Classification of barley U-box E3 ligases and their expression patterns in response to drought and pathogen stresses

Studies on the regulation of E3 ubiquitin ligase APC3 and its interacting proteins on the tetraspore formation and release in Gracilariopsis lemaneiformis (Rhodophyta)

E3 ubiquitin ligases play significant roles in development of high plants and animals. We recently found that E3 ubiquitin ligase APC3, the subunit of the anaphase promoting complex/cyclosome, was involved in tetraspore formation and release in Gracilariopsis lemaneiformis, an economically important red alga. GlAPC3 showed opposite expression pattern in low-fertility cultivar 981 and high-fertility strain WLP during the process of tetraspore formation and release, up-regulated in 981 and down-regulated in WLP. Five proteins related to chromosome segregation, SMC3, NUF2, APC2, APC8 and APC10, were detected to interact with APC3, which were all located in the nucleus. NUF2 and CDC20 were the substrates of APC3, combined with Lysine-11, Lysine-48 and Lysine-63 of ubiquitin chains containing two or four ubiquitin. The key amino acids for ubiquitination of APC3 covered 474th Aspartate, 502nd tyrosine and 506th leucine, any mutation of which resulted in a loss of ubiquitination. During the process of tetraspore formation and release, SMC3 was significantly up-regulated only in 981, low number of tetraspore release. NUF2 and APC2 were significantly down-regulated only in WLP, with high frequency and large amount of tetraspores release. The data provided that APC3, SMC3 and NUF2 might be the key gene affecting the fertility of Gp. lemaneiformis. The study helps to explore the regulation mechanism of APC3 with SMC3 and NUF2 by the process of chromatids segregation in regulating tetraspore formation and release of Gp. lemaneiformis.

Wheat E3 ligase TaPRP19 is involved in drought stress tolerance in transgenic Arabidopsis

TaPRP19, a wheat U-box E3 ligase gene, was isolated and characterized for its role in drought stress tolerance. The gene encodes a 531 amino acid protein with a U-box domain at the N-terminal and a WD40 domain at the C-terminal. Subcellular localization studies using TaPRP19-GFP fusion in Nicotiana benthamiana confirmed predominant nucleus localization. In vitro ubiquitination assays demonstrated that TaPRP19 possesses E3 ligase activity. RT-qPCR analysis revealed higher expression of TaPRP19 in wheat leaves, which increased under PEG, mannitol, and ABA treatments. Transgenic Arabidopsis lines overexpressing TaPRP19 exhibited improved seed germination rates and root elongation under mannitol and ABA stress, as well as enhanced survival rates under drought conditions compared to wild-type (WT) plants. Additionally, these transgenic lines showed upregulated expression of antioxidant-related and drought-marker genes, reduced ROS accumulation, and increased activities of antioxidant enzymes, suggesting enhanced oxidative stress mitigation. These findings highlight TaPRP19 as a potential target for developing drought-tolerant crops, providing insights into its functional mechanisms and paving the way for future genetic engineering applications in wheat and other crops.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-025-01557-7.

Proteasomal Dysfunction in Cancer: Mechanistic Pathways and Targeted Therapies

Proteasomes are the catalytic complexes in eukaryotic cells that decide the fate of proteins involved in various cellular processes in an energy-dependent manner. The proteasomal system performs its function by selectively destroying the proteins labelled with the small protein ubiquitin. Dysfunctional proteasomal activity is allegedly involved in various clinical disorders such as cancer, neurodegenerative disorders, ageing, and so forth, making it an important therapeutic target. Notably, compared to healthy cells, cancer cells have a higher protein homeostasis requirement and a faster protein turnover rate. The ubiquitin-proteasome system (UPS) helps cancer cells increase rapidly and experience less apoptotic cell death. Therefore, understanding UPS is essential to design and discover some effective inhibitors for cancer therapy. Hereby, we have focused on the role of the 26S proteasome complex, mainly the UPS, in carcinogenesis and seeking potential therapeutic targets in treating numerous cancers.

Cullin-Conciliated Regulation of Plant Immune Responses: Implications for Sustainable Crop Protection

Cullins are crucial components of the ubiquitin-proteasome system, playing pivotal roles in the regulation of protein metabolism. This review provides insight into the wide-ranging functions of cullins, particularly focusing on their impact on plant growth, development, and environmental stress responses. By modulating cullin-mediated protein mechanisms, researchers can fine-tune hormone-signaling networks to improve various agronomic traits, including plant architecture, flowering time, fruit development, and nutrient uptake. Furthermore, the targeted manipulation of cullins that are involved in hormone-signaling pathways, e.g., cytokinin, auxin, gibberellin, abscisic acids, and ethylene, can boost crop growth and development while increasing yield and enhancing stress tolerance. Furthermore, cullins also play important roles in plant defense mechanisms through regulating the defense-associated protein metabolism, thus boosting resistance to pathogens and pests. Additionally, this review highlights the potential of integrating cullin-based strategies with advanced biological tools, such as CRISPR/Cas9-mediated genome editing, genetic engineering, marker-associated selections, gene overexpression, and gene knockout, to achieve precise modifications for crop improvement and sustainable agriculture, with the promise of creating resilient, high-yielding, and environmentally friendly crop varieties.

