PatWRKY71 transcription factor regulates patchoulol biosynthesis and plant defense response.

Patchoulol, a valuable compound belonging to the sesquiterpenoid family, is the primary component of patchouli oil produced by Pogostemon cablin (P. cablin). It has a variety of pharmacological and biological activities and is widely used in the medical and cosmetic industries. However, despite its significance, there is a lack of research on the transcriptional modulation of patchoulol biosynthesis.Salicylic acid (SA), is a vital plant hormone that serves as a critical signal molecule and plays an essential role in plant growth and defense. However, to date, no studies have explored the modulation of patchoulol biosynthesis by SA. In our study, we discovered that the application of SA can enhance the production of patchoulol. Utilizing transcriptome analysis of SA-treated P. cablin, we identified a crucial downstream transcription factor, PatWRKY71. The transcription level of PatWRKY71 was significantly increased with the use of SA. Furthermore, our research has revealed that PatWRKY71 was capable of binding to the promoter of PatPTS, ultimately leading to an increase in its expression. When PatWRKY71 was silenced by a virus, the expression of both PatWRKY71 and PatPTS was reduced, resulting in the down-regulation of patchoulol production. Through our studies, we discovered that heterologous expression of PatWRKY71 leads to an increase in the sensitivity of Arabidopsis to salt and Cd, as well as an outbreak of reactive oxygen species (ROS). Additionally, we uncovered the regulatory role of PatWRKY71 in both patchoulol biosynthesis and plant defense response. This discovery provided a theoretical basis for the improvement of the content of patchoulol and the resistance of P. cablin through genetic engineering.

Aromatic Terpenes and Their Biosynthesis in Dendrobium, and Conjecture on the Botanical Perfumer Mechanism.

This review presents a systematic analysis of the studies on volatiles in Dendrobium. Among the various components, aromatic terpenes are a crucial component in the development of the aromatic characteristics of Dendrobium and other plants. Recent advancements in detection and sequencing technology have resulted in a considerable rise in research on the biosynthetic processes of aromatic terpenes in Dendrobium and other flowering plants. Nevertheless, the inquiry into the precise means by which plants regulate the proportion of diverse aromatic terpenes in their floral scent, thereby preserving their olfactory traits, requires further investigation. A conjecture on the botanical perfumer mechanism, which condensed the findings of earlier studies, was put forward to address this area of interest. Specific transcription factors likely govern the coordinated expression of multiple key terpene synthase (TPS) genes during the flowering stage of plants, thereby regulating the proportional biosynthesis of diverse aromatic terpenes and sustaining the distinctive aromatic properties of individual plants. This review serves as a significant theoretical reference for further investigations into aromatic volatile compounds in Dendrobium.

miR2105 and the kinase OsSAPK10 co-regulate OsbZIP86 to mediate drought-induced ABA biosynthesis in rice.

Mediating induced abscisic acid (ABA) biosynthesis is important for enhancing plant stress tolerance. Here, we found that rice (Oryza sativa L.) osa-miR2105 (miR2105) and the Stress/ABA-activated protein kinase (OsSAPK10) coordinately regulate the rice basic region-leucine zipper transcription factor (bZIP TF; OsbZIP86) at the posttranscriptional and posttranslational levels to control drought-induced ABA biosynthesis via modulation of rice 9-cis-epoxycarotenoid dioxygenase (OsNCED3) expression. OsbZIP86 expression is regulated by miR2105-directed cleavage of the OsbZIP86 mRNA. OsbZIP86 encodes a nuclear TF that binds to the promoter of the ABA biosynthetic gene OsNCED3. OsSAPK10 can phosphorylate and activate OsbZIP86 to enhance the expression of OsNCED3. Under normal growth conditions, altered expression of miR2105 and OsbZIP86 displayed no substantial effect on rice growth. However, under drought conditions, miR2105 knockdown or OsbZIP86 overexpression transgenic rice plants showed higher ABA content, enhanced tolerance to drought, lower rates of water loss, and more stomatal closure of seedlings, compared with wild-type rice Zhonghua 11; in contrast, miR2105 overexpression, OsbZIP86 downregulation, and OsbZIP86 knockout plants displayed opposite phenotypes. Collectively, our results show that the "miR2105-(OsSAPK10)-OsbZIP86-OsNCED3" module regulates the drought-induced ABA biosynthesis without penalty on rice growth under normal conditions, suggesting candidates for improving drought tolerance in rice.

Genomic Identification of CCCH-Type Zinc Finger Protein Genes Reveals the Role of HuTZF3 in Tolerance of Heat and Salt Stress of Pitaya (Hylocereus polyrhizus).

Pitaya (Hylocereus polyrhizus) is cultivated in a broad ecological range, due to its tolerance to drought, heat, and poor soil. The zinc finger proteins regulate gene expression at the transcriptional and post-transcriptional levels, by interacting with DNA, RNA, and proteins, to play roles in plant growth and development, and stress response. Here, a total of 81 CCCH-type zinc finger protein genes were identified from the pitaya genome. Transcriptomic analysis showed that nine of them, including HuTZF3, responded to both salt and heat stress. RT-qPCR results showed that HuTZF3 is expressed in all tested organs of pitaya, with a high level in the roots and stems, and confirmed that expression of HuTZF3 is induced by salt and heat stress. Subcellular localization showed that HuTZF3 is targeted in the processing bodies (PBs) and stress granules (SGs). Heterologous expression of HuTZF3 could improve both salt and heat tolerance in Arabidopsis, reduce oxidative stress, and improve the activity of catalase and peroxidase. Therefore, HuTZF3 may be involved in post-transcriptional regulation via localizing to PBs and SGs, contributing to both salt and heat tolerance in pitaya.

The putative obtusifoliol 14α-demethylase OsCYP51H3 affects multiple aspects of rice growth and development.

Some members of the CYP51G subfamily has been shown to be obtusifoliol 14α-demethylase, key enzyme of the sterol and brassinosteroid (BR) biosynthesis, which mediate plant development and response to stresses. However, little is known about the functions of CYP51H subfamily in rice. Here, OsCYP51H3, an ortholog of rice OsCYP51G1 was identified. Compared with wild type, the mutants oscyp51H3 and OsCYP51H3-RNAi showed dwarf phenotype, late flowering, erected leaves, lower seed-setting rate, and smaller and shorter seeds. In contrast, the phenotypic changes of OsCYP51H3-OE plants are not obvious. Metabolomic analysis of oscyp51H3 mutant indicated that OsCYP51H3 may also encode an obtusifoliol 14α-demethylase involved in phytosterol and BR biosynthesis, but possibly not that of triterpenes. The RNA-seq results showed that OsCYP51H3 may affect the expression of a lot of genes related to rice development. These findings showed that OsCYP51H3 codes for a putative obtusifoliol 14α-demethylase involved in phytosterol and BR biosynthesis, and mediates rice development.

Obtusifoliol 14α-demethylase OsCYP51G1 is involved in phytosterol synthesis and affects pollen and seed development.

As structural components of biological membranes, phytosterols are essential not only for a variety of cellular functions but are also precursors for brassinosteroid (BR) biosynthesis. Plant CYP51 is the oldest and most conserved obtusifoliol 14α-demethylase in eukaryotes and is an essential component of the sterol biosynthesis pathway. However, little is known about rice (Oryza sativa L.) CYP51G1. In this study, we showed that rice OsCYP51G1 shared high homology with obtusifoliol 14α-demethylase and OsCYP51G1 was strongly expressed in most of rice organs. Subcellular localization analysis indicated that OsCYP51G1 was localized to the endoplasmic reticulum. Knockdown and knockout of OsCYP51G1 resulted in delayed flowering, impaired membrane integrity, abnormal pollen, and reduced grain yield, whereas OsCYP51G1 overexpression led to increased grain yield. Knockdown of OsCYP51G1 also reduced the levels of end-products (sitosterol and stigmasterol) and increased those of upstream intermediates (24-methylene-cycloartenol and cycloeucalenol) of the OsCYP51G1-mediated sterol biosynthesis step. In contrast, overexpression of OsCYP51G1 increased the sitosterol and stigmasterol content and reduced that of cycloeucalenol. However, knockdown of OsCYP51G1 by RNAi did not elicit these BR deficiency-related phenotypes, such as dwarfism, erect leaves and small seeds, nor was the leaf lamina angle sensitive to brassinolide treatment. These results revealed that rice OsCYP15G1 encodes an obtusifoliol 14α-demethylase for the phytosterols biosynthesis and possible without affecting the biosynthesis of downstream BRs, which was different from its homolog, OsCYP51G3.

CRISPR/Cas9-mediated mutation of OsSWEET14 in rice cv. Zhonghua11 confers resistance to Xanthomonas oryzae pv. oryzae without yield penalty.

BACKGROUND: Bacterial blight of rice, caused by Xanthomonas oryzae pv. oryzae (Xoo), is a devastating rice disease in Southeast Asia and West Africa. OsSWEET14, encoding a sugar transporter, is known to be a major susceptible gene of bacterial blight targeted by four different transcription activator-like (TAL) effectors from either Asian or African Xoo strains. However, the OsSWEET14 single knockout or promoter mutants in the Kitaake background are moderately resistant or even susceptible to African Xoo strains. Therefore, in this study, we knocked out OsSWEET14 in rice cv. Zhonghua 11 background for disease assessment. RESULTS: In this study, CRISPR/Cas9 was utilized to disrupt the function of OsSWEET14 by modifying its corresponding coding region in the genome of rice cv. Zhonghua 11 (CR-S14). In total, we obtained nine different OsSWEET14-mutant alleles. Besides conferring broad-spectrum resistance to Asian Xoo strains, tested mutant alleles also showed strong resistance to African Xoo strain AXO1947. Moreover, the expression of OsSWEET14 was detected in vascular tissues, including the stem, leaf sheath, leaf blade and root. The disruption of OsSWEET14 led to increased plant height without a reduction in yield. CONCLUSIONS: Disruption of OsSWEET14 in the Zhonghua 11 background is able to confer strong resistance to African Xoo strain AXO1947 and Asian Xoo strain PXO86. CR-S14 has normal reproductive growth and enhanced plant height under normal growth conditions. These results imply that CR-S14 may serve as a better tester line than sweet14 single-knockout mutant in the Kitaake background for the diagnostic kit for rice blight resistance. The genetic background and increased plant height need to be taken into consideration when utilizing OsSWEET14 for resistant rice breeding.

An AP2/ERF Gene, HuERF1, from Pitaya (Hylocereus undatus) Positively Regulates Salt Tolerance.

Pitaya (Hylocereus undatus) is a high salt-tolerant fruit, and ethylene response factors (ERFs) play important roles in transcription-regulating abiotic tolerance. To clarify the function of HuERF1 in the salt tolerance of pitaya, HuERF1 was heterogeneously expressed in Arabidopsis. HuERF1 had nuclear localization when HuERF1::GFP was expressed in Arabidopsis protoplasts and had transactivation activity when HuERF1 was expressed in yeast. The expression of HuERF1 in pitaya seedlings was significantly induced after exposure to ethylene and high salinity. Overexpression of HuERF1 in Arabidopsis conferred enhanced tolerance to salt stress, reduced the accumulation of superoxide (O2∙) and hydrogen peroxide (H2O2), and improved antioxidant enzyme activities. These results indicate that HuERF1 is involved in ethylene-mediated salt stress tolerance, which may contribute to the salt tolerance of pitaya.

Formation of Protein Disulfide Bonds Catalyzed by OsPDIL1;1 is Mediated by MicroRNA5144-3p in Rice.

Correct folding of proteins in the endoplasmic reticulum is important for their stability and function under stress. The protein disulfide isomerase (PDI) OsPDIL1;1 is a key protein-folding catalyst in rice (Oryza sativa L.). Here, microRNA5144 (osa-miR5144-3p) is reported to mediate the formation of protein disulfide bonds via targeting OsPDIL1;1 mRNA in rice seeds and seedlings during development and under conditions of abiotic stress, respectively. Expression analysis of transgenic rice and identification of cleavage sites showed that OsPDIL1;1 mRNA is a target of osa-miR5144-3p. Expression of osa-miR5144-3p and OsPDIL1;1 was shown to be inversely regulated in developing organs and under abiotic stress. The down-regulation of osa-miR5144-3p or overexpression of OsPDIL1;1 in transgenic rice showed increased total protein-disulfide bond content, compared with the wild type. This indicates that protein-disulfide bond formation is enhanced by down-regulation of osa-miR5144-3p or overexpression of OsPDIL1;1. These transgenic rice plants also displayed strong resistance to salinity and mercury stress, in comparison with the wild type. In contrast, the transgenic rice plants overexpressing osa-miR5144-3p or down-regulating OsPDIL1;1 had a lower protein-disulfide bond content; they were susceptible to abiotic stress and produced abnormal grains with small and loosely packed starch granules. These results indicate that protein-disulfide bond formation catalyzed by OsPDIL1;1 is modulated by osa-miR5144-3p in rice during development and is involved in resistance to abiotic stress.

Ipomoea pes-caprae IpASR Improves Salinity and Drought Tolerance in Transgenic Escherichia coli and Arabidopsis.

Ipomoea pes-caprae L. is an extremophile halophyte with strong adaptability to seawater and drought. It is widely used in the ecological restoration of coastal areas or degraded islands in tropical and subtropical regions. In this study, a new abscisic acid, stressandripening (ASR) gene, IpASR, was reported, and is mainly associated with biological functions involved in salt and drought tolerance. Sequence analysis of IpASR showed that this protein contains an ABA/WDS (abscisic acid/water deficit stress) domain, which is a common feature of all plant ASR members. Overexpression of IpASR improved Escherichia coli growth performance compared with the control under abiotic stress treatment. The transgenic overexpressing IpASR Arabidopsis showed higher tolerance to salt and drought stress than the wild type and lower accumulation of hydrogen peroxide (H2O2) and superoxide (O2-) accompanied by increased antioxidant enzyme activity in vivo. IpASR exhibits transcription factor's activity. Therefore, the overexpression of IpASR in Arabidopsis is supposed to influence the expression of some genes involved in anti-oxidative and abiotic stresses. The results indicate that IpASR is involved in the plant response to salt and drought and probably acts as a reactive oxygen species scavenger or transcription factor, and therefore influences physiological processes associated with various abiotic stresses in plants.

Functional Identification of Salt-Stress-Related Genes Using the FOX Hunting System from Ipomoea pes-caprae.

Ipomoea pes-caprae is a seashore halophytic plant and is therefore a good model for studying the molecular mechanisms underlying salt and stress tolerance in plant research. Here, we performed Full-length cDNA Over-eXpressor (FOX) gene hunting with a functional screening of a cDNA library using a salt-sensitive yeast mutant strain to isolate the salt-stress-related genes of I. pes-caprae (IpSR genes). The library was screened for genes that complemented the salt defect of yeast mutant AXT3 and could grow in the presence of 75 mM NaCl. We obtained 38 candidate salt-stress-related full-length cDNA clones from the I. pes-caprae cDNA library. The genes are predicted to encode proteins involved in water deficit, reactive oxygen species (ROS) scavenging, cellular vesicle trafficking, metabolic enzymes, and signal transduction factors. When combined with the quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses, several potential functional salt-tolerance-related genes were emphasized. This approach provides a rapid assay system for the large-scale screening of I. pes-caprae genes involved in the salt stress response and supports the identification of genes responsible for the molecular mechanisms of salt tolerance.

Rice microRNA osa-miR1848 targets the obtusifoliol 14α-demethylase gene OsCYP51G3 and mediates the biosynthesis of phytosterols and brassinosteroids during development and in response to stress.

Phytosterols are membrane components or precursors for brassinosteroid (BR) biosynthesis. As they cannot be transported long distances, their homeostasis is tightly controlled through their biosynthesis and metabolism. However, it is unknown whether microRNAs are involved in their homeostatic regulation. Rice (Oryza sativa) plants transformed with microRNA osa-miR1848 and its target, the obtusifoliol 14α-demethylase gene, OsCYP51G3, were used to investigate the role of osa-miR1848 in the regulation of phytosterol biosynthesis. osa-miR1848 directs OsCYP51G3 mRNA cleavage to regulate phytosterol and BR biosynthesis in rice. The role of OsCYP51G3 as one of the osa-miR1848 targets is supported by the opposite expression patterns of osa-miR1848 and OsCYP51G3 in transgenic rice plants, and by the identification of OsCYP51G3 mRNA cleavage sites. Increased osa-miR1848 and decreased OsCYP51G3 expression reduced phytosterol and BR concentrations, and caused typical phenotypic changes related to phytosterol and BR deficiency, including dwarf plants, erect leaves, semi-sterile pollen grains, and shorter cells. Circadian expression of osa-miR1848 regulated the diurnal abundance of OsCYP51G3 transcript in developing organs, and the response of OsCYP51G3 to salt stress. We propose that osa-miR1848 regulates OsCYP51G3 expression posttranscriptionally, and mediates phytosterol and BR biosynthesis. osa-miR1848 and OsCYP51G3 might have potential applications in rice breeding to modulate leaf angle, and the size and quality of seeds.

OsWS1 involved in cuticular wax biosynthesis is regulated by osa-miR1848.

Cuticular wax forms a hydrophobic layer covering aerial plant organs and acting as a protective barrier against biotic and abiotic stresses. Compared with well-known wax biosynthetic pathway, molecular regulation of wax biosynthesis is less known. Here, we show that rice OsWS1, a member of the membrane-bound O-acyl transferase gene family, involved in wax biosynthesis and was regulated by an osa-miR1848. OsWS1-tagged green fluorescent protein localized to the endoplasmic reticulum (ER). Compared with wild-type rice, OsWS1 overexpression plants displayed a 3% increase in total wax, especially a 35% increase in very long-chain fatty acids, denser wax papillae around the stoma, more cuticular wax crystals formed on leaf and stem surfaces, pollen coats were thicker and more seedlings survived after water-deficit treatment. In contrast, OsWS1-RNAi and osa-miR1848 overexpression plants exhibited opposing changes. Gene expression analysis showed that overexpression of osa-miR1848 down-regulated OsWS1 transcripts; furthermore, expression profiles of OsWS1 and osa-miR1848 were inversely correlated in the leaf, panicle and stem, and upon water-deficit treatment. These results suggest that OsWS1 is regulated by osa-miR1848 and participates in cuticular wax formation.

Knockdown of LjIPT3 influences nodule development in Lotus japonicus.

Cytokinins play important roles in legume-rhizobia symbiosis. Here we report isolation of six genes encoding isopentenyl transferase (IPT) from Lotus japonicus, which catalyze the rate-limiting step of cytokinin biosynthesis. The LjIPT3 gene was found to be up-regulated in infected roots and mature nodules. Histochemical analysis demonstrated expression of Pro(LjIPT3):GUS (ß-glucuronidase) in vegetative and reproductive organs, and was especially high in the vascular bundles of roots. When inoculated with Mesorhizobium loti MAFF303099, LjIPT3 was undetectable in the nodule primordia and developing nodules, and later it was expressed only in the vascular bundles of mature nodules. In addition, knockdown of LjIPT3 (LjIPT3i) by RNA interference reduced levels of endogenous cytokinins, affected plant development and accelerated Chl degradation during dark-induced leaf senescence. Compared with the wild type, LjIPT3i plants produced fewer infection threads and nodules. In addition, expression of downstream nodulation-related transcription factor genes LjNSP1, LjNSP2 and LjNIN decreased dramatically in LjIPT3i plants. These results suggest that LjIPT3 regulates the CRE1-dependent cytokinin pathway, affecting nodule initiation and thereby influencing the number of infection threads and nodules. Detection of nitrogenase activity and observation of nodule structure showed that endogenous cytokinins are required for full development of the infected cells in mature nodules by preventing early senescence. Therefore, our results indicate that the LjIPT3 gene product is required for nodule initiation and development, and does not appear to be involved in early infection events.

Multi-omics analyses and botanical perfumer hypothesis provide insights into the formation and maintenance of aromatic characteristics of Dendrobium loddigesii flowers.

Dendrobium loddigesii, a member of the Orchidaceae family, is a valuable horticultural crop known for its aromatic qualities. However, the mechanisms responsible for the development of its aromatic characteristics remain poorly understood. To elucidate these underlying mechanisms, we assembled the first chromosome-level reference genome of D. loddigesii using PacBio HiFi-reads, Illumina short-reads, and Hi-C data. The assembly comprises 19 pseudochromosomes with N50 contig and N50 scaffold sizes of 55.15 and 89.94 Mb, respectively, estimating the genome size to be 1.68 Gb, larger than that of other sequenced Dendrobium species. During the flowering stages, we conducted a comprehensive analysis combining volatilomics and transcriptomics to understand the characteristics and biosynthetic mechanisms pathways of the floral scent. Our findings emphasize the significant contribution of aromatic terpenoids, especially monoterpenoids, in defining the floral aroma. Furthermore, we identified two crucial terpene synthase (TPS) genes that play a key role in maintaining the aroma during flowering. Through the integration volatilomics data with catalytic assays of DlTPSbs proteins, we identified specific compounds responsible for the aromatic characteristics of D. loddigesii. This integrated analysis of the genome, transcriptome, and volatilome, offers valuable insights into the development and preservation of D. loddigesii's aromatic characteristics, setting the stage for further exploration of the botanical perfumer hypothesis.

Endoplasmic reticulum stress response modulator OsbZIP39 regulates cadmium accumulation via activating the expression of defensin-like gene OsCAL2 in rice.

Accumulation of cadmium (Cd) in rice is not only harmful to the growth of plants but also poses a threat to human health. Exposure to Cd triggers unfolded protein response (UPR) within cells, a process that is still not completely understood. The study demonstrated that the lack of OsbZIP39, an essential endoplasmic reticulum (ER)-resident regulator of the UPR, resulted in decreased Cd intake and reduced Cd levels in the roots, stems, and grains of rice. Upon exposure to Cd stress, GFP-OsbZIP39 translocated from ER to nucleus, initiating UPR. Further investigation revealed that Cd treatment caused changes in sphingolipid levels in the membrane, influencing the localization and activation of OsbZIP39. Yeast one-hybrid and dual-LUC assays were conducted to validate the interaction between activated OsbZIP39 and the promoter of the defensin-like gene OsCAL2, resulting in an increase in its expression. Different variations were identified in the coding region of OsbZIP39, which may explain the varying levels of Cd accumulation observed in the indica and japonica subspecies. Under Cd treatment, OsbZIP39ind exhibited a more significant enhancement in the transcription of OsCAL2 compared to OsbZIP39jap. Our data suggest that OsbZIP39 positively regulates Cd uptake in rice, offering an encouraging objective for the cultivation of low-Cd rice.

Altered expression of the PTR/NRT1 homologue OsPTR9 affects nitrogen utilization efficiency, growth and grain yield in rice.

The plant PTR/NRT1 (peptide transporter/nitrate transporter 1) gene family comprises di/tripeptide and low-affinity nitrate transporters; some members also recognize other substrates such as carboxylates, phytohormones (auxin and abscisic acid), or defence compounds (glucosinolates). Little is known about the members of this gene family in rice (Oryza sativa L.). Here, we report the influence of altered OsPTR9 expression on nitrogen utilization efficiency, growth, and grain yield. OsPTR9 expression is regulated by exogenous nitrogen and by the day-night cycle. Elevated expression of OsPTR9 in transgenic rice plants resulted in enhanced ammonium uptake, promotion of lateral root formation and increased grain yield. On the other hand, down-regulation of OsPTR9 in a T-DNA insertion line (osptr9) and in OsPTR9-RNAi rice plants had the opposite effect. These results suggest that OsPTR9 might hold potential for improving nitrogen utilization efficiency and grain yield in rice breeding.

Genome-Wide Identification and Characterization of Long Non-Coding RNAs in Roots of Rice Seedlings under Nitrogen Deficiency.

Long non-coding RNAs (lncRNAs) regulate gene expression in eukaryotic organisms. Research suggests that lncRNAs may be involved in the regulation of nitrogen use efficiency in plants. In this study, we identified 1628 lncRNAs based on the transcriptomic sequencing of rice roots under low-nitrogen (LN) treatment through the implementation of an integrated bioinformatics pipeline. After 4 h of LN treatment, 50 lncRNAs and 373 mRNAs were significantly upregulated, and 17 lncRNAs and 578 mRNAs were significantly downregulated. After 48 h LN treatment, 43 lncRNAs and 536 mRNAs were significantly upregulated, and 42 lncRNAs and 947 mRNAs were significantly downregulated. Moreover, the interaction network among the identified lncRNAs and mRNAs was investigated and one of the LN-induced lncRNAs (lncRNA24320.6) was further characterized. lncRNA24320.6 was demonstrated to positively regulate the expression of a flavonoid 3'-hydroxylase 5 gene (OsF3'H5). The overexpression of lncRNA24320.6 was shown to improve nitrogen absorption and promote growth in rice seedlings under LN conditions. Our results provide valuable insights into the roles of lncRNAs in the rice response to nitrogen starvation.

Rice miR168a-5p regulates seed length, nitrogen allocation and salt tolerance by targeting OsOFP3, OsNPF2.4 and OsAGO1a, respectively.

Rice microRNA168a (osa-miR168a) plays important roles in mediating flowering time, grain yield and vigor, seeding growth, and immunity by targeting the RNA-induced silencing complex component Argonaute 1 (AGO1). However, the functions of miR168a exerted by targeting other genes require further clarification before it could be used in rice molecular breeding. In this study, we identified a new target gene of osa-miR168a-5p (miR168a-5p) in rice called OsOFP3 (ovate family protein 3) and investigated the roles of miR168a-5p in response to brassinosteroids (BRs), salt stress, and nitrogen allocation. Up- and downregulated miR168a-5p expression respectively decreased and increased the expression of the BR-negative regulator OsOPF3. The results of RNA ligase-mediated rapid amplification of cDNA ends (5'RLM-RACE) revealed cleavage sites in OsOPF3 and OsNPF2.4 mRNAs. The phenotype of miR168a-5p transgenic rice was BR-associated and included the lamina bending response to BR, short seeds, and low 1000-grain weight. MicroRNA 168a-5p also regulated the expression of the nitrate transporter, OsNPF2.4, which affected nitrogen allocation, and regulated OsAGO1a expression in response to salt stress. Taken together, rice miR168a-5p regulates BR-associated pathways, nitrogen transport, and stress by targeting OsOFP3, OsNPF2.4, and OsAGO1a, respectively, resulting in a series of important agronomic traits for rice breeding.

Molecular and metabolic insights into floral scent biosynthesis during flowering in Dendrobium chrysotoxum.

Dendrobium chrysotoxum is considered as an important ornamental dendrobium because of its strong and long-lasting floral scent. Nevertheless, few information is known about the dynamic changes and related formation mechanism of dendrobium floral scent at different flowering stages. In this study, the characteristics and biosynthetic mechanism of floral scent in D. chrysotoxum during flowering was revealed by using widely-targeted volatilomics (WTV) combined with transcriptome analysis. Over 500 kinds of volatile organic compounds (VOCs) were detected in the floral scents of D. chrysotoxum, which improved the knowledge about floral scent components of dendrobium. A total of 153 differential VOCs and 4,487 differentially expressed genes (DEGs) were identified between flowers of different flowering stages, respectively. The results for both volatilomics and transcriptomics data indicated that terpenes and related genes played an important role in the formation of floral characteristics of D. chrysotoxum. But in general, the expression of genes showed an opposite trend to the accumulation of metabolites during flowering, suggesting that the regulation of floral scent biosynthesis might have started at the budding stage in D. chrysotoxum. Additionally, a transcriptional metabolic regulatory network consisting of terpenes, terpene synthases and candidate transcription factors was established. This research is the first systematic and comprehensive exploration of floral characteristics and related mechanisms during flowering in D. chrysotoxum. It provides basis for exploration of mechanisms on the floral scents and the breeding of aromatic dendrobium.