetyl-ornithine, ornithine, and N-acetyl-glutamate, in Yunyan 77-4 than in Reyan 8-79 after prolonged low-temperature treatment. Phylogenetic analysis identified the genes, such as CHS (gene356) and F3H (gene33147) of flavonoid biosynthesis and NAGS (gene16028, gene33765), ArgC (gene2487), and ASS (gene6161) of arginine biosynthesis were the key genes involved in the cold resistant of rubber tree. Thus, the present study provides novel insights into how rubber clones resist cold and is a valuable reference for cold-resistance breeding.

LncRNAs elevate plant adaptation under low temperature by maintaining local chromatin landscape

Epigenetic regulation is one of the most precise and subtle ways of gene regulation, including DNA modification, histone modification, RNA modification, histone variants, chromatin remodeling, and long non-coding RNAs (lncRNAs). Chromatin modification is the most basic type of epigenetic regulation, which plays a key role in a myriad of developmental and physiological processes that have been thoroughly studied. These modifications are usually completed by a series of conserved chromatin modification complexes in eukaryotes. In recent years, a series of lncRNAs in organisms also have been described as having irreplaceable functions in biological environment adaptation, especially in biotic and abiotic stresses. Moreover, these molecules form a sophisticated regulatory network through mutual cross-regulation to achieve quantitative expression of key environmental response genes to external signals. For instance, the function of lncRNAs will directly or indirectly depend on the function of the chromatin modification complex. In this review, we mainly focus on chromatin modification, lncRNA, and their coordination mechanism to achieve the high adaptability of plants in low-temperature environments. We highlight recent findings and insights into lncRNA-mediated local chromatin environment changes during plant growth under low temperature via chromatin modification complexes, including target gene specificity for different lncRNA.

LncRNA-mediated ceRNA regulatory network provides new insight into chlorogenic acid synthesis in sweet potato

Sweet potato (Ipomoea batatas L.) is considered a highly nutritional and economical crop due to its high contents of bioactive substances, such as anthocyanin and chlorogenic acid (CGA), especially in leaves and stems. The roles of noncoding RNAs (ncRNA), including long noncoding RNA (lncRNA) and microRNA (miRNA), in CGA synthesis, are still unknown. In this study, the differentially expressed (DE) mRNAs, miRNAs, and lncRNAs in two leafy vegetable genotypes "FS7-6-14-7" (high CGA content) and "FS7-6" (low CGA content) were identified. The cis-regulation between lncRNA and mRNA was analyzed. Then, the CGA synthesis-related modules MEBlue and MEYellow were identified to detect trans-regulation mRNA-lncRNA pairs. The GO and KEGG annotations suggested that mRNA in these two modules was significantly enriched in the secondary metabolite synthesis biosynthesis category. A competing endogenous RNAs (ceRNA) network, including 8730 miRNA-mRNA and 444 miRNA-lncRNA pairs, was constructed by DEmiRNA target prediction. Then, a CGA synthesis-related ceRNA network was obtained with lncRNA and mRNA from MEBlue and MEYellow. Finally, one relational pair, MSTRG.47662.1/mes-miR398/itb04g00990, was selected for functional validation. Overexpression of lncRNA MSTRG.47662.1 and mRNA itb04g00990 increased CGA content in both tobacco and sweet potato callus, while overexpression of miRNA mes-miR398 decreased CGA content. Meanwhile, regression analysis of the expression patterns demonstrated that MSTRG.47662.1, acting as a ceRNA, promoted itb04g00990 expression by competitively binding mes-miR398 in CGA synthesis in sweet potato. Our results provide insights into how ncRNA-mediated ceRNA regulatory networks likely contribute to CGA synthesis in leafy sweet potato.

Identification of long non-coding RNA-microRNA-mRNA regulatory modules and their potential roles in drought stress response in wheat (Triticum aestivum L.)

Drought is one of the most severe abiotic stresses that influence wheat production across the globe. Understanding the molecular regulatory network of wheat in response to drought is of great importance in molecular breeding. Noncoding RNAs influence plant development and resistance to abiotic stresses by regulating gene expression. In this study, whole-transcriptome sequencing was performed on the seedlings of two wheat varieties with contrasting levels of drought tolerance under drought and control conditions to identify long noncoding RNAs (lncRNAs), micro RNAs (miRNAs), and mRNAs related to drought stress and explore the potential lncRNA-miRNA-mRNA regulatory modules in controlling wheat drought stress response. A total of 1515 differentially expressed lncRNAs (DELs), 209 differentially expressed miRNAs (DEMs), and 20462 differentially expressed genes (DEGs) were identified. Of the 20462 DEGs, 1025 were identified as potential wheat drought resistance-related DEGs. Based on the regulatory relationship and expression patterns of DELs, DEMs, and DEGs, 10 DEL-DEM-DEG regulatory modules related to wheat drought stress response were screened, and preliminary expression verification of two important candidate modules was performed. Our results revealed the possible roles of lncRNA-miRNA-mRNA modules in regulatory networks related to drought tolerance and provided useful information as valuable genomic resources in molecular breeding of wheat.

Identification of long non-coding RNAs involved in floral scent of Rosa hybrida

Long non-coding RNAs (lncRNAs) were found to play important roles in transcriptional, post-transcriptional, and epigenetic gene regulation in various biological processes. However, lncRNAs and their regulatory roles remain poorly studied in horticultural plants. Rose is economically important not only for their wide use as garden and cut flowers but also as important sources of natural fragrance for perfume and cosmetics industry, but presently little was known about the regulatory mechanism of the floral scent production. In this paper, a RNA-Seq analysis with strand-specific libraries, was performed to rose flowers in different flowering stages. The scented variety 'Tianmidemeng' (Rosa hybrida) was used as plant material. A total of 13,957 lncRNAs were identified by mining the RNA-Seq data, including 10,887 annotated lncRNAs and 3070 novel lncRNAs. Among them, 10,075 lncRNAs were predicted to possess a total of 29,622 target genes, including 54 synthase genes and 24 transcription factors related to floral scent synthesis. 425 lncRNAs were differentially expressed during the flowering process, among which 19 were differentially expressed among all the three flowering stages. Using weighted correlation network analysis (WGCNA), we correlate the differentially-expressed lncRNAs to synthesis of individual floral scent compounds. Furthermore, regulatory function of one of candidate lncRNAs for floral scent synthesis was verified using VIGS method in the rose. In this study, we were able to show that lncRNAs may play important roles in floral scent production in the rose. This study also improves our understanding of how plants regulate their secondary metabolism by lncRNAs.

MicroRNA398: A Master Regulator of Plant Development and Stress Responses

MicroRNAs (miRNAs) play crucial roles in plant development and stress responses, and a growing number of studies suggest that miRNAs are promising targets for crop improvement because they participate in the regulation of diverse, important agronomic traits. MicroRNA398 (miR398) is a conserved miRNA in plants and has been shown to control multiple stress responses and plant growth in a variety of species. There are many studies on the stress response and developmental regulation of miR398. To systematically understand its function, it is necessary to summarize the evolution and functional roles of miR398 and its target genes. In this review, we analyze the evolution of miR398 in plants and outline its involvement in abiotic and biotic stress responses, in growth and development and in model and non-model plants. We summarize recent functional analyses, highlighting the role of miR398 as a master regulator that coordinates growth and diverse responses to environmental factors. We also discuss the potential for fine-tuning miR398 to achieve the goal of simultaneously improving plant growth and stress tolerance.

Identification and Characterization of Long Non-coding RNA in Tomato Roots Under Salt Stress

As one of the most important vegetable crops in the world, the production of tomatoes was restricted by salt stress. Therefore, it is of great interest to analyze the salt stress tolerance genes. As the non-coding RNAs (ncRNAs) with a length of more than 200 nucleotides, long non-coding RNAs (lncRNAs) lack the ability of protein-coding, but they can play crucial roles in plant development and response to abiotic stresses by regulating gene expression. Nevertheless, there are few studies on the roles of salt-induced lncRNAs in tomatoes. Therefore, we selected wild tomato Solanum pennellii (S. pennellii) and cultivated tomato M82 to be materials. By high-throughput sequencing, 1,044 putative lncRNAs were identified here. Among them, 154 and 137 lncRNAs were differentially expressed in M82 and S. pennellii, respectively. Through functional analysis of target genes of differentially expressed lncRNAs (DE-lncRNAs), some genes were found to respond positively to salt stress by participating in abscisic acid (ABA) signaling pathway, brassinosteroid (BR) signaling pathway, ethylene (ETH) signaling pathway, and anti-oxidation process. We also construct a salt-induced lncRNA-mRNA co-expression network to dissect the putative mechanisms of high salt tolerance in S. pennellii. We analyze the function of salt-induced lncRNAs in tomato roots at the genome-wide levels for the first time. These results will contribute to understanding the molecular mechanisms of salt tolerance in tomatoes from the perspective of lncRNAs.

Genetic Mechanisms of Cold Signaling in Wheat (Triticum aestivum L.)

Cold stress is a major environmental factor affecting the growth, development, and productivity of various crop species. With the current trajectory of global climate change, low temperatures are becoming more frequent and can significantly decrease crop yield. Wheat (Triticum aestivum L.) is the first domesticated crop and is the most popular cereal crop in the world. Because of a lack of systematic research on cold signaling pathways and gene regulatory networks, the underlying molecular mechanisms of cold signal transduction in wheat are poorly understood. This study reviews recent progress in wheat, including the ICE-CBF-COR signaling pathway under cold stress and the effects of cold stress on hormonal pathways, reactive oxygen species (ROS), and epigenetic processes and elements. This review also highlights possible strategies for improving cold tolerance in wheat.

Using the Knowledge of Post-transcriptional Regulations to Guide Gene Selections for Molecular Breeding in Soybean

The omics approaches allow the scientific community to successfully identify genomic regions associated with traits of interest for marker-assisted breeding. Agronomic traits such as seed color, yield, growth habit, and stress tolerance have been the targets for soybean molecular breeding. Genes governing these traits often undergo post-transcriptional modifications, which should be taken into consideration when choosing elite genes for molecular breeding. Post-transcriptional regulations of genes include transcript regulations, protein modifications, and even the regulation of the translational machinery. Transcript regulations involve elements such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) for the maintenance of transcript stability or regulation of translation efficiency. Protein modifications involve molecular modifications of target proteins and the alterations of their interacting partners. Regulations of the translational machinery include those on translation factors and the ribosomal protein complex. Post-transcriptional regulations usually involve a set of genes instead of a single gene. Such a property may facilitate molecular breeding. In this review, we will discuss the post-transcriptional modifications of genes related to favorable agronomic traits such as stress tolerance, growth, and nutrient uptake, using examples from soybean as well as other crops. The examples from other crops may guide the selection of genes for marker-assisted breeding in soybean.

Integrated analysis of the lncRNA/circRNA-miRNA-mRNA expression profiles reveals novel insights into potential mechanisms in response to root-knot nematodes in peanut

Background

Peanut is the most essential oil and food crop globally due to its high oil and protein content. Root-knot nematode infects peanut roots, causing poor development and severely limiting peanut yields worldwide. The discovery of peanut genome identified a considerable number of genetic loci controlling the peanut root-knot nematode; however, the molecular mechanism of root-knot nematode remains unknown.

Results

The heterogeneous response to root-knot nematode stress in peanut roots was identified using whole-transcriptome RNA-seq. A total of 430 mRNAs, 111 miRNAs, 4453 lncRNAs, and 123 circRNAs were found to have differential expression between infected and non-infected peanuts. The expression profiles of the lncRNA/circRNA-miRNA-mRNA network were developed to understand the potential pathways that lead to root-knot nematodes in peanut roots. During root-knot nematodes stress, a total of 10 lncRNAs, 4 circRNAs, 5 miRNAs, and 13 mRNAs can create competing endogenous RNA and participate in the oxidation–reduction process as well as other biological metabolism processes in peanuts. The findings will highlight the role of peanut ceRNAs in response to root-knot nematodes.

Conclusion

The GO classification and KEGG pathway enrichment study of core regulatory networks revealed that ceRNAs are involved in oxidation–reduction, peroxidase activity, lignin synthesis in the xylem, and flavonoid synthesis. Overall, these findings may help researchers better understand the role of non-coding RNAs in response to root-knot nematodes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08470-3.

Identification and characterization of heat-responsive lncRNAs in maize inbred line CM1

BACKGROUND

Frequent occurrence of extreme high temperature is a major threat to crop production. Increasing evidence demonstrates that long non-coding RNAs (lncRNAs) have important biological functions in the regulation of the response to heat stress. However, the regulatory mechanism of lncRNAs involved in heat response requires further exploration and the regulatory network remains poorly understood in maize.

RESULTS

In this research, high-throughput sequencing was adopted to systematically identify lncRNAs in maize inbred line CM1. In total, 53,249 lncRNAs (259 known lncRNAs and 52,990 novel lncRNAs) were detected, of which 993 lncRNAs showed significantly differential expression (DElncRNAs) under heat stress. By predicting the target genes, 953 common targets shared by cis- and trans-regulation of the DElncRNAs were identified, which exhibited differential expression between the control and the heat stress treatments. Functional annotation indicated that a number of important biological processes and pathways, including photosynthesis, metabolism, translation, stress response, hormone signal transduction, and spliceosome, were enriched for the common targets, suggesting that they play important roles in heat response. A lncRNA-mediated regulatory network was constructed to visualize the molecular response mechanism in response to heat stress, which represented the direct regulatory relationships of DElncRNAs, differentially expressed miRNAs, target genes, and functional annotations.

CONCLUSIONS

This study lays a foundation for further elucidation of the regulatory mechanism for the response to heat stress in the maize inbred line CM1. The findings provide important information for identification of heat-responsive genes, which will be beneficial for the molecular breeding in the cultivation of heat-tolerant maize germplasm.

Genome-Wide Identification and Analysis of bZIP Gene Family and Resistance of TaABI5 (TabZIP96) under Freezing Stress in Wheat (Triticum aestivum)

The basic leucine zipper (bZIP) regulates plant growth and responds to stress as a key transcription factor of the Abscisic acid (ABA) signaling pathway. In this study, TabZIP genes were identified in wheat and the gene structure, physicochemical properties, cis-acting elements, and gene collinearity were analyzed. RNA-Seq and qRT-PCR analysis showed that ABA and abiotic stress induced most TabZIP genes expression. The ectopic expression of TaABI5 up-regulated the expression of several cold-responsive genes in Arabidopsis. Physiological indexes of seedlings of different lines under freezing stress showed that TaABI5 enhanced the freezing tolerance of plants. Subcellular localization showed that TaABI5 is localized in the nucleus. Furthermore, TaABI5 physically interacted with cold-resistant transcription factor TaICE1 in yeast two-hybrid system. In conclusion, this study identified and analyzed members of the TabZIP gene family in wheat. It proved for the first time that the gene TaABI5 affected the cold tolerance of transgenic plants and was convenient for us to understand the cold resistance molecular mechanism of TaABI5. These results will provide a new inspiration for further study on improving plant abiotic stress resistance.

tae-miR399-UBC24 Module Enhances Freezing Tolerance in Winter Wheat via a CBF Signaling Pathway

Although the regulation of Pi homeostasis by miR399 has been studied in various plant species, its underlying molecular mechanism in response to freezing stress is still poorly understood. In this work, we found that the expression of tae-miR399 and its target gene TaUBC24 in the tillering nodes of the strong cold-resistant winter wheat cultivar Dongnongdongmai1 (Dn1) was not only significantly altered after severe winters but also responsive to short-term freezing stress. TaUBC24 physically interacted with TaICE1. Enhanced freezing tolerance was observed for tae-miR399-overexpressing Arabidopsis lines. Under freezing stress, overexpression of tae-miR399 ultimately decreased the expression of AtUBC24, inhibiting the degradation of AtICE1, which increased the expression of genes involved in the CBF signaling pathway and starch metabolism and promoted the activities of antioxidant enzymes. These results will improve our understanding of the molecular mechanism through which the miR399-UBC24 module plays a cardinal role in regulating plant freezing stress tolerance through mediation of downstream pathways.

Expression Patterns of miR398, miR167, and miR159 in the Interaction between Bread Wheat (Triticum aestivum L.) and Pathogenic Fusarium culmorum and Beneficial Trichoderma Fungi

Bread wheat (Triticum aestivum L.) is an agronomically significant cereal cultivated worldwide. Wheat breeding is limited by numerous abiotic and biotic stresses. One of the most deleterious factors is biotic stress provoked by the Fusarium culmorum fungus. This pathogen is a causative agent of Fusarium root rot and Fusarium head blight. Beneficial fungi Trichoderma atroviride and T. cremeum are strong antagonists of mycotoxigenic Fusarium spp. These fungi promote plant growth and enhance their tolerance of negative environmental conditions. The aim of the study was to determine and compare the spatial (in above- and underground organs) and temporal (early: 6 and 22 hpi; and late: 5 and 7 dpi reactions) expression profiles of three mature miRNAs (miR398, miR167, and miR159) in wheat plants inoculated with two strains of F. culmorum (KF846 and EW49). Moreover, the spatial expression patterns in wheat response between plants inoculated with beneficial T. atroviride (AN35) and T. cremeum (AN392) were assessed. Understanding the sophisticated role of miRNAs in wheat-fungal interactions may initiate a discussion concerning the use of this knowledge to protect wheat plants from the harmful effects of fungal pathogens. With the use of droplet digital PCR (ddPCR), the absolute quantification of the selected miRNAs in the tested material was carried out. The differential accumulation of miR398, miR167, and miR159 in the studied groups was observed. The abundance of all analyzed miRNAs in the roots demonstrated an increase in the early and reduction in late wheat response to F. culmorum inoculation, suggesting the role of these particles in the initial wheat reaction to the studied fungal pathogen. The diverse expression patterns of the studied miRNAs between Trichoderma-inoculated or F. culmorum-inoculated plants and control wheat, as well as between Trichoderma-inoculated and F. culmorum-inoculated plants, were noticed, indicating the need for further analysis.

LncRNA TCONS_00021861 is functionally associated with drought tolerance in rice (Oryza sativa L.) via competing endogenous RNA regulation

BACKGROUND

Water deficit is an abiotic stress that retards plant growth and destabilizes crop production. Long non coding RNAs (lncRNAs) are a class of non-coding endogenous RNAs that participate in diverse cellular processes and stress responses in plants. lncRNAs could function as competing endogenous RNAs (ceRNA) and represent a novel layer of gene regulation. However, the regulatory mechanism of lncRNAs as ceRNA in drought stress response is yet unclear.

RESULTS

In this study, we performed transcriptome-wide identification of drought-responsive lncRNAs in rice. Thereafter, we constructed a lncRNA-mediated ceRNA network by analyzing competing relationships between mRNAs and lncRNAs based on ceRNA hypothesis. A drought responsive ceRNA network with 40 lncRNAs, 23 miRNAs and 103 mRNAs was obtained. Network analysis revealed TCONS_00021861/miR528-3p/YUCCA7 regulatory axis as a hub involved in drought response. The miRNA-target expression and interaction were validated by RT-qPCR and RLM-5'RACE. TCONS_00021861 showed significant positive correlation (r = 0.7102) with YUCCA7 and negative correlation with miR528-3p (r = -0.7483). Overexpression of TCONS_00021861 attenuated the repression of miR528-3p on YUCCA7, leading to increased IAA (Indole-3-acetic acid) content and auxin overproduction phenotypes.

CONCLUSIONS

TCONS_00021861 could regulate YUCCA7 by sponging miR528-3p, which in turn activates IAA biosynthetic pathway and confer resistance to drought stress. Our findings provide a new perspective of the regulatory roles of lncRNAs as ceRNAs in drought resistance of rice.

Integrated study of circRNA, lncRNA, miRNA, and mRNA networks in mediating the effects of testicular heat exposure

The World Health Organization has recognized that testicular function is temperature dependent. Testicular heat exposure caused by occupational factors, lifestyle, and clinical diseases can lead to different degrees of reproductive problems. The aim of this study was to reveal the transcriptional regulatory network and its potential crucial roles in mediating the effects of testicular heat exposure. Testicular tissue was collected from a group of mice subjected to scrotal heat exposure as well as a control group. RNA was isolated from both groups and used for high-throughput sequencing. Using differential transcriptome expression analysis, 172 circRNAs, 279 miRNAs, 465 lncRNAs, and 2721 mRNAs were identified as significantly differentially expressed in mouse testicular tissue after heat exposure compared with the control group. Through Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, differentially expressed lncRNAs and mRNAs were found to have potentially important functions in meiotic cell cycle (GO:0051321), cytoplasm (GO:0005737), membrane raft (GO:0045121), MAPK signaling (mmu04010), purine metabolism (mmu00230), and homologous recombination (mmu03440). Some of the most upregulated and downregulated lncRNAs and circRNAs were predicted to be associated with numerous miRNAs and mRNAs through competing endogenous RNA regulatory network analysis, which were validated with molecular biology experiments. This research provides high-throughput sequencing data of a testicular heat exposure model and lays the foundation for further study on circRNAs, miRNAs, and lncRNAs that are involved in male reproductive diseases related to elevated testicular temperature.

Interplay between miRNAs and lncRNAs: Mode of action and biological roles in plant development and stress adaptation

Plants employ sophisticated mechanisms to control developmental processes and to cope with environmental changes at transcriptional and post-transcriptional levels. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs), two classes of endogenous noncoding RNAs, are key regulators of gene expression in plants. Recent studies have identified the interplay between miRNAs and lncRNAs as a novel regulatory layer of gene expression in plants. On one hand, miRNAs target lncRNAs for the production of phased small interfering RNAs (phasiRNAs). On the other hand, lncRNAs serve as origin of miRNAs or regulate the accumulation or activity of miRNAs at transcription and post-transcriptional levels. Theses lncRNA-miRNA interplays are crucial for plant development, physiology and responses to biotic and abiotic stresses. In this review, we summarize recent advances in the biological roles, interaction mechanisms and computational predication methods of the interplay between miRNAs and lncRNAs in plants.

Regulatory Network of Preharvest Sprouting Resistance Revealed by Integrative Analysis of mRNA, Noncoding RNA, and DNA Methylation in Wheat

Preharvest sprouting (PHS) of grain occurs universally and sharply decreases grain quality and yield, but the mechanism remains unclear. MingXian169, a breeding inducer wheat for stripe rust, is widely used in the Huanghuai wheat-producing region, China. In this study, we found that MingXian169 could be considered an ideal material for PHS research because of its high PHS resistance. To further analyze the network of PHS, transcriptome sequencing of mRNA, noncoding RNA (ncRNA), and DNA methylome data were used to comparison germination seeds (GS) and dormant seeds (DS); 3027, 1516, and 22 genes and 95 103 methylation regions were identified as differentially expressed mRNA, DE-microRNAs (DE-miRNA), DE-long noncoding RNAs (DE-lncRNA), and differentially methylated regions (DMRs). Pathway enrichment tests highlighted plant hormone biosynthesis and signal transduction, glutathione-ascorbate metabolism, and starch and sucrose metabolism processes related to PHS mechanisms. Further analysis demonstrated that long noncoding RNA, miRNA, and DNA methylation played critical roles in transcriptional regulation of critical pathways during PHS by modifying and interacting with target genes. Quantitative real-time polymerase chain reaction (PCR) analyses of mRNA and miRNA confirmed the sequencing results. In the phytohormone content assay, abscisic acid (ABA) and jasmonic acid (JA) increased significantly in DS, and GA19 increased in GS. The ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), and β-d-glucosidase (BGLU) enzyme activities and the substance content of glutathione and sucrose were significantly higher in GS than in DS, implying that they were responsible for increasing PHS in MingXian169. Our results provide new insights into wheat PHS resistance at mRNA, ncRNA, and DNA methylation levels, with suggestions for crop breeding and production.