A review on ubiquitin ligases: Orchestrators of plant resilience in adversity

Ubiquitin- proteasome system (UPS) is universally present in plants and animals, mediating many cellular processes needed for growth and development. Plants constantly defend themselves against endogenous and exogenous stimuli such as hormonal signaling, biotic stresses such as viruses, fungi, nematodes, and abiotic stresses like drought, heat, and salinity by developing complex regulatory mechanisms. Ubiquitination is a regulatory mechanism involving selective elimination and stabilization of regulatory proteins through the UPS system where E3 ligases play a central role; they can bind to the targets in a substrate-specific manner, followed by poly-ubiquitylation, and subsequent protein degradation by 26 S proteasome. Increasing evidence suggests different types of E3 ligases play important roles in plant development and stress adaptation. Herein, we summarize recent advances in understanding the regulatory roles of different E3 ligases and primarily focus on protein ubiquitination in plant-environment interactions. It also highlights the diversity and complexity of these metabolic pathways that enable plant to survive under challenging conditions. This reader-friendly review provides a comprehensive overview of E3 ligases and their substrates associated with abiotic and biotic stresses that could be utilized for future crop improvement.

GL5.2, a Quantitative Trait Locus for Rice Grain Shape, Encodes a RING-Type E3 Ubiquitin Ligase

Grain weight and grain shape are important traits that determine rice grain yield and quality. Mining more quantitative trait loci (QTLs) that control grain weight and shape will help to further improve the molecular regulatory network of rice grain development and provide gene resources for high-yield and high-quality rice varieties. In the present study, a QTL for grain length (GL) and grain width (GW), qGL5.2, was firstly fine-mapped into a 21.4 kb region using two sets of near-isogenic lines (NILs) derived from the indica rice cross Teqing (TQ) and IRBB52. In the NIL populations, the GL and ratio of grain length to grain width (RLW) of the IRBB52 homozygous lines increased by 0.16-0.20% and 0.27-0.39% compared with the TQ homozygous lines, but GW decreased by 0.19-0.75%. Then, by analyzing the grain weight and grain shape of the knock-out mutant, it was determined that the annotation gene Os05g0551000 encoded a RING-type E3 ubiquitin ligase, which was the cause gene of qGL5.2. The results show that GL and RLW increased by 2.44-5.48% and 4.19-10.70%, but GW decreased by 1.69-4.70% compared with the recipient. Based on the parental sequence analysis and haplotype analysis, one InDel variation located at -1489 in the promoter region was likely to be the functional site of qGL5.2. In addition, we also found that the Hap 5 (IRBB52-type) increased significantly in grain length and grain weight compared with other haplotypes, indicating that the Hap 5 can potentially be used in rice breeding to improve grain yield and quality.

RING/U-box E3 protein BIR1 interacts with and ubiquitinates barley growth repressor BROAD LEAF1

Establishment of final leaf size in plants relies on the precise regulation of 2 interconnected processes, cell division and cell expansion. The barley (Hordeum vulgare) protein BROAD LEAF1 (BLF1) limits cell proliferation and leaf growth in the width direction. However, how the levels of this potent repressor of leaf growth are controlled remains unclear. Here, we used a yeast 2-hybrid screen to identify the BLF1-INTERACTING RING/U-BOX 1 (BIR1) E3 ubiquitin ligase that interacts with BLF1 and confirmed the interaction of the 2 proteins in planta. Inhibiting the proteasome caused overaccumulation of a BLF1-eGFP fusion protein when co-expressed with BIR1, and an in vivo ubiquitination assay in bacteria confirmed that BIR1 can mediate ubiquitination of BLF1 protein. Consistent with regulation of endogenous BLF1 in barley by proteasomal degradation, inhibition of the proteasome in BLF1-vYFP-expressing barley plants caused an accumulation of the BLF1 protein. The BIR1 protein co-localized with BLF1 in nuclei and appeared to reduce BLF1 protein levels. Analysis of bir1-1 knockout mutants suggested the involvement of BIR1 in leaf growth control, although mainly on leaf length. Together, our results suggest that proteasomal degradation, in part mediated by BIR1, helps fine-tune BLF1 protein levels in barley.

Genome-wide identification and expression analysis of the U-box E3 ubiquitin ligase gene family related to bacterial wilt resistance in tobacco (Nicotiana tabacum L.) and eggplant (Solanum melongena L.)

The E3 enzyme in the UPS pathway is a crucial factor for inhibiting substrate specificity. In Solanaceae, the U-box E3 ubiquitin ligase has a complex relationship with plant growth and development, and plays a pivotal role in responding to various biotic and abiotic stresses. The analysis of the U-box gene family in Solanaceae and its expression profile under different stresses holds significant implications. A total of 116 tobacco NtU-boxs and 56 eggplant SmU-boxs were identified based on their respective genome sequences. Phylogenetic analysis of U-box genes in tobacco, eggplant, tomato, Arabidopsis, pepper, and potato revealed five distinct subgroups (I-V). Gene structure and protein motifs analysis found a high degree of conservation in both exon/intron organization and protein motifs among tobacco and eggplant U-box genes especially the members within the same subfamily. A total of 15 pairs of segmental duplication and 1 gene pair of tandem duplication were identified in tobacco based on the analysis of gene duplication events, while 10 pairs of segmental duplication in eggplant. It is speculated that segmental duplication events are the primary driver for the expansion of the U-box gene family in both tobacco and eggplant. The promoters of NtU-box and SmU-box genes contained cis-regulatory elements associated with cellular development, phytohormones, environment stress, and photoresponsive elements. Transcriptomic data analysis shows that the expression levels of the tobacco and eggplant U-box genes in different tissues and various abiotic stress conditions. Using cultivar Hongda of tobacco and cultivar Yanzhi of eggplant as materials, qRT-PCR analysis has revealed that 15 selected NtU-box genes and 8 SmU-box may play important roles in response to pathogen Ras invasion both in tobacco and eggplant.

The MYC2-PUB22-JAZ4 module plays a crucial role in jasmonate signaling in tomato

Jasmonates (JAs), a class of lipid-derived stress hormones, play a crucial role across an array of plant physiological processes and stress responses. Although JA signaling is thought to rely predominantly on the degradation of specific JAZ proteins by SCFCOI1, it remains unclear whether other pathways are involved in the regulation of JAZ protein stability. Here, we report that PUB22, a plant U-box type E3 ubiquitin ligase, plays a critical role in the regulation of plant resistance against Helicoverpa armigera and other JA responses in tomato. Whereas COI1 physically interacts with JAZ1/2/5/7, PUB22 physically interacts with JAZ1/3/4/6. PUB22 ubiquitinates JAZ4 to promote its degradation via the 26S proteasome pathway. Importantly, we observed that pub22 mutants showreduced resistance to H. armigera, whereas jaz4 single mutants and jaz1 jaz3 jaz4 jaz6 quadruple mutants have enhanced resistance. The hypersensitivity of pub22 mutants to herbivores could be partially rescued by JAZ4 mutation. Moreover, we found that expression of PUB22 can be transcriptionally activated by MYC2, thus forming a positive feedback circuit in JA signaling. We noticed that the PUB22-JAZ4 module also regulates other JA responses, including defense against B. cinerea, inhibition of root elongation, and anthocyanin accumulation. Taken together, these results indicate that PUB22 plays a crucial role in plant growth and defense responses, together with COI1-regulated JA signaling, by targeting specific JAZs.

The OsCPK17-OsPUB12-OsRLCK176 module regulates immune homeostasis in rice

Plant immunity is fine-tuned to balance growth and defense. However, little is yet known about molecular mechanisms underlying immune homeostasis in rice (Oryza sativa). In this study, we reveal that a rice calcium-dependent protein kinase (CDPK), OsCPK17, interacts with and stabilizes the receptor-like cytoplasmic kinase (RLCK) OsRLCK176, a close homolog of Arabidopsis thaliana BOTRYTIS-INDUCED KINASE 1 (AtBIK1). Oxidative burst and pathogenesis-related gene expression triggered by pathogen-associated molecular patterns are significantly attenuated in the oscpk17 mutant. The oscpk17 mutant and OsCPK17-silenced lines are more susceptible to bacterial diseases than the wild-type plants, indicating that OsCPK17 positively regulates rice immunity. Furthermore, the plant U-box (PUB) protein OsPUB12 ubiquitinates and degrades OsRLCK176. OsCPK17 phosphorylates OsRLCK176 at Ser83, which prevents the ubiquitination of OsRLCK176 by OsPUB12 and thereby enhances the stability and immune function of OsRLCK176. The phenotypes of the ospub12 mutant in defense responses and disease resistance show that OsPUB12 negatively regulates rice immunity. Therefore, OsCPK17 and OsPUB12 reciprocally maintain OsRLCK176 homeostasis and function as positive and negative immune regulators, respectively. This study uncovers positive cross talk between CDPK- and RLCK-mediated immune signaling in plants and reveals that OsCPK17, OsPUB12, and OsRLCK176 maintain rice immune homeostasis.

Genome-wide identification and transcriptome profiling expression analysis of the U-box E3 ubiquitin ligase gene family related to abiotic stress in maize (Zea mays L.)

BACKGROUND

The U-box gene family encodes E3 ubiquitin ligases involved in plant hormone signaling pathways and abiotic stress responses. However, there has yet to be a comprehensive analysis of the U-box gene family in maize (Zea mays L.) and its responses to abiotic stress.

RESULTS

In this study, 85 U-box family proteins were identified in maize and were classified into four subfamilies based on phylogenetic analysis. In addition to the conserved U-box domain, we identified additional functional domains, including Pkinase, ARM, KAP and Tyr domains, by analyzing the conserved motifs and gene structures. Chromosomal localization and collinearity analysis revealed that gene duplications may have contributed to the expansion and evolution of the U-box gene family. GO annotation and KEGG pathway enrichment analysis identified a total of 105 GO terms and 21 KEGG pathways that were notably enriched, including ubiquitin-protein transferase activity, ubiquitin conjugating enzyme activity and ubiquitin-mediated proteolysis pathway. Tissue expression analysis showed that some ZmPUB genes were specifically expressed in certain tissues and that this could be due to their functions. In addition, RNA-seq data for maize seedlings under salt stress revealed 16 stress-inducible plant U-box genes, of which 10 genes were upregulated and 6 genes were downregulated. The qRT-PCR results for genes responding to abiotic stress were consistent with the transcriptome analysis. Among them, ZmPUB13, ZmPUB18, ZmPUB19 and ZmPUB68 were upregulated under all three abiotic stress conditions. Subcellular localization analysis showed that ZmPUB19 and ZmPUB59 were located in the nucleus.

CONCLUSIONS

Overall, our study provides a comprehensive analysis of the U-box gene family in maize and its responses to abiotic stress, suggesting that U-box genes play an important role in the stress response and providing insights into the regulatory mechanisms underlying the response to abiotic stress in maize.

Targeting the Ubiquitin-Proteasome System and Recent Advances in Cancer Therapy

Ubiquitination is a reversible post-translational modification based on the chemical addition of ubiquitin to proteins with regulatory effects on various signaling pathways. Ubiquitination can alter the molecular functions of tagged substrates with respect to protein turnover, biological activity, subcellular localization or protein-protein interaction. As a result, a wide variety of cellular processes are under ubiquitination-mediated control, contributing to the maintenance of cellular homeostasis. It follows that the dysregulation of ubiquitination reactions plays a relevant role in the pathogenic states of human diseases such as neurodegenerative diseases, immune-related pathologies and cancer. In recent decades, the enzymes of the ubiquitin-proteasome system (UPS), including E3 ubiquitin ligases and deubiquitinases (DUBs), have attracted attention as novel druggable targets for the development of new anticancer therapeutic approaches. This perspective article summarizes the peculiarities shared by the enzymes involved in the ubiquitination reaction which, when deregulated, can lead to tumorigenesis. Accordingly, an overview of the main pharmacological interventions based on targeting the UPS that are in clinical use or still in clinical trials is provided, also highlighting the limitations of the therapeutic efficacy of these approaches. Therefore, various attempts to circumvent drug resistance and side effects as well as UPS-related emerging technologies in anticancer therapeutics are discussed.

Genome-wide analysis of the U-box E3 ubiquitin ligase family role in drought tolerance in sesame (Sesamum indicum L.)

Plant U-box (PUB) proteins belong to a class of ubiquitin ligases essential in various biological processes. Sesame (Sesamum indicum L.) is an important and worldwide cultivated oilseed crop. However few studies have been conducted to explore the role of PUBs in drought tolerance in sesame. This study identified a total of 56 members of the sesame PUB family (SiPUB) genes distributed unevenly across all 13 chromosomes. Based on phylogenetic analysis, all 56 SiPUB genes were classified into six groups with various structures and motifs. Cis-acting element analysis suggested that the SiPUB genes are involved in response to various stresses including drought. Based on RNA-seq analysis and quantitative real-time PCR, we identified nine SiPUB genes with significantly different expression profiles under drought stress. The expression patterns of six SiPUB genes in root, leaf and stem tissues corroborated the reliability of the RNA-seq datasets. These findings underscore the importance of SiPUB genes in enhancing drought tolerance in sesame plants. Our study provides novel insights into the evolutionary patterns and variations of PUB genes in sesame and lays the foundation for comprehending the functional characteristics of SiPUB genes under drought-induced stress conditions.

Identification, characterization and expression profiles of E2 and E3 gene superfamilies during the development of tetrasporophytes in Gracilariopsis lemaneiformis (Rhodophyta)

E2 ubiquitin conjugating enzymes and E3 ubiquitin ligases play important roles in the growth and development of plants and animals. To date, the systematic analysis of E2 and E3 genes in Rhodophyta is limited. In this study, 14 E2 genes and 51 E3 genes were identified in Gracilariopsis lemaneiformis, an economically important red alga. E2 genes were classified into four classes according to the structure of the conserved domain, UBC. E3 genes were classified into 12 subfamilies according to individual conserved domains. A phylogenetic tree of seven algae species showed that functional differentiation of RING-type E3s was the highest, and the similarity between orthologous genes was high except in Chlamydomonas reinhardtii and Chara braunii. RNA-seq data analysis showed significant differential expression levels of E2 and E3 genes under the life stages of tetraspore formation and release, especially GlUBCN and GlAPC3. According to GO and KEGG analysis of two transcriptomes, GlUBCN and GlAPC3 were involved in ubiquitin-mediated proteolysis, and other subunits of the anaphase promoting complex or cyclosome (APC/C) and its activators GlCDC20 and GlCDH1 were also enriched into this process. The CDH1 and CDC20 in 981 were down-regulated during tetraspores formation and release, with the down-regulation of CDH1 being particularly significant; CDH1 and CDC20 in WLP-1, ZC, and WT were up-regulated during tetraspores formation and release, with CDC20 being more significantly up-regulated. Therefore, GlCDH1, rather than GlCDC20, in '981' might play the leading role in the activation of the APC/C, and GlCDC20 might play the leading role rather than GlCDH1 in strains WLP-1, ZC and wild type. The low fertility of cultivar 981 might be highly correlated with the inactivity of activators CDH1 and CDC20. This study provided a basic and comprehensive understanding of characteristic of E2 and E3 genes in Gp. lemaneiformis and set a foundation for further understanding of E2 ubiquitin conjugating enzymes and E3 ubiquitin ligase in regulating tetrasporophytes development of Gp. lemaneiformis.

E3 ubiquitin ligases in cancer stem cells: key regulators of cancer hallmarks and novel therapeutic opportunities

BACKGROUND

Human malignancies are composed of heterogeneous subpopulations of cancer cells with phenotypic and functional diversity. Among them, a unique subset of cancer stem cells (CSCs) has both the capacity for self-renewal and the potential to differentiate and contribute to multiple tumor properties. As such, CSCs are promising cellular targets for effective cancer therapy. At the molecular level, hyper-activation of multiple stemness regulatory signaling pathways and downstream transcription factors play critical roles in controlling CSCs establishment and maintenance. To regulate CSC properties, these stemness pathways are controlled by post-translational modifications including, but not limited to phosphorylation, acetylation, methylation, and ubiquitination.

CONCLUSION

In this review, we focus on E3 ubiquitin ligases and their roles and mechanisms in regulating essential hallmarks of CSCs, such as self-renewal, invasion and metastasis, metabolic reprogramming, immune evasion, and therapeutic resistance. Moreover, we discuss emerging therapeutic approaches to eliminate CSCs through targeting E3 ubiquitin ligases by chemical inhibitors and proteolysis-targeting chimera (PROTACs) which are currently under development at the discovery, preclinical, and clinical stages. Several outstanding issues such as roles for E3 ubiquitin ligases in heterogeneity and phenotypical/functional evolution of CSCs remain to be studied under pathologically and clinically relevant conditions. With the rapid application of functional genomic and proteomic approaches at single cell, spatiotemporal, and even single molecule levels, we anticipate that more specific and precise functions of E3 ubiquitin ligases will be delineated in dictating CSC properties. Rational design and proper translation of these mechanistic understandings may lead to novel therapeutic modalities for cancer procession medicine.

Genome-wide characterization of the U-box gene in Camellia sinensis and functional analysis in transgenic tobacco under abiotic stresses

Plants U-box genes are crucial for plant survival, and they extensively regulate plant growth, reproduction and development as well as coping with stress and other processes. In this study, we identified 92 CsU-box genes through genome-wide analysis in the tea plant (Camellia sinensis), all of them contained the conserved U-box domain and were divided into 5 groups, which supported by the further genes structure analysis. The expression profiles in eight tea plant tissues and under abiotic and hormone stresses were analyzed using the TPIA database. 7 CsU-box genes (CsU-box27/28/39/46/63/70/91) were selected to verify and analyze expression patterns under PEG-induced drought and heat stress in tea plant respectively, the qRT-PCR results showed consistent with transcriptome datasets; and the CsU-box39 were further heterologous expressed in tobacco to perform gene function analysis. Phenotypic analyses of overexpression transgenic tobacco seedlings and physiological experiments revealed that CsU-box39 positively regulated the plant response to drought stress. These results lay a solid foundation for studying the biological function of CsU-box, and will provide breeding strategy basis for tea plant breeders.

HERC2 promotes inflammation-driven cancer stemness and immune evasion in hepatocellular carcinoma by activating STAT3 pathway

BACKGROUND

Hepatic inflammation is a common initiator of liver diseases and considered as the primary driver of hepatocellular carcinoma (HCC). However, the precise mechanism of inflammation-induced HCC development and immune evasion remains elusive and requires extensive investigation. This study sought to identify the new target that is involved in inflammation-related liver tumorigenesis.

METHODS

RNA-sequencing (RNA-seq) analysis was performed to identify the differential gene expression signature in primary human hepatocytes treated with or without inflammatory stimulus. A giant E3 ubiquitin protein ligase, HECT domain and RCC1-like domain 2 (HERC2), was identified in the analysis. Prognostic performance in the TCGA validation dataset was illustrated by Kaplan-Meier plot. The functional role of HERC2 in HCC progression was determined by knocking out and over-expressing HERC2 in various HCC cells. The precise molecular mechanism and signaling pathway networks associated with HERC2 in HCC stemness and immune evasion were determined by quantitative real-time PCR, immunofluorescence, western blot, and transcriptomic profiling analyses. To investigate the role of HERC2 in the etiology of HCC in vivo, we applied the chemical carcinogen diethylnitrosamine (DEN) to hepatocyte-specific HERC2-knockout mice. Additionally, the orthotopic transplantation mouse model of HCC was established to determine the effect of HERC2 during HCC development.

RESULTS

We found that increased HERC2 expression was correlated with poor prognosis in HCC patients. HERC2 enhanced the stemness and PD-L1-mediated immune evasion of HCC cells, which is associated with the activation of signal transducer and activator of transcription 3 (STAT3) pathway during the inflammation-cancer transition. Mechanically, HERC2 coupled with the endoplasmic reticulum (ER)-resident protein tyrosine phosphatase 1B (PTP1B) and limited PTP1B translocation from ER to ER-plasma membrane junction, which ameliorated the inhibitory role of PTP1B in Janus kinase 2 (JAK2) phosphorylation. Furthermore, HERC2 knockout in hepatocytes limited hepatic PD-L1 expression and ameliorated HCC progression in DEN-induced mouse liver carcinogenesis. In contrast, HERC2 overexpression promoted tumor development and progression in the orthotopic transplantation HCC model.

CONCLUSION

Our data identified HERC2 functions as a previously unknown modulator of the JAK2/STAT3 pathway, thereby promoting inflammation-induced stemness and immune evasion in HCC.

The E3 Ligases in Cervical Cancer and Endometrial Cancer

Endometrial (EC) and cervical (CC) cancers are the most prevalent malignancies of the female reproductive system. There is a global trend towards increasing incidence and mortality, with a decreasing age trend. E3 ligases label substrates with ubiquitin to regulate their activity and stability and are involved in various cellular functions. Studies have confirmed abnormal expression or mutations of E3 ligases in EC and CC, indicating their vital roles in the occurrence and progression of EC and CC. This paper provides an overview of the E3 ligases implicated in EC and CC and discusses their underlying mechanism. In addition, this review provides research advances in the target of ubiquitination processes in EC and CC.

The Ubiquitin–Proteasome System (UPS) and Viral Infection in Plants

The ubiquitin–proteasome system (UPS) is crucial in maintaining cellular physiological balance. The UPS performs quality control and degrades proteins that have already fulfilled their regulatory purpose. The UPS is essential for cellular and organic homeostasis, and its functions regulate DNA repair, gene transcription, protein activation, and receptor trafficking. Besides that, the UPS protects cellular immunity and acts on the host’s defense system. In order to produce successful infections, viruses frequently need to manipulate the UPS to maintain the proper level of viral proteins and hijack defense mechanisms. This review highlights and updates the mechanisms and strategies used by plant viruses to subvert the defenses of their hosts. Proteins involved in these mechanisms are important clues for biotechnological approaches in viral resistance.

Classification and Expression Profile of the U-Box E3 Ubiquitin Ligase Enzyme Gene Family in Maize (Zea mays L.)

The U-box E3 (PUB) family genes encode the E3 ubiquitin ligase enzyme, which determines substrate specific recognition during protein ubiquitination. They are widespread in plants and are critical for plant growth, development, and response to external stresses. However, there are few studies on the functional characteristic of PUB gene family in the important staple crop, maize (Zea mays L.). In this study, the PUB gene in maize was aimed to identify and classify through whole-genome screening. Phylogenetic tree, gene structure, conserved motif, chromosome location, gene duplication (GD), synteny, and cis-acting regulatory element of PUB member were analyzed. The expression profiles of ZmPUB gene family in maize during development and under abiotic stress and hormones treatment were analyzed by the RNA-seq data. A total of 79 PUB genes were identified in maize genome, and they were stratified into seven categories. There were 25 pairs of segmental duplications (SD) and 1 pair of tandem duplication (TD) identified in the maize PUB gene family. A close relationship was observed between the monocot plant maize and rice in PUB gene family. There were 94 kinds of cis-acting elements identified in the maize PUB gene family, which included 46 biotic- and abiotic-responsive elements, 19 hormone-responsive elements, 13 metabolic and growth-related elements. The expression profiles of maize PUB gene family showed characteristics of tissue specificity and response to abiotic stress and hormones treatment. These results provided an extensive overview of the maize PUB gene family.

MDM2-Based Proteolysis-Targeting Chimeras (PROTACs): An Innovative Drug Strategy for Cancer Treatment

Proteolysis-targeting chimeras (PROTACs) are molecules that selectively degrade a protein of interest (POI). The incorporation of ligands that recruit mouse double minute 2 (MDM2) into PROTACs, forming the so-called MDM2-based PROTACs, has shown promise in cancer treatment due to its dual mechanism of action: a PROTAC that recruits MDM2 prevents its binding to p53, resulting not only in the degradation of POI but also in the increase of intracellular levels of the p53 suppressor, with the activation of a whole set of biological processes, such as cell cycle arrest or apoptosis. In addition, these PROTACs, in certain cases, allow for the degradation of the target, with nanomolar potency, in a rapid and sustained manner over time, with less susceptibility to the development of resistance and tolerance, without causing changes in protein expression, and with selectivity to the target, including the respective isoforms or mutations, and to the cell type, overcoming some limitations associated with the use of inhibitors for the same therapeutic target. Therefore, the aim of this review is to analyze and discuss the characteristics of MDM2-based PROTACs developed for the degradation of oncogenic proteins and to understand what potential they have as future anticancer drugs.

Identification of Quantitative Trait Locus and Candidate Genes for Drought Tolerance in a Soybean Recombinant Inbred Line Population

With global warming and regional decreases in precipitation, drought has become a problem worldwide. As the number of arid regions in the world is increasing, drought has become a major factor leading to significant crop yield reductions and food crises. Soybean is a crop that is relatively sensitive to drought. It is also a crop that requires more water during growth and development. The aim of this study was to identify the quantitative trait locus (QTL) that affects drought tolerance in soybean by using a recombinant inbred line (RIL) population from a cross between the drought-tolerant cultivar 'Jindou21' and the drought-sensitive cultivar 'Zhongdou33'. Nine agronomic and physiological traits were identified under drought and well-watered conditions. Genetic maps were constructed with 923,420 polymorphic single nucleotide polymorphism (SNP) markers distributed on 20 chromosomes at an average genetic distance of 0.57 centimorgan (cM) between markers. A total of five QTLs with a logarithm of odds (LOD) value of 4.035-8.681 were identified on five chromosomes. Under well-watered conditions and drought-stress conditions, one QTL related to the main stem node number was located on chromosome 16, accounting for 17.177% of the phenotypic variation. Nine candidate genes for drought resistance were screened from this QTL, namely Glyma.16G036700, Glyma.16G036400, Glyma.16G036600, Glyma.16G036800, Glyma.13G312700, Glyma.13G312800, Glyma.16G042900, Glyma.16G043200, and Glyma.15G100700. These genes were annotated as NAC transport factor, GATA transport factor, and BTB/POZ-MATH proteins. This result can be used for molecular marker-assisted selection and provide a reference for breeding for drought tolerance in soybean.

Genome-Wide Association Mapping Reveals Novel Putative Gene Candidates Governing Reproductive Stage Heat Stress Tolerance in Rice

Temperature rise predicted for the future will severely affect rice productivity because the crop is highly sensitive to heat stress at the reproductive stage. Breeding tolerant varieties is an economically viable option to combat heat stress, for which the knowledge of target genomic regions associated with the reproductive stage heat stress tolerance (RSHT) is essential. A set of 192 rice genotypes of diverse origins were evaluated under natural field conditions through staggered sowings for RSHT using two surrogate traits, spikelet fertility and grain yield, which showed significant reduction under heat stress. These genotypes were genotyped using a 50 k SNP array, and the association analysis identified 10 quantitative trait nucleotides (QTNs) for grain yield, of which one QTN (qHTGY8.1) was consistent across the different models used. Only two out of 10 MTAs coincided with the previously reported QTLs, making the remaing eight novel. A total of 22 QTNs were observed for spikelet fertility, among which qHTSF5.1 was consistently found across three models. Of the QTNs identified, seven coincided with previous reports, while the remaining QTNs were new. The genes near the QTNs were found associated with the protein–protein interaction, protein ubiquitination, stress signal transduction, and so forth, qualifying them to be putative for RSHT. An in silico expression analysis revealed the predominant expression of genes identified for spikelet fertility in reproductive organs. Further validation of the biological relevance of QTNs in conferring heat stress tolerance will enable their utilization in improving the reproductive stage heat stress tolerance in rice.

Association Mapping of Drought Tolerance Indices in Ethiopian Durum Wheat (Triticum turgidum ssp. durum)

Ethiopia is a major producer of durum wheat in sub-Saharan Africa. However, its production is prone to drought stress as it is fully dependent on rain, which is erratic and unpredictable. This study aimed to detect marker-trait associations (MTAs) and quantitative trait loci (QTLs) related to indices. Six drought tolerance indices, i.e., drought susceptibility index (DSI), geometric mean productivity (GMP), relative drought index (RDI), stress tolerance index (STI), tolerance index (TOL), and yield stability index (YSI) were calculated from least-square means (lsmeans) of grain yield (GY) and traits significantly (p < 0.001) correlated with grain yield (GY) under field drought stress (FDS) and field non-stress (FNS) conditions. GY, days to grain filling (DGF), soil plant analysis development (SPAD) chlorophyll meter, seeds per spike (SPS), harvest index (HI), and thousand kernel weight (TKW) were used to calculate DSI, GMP, RDI, STI, TOL, and YSI drought indices. Accessions, DW084, DW082, DZ004, C037, and DW092 were selected as the top five drought-tolerant based on DSI, RDI, TOL, and YSI combined ranking. Similarly, C010, DW033, DW080, DW124-2, and C011 were selected as stable accessions based on GMP and STI combined ranking. A total of 184 MTAs were detected linked with drought indices at -log₁₀p ≥ 4.0,79 of which were significant at a false discovery rate (FDR) of 5%. Based on the linkage disequilibrium (LD, r ² ≥ 0.2), six of the MTAs with a positive effect on GY-GMP were detected on chromosomes 2B, 3B, 4A, 5B, and 6B, explaining 14.72, 10.07, 26.61, 21.16, 21.91, and 22.21% of the phenotypic variance, respectively. The 184 MTAs were clustered into 102 QTLs. Chromosomes 1A, 2B, and 7A are QTL hotspots with 11 QTLs each. These chromosomes play a key role in drought tolerance and respective QTL may be exploited by marker-assisted selection for improving drought stress tolerance in wheat.

A BTB/POZ domain-containing protein negatively regulates plant immunity in Nicotiana benthamiana

Plants have evolved immune systems to fight against pathogens. However, it is still largely unknown how the plant immunity is finely regulated. Here we identified a BTB/POZ domain-containing protein, namely NbBTB, which is predicted to be a member of the ubiquitin E3 ligase complex. The NbBTB expression is downregulated upon the oomycete pathogen Phytophthora parasitica infection. Overexpression of NbBTB in Nicotiana benthamiana promoted plant susceptibility to P. parasitica infection, and silencing NbBTB increased plant resistance to P. parasitica, indicating that NbBTB negatively modulates plant basal defense. Interestingly, overexpressing or silencing NbBTB did not affect plant resistance to two bacterial pathogens Ralstonia solanacearum and Pseudomonas syringae, suggesting that NbBTB is specifically involved in basal defense against oomycete pathogen. Expression of NbBTB suppressed hypersensitive response (HR) triggered by avirulence proteins from both R. sonanacearum and P. infestans, and silencing NbBTB showed the opposite effect, indicating that NbBTB negatively regulates effector-triggered immunity (ETI). Protein accumulation of avirulence effectors in NbBTB-silenced plants was significantly enhanced, suggesting that NbBTB is likely to negatively modulate ETI by affecting effector protein accumulation. Together, our results demonstrated that NbBTB is a negative regulator in both plant basal defense and ETI.

How Many Faces Does the Plant U-Box E3 Ligase Have?

Ubiquitination is a major type of post-translational modification of proteins in eukaryotes. The plant U-Box (PUB) E3 ligase is the smallest family in the E3 ligase superfamily, but plays a variety of essential roles in plant growth, development and response to diverse environmental stresses. Hence, PUBs are potential gene resources for developing climate-resilient crops. However, there is a lack of review of the latest advances to fully understand the powerful gene family. To bridge the gap and facilitate its use in future crop breeding, we comprehensively summarize the recent progress of the PUB family, including gene evolution, classification, biological functions, and multifarious regulatory mechanisms in plants.

Revealing the early response of pear (Pyrus bretschneideri Rehd) leaves during Botryosphaeria dothideainfection by transcriptome analysis

Ring rot disease, which is caused by Botryosphaeria dothidea (B. dothidea), is one of the most serious diseases affecting the pear industry. Currently, knowledge of the mechanism about pear-pathogen interactions is unclear. To explore the early response of pear leaves to B. dothidea infection, we compared the early transcriptome of pear leaves infected with B. dothidea. The results revealed 3248 differentially expressed genes (DEGs) and 4862 DEGs at D2 and D4, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation of DEGs showed that these genes were predominately involved in plant-pathogen interactions, hormone signal transduction and other biosynthesis-related metabolic processes, including glucosinolate accumulation and flavonoid pathway enhancement. However, many hormone- and disease resistance-related genes and transcription factors (TFs) were differentially expressed during B. dothidea infection. These results were consistent with the changes in the physiological characteristics of B. dothidea. In addition, the expression of PbrPUB29, an E3 ubiquitin ligase with a U-box domain, was significantly higher than it was at 0 dpi. PbrPUB29 silencing enhanced the sensitivity of pear leaves to B. dothidea, reflected by more severe symptoms and higher reactive oxygen species (ROS) content in the defective pear seedlings after inoculation, revealing that PbrPUB29 has a significant role in pear disease resistance. In brief, we explored the interaction between pear leaves and B. dothidea at the transcriptome level, implied the early response of pear leaves to pathogens, and identified a hub gene in a B. dothidea-infected pear. These results provide a basis and new strategy for exploring the molecular mechanisms underlying pear-pathogen interactions and disease resistance breeding.

Genome-wide identification of U-box genes and protein ubiquitination under PEG-induced drought stress in potato

Protein ubiquitination is one of the most important posttranslational modifications in eukaryotic cells, and it is involved in a variety of biological processes, including abiotic stress response. The ubiquitination modification is highly specific, which depends on the accurate recognition of substