Transcriptome profiling of abiotic responses to heat, cold, salt, and osmotic stress of Capsicum annuum L

Beyond NGS data sharing for plant ecological resilience and improvement of agronomic traits

Decoding complex plant omics is essential for advancing our understanding of plant biology, evolution, and breeding as well as for practical applications in agriculture, conservation, and biotechnology. The advent of Next-Generation Sequencing (NGS) has revolutionized global plant genomic research, offering high-throughput, cost-effective, and accurate methods for generating genomic data. However, challenges still exist that suggest an entirely unresolved genome characterized by high heterozygosity, extensive repetitive sequences, and complex ploidy features. In addition, individual investigation of genomic information from various genetic resources is essential for omics research, as there are differences in traits within a single breed beyond a species due to the uniqueness of sequence variation. This article provides high-quality genomic and transcriptomic insights targeted at the agronomical background.

The landscape of abiotic and biotic stress-responsive splice variants with deep RNA-seq datasets in hot pepper

Alternative splicing (AS) is a widely observed phenomenon in eukaryotes that plays a critical role in development and stress responses. In plants, the large number of RNA-seq datasets in response to different environmental stressors can provide clues for identification of condition-specific and/or common AS variants for preferred agronomic traits. We report RNA-seq datasets (350.7 Gb) from Capsicum annuum inoculated with one of three bacteria, one virus, or one oomycete and obtained additional existing transcriptome datasets. In this study, we investigated the landscape of AS in response to environmental stressors, signaling molecules, and tissues from 425 total samples comprising 841.49 Gb. In addition, we identified genes that undergo AS under specific and shared stress conditions to obtain potential genes that may be involved in enhancing tolerance to stressors. We uncovered 1,642,007 AS events and identified 4,354 differential alternative splicing genes related to environmental stressors, tissues, and signaling molecules. This information and approach provide useful data for basic-research focused on enhancing tolerance to environmental stressors in hot pepper or establishing breeding programs.

Identification and expression analyses of B3 genes reveal lineage-specific evolution and potential roles of REM genes in pepper

BACKGROUND

The B3 gene family, one of the largest plant-specific transcription factors, plays important roles in plant growth, seed development, and hormones. However, the B3 gene family, especially the REM subfamily, has not been systematically and functionally studied.

RESULTS

In this study, we performed genome-wide re-annotation of B3 genes in five Solanaceae plants, Arabidopsis thaliana, and Oryza sativa, and finally predicted 1,039 B3 genes, including 231 (22.2%) newly annotated genes. We found a striking abundance of REM genes in pepper species (Capsicum annuum, Capsicum baccatum, and Capsicum chinense). Comparative motif analysis revealed that REM and other subfamilies (ABI3/VP1, ARF, RAV, and HSI) consist of different amino acids. We verified that the large number of REM genes in pepper were included in the specific subgroup (G8) through the phylogenetic analysis. Chromosome location and evolutionary analyses suggested that the G8 subgroup genes evolved mainly via a pepper-specific recent tandem duplication on chromosomes 1 and 3 after speciation between pepper and other Solanaceae. RNA-seq analyses suggested the potential functions of REM genes under salt, heat, cold, and mannitol stress conditions in pepper (C. annuum).

CONCLUSIONS

Our study provides evolutionary and functional insights into the REM gene family in pepper.

Tolerance and adaptation mechanism of Solanaceous crops under salinity stress

Solanaceous crops act as a source of food, nutrition and medicine for humans. Soil salinity is a damaging environmental stress, causing significant reductions in cultivated land area, crop productivity and quality, especially under climate change. Solanaceous crops are extremely vulnerable to salinity stress due to high water requirements during the reproductive stage and the succulent nature of fruits and tubers. Salinity stress impedes morphological and anatomical development, which ultimately affect the production and productivity of the economic part of these crops. The morpho-physiological parameters such as root-to-shoot ratio, leaf area, biomass production, photosynthesis, hormonal balance, leaf water content are disturbed under salinity stress in Solanaceous crops. Moreover, the synthesis and signalling of reactive oxygen species, reactive nitrogen species, accumulation of compatible solutes, and osmoprotectant are significant under salinity stress which might be responsible for providing tolerance in these crops. The regulation at the molecular level is mediated by different genes, transcription factors, and proteins, which are vital in the tolerance mechanism. The present review aims to redraw the attention of the researchers to explore the mechanistic understanding and potential mitigation strategies against salinity stress in Solanaceous crops, which is an often-neglected commodity.

The RNA landscape of Dunaliella salina in response to short-term salt stress

Using the halotolerant green microalgae Dunaliella salina as a model organism has special merits, such as a wide range of salt tolerance, unicellular organism, and simple life cycle and growth conditions. These unique characteristics make it suitable for salt stress study. In order to provide an overview of the response of Dunaliella salina to salt stress and hopefully to reveal evolutionarily conserved mechanisms of photosynthetic organisms in response to salt stress, the transcriptomes and the genome of the algae were sequenced by the second and the third-generation sequencing technologies, then the transcriptomes under salt stress were compared to the transcriptomes under non-salt stress with the newly sequenced genome as the reference genome. The major cellular biological processes that being regulated in response to salt stress, include transcription, protein synthesis, protein degradation, protein folding, protein modification, protein transport, cellular component organization, cell redox homeostasis, DNA repair, glycerol synthesis, energy metabolism, lipid metabolism, and ion homeostasis. This study gives a comprehensive overview of how Dunaliella salina responses to salt stress at transcriptomic level, especially characterized by the nearly ubiquitous up-regulation of the genes involving in protein folding, DNA repair, and cell redox homeostasis, which may confer the algae important mechanisms to survive under salt stress. The three fundamental biological processes, which face huge challenges under salt stress, are ignored by most scientists and are worth further deep study to provide useful information for breeding economic important plants competent in tolerating salt stress, other than only depending on the commonly acknowledged osmotic balance and ion homeostasis.

Global co-expression network for key factor selection on environmental stress RNA-seq dataset in Capsicum annuum

Environmental stresses significantly affect plant growth, development, and productivity. Therefore, a deeper understanding of the underlying stress responses at the molecular level is needed. In this study, to identify critical genetic factors associated with environmental stress responses, the entire 737.3 Gb clean RNA-seq dataset across abiotic, biotic stress, and phytohormone conditions in Capsicum annuum was used to perform individual differentially expressed gene analysis and to construct gene co-expression networks for each stress condition. Subsequently, gene networks were reconstructed around transcription factors to identify critical factors involved in the stress responses, including the NLR gene family, previously implicated in resistance. The abiotic and biotic stress networks comprise 233 and 597 hubs respectively, with 10 and 89 NLRs. Each gene within the NLR groups in the network exhibited substantial expression to particular stresses. The integrated analysis strategy of the transcriptome network revealed potential key genes for complex environmental conditions. Together, this could provide important clues to uncover novel key factors using high-throughput transcriptome data in other species as well as plants.

Genome and Transcriptome Analyses of Genes Involved in Ascorbate Biosynthesis in Pepper Indicate Key Genes Related to Fruit Development, Stresses, and Phytohormone Exposures

Pepper (Capsicum annuum L.) is a vegetable consumed worldwide, primarily used for vitamin C uptake and condiment purposes. Ascorbate (Asc) is a multifunctional metabolite, acting as an antioxidant and enzymatic cofactor involved in multiple cellular processes. Nevertheless, there is no evidence about the contribution of biosynthesis pathways and regulatory mechanisms responsible for Asc reserves in pepper plants. Here, we present a genome- and transcriptome-wide investigation of genes responsible for Asc biosynthesis in pepper during fruit development, stresses, and phytohormone exposures. A total of 21 genes, scattered in ten of twelve pepper chromosomes were annotated. Gene expression analyses of nine transcriptomic experiments supported the primary role of the L-galactose pathway in the Asc-biosynthesizing process, given its constitutive, ubiquitous, and high expression profile observed in all studied conditions. However, genes from alternative pathways generally exhibited low expression or were unexpressed and appeared to play some secondary role under specific stress conditions and phytohormone treatments. Taken together, our findings provide a deeper spatio-temporal understanding of expression levels of genes involved in Asc biosynthesis, and they highlight GGP2, GME1 and 2, and GalLDH members from L-galactose pathway as promising candidates for future wet experimentation, addressing the attainment of increase in ascorbate content of peppers and other crops.

Comprehensive investigation of cucumber heat shock proteins under abiotic stress conditions: A multi-omics survey

Heat-shock proteins (Hsps) are a family of proteins essential in preserving the vitality and functionality of proteins under stress conditions. Cucumber (Cucumis sativus) is a widely grown plant with high nutritional value and is used as a model organism in many studies. This study employed a genomics, transcriptomics, and metabolomics approach to investigate cucumbers' Hsps against abiotic stress conditions. Bioinformatics methods were used to identify six Hsp families in the cucumber genome and to characterize family members. Transcriptomics data from the Sequence Read Archive (SRA) database was also conducted to select CsHsp genes for further study. Real-time PCR was used to evaluate gene expression levels under different stress conditions, revealing that CssHsp-08 was a vital gene for resistance to stress conditions; including drought, salinity, cold, heat stresses, and ABA application. Gas Chromatography-Mass Spectrometry (GC-MS) analysis of plant extracts revealed that amino acids accumulate in leaves under high temperatures and roots under drought, while sucrose accumulates in both tissues under applied most stress factors. The study provides valuable insights into the structure, organization, evolution, and expression profiles of the Hsp family and contributes to a better understanding of plant stress mechanisms. These findings have important implications for developing crops that can withstand environmental stress conditions better.

Integrated transcriptome and metabonomic analysis of key metabolic pathways in response to cadmium stress in novel buckwheat and cultivated species

INTRODUCTION

Buckwheat (Fagopyrum tataricum), an important food crop, also has medicinal uses. It is widely planted in Southwest China, overlapping with planting areas remarkably polluted by cadmium (Cd). Therefore, it is of great significance to study the response mechanism of buckwheat under Cd stress and further develop varieties with excellent Cd tolerance.

METHODS

In this study, two critical periods of Cd stress treatment (days 7 and 14 after Cd treatment) of cultivated buckwheat (Pinku-1, named K33) and perennial species (F. tatari-cymosum Q.F. Chen) (duoku, named DK19) were analyzed using transcriptome and metabolomics.

RESULTS

The results showed that Cd stress led to changes in reactive oxygen species (ROS) and the chlorophyll system. Moreover, Cd-response genes related to stress response, amino acid metabolism, and ROS scavenging were enriched or activated in DK19. Transcriptome and metabolomic analyses highlighted the important role of galactose, lipid (glycerophosphatide metabolism and glycerophosphatide metabolism), and glutathione metabolism in response to Cd stress in buckwheat, which are significantly enriched at the gene and metabolic levels in DK19.

DISCUSSION

The results of the present study provide valuable information for a better understanding of the molecular mechanisms underlying Cd tolerance in buckwheat and useful clues for the genetic improvement of drought tolerance in buckwheat.

MYB24 Negatively Regulates the Biosynthesis of Lignin and Capsaicin by Affecting the Expression of Key Genes in the Phenylpropanoid Metabolism Pathway in Capsicum chinense

The wide application of pepper is mostly related to the content of capsaicin, and phenylpropanoid metabolism and its branch pathways may play an important role in the biosynthesis of capsaicin. The expression level of MYB24, a transcription factor screened from the transcriptome data of the pepper fruit development stage, was closely related to the spicy taste. In this experiment, CcMYB24 was cloned from Hainan Huangdenglong pepper, a hot aromatic pepper variety popular in the world for processing, and its function was confirmed by tissue expression characteristics, heterologous transformation in Arabidopsis thaliana, and VIGS technology. The results showed that the relative expression level of CcMYB24 was stable in the early stage of pepper fruit development, and increased significantly from 30 to 50 days after flowering. Heterologous expression led to a significant increase in the expression of CcMYB24 and decrease in lignin content in transgenic Arabidopsis thaliana plants. CcMYB24 silencing led to a significant increase in the expression of phenylpropanoid metabolism pathway genes PAL, 4CL, and pAMT; lignin branch CCR1 and CAD; and capsaicin pathway CS, AT3, and COMT genes in the placenta of pepper, with capsaicin content increased by more than 31.72% and lignin content increased by 20.78%. However, the expression of PAL, pAMT, AT3, COMT, etc., in the corresponding pericarps did not change significantly. Although CS, CCR1, and CAD increased significantly, the relative expression amount was smaller than that in placental tissue, and the lignin content did not change significantly. As indicated above, CcMYB24 may negatively regulate the formation of capsaicin and lignin by regulating the expression of genes from phenylpropanoid metabolism and its branch pathways.

Developing future heat-resilient vegetable crops

Climate change seriously impacts global agriculture, with rising temperatures directly affecting the yield. Vegetables are an essential part of daily human consumption and thus have importance among all agricultural crops. The human population is increasing daily, so there is a need for alternative ways which can be helpful in maximizing the harvestable yield of vegetables. The increase in temperature directly affects the plants' biochemical and molecular processes; having a significant impact on quality and yield. Breeding for climate-resilient crops with good yields takes a long time and lots of breeding efforts. However, with the advent of new omics technologies, such as genomics, transcriptomics, proteomics, and metabolomics, the efficiency and efficacy of unearthing information on pathways associated with high-temperature stress resilience has improved in many of the vegetable crops. Besides omics, the use of genomics-assisted breeding and new breeding approaches such as gene editing and speed breeding allow creation of modern vegetable cultivars that are more resilient to high temperatures. Collectively, these approaches will shorten the time to create and release novel vegetable varieties to meet growing demands for productivity and quality. This review discusses the effects of heat stress on vegetables and highlights recent research with a focus on how omics and genome editing can produce temperature-resilient vegetables more efficiently and faster.

Comparative and expression analyses of AP2/ERF genes reveal copy number expansion and potential functions of ERF genes in Solanaceae

BACKGROUND

The AP2/ERF gene family is a superfamily of transcription factors that are important in the response of plants to abiotic stress and development. However, comprehensive research of the AP2/ERF genes in the Solanaceae family is lacking.

RESULTS

Here, we updated the annotation of AP2/ERF genes in the genomes of eight Solanaceae species, as well as Arabidopsis thaliana and Oryza sativa. We identified 2,195 AP2/ERF genes, of which 368 (17%) were newly identified. Based on phylogenetic analyses, we observed expansion of the copy number of these genes, especially those belonging to specific Ethylene-Responsive Factor (ERF) subgroups of the Solanaceae. From the results of chromosomal location and synteny analyses, we identified that the AP2/ERF genes of the pepper (Capsicum annuum), the tomato (Solanum lycopersicum), and the potato (Solanum tuberosum) belonging to ERF subgroups form a tandem array and most of them are species-specific without orthologs in other species, which has led to differentiation of AP2/ERF gene repertory among Solanaceae. We suggest that these genes mainly emerged through recent gene duplication after the divergence of these species. Transcriptome analyses showed that the genes have a putative function in the response of the pepper and tomato to abiotic stress, especially those in ERF subgroups.

CONCLUSIONS

Our findings will provide comprehensive information on AP2/ERF genes and insights into the structural, evolutionary, and functional understanding of the role of these genes in the Solanaceae.

CPR5-mediated nucleo-cytoplasmic localization of IAA12 and IAA19 controls lateral root development during abiotic stress

Plasticity of the root system architecture (RSA) is essential in enabling plants to cope with various environmental stresses and is mainly controlled by the phytohormone auxin. Lateral root development is a major determinant of RSA. Abiotic stresses reduce auxin signaling output, inhibiting lateral root development; however, how abiotic stress translates into a lower auxin signaling output is not fully understood. Here, we show that the nucleo-cytoplasmic distribution of the negative regulators of auxin signaling AUXIN/INDOLE-3-ACETIC ACID INDUCIBLE 12 (AUX/IAA12 or IAA12) and IAA19 determines lateral root development under various abiotic stress conditions. The cytoplasmic localization of IAA12 and IAA19 in the root elongation zone enforces auxin signaling output, allowing lateral root development. Among components of the nuclear pore complex, we show that CONSTITUTIVE EXPRESSOR OF PATHOGENESIS-RELATED GENES 5 (CPR5) selectively mediates the cytoplasmic translocation of IAA12/19. Under abiotic stress conditions, CPR5 expression is strongly decreased, resulting in the accumulation of nucleus-localized IAA12/19 in the root elongation zone and the suppression of lateral root development, which is reiterated in the cpr5 mutant. This study reveals a regulatory mechanism for auxin signaling whereby the spatial distribution of AUX/IAA regulators is critical for lateral root development, especially in fluctuating environmental conditions.

Phylogenomic analysis of cytochrome P450 multigene family and its differential expression analysis in pepper (Capsicum annuum L.)

Plant cytochrome P450 is a multifamily enzyme widely involved in biochemical reactions for the synthesis of antioxidants, pigments, structural polymers, and defense-related compounds. Pepper (Capsicum annuum L.) is an economically important plant. A comprehensive identification and characterization of P450 genes would provide valuable information on the evolutionary relationships of genes and their functional characteristics. In this study, we identified P450 genes in pepper with the aid of bioinformatics methods to investigate the phylogenetic relation, gene structure, chromosomal localization, duplicated events, and collinearity among Solanaceae species. We identified and classified 478 genes of P450 from the pepper genome into two major clades and nine subfamilies through phylogenetic analysis. Massive duplication events were found in the P450 gene family, which may explain the expansion of the P450 gene family. In addition, we also found that these duplication genes may have undergone strict purification selection during evolution. Gene expression analysis showed that some P450 genes that belong to clan 71 in pepper may play an important role in placenta and pericarp development. Through quantitative real-time polymerase chain reaction and transcriptome analysis, we also found that many P450 genes were related to defensive and phytohormone response in pepper. These findings provide insight for further studies to identify the biological functions of the P450 genes in pepper.

Two different domain architectures generate structural and functional diversity among bZIP genes in the Solanaceae family

The bZIP gene family is one of the largest transcription factor families and has important roles in plant growth, development, and stress responses. However, bZIP genes in the Solanaceae family have not been extensively investigated. Here, we conducted genome-wide re-annotation in nine Solanaceae species and Arabidopsis thaliana. We annotated 935 bZIP genes, including 107 (11%) that were newly identified. Structural analyses of bZIP genes in the Solanaceae family revealed that the bZIP domain displayed two types of architectures depending on the presence of an additional domain, suggesting that these architectures generate diversified structures and functions. Motif analyses indicated that the two types of bZIP genes had distinct sequences adjacent to the bZIP domain. Phylogenetic analyses suggested that the two types of bZIP genes distinctly evolved and ultimately adapted in different lineages. Transcriptome analyses in pepper (Capsicum annuum) and tomato (Solanum lycopersicum) revealed putative functional diversity between the two types of bZIP genes in response to various abiotic stresses. This study extensively updated bZIP gene family annotations and provided novel evolutionary and functional evidence for the role of bZIP genes in Solanaceae plants. Our findings provide evolutionary and functional characteristics of bZIP genes for a better understanding of their roles in Solanaceae plants.

Transcriptome-based gene regulatory network analyses of differential cold tolerance of two tobacco cultivars

BACKGROUND

Cold is one of the main abiotic stresses that severely affect plant growth and development, and crop productivity as well. Transcriptional changes during cold stress have already been intensively studied in various plant species. However, the gene networks involved in the regulation of differential cold tolerance between tobacco varieties with contrasting cold resistance are quite limited.

RESULTS

Here, we conducted multiple time-point transcriptomic analyses using Tai tobacco (TT, cold susceptibility) and Yan tobacco (YT, cold resistance) with contrasting cold responses. We identified similar DEGs in both cultivars after comparing with the corresponding control (without cold treatment), which were mainly involved in response to abiotic stimuli, metabolic processes, kinase activities. Through comparison of the two cultivars at each time point, in contrast to TT, YT had higher expression levels of the genes responsible for environmental stresses. By applying Weighted Gene Co-Expression Network Analysis (WGCNA), we identified two main modules: the pink module was similar while the brown module was distinct between the two cultivars. Moreover, we obtained 100 hub genes, including 11 important transcription factors (TFs) potentially involved in cold stress, 3 key TFs in the brown module and 8 key TFs in the pink module. More importantly, according to the genetic regulatory networks (GRNs) between TFs and other genes or TFs by using GENIE3, we identified 3 TFs (ABI3/VP1, ARR-B and WRKY) mainly functioning in differential cold responses between two cultivars, and 3 key TFs (GRAS, AP2-EREBP and C2H2) primarily involved in cold responses.

CONCLUSION

Collectively, our study provides valuable resources for transcriptome- based gene network studies of cold responses in tobacco. It helps to reveal how key cold responsive TFs or other genes are regulated through network. It also helps to identify the potential key cold responsive genes for the genetic manipulation of tobacco cultivars with enhanced cold tolerance in the future.

De novo transcriptome sequencing of Capsicum frutescens. L and comprehensive analysis of salt stress alleviating mechanism by Bacillus atrophaeus WU-9

Salt stress, as one of the most severe environmental stresses, can cause a series of changes in plants. However, the explanation of plant salt stress alleviating mechanism of plant growth-promoting rhizobacteria (PGPR) was hindered by the limited availability of transcriptomic information for salt stress-treated plants grown in a microorganism-controlled environment. Our previous reports have selected Bacillus atrophaeus WU-9 as PGPR significantly alleviating pepper (Capsicum frutescens. L) salt stress. In this work, the RNA-seq analysis of salt stress-treated and untreated plants, grown with and without WU-9 in a microorganism-controlled environment, was used to reveal the plant salt stress alleviating mechanisms of WU-9. Twelve sequencing libraries, prepared by treating with WU-9 and salt (150 mM NaCl for 36 h), were constructed by RNA-Seq technique. Non-inoculated seedlings mainly respond to salt stress through regulation of signal transduction, such as ethylene-activated signaling pathway, signaling and cell communication, etc. And ethylene signal participated in salt stress response in pepper through regulating defense responses, fruit ripening and senescence. WU-9 inoculation under salt stress mainly improves salt tolerance and plant growth by regulating salt stress-responding ethylene and auxin signal transduction, utilization of proline, photosynthesis, antioxidant enzyme activities and cell enlargement. Furthermore, 86 differentially expressed genes and 20 transcription factors were identified as associated with salt stress response and tolerance. Thus, this innovative transcriptomic study identified the salt stress response and alleviation in C. frutescens. L with PGPR inoculation. This result provided novel insights into the salinity alleviation in pepper regulated by PGPR.

RNA-Seq Analysis of Developing Grains of Wheat to Intrigue Into the Complex Molecular Mechanism of the Heat Stress Response

Heat stress is one of the significant constraints affecting wheat production worldwide. To ensure food security for ever-increasing world population, improving wheat for heat stress tolerance is needed in the presently drifting climatic conditions. At the molecular level, heat stress tolerance in wheat is governed by a complex interplay of various heat stress-associated genes. We used a comparative transcriptome sequencing approach to study the effect of heat stress (5°C above ambient threshold temperature of 20°C) during grain filling stages in wheat genotype K7903 (Halna). At 7 DPA (days post-anthesis), heat stress treatment was given at four stages: 0, 24, 48, and 120 h. In total, 115,656 wheat genes were identified, including 309 differentially expressed genes (DEGs) involved in many critical processes, such as signal transduction, starch synthetic pathway, antioxidant pathway, and heat stress-responsive conserved and uncharacterized putative genes that play an essential role in maintaining the grain filling rate at the high temperature. A total of 98,412 Simple Sequences Repeats (SSR) were identified from de novo transcriptome assembly of wheat and validated. The miRNA target prediction from differential expressed genes was performed by psRNATarget server against 119 mature miRNA. Further, 107,107 variants including 80,936 Single nucleotide polymorphism (SNPs) and 26,171 insertion/deletion (Indels) were also identified in de novo transcriptome assembly of wheat and wheat genome Ensembl version 31. The present study enriches our understanding of known heat response mechanisms during the grain filling stage supported by discovery of novel transcripts, microsatellite markers, putative miRNA targets, and genetic variant. This enhances gene functions and regulators, paving the way for improved heat tolerance in wheat varieties, making them more suitable for production in the current climate change scenario.

Comparative transcriptomic analyses of citrus cold-resistant vs. sensitive rootstocks might suggest a relevant role of ABA signaling in triggering cold scion adaption

BACKGROUND

The citrus genus comprises a number of sensitive tropical and subtropical species to cold stress, which limits global citrus distribution to certain latitudes and causes major economic loss. We used RNA-Seq technology to analyze changes in the transcriptome of Valencia delta seedless orange in response to long-term cold stress grafted on two frequently used citrus rootstocks: Carrizo citrange (CAR), considered one of the most cold-tolerant accessions; C. macrophylla (MAC), a very sensitive one. Our objectives were to identify the genetic mechanism that produce the tolerant or sensitive phenotypes in citrus, as well as to gain insights of the rootstock-scion interactions that induce the cold tolerance or sensitivity in the scion.

RESULTS

Plants were kept at 1 ºC for 30 days. Samples were taken at 0, 15 and 30 days. The metabolomic analysis showed a significant increase in the concentration of free sugars and proline, which was higher for the CAR plants. Hormone quantification in roots showed a substantially increased ABA concentration during cold exposure in the CAR roots, which was not observed in MAC. Different approaches were followed to analyze gene expression. During the stress treatment, the 0-15-day comparison yielded the most DEGs. The functional characterization of DEGs showed enrichment in GO terms and KEGG pathways related to abiotic stress responses previously described in plant cold adaption. The DEGs analysis revealed that several key genes promoting cold adaption were up-regulated in the CAR plants, and those repressing it had higher expression levels in the MAC samples.

CONCLUSIONS

The metabolomic and transcriptomic study herein performed indicates that the mechanisms activated in plants shortly after cold exposure remain active in the long term. Both the hormone quantification and differential expression analysis suggest that ABA signaling might play a relevant role in promoting the cold hardiness or sensitiveness of Valencia sweet orange grafted onto Carrizo citrange or Macrophylla rootstocks, respectively. Our work provides new insights into the mechanisms by which rootstocks modulate resistance to abiotic stress in the production variety grafted onto them.

Identification of novel PHD-finger genes in pepper by genomic re-annotation and comparative analyses

BACKGROUND

The plant homeodomain (PHD)-finger gene family that belongs to zinc-finger genes, plays an important role in epigenetics by regulating gene expression in eukaryotes. However, inaccurate annotation of PHD-finger genes hinders further downstream comparative, evolutionary, and functional studies.

RESULTS

We performed genome-wide re-annotation in Arabidopsis thaliana (Arabidopsis), Oryza sativa (rice), Capsicum annuum (pepper), Solanum tuberosum (potato), and Solanum lycopersicum (tomato) to better understand the role of PHD-finger genes in these species. Our investigation identified 875 PHD-finger genes, of which 225 (26% of total) were newly identified, including 57 (54%) novel PHD-finger genes in pepper. The PHD-finger genes of the five plant species have various integrated domains that may be responsible for the diversification of structures and functions of these genes. Evolutionary analyses suggest that PHD-finger genes were expanded recently by lineage-specific duplication, especially in pepper and potato, resulting in diverse repertoires of PHD-finger genes among the species. We validated the expression of six newly identified PHD-finger genes in pepper with qRT-PCR. Transcriptome analyses suggest potential functions of PHD-finger genes in response to various abiotic stresses in pepper.

CONCLUSIONS

Our data, including the updated annotation of PHD-finger genes, provide useful information for further evolutionary and functional analyses to better understand the roles of the PHD-finger gene family in pepper.

Chemical genetics in Silene latifolia elucidate regulatory pathways involved in gynoecium development

Dioecious plants possess diverse sex determination systems and unique mechanisms of reproductive organ development; however, little is known about how sex-linked genes shape the expression of regulatory cascades that lead to developmental differences between sexes. In Silene latifolia, a dioecious plant with stable dimorphism in floral traits, early experiments suggested that female-regulator genes act on the factors that determine the boundaries of the flower whorls. To identify these regulators, we sequenced the transcriptome of male flowers with fully developed gynoecia, induced by rapid demethylation in the parental generation. Eight candidates were found to have a positive role in gynoecium promotion, floral organ size, and whorl boundary, and affect the expression of class B MADS-box flower genes. To complement our transcriptome analysis, we closely examined the floral organs in their native state using field emission environmental scanning electron microscopy, and examined the differences between females and androhermaphrodites in their placenta and ovule organization. Our results reveal the regulatory pathways potentially involved in sex-specific flower development in the classical model of dioecy, S. latifolia. These pathways include previously hypothesized and unknown female-regulator genes that act on the factors that determine the flower boundaries, and a negative regulator of anther development, SUPERMAN-like (SlSUP).

Capsicum Leaves under Stress: Using Multi-Omics Analysis to Detect Abiotic Stress Network of Secondary Metabolism in Two Species

The plant kingdom contains an enormous diversity of bioactive compounds which regulate plant growth and defends against biotic and abiotic stress. Some of these compounds, like flavonoids, have properties which are health supporting and relevant for industrial use. Many of these valuable compounds are synthesized in various pepper (Capsicum sp.) tissues. Further, a huge amount of biomass residual remains from pepper production after harvest, which provides an important opportunity to extract these metabolites and optimize the utilization of crops. Moreover, abiotic stresses induce the synthesis of such metabolites as a defense mechanism. Two different Capsicum species were therefore exposed to chilling temperature (24/18 ℃ vs. 18/12 ℃), to salinity (200 mM NaCl), or a combination thereof for 1, 7 and 14 days to investigate the effect of these stresses on the metabolome and transcriptome profiles of their leaves. Both profiles in both species responded to all stresses with an increase over time. All stresses resulted in repression of photosynthesis genes. Stress involving chilling temperature induced secondary metabolism whereas stresses involving salt repressed cell wall modification and solute transport. The metabolome analysis annotated putatively many health stimulating flavonoids (apigetrin, rutin, kaempferol, luteolin and quercetin) in the Capsicum biomass residuals, which were induced in response to salinity, chilling temperature or a combination thereof, and supported by related structural genes of the secondary metabolism in the network analysis.

Transcriptome and Metabolome Analyses Reveal Molecular Responses of Two Pepper (Capsicum annuum L.) Cultivars to Cold Stress

Low temperature is a significant factor affecting field-grown pepper. The molecular mechanisms behind peppers' response to cold stress remain unknown. Transcriptomic and metabolomic analyses were used to investigate the responses of two pepper cultivars, XS (cold-sensitive) and GZ (cold-resistant), to cold stress; these were screened from 45 pepper materials. In this study, compared with the control group (0 h), we identified 10,931 differentially expressed genes (DEGs) in XS and GZ, 657 differentially expressed metabolites (DEMs) in the positive ion mode, and 390 DEMs in the negative ion mode. Most DEGs were involved in amino acid biosynthesis, plant hormone signal transduction, and the mitogen-activated protein kinase (MAPK) signaling pathway. Furthermore, metabolomic analysis revealed that the content of free polyamines (PAs), plant hormones, and osmolytes, mainly contained increased putrescine, spermine, spermidine, abscisic acid (ABA), jasmonic acid (JA), raffinose, and proline, in response to cold stress. Importantly, the regulation of the ICE (inducer of CBF expression)-CBF (C repeat binding factors)-COR (cold regulated) pathway by Ca²⁺ signaling, MAPK signaling, and reactive oxygen species (ROS) signaling plays a key role in regulating responses of peppers to cold stress. Above all, the results of the present study provide important insights into the response of peppers to cold stress, which will reveal the potential molecular mechanisms and contribute to pepper screening and breeding in the future.

Universal gene co-expression network reveals receptor-like protein genes involved in broad-spectrum resistance in pepper (Capsicum annuum L.)

Receptor-like proteins (RLPs) on plant cells have been implicated in immune responses and developmental processes. Although hundreds of RLP genes have been identified in plants, only a few RLPs have been functionally characterized in a limited number of plant species. Here, we identified RLPs in the pepper (Capsicum annuum) genome and performed comparative transcriptomics coupled with the analysis of conserved gene co-expression networks (GCNs) to reveal the role of core RLP regulators in pepper-pathogen interactions. A total of 102 RNA-seq datasets of pepper plants infected with four pathogens were used to construct CaRLP-targeted GCNs (CaRLP-GCNs). Resistance-responsive CaRLP-GCNs were merged to construct a universal GCN. Fourteen hub CaRLPs, tightly connected with defense-related gene clusters, were identified in eight modules. Based on the CaRLP-GCNs, we evaluated whether hub CaRLPs in the universal GCN are involved in the biotic stress response. Of the nine hub CaRLPs tested by virus-induced gene silencing, three genes (CaRLP264, CaRLP277, and CaRLP351) showed defense suppression with less hypersensitive response-like cell death in race-specific and non-host resistance response to viruses and bacteria, respectively, and consistently enhanced susceptibility to Ralstonia solanacearum and/or Phytophthora capsici. These data suggest that key CaRLPs are involved in the defense response to multiple biotic stresses and can be used to engineer a plant with broad-spectrum resistance. Together, our data show that generating a universal GCN using comprehensive transcriptome datasets can provide important clues to uncover genes involved in various biological processes.

[Ribosomal profiling as a tool for studying translation in plants: main results, problems and future prospects]

The expression of eukaryotic genes can be regulated at several stages, including the translation of mRNA. It is known that the structure of mRNA can affect both the efficiency of interaction with the translation apparatus in general and the choice of translation initiation sites. To study the translated fraction of the transcriptome, experimental methods of analysis were developed, the most informative of which is ribosomal profiling (RP, Ribo-seq). Originally developed for use in yeast systems, this method has been adapted for research in translation mechanisms in many plant species. This technology includes the isolation of the polysomal fraction and high-performance sequencing of a pool of mRNA fragments associated with ribosomes. Comparing the results of transcript coverage with reads obtained using the ribosome profiling with the transcriptional efficiency of genes allows the translation efficiency to be evaluated for each transcript. The exact positions of ribosomes determined on mRNA sequences allow determining the translation of open reading frames and switching between the translation of several reading frames - a phenomenon in which two or more overlapping frames are read from one mRNA and different proteins are synthesized. The advantage of this method is that it provides quantitative estimates of ribosome coverage of mRNA and can detect relatively rare translation events. Using this technology, it was possible to identify and classify plant genes by the type of regulation of their expression at the transcription, translation, or both levels. Features of the mRNA structure that affect translation levels have been revealed: the formation of G2 quadruplexes and the presence of specific motifs in the 5'-UTR region, GC content, the presence of alternative translation starts, and the influence of uORFs on the translation of downstream mORFs. In this review, we briefly reviewed the RP methodology and the prospects for its application to study the structural and functional organization and regulation of plant gene expression.

Differential Functions of Pepper Stress-Associated Proteins in Response to Abiotic Stresses

Stress-associated proteins (SAPs), a group of zinc-finger-type proteins, have been identified as novel regulators of plant abiotic and biotic stresses. However, although they have been discovered in different plant species, their precise functional roles remain unclear. Here, we identified 14 SAP subfamily genes in the pepper genome. An investigation of the promoter regions of these genes for cis-regulatory elements associated with abiotic stress responses revealed the presence of multiple stress-related elements. Domain and phylogenetic analyses using the corresponding protein sequences revealed that the CaSAP genes can be classified into six groups (I-VI) and sorted into two broad types. Expression levels of the CaSAP genes were found to be differentially induced by low temperature, the dehydration stress, or exogenous abscisic acid. Group II and IV genes were highly induced by the low temperature and dehydration treatments, respectively. Moreover, subcellular localization analysis indicated that the proteins in these two groups are distributed in the nucleus, cytoplasm, and plasma membrane. Among the pepper plants silenced with the three identified group II CaSAP genes, the CA02g10410-silenced plants showed tolerance to low temperature, whereas the CA03g17080-silenced plants were found to have temperature-sensitive phenotypes. Interestingly, group IV CaSAP-silenced pepper plants showed drought-tolerant phenotypes. These findings contribute to a preliminary characterization of CaSAP genes and provide directions for future research on the biological role of CaSAPs in response to different abiotic stresses.

Expression Profiling of Heat Shock Protein Genes as Putative Early Heat-Responsive Members in Lettuce

High temperatures due to global warming can cause harmful effects on the productivity of lettuce, a cool-season crop. To identify lettuce heat shock protein (HSP) genes that could be involved in early responses to heat stress in plants, we compared RNA transcriptomes between lettuce plants with and without heat treatment of 37 °C for 1 h. Using transcriptome sequencing analyses, a total of 7986 differentially expressed genes (DEGs) were identified including the top five, LsHSP70A, LsHSP70B, LsHSP17.3A, LsHSP17.9A and LsHSP17.9B, which were the most highly differentially expressed genes. In order to investigate the temporal expression patterns of 24 lettuce HSP genes with a fold-change greater than 100 under heat stress, the expression levels of the genes were measured by qRT-PCR at 0, 1, 4, 8, 14, and 24 h time points after heat treatment. The 24 LsHSP genes were classified into three groups based on the phylogenetic analysis and/or major domains available in each protein, and we provided a potential link between the phylogenetic relationships and expression patterns of the LsHSP genes. Our results showed putative early heat-responsive lettuce HSP genes that could be possible candidates as breeding guides for the development of heat-tolerant lettuce cultivars.

AP2/ERF, an important cold stress-related transcription factor family in plants: A review

Increasing the vulnerability of plants especially crops to a wide range of cold stress reduces plant growth, development, yield production, and plant distribution. Cold stress induces physiological, morphological, biochemical, phenotypic, and molecular changes in plants. Transcription factor (TF) is one of the most important regulators that mediate gene expression. TF is activated by the signal transduction pathway, together with cis-acting element modulate the transcription of cold-responsive genes which contribute to increasing cold tolerance in plants. Here, AP2/ERF TF family is one of the most important cold stress-related TF families that along with other TF families, such as WRKY, bHLH, bZIP, MYB, NAC, and C2H2 interrelate to enhance cold stress tolerance. Over the past decade, significant progress has been found to solve the role of transcription factors (TFs) in improving cold tolerance in plants, such as omics analysis. Furthermore, numerous studies have identified and characterized the complexity of cold stress mechanisms among TFs or between TFs and other factors (endogenous and exogenous) including phytohormones, eugenol, and light. The role, function, and relationship among these TFs or between TFs and other factors to enhance cold tolerance still need to be clarified. Here, the current study analysed the role of AP2/ERF TF and the linkages among AP2/ERF with MYB, WRKY, bZIP, bHLH, C2H2, or NAC against cold stress tolerance.

Epigenetic approaches to crop breeding: current status and perspectives

In order to tackle the cumulative adverse effects of global climate change, reduced farmland, and heightened needs of an ever-increasing world population, modern agriculture is in urgent search of solutions that can ensure world food security and sustainable development. Classical crop breeding is still a powerful method to obtain crops with valued agronomical traits, but its potential is gradually being compromised by the menacing decline of genetic variation. Resorting to the epigenome as a source of variation could serve as a promising alternative. Here, we discuss current status of epigenetics-mediated crop breeding (epibreeding), highlight its advances and limitations, outline currently available methodologies, and propose novel RNA-based strategies to modify the epigenome in a gene-specific and transgene-free manner.

OMICs, Epigenetics, and Genome Editing Techniques for Food and Nutritional Security

The incredible success of crop breeding and agricultural innovation in the last century greatly contributed to the Green Revolution, which significantly increased yields and ensures food security, despite the population explosion. However, new challenges such as rapid climate change, deteriorating soil, and the accumulation of pollutants require much faster responses and more effective solutions that cannot be achieved through traditional breeding. Further prospects for increasing the efficiency of agriculture are undoubtedly associated with the inclusion in the breeding strategy of new knowledge obtained using high-throughput technologies and new tools in the future to ensure the design of new plant genomes and predict the desired phenotype. This article provides an overview of the current state of research in these areas, as well as the study of soil and plant microbiomes, and the prospective use of their potential in a new field of microbiome engineering. In terms of genomic and phenomic predictions, we also propose an integrated approach that combines high-density genotyping and high-throughput phenotyping techniques, which can improve the prediction accuracy of quantitative traits in crop species.

Quantitative proteomic analysis to capture the role of heat-accumulated proteins in moss plant acquired thermotolerance

At dawn of a scorching summer day, land plants must anticipate upcoming extreme midday temperatures by timely establishing molecular defences that can keep heat-labile membranes and proteins functional. A gradual morning pre-exposure to increasing sub-damaging temperatures induces heat-shock proteins (HSPs) that are central to the onset of plant acquired thermotolerance (AT). To gain knowledge on the mechanisms of AT in the model land plant Physcomitrium patens, we used label-free LC-MS/MS proteomics to quantify the accumulated and depleted proteins before and following a mild heat-priming treatment. High protein crowding is thought to promote protein aggregation, whereas molecular chaperones prevent and actively revert aggregation. Yet, we found that heat priming (HP) did not accumulate HSP chaperones in chloroplasts, although protein crowding was six times higher than in the cytosol. In contrast, several HSP20s strongly accumulated in the cytosol, yet contributing merely 4% of the net mass increase of heat-accumulated proteins. This is in poor concordance with their presumed role at preventing the aggregation of heat-labile proteins. The data suggests that under mild HP unlikely to affect protein stability. Accumulating HSP20s leading to AT, regulate the activity of rare and specific signalling proteins, thereby preventing cell death under noxious heat stress.

Genetic Improvement in Sunflower Breeding—Integrated Omics Approach

Foresight in climate change and the challenges ahead requires a systematic approach to sunflower breeding that will encompass all available technologies. There is a great scarcity of desirable genetic variation, which is in fact undiscovered because it has not been sufficiently researched as detection and designing favorable genetic variation largely depends on thorough genome sequencing through broad and deep resequencing. Basic exploration of genomes is insufficient to find insight about important physiological and molecular mechanisms unique to crops. That is why integrating information from genomics, epigenomics, transcriptomics, proteomics, metabolomics and phenomics enables a comprehensive understanding of the molecular mechanisms in the background of architecture of many important quantitative traits. Omics technologies offer novel possibilities for deciphering the complex pathways and molecular profiling through the level of systems biology and can provide important answers that can be utilized for more efficient breeding of sunflower. In this review, we present omics profiling approaches in order to address their possibilities and usefulness as a potential breeding tools in sunflower genetic improvement.

Comparative Analysis of Re-Annotated Genes Provides Insight into Evolutionary Divergence and Expressions of Aquaporin Family in Pepper

Aquaporins (AQPs) are known to have a vital role in water transport in all living organisms including agriculturally important crops, but a comprehensive genomic study of AQPs in pepper has not been implemented. Here, we updated previous gene annotations and generated a total of 259 AQP genes from five plants, including pepper. Phylogenetic and motif analyses revealed that a large proportion of pepper AQP genes belong to the specific subgroup of tonoplast intrinsic protein (TIP) subfamily, TIP4. Chromosomal localization and estimated duplication times illustrated that genes in TIP4 formed a tandem array on the short arm of chromosome 1, resulting from pepper-specific expansion after its divergence with Solanaceae species. Transcriptome analyses under various abiotic stress conditions revealed that transport-, photosystem-, and thylakoid-related genes were generally enriched in expression clusters containing AQP genes in pepper. These results provide valuable genomic resources and insight into the evolutionary mechanism that generate genomic diversity of the AQP gene family in pepper.

Tissue-Specific RNA-Seq Analysis and Identification of Receptor-Like Proteins Related to Plant Growth in Capsicum annuum

Receptor-like proteins (RLPs) are a gene family of cell surface receptors that are involved in plant growth, development, and disease resistance. In a recent study, 438 pepper RLP genes were identified in the Capsicum annuum genome (CaRLPs) and determined to be present in response to multiple biotic stresses. To further understand the role of CaRLPs in plant growth and development, we analyzed expression patterns of all CaRLPs from various pepper tissues and developmental stages using RNA-seq. Ten CaRLP genes were selected for further analysis according to transcript levels with hierarchical clustering. The selected CaRLP genes displayed similarity of motifs within the same groups and structures typical of RLPs. To examine RLP function in growth and development, we performed loss-of-function analysis using a virus-induced gene silencing system. Three of the ten tested CaRLPs (CaRLP238, 253, and 360) in silenced plants exhibited phenotypic alteration with growth retardation compared to controls. All three gene-silenced peppers showed significant differences in root dry weight. Only CaRLP238 had significant differences in both root and shoot dry weight. Our results suggest that CaRLPs may play important roles in regulation of plant growth and development as well as function in defense responses to biotic stresses in the RLP gene family.

Genome wide identification and characterization of abiotic stress responsive lncRNAs in Capsicum annuum

Long non-coding RNAs (lncRNAs) are a type of non-coding transcripts having length of more than 200 nucleotides lacking protein-coding ability. In the present study, 12807 lncRNAs were identified in Capsicum annuum tissues exposed to abiotic stress conditions viz. heat, cold, osmotic and salinity stress. Expression analysis of lncRNAs in different treatment conditions demonstrates their stress-specific expression. Thirty lncRNAs were found to act as precursors for 10 microRNAs (miRNAs) of C. annuum. Additionally, a total of 1807 lncRNAs were found to interact with 194 miRNAs which targeted 621 mRNAs of C. annuum. Among these, 344 lncRNAs were found to act as target mimics for 621 genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that out of those 621 gene sequences, 546 were tagged with GO terms, 105 Enzyme Code (EC) numbers were assigned to 246 genes and 223 genes are found to be involved in 63 biological pathways. In this report, we have highlighted the prospective role of lncRNAs in different abiotic stress conditions by interacting with miRNAs and regulating stress responsive transcription factors (TFs) such as DoF, WRKY, MYB, bZIP and ERF in C. annuum.

Can omics deliver temperature resilient ready-to-grow crops?

Plants are extensively well-thought-out as the main source for nourishing natural life on earth. In the natural environment, plants have to face several stresses, mainly heat stress (HS), chilling stress (CS) and freezing stress (FS) due to adverse climate fluctuations. These stresses are considered as a major threat for sustainable agriculture by hindering plant growth and development, causing damage, ultimately leading to yield losses worldwide and counteracting to achieve the goal of "zero hunger" proposed by the Food and Agricultural Organization (FAO) of the United Nations. Notably, this is primarily because of the numerous inequities happening at the cellular, molecular and/or physiological levels, especially during plant developmental stages under temperature stress. Plants counter to temperature stress via a complex phenomenon including variations at different developmental stages that comprise modifications in physiological and biochemical processes, gene expression and differences in the levels of metabolites and proteins. During the last decade, omics approaches have revolutionized how plant biologists explore stress-responsive mechanisms and pathways, driven by current scientific developments. However, investigations are still required to explore numerous features of temperature stress responses in plants to create a complete idea in the arena of stress signaling. Therefore, this review highlights the recent advances in the utilization of omics approaches to understand stress adaptation and tolerance mechanisms. Additionally, how to overcome persisting knowledge gaps. Shortly, the combination of integrated omics, genome editing, and speed breeding can revolutionize modern agricultural production to feed millions worldwide in order to accomplish the goal of "zero hunger."

Leaf-to-Whole Plant Spread Bioassay for Pepper and Ralstonia solanacearum Interaction Determines Inheritance of Resistance to Bacterial Wilt for Further Breeding

Bacterial wilt (BW) disease from Ralstonia solanacearum is a serious disease and causes severe yield losses in chili peppers worldwide. Resistant cultivar breeding is the most effective in controlling BW. Thus, a simple and reliable evaluation method is required to assess disease severity and to investigate the inheritance of resistance for further breeding programs. Here, we developed a reliable leaf-to-whole plant spread bioassay for evaluating BW disease and then, using this, determined the inheritance of resistance to R. solanacearum in peppers. Capsicum annuum ‘MC4′ displayed a completely resistant response with fewer disease symptoms, a low level of bacterial cell growth, and significant up-regulations of defense genes in infected leaves compared to those in susceptible ‘Subicho’. We also observed the spreading of wilt symptoms from the leaves to the whole susceptible plant, which denotes the normal BW wilt symptoms, similar to the drenching method. Through this, we optimized the evaluation method of the resistance to BW. Additionally, we performed genetic analysis for resistance inheritance. The parents, F₁ and 90 F₂ progenies, were evaluated, and the two major complementary genes involved in the BW resistance trait were confirmed. These could provide an accurate evaluation to improve resistant pepper breeding efficiency against BW.

An insight into the role of silicon on retaliation to osmotic stress in finger millet (Eleusine coracana (L.) Gaertn)

Finger millet, a vital nutritional cereal crop provides food security. It is a well-established fact that silicon (Si) supplementation to plants alleviates both biotic and abiotic stresses. However, precise molecular targets of Si remain elusive. The present study attempts to understand the alterations in the metabolic pathways after Si amendment under osmotic stress. The analysis of transcriptome and metabolome of finger millet seedlings treated with distilled water (DW) as control, Si (10 ppm), PEG (15%), and PEG (15%) + Si (10 ppm) suggest the molecular alterations mediated by Si for ameliorating the osmotic stress. Under osmotic stress, uptake of Si has increased mediating the diversion of an enhanced pool of acetyl CoA to lipid biosynthesis and down-regulation of TCA catabolism. The membrane lipid damage reduced significantly by Si under osmotic stress. A significant decrease in linolenic acid and an increase of jasmonic acid (JA) in PEG + Si treatment suggest the JA mediated regulation of osmotic stress. The relative expression of transcripts corroborated with the corresponding metabolites abundance levels indicating the activity of genes in assuaging the osmotic stress. This work substantiates the role of Si in osmotic stress tolerance by reprogramming of fatty acids biosynthesis in finger millet.

Integration of mRNA and miRNA profiling reveals the heterosis of three hybrid combinations of Capsicum annuum varieties

Capsicum annuum is also known as chili which is one of the most important vegetable crops grown in the world. Breeding new varieties with heterosis could improve the quality of pepper, increase yield, growth potential, disease resistance, adaptability, and seed viability. To investigate the heterosis among three cross combinations of different parents, the mRNA-miRNA integrated analysis was performed. A total number of 22,659,009 to 36,423,818 clean data were generated from mRNA-seq with 81 libraries, and the unique mapped reads were from 35,495,567 (86.81%) to 46,466,622 (88.95%). The plant-hormone signal transduction pathway (40 genes) was detected with a higher DEG number. The SAUR32L, GID1, PYR1, EIN2. ERF1, PR1, JAR1-like, IAA from this pathway play a key role in plant development. From the miRNA-seq, the number of clean reads was ranging from 12,132,221 to 25,632,680. A total of 220 miRNAs were predicted in this study, and all of them were identified as novel miRNA. The top three candidate KEGG pathways of miRNA were ribosome signaling pathway (13 miRNAs), spliceosome pathway (13 miRNAs), and plant hormone signal transduction pathways (10 miRNAs). With the mRNA and miRNA integrated analysis, we found some key genes were regulated by some miRNAs. Among them, the scarecrow-like 6 protein can be up or down regulated by mir8, mir120, mir184, mir_214, mir125, and mir130. The function of Della protein was regulated by mir24, mir74, mir94, mir139, and mir190. This study contributes to understanding how heterosis regulates the traits, such as crop production, fruit weight, and fruit length.

Characterization of novel regulators for heat stress tolerance in tomato from Indian sub-continent

The footprint of tomato cultivation, a cool region crop that exhibits heat stress (HS) sensitivity, is increasing in the tropics/sub-tropics. Knowledge of novel regulatory hot spots from varieties growing in the Indian sub-continent climatic zones could be vital for developing HS-resilient crops. Comparative transcriptome-wide signatures of a tolerant (CLN1621L) and sensitive (CA4) cultivar pair shortlisted from a pool of varieties exhibiting variable thermo-sensitivity using physiological-, survival- and yield-related traits revealed redundant to cultivar-specific HS regulation. The antagonistically expressing genes encode enzymes and proteins that have roles in plant defence and abiotic stresses. Functional characterization of three antagonistic genes by overexpression and silencing established Solyc09g014280 (Acylsugar acyltransferase) and Solyc07g056570 (Notabilis) that are up-regulated in tolerant cultivar, as positive regulators of HS tolerance and Solyc03g020030 (Pin-II proteinase inhibitor), that are down-regulated in CLN1621L, as negative regulator of thermotolerance. Transcriptional assessment of promoters of these genes by SNPs in stress-responsive cis-elements and promoter swapping experiments in opposite cultivar background showed inherent cultivar-specific orchestration of transcription factors in regulating transcription. Moreover, overexpression of three ethylene response transcription factors (ERF.C1/F4/F5) also improved HS tolerance in tomato. This study identifies several novel HS tolerance genes and provides proof of their utility in tomato thermotolerance.

Ribosome profiling in plants: what is not lost in translation?

Translation is a highly dynamic cellular process whereby genetic information residing in an mRNA molecule is converted into a protein that in turn executes specific functions. However, pre-synthesized mRNA levels do not always correlate with corresponding protein levels, suggesting that translational control plays an essential role in gene regulation. A better understanding of how gene expression is regulated during translation will enable the discovery of new genes and mechanisms that control important traits in plants. Therefore, in recent years, several methods have been developed to analyse the translatome; that is, all mRNAs being actively translated at a given time, tissue, and/or developmental stage. Ribosome profiling or ribo-seq is one such technology revolutionizing our ability to analyse the translatome and in turn understand translational control of gene expression. Ribo-seq involves isolating mRNA-ribosome complexes, treating them with a RNase, and then identifying ribosome-protected mRNA regions by deep sequencing. Here, we briefly review recent ribosome profiling studies that revealed new insights into plant biology. Manipulation of novel genes identified using ribosome profiling could prove useful for increasing yield through improved biotic and abiotic stress tolerance.

Comprehensive transcriptome resource for response to phytohormone-induced signaling in Capsicum annuum L

OBJECTIVES

Phytohormones are small signaling molecules with crucial roles in plant growth, development, and environmental adaptation to biotic and abiotic stress responses. Despite several previously published molecular studies focused on plant hormones, our understanding of the transcriptome induced by phytohormones remains unclear, especially in major crops. Here, we aimed to provide transcriptome dataset using RNA sequencing for phytohormone-induced signaling in plant.

DATA DESCRIPTION

We used high-throughput RNA sequencing profiling to investigate the pepper plant response to treatment with four major phytohormones (salicylic acid, jasmonic acid, ethylene, and abscisic acid). This dataset yielded 78 samples containing three biological replicates per six different time points for each treatment and the control, constituting 187.8 Gb of transcriptome data (2.4 Gb of each sample). This comprehensive parallel transcriptome data provides valuable information for understanding the relationships and molecular networks that regulate the expression of phytohormone-related genes involved in plant developments and environmental stress adaptation.

Capsidiol-related genes are highly expressed in response to Colletotrichum scovillei during Capsicum annuum fruit development stages

Capsicum annuum is one of the most important horticultural crops worldwide. Anthracnose disease (Colletotrichum spp.) is a major constraint for chili production, causing substantial losses. Capsidiol is a sesquiterpene phytoalexin present in pepper fruits that can enhance plant resistance. The genetic mechanisms involved in capisidiol biosynthesis are still poorly understood. In this study, a 3′ RNA sequencing approach was used to develop the transcriptional profile dataset of C. annuum genes in unripe (UF) and ripe fruits (RF) in response to C. scovillei infection. Results showed 4,845 upregulated and 4,720 downregulated genes in UF, and 2,560 upregulated and 1,762 downregulated genes in RF under fungus inoculation. Four capsidiol-related genes were selected for RT-qPCR analysis, two 5-epi-aristolochene synthase (CA12g05030, CA02g09520) and two 5-epi-aristolochene-1,3-dihydroxylase genes (CA12g05070, CA01g05990). CA12g05030 and CA01g05990 genes showed an early response to fungus infection in RF (24 h post-inoculation—HPI), being 68-fold and 53-fold more expressed at 96 HPI, respectively. In UF, all genes showed a late response, especially CA12g05030, which was 700-fold more expressed at 96 HPI compared to control plants. We are proving here the first high-throughput expression dataset of pepper fruits in response to anthracnose disease in order to contribute for future pepper breeding programs.

Comparative transcriptomics of the pheromone glands provides new insights into the differentiation of sex pheromone between two host populations of Chilo suppressalis

Reproductive isolation between different host populations is often based on intraspecific sex pheromone differences. The mechanisms underlying these differences have not been thoroughly elucidated to date. Previous studies suggested that Chilo suppressalis has differentiated into rice and water-oat host populations, and these two populations manifest clear differences in sex pheromone titer and mating rhythm. Hence, this moth is an ideal model to investigate the endogenous mechanisms of intraspecific reproductive isolation. Here, we identified a series of putative genes associated with sex pheromone biosynthesis based on the C. suppressalis pheromone gland transcriptome data. Transcripts of most genes were at higher level in the rice population. Then we obtained 11 pivotal differentially expressed genes (DEGs). The expression levels of these DEGs exhibited a distinct increase in the rice population. Moreover, we also observed the expression rhythm of these DEGs is discrepant between two host populations. Our study offers a new understanding to elucidate the mechanisms of intraspecific reproductive isolation.