Transcriptome Profile Analysis of Arabidopsis Reveals the Drought Stress-Induced Long Non-coding RNAs Associated With Photosynthesis, Chlorophyll Synthesis, Fatty Acid Synthesis and Degradation

Effects of exogenous melatonin on drought stress in celery (Apium graveolens L.): unraveling the modulation of chlorophyll and glucose metabolism pathways

Drought, a prevalent abiotic stressor, significantly impacts plant yield and quality. Melatonin (MT), a potent and economical growth regulator, plays a pivotal role in augmenting crop resilience against stress. This study investigated the efficacy of exogenous MT on drought-stressed celery seedlings by comprehensively analyzing phenotypic, physiological, and molecular attributes. The results revealed that exogenous MT mitigated celery seedling damage under drought stress, lowered malondialdehyde (MDA) concentrations, elevated oxidase activities, osmolyte levels, chlorophyll content, and augmented light energy conversion efficiency. Transcriptomic analysis demonstrated that MT could regulate chlorophyll synthesis genes (AgPORA1 and AgDVR2), contributing to heightened photosynthetic potential and increased drought tolerance in celery. Moreover, MT was found to modulate glycolytic pathways, upregulate pyruvate synthesis genes (AgPEP1 and AgPK3), and downregulate degradation genes (AgPDC2 and AgPDHA2), thereby promoting pyruvate accumulation and enhancing peroxidase activity and drought tolerance. The RNA-seq and qRT-PCR analyses demonstrated similar results, showing the same general expression trends. The study elucidates the physiological and molecular mechanisms underlying MT's stress-alleviating effects in celery seedlings, offering insights into MT-based strategies in plant cultivation and breeding for arid environments.

Exploration of GmDof11-lncRNA13082 Module Regulating Oil Synthesis in Plants

Soybean (Glycine max [Linn.] Merr.) is an important oilseed crop. Although transcription factors (TFs) can coordinate the expression of mRNA and lncRNA, their coordination in the soybean oil synthesis pathway remains unclear. This study examined the interaction between the TF GmDof11 and lncRNA13082 and found that overexpression of GmDof11 led to an increase in the number of Arabidopsis seeds, thousand seed weight, crude protein, hydrolysis amino acid, and soluble sugar. Additionally, it reduced the triglyceride and starch contents and affected the proportion of fatty acids, increasing the contents of palmitic acid, stearic acid, and linolenic acid. The yeast two-hybrid experiments revealed that GmDof11 interacts with GmBCCP1, GmLEC1b, and GmFAB2 proteins. In the RT-qPCR analysis of transgenic soybean roots, it was found that GmDof11 can activate the production of lncRNA13082 and work in conjunction with lncRNA13082 to oversee oil synthesis and nutrient storage. Our research provides robust theoretical evidence for a comprehensive resolution of TF-lncRNA regulation in the soybean oil synthesis network.

Transcriptome analysis suggested that lncRNAs regulate rapeseed seedlings in responding to drought stress by coordinating the phytohormone signal transduction pathways

The growth, yield, and seed quality of rapeseed are negatively affected by drought stress. Therefore, it is of great value to understand the molecular mechanism behind this phenomenon. In a previous study, long non-coding RNAs (lncRNAs) were found to play a key role in the response of rapeseed seedlings to drought stress. However, many questions remained unanswered. This study was the first to investigate the expression profile of lncRNAs not only under control and drought treatment, but also under the rehydration treatment. A total of 381 differentially expressed lncRNA and 10,253 differentially expressed mRNAs were identified in the comparison between drought stress and control condition. In the transition from drought stress to rehydration, 477 differentially expressed lncRNAs and 12,543 differentially expressed mRNAs were detected. After identifying the differentially expressed (DE) lncRNAs, the comprehensive lncRNAs-engaged network with the co-expressed mRNAs in leaves under control, drought and rehydration was investigated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of co-expressed mRNAs identified the most significant pathways related with plant hormones (expecially abscisic acid, auxin, cytokinins, and gibberellins) in the signal transduction. The genes, co-expressed with the most-enriched DE-lncRNAs, were considered as the most effective candidates in the water-loss and water-recovery processes, including protein phosphatase 2 C (PP2C), ABRE-binding factors (ABFs), and SMALL AUXIN UP-REGULATED RNAs (SAURs). In summary, these analyses clearly demonstrated that DE-lncRNAs can act as a regulatory hub in plant-water interaction by controlling phytohormone signaling pathways and provided an alternative way to explore the complex mechanisms of drought tolerance in rapeseed.

Elucidating the regulatory role of long non-coding RNAs in drought stress response during seed germination in leaf mustard

Leaf mustard (Brassica juncea L. Czern & Coss), an important vegetable crop, experiences pronounced adversity due to seasonal drought stress, particularly at the seed germination stage. Although there is partial comprehension of drought-responsive genes, the role of long non-coding RNAs (lncRNAs) in adjusting mustard's drought stress response is largely unexplored. In this study, we showed that the drought-tolerant cultivar 'Weiliang' manifested a markedly lower base water potential (-1.073 MPa vs -0.437 MPa) and higher germination percentage (41.2% vs 0%) than the drought-susceptible cultivar 'Shuidong' under drought conditions. High throughput RNA sequencing techniques revealed a significant repertoire of lncRNAs from both cultivars during germination under drought stress, resulting in the identification of 2,087 differentially expressed lncRNAs (DELs) and their correspondingly linked 12,433 target genes. It was noted that 84 genes targeted by DEL exhibited enrichment in the photosynthesis pathway. Gene network construction showed that MSTRG.150397, a regulatory lncRNA, was inferred to potentially modulate key photosynthetic genes (Psb27, PetC, PetH, and PsbW), whilst MSTRG.107159 was indicated as an inhibitory regulator of six drought-responsive PIP genes. Further, weighted gene co-expression network analysis (WGCNA) corroborated the involvement of light intensity and stress response genes targeted by the identified DELs. The precision and regulatory impact of lncRNA were verified through qPCR. This study extends our knowledge of the regulatory mechanisms governing drought stress responses in mustard, which will help strategies to augment drought tolerance in this crop.

Transcriptome Shock in Developing Embryos of a Brassica napus and Brassica rapa Hybrid

Interspecific crosses that fuse the genomes of two different species may result in overall gene expression changes in the hybrid progeny, called 'transcriptome shock'. To better understand the expression pattern after genome merging during the early stages of allopolyploid formation, we performed RNA sequencing analysis on developing embryos of Brassica rapa, B. napus, and their synthesized allotriploid hybrids. Here, we show that the transcriptome shock occurs in the developing seeds of the hybrids. Of the homoeologous gene pairs, 17.1% exhibit expression bias, with an overall expression bias toward B. rapa. The expression level dominance also biases toward B. rapa, mainly induced by the expression change in homoeologous genes from B. napus. Functional enrichment analysis revealed significant differences in differentially expressed genes (DEGs) related to photosynthesis, hormone synthesis, and other pathways. Further study showed that significant changes in the expression levels of the key transcription factors (TFs) could regulate the overall interaction network in the developing embryo, which might be an essential cause of phenotype change. In conclusion, the present results have revealed the global changes in gene expression patterns in developing seeds of the hybrid between B. rapa and B. napus, and provided novel insights into the occurrence of transcriptome shock for harnessing heterosis.

Response patterns of lncRNAs of the Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae under 23 pesticide treatments

The response of Spodoptera frugiperda genes toward insecticides is crucial for guiding insecticide use. The regulation of the S. frugiperda genes via long noncoding RNAs (lncRNAs) under insecticide treatment should be investigated. In this study, 452 differentially expressed lncRNAs were identified by analyzing RNA-sequencing data of S. frugiperda under 23 pesticide treatments. We found 59 and 43 differentially expressed lncRNAs that could regulate detoxification-related cytochrome P450 and UDP-glucuronosyltransferase genes, respectively. Furthermore, the target genes of differentially expressed lncRNAs were enriched in Pfam, including chitin bind 4 and gene ontology terms such as structural constituent of the cuticle, revealing their potential mechanism of action on the growth inhibition of S. frugiperda larvae. Insecticide-specific expression of lncRNAs highlights the properties and commonalities of different insecticide-induced lncRNA regulatory mechanisms. To conclude, the results of this study provide new insights and perspectives on the use of 23 insecticides via lncRNA regulation of mRNAs.

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.

Targeted and untargeted metabolomics reveals deep analysis of drought stress responses in needles and roots of Pinus taeda seedlings

Drought stress is one of major environmental stresses affecting plant growth and yield. Although Pinus taeda trees are planted in rainy southern China, local drought sometime occurs and can last several months, further affecting their growth and resin production. In this study, P. taeda seedlings were treated with long-term drought (42 d), and then targeted and untargeted metabolomics analysis were carried out to evaluate drought tolerance of P. taeda. Targeted metabolomics analysis showed that levels of some sugars, phytohormones, and amino acids significantly increased in the roots and needles of water-stressed (WS) P. taeda seedlings, compared with well-watered (WW) pine seedlings. These metabolites included sucrose in pine roots, the phytohormones abscisic acid and sacylic acid in pine needles, the phytohormone gibberellin (GA4) and the two amino acids, glycine and asparagine, in WS pine roots. Compared with WW pine seedlings, the neurotransmitter acetylcholine significantly increased in needles of WS pine seedlings, but significantly reduced in their roots. The neurotransmitters L-glutamine and hydroxytyramine significantly increased in roots and needles of WS pine seedlings, respectively, compared with WW pine seedlings, but the neurotransmitter noradrenaline significantly reduced in needles of WS pine seedlings. Levels of some unsaturated fatty acids significantly reduced in roots or needles of WS pine seedlings, compared with WW pine seedlings, such as linoleic acid, oleic acid, myristelaidic acid, myristoleic acid in WS pine roots, and palmitelaidic acid, erucic acid, and alpha-linolenic acid in WS pine needles. However, three saturated fatty acids significantly increased in WS pine seedlings, i.e., dodecanoic acid in WS pine needles, tricosanoic acid and heptadecanoic acid in WS pine roots. Untargeted metabolomics analysis showed that levels of some metabolites increased in WS pine seedlings, especially sugars, long-chain lipids, flavonoids, and terpenoids. A few of specific metabolites increased greatly, such as androsin, piceatanol, and panaxatriol in roots and needles of WS pine seedlings. Comparing with WW pine seedlings, it was found that the most enriched pathways in WS pine needles included flavone and flavonol biosynthesis, ABC transporters, diterpenoid biosynthesis, plant hormone signal transduction, and flavonoid biosynthesis; in WS pine roots, the most enriched pathways included tryptophan metabolism, caffeine metabolism, sesquiterpenoid and triterpenoid biosynthesis, plant hormone signal transduction, biosynthesis of phenylalanine, tyrosine, and tryptophan. Under long-term drought stress, P. taeda seedlings showed their own metabolomics characteristics, and some new metabolites and biosynthesis pathways were found, providing a guideline for breeding drought-tolerant cultivars of P. taeda.

Serine Hydroxymethyltransferase 1 Is Essential for Primary-Root Growth at Low-Sucrose Conditions

Plant roots are essential organs for absorbing nutrients from the soil or medium. Sucrose functions as a vital carbon source in root development, and sucrose starvation interferes with the redox state of plant cells. However, the mechanism of root growth at sucrose starvation remains unclear. Here, we report that SHMT1 (serine hydroxymethyltransferase 1) plays a crucial role in primary-root growth. SHMT1 mutation caused decreased sugar levels, excessive H₂O₂ accumulation, and severe root-growth arrest at sucrose-free conditions, whereas plants with SHMT1 overexpression had increased sugar and decreased H₂O₂ levels, and longer primary roots. Sucrose supply fully restored root growth of shm1-2, but CO₂ alone could not, and SHMT1 is much more stable in roots than shoots at sucrose conditions, suggesting that SHMT1 accumulation in roots is critical for sucrose accumulation and root growth. Further ROS scavenging by GSH application or ROS synthesis inhibition by apocynin application or RBOHD mutation reduced H₂O₂ levels and partially restored the root-growth arrest phenotype of shm1-2 at low-sucrose conditions, suggesting that SHMT1 modulates root growth via sucrose-mediated ROS accumulation. Our findings demonstrated the role of SHMT1 in primary-root growth by regulating sucrose accumulation and ROS homeostasis in roots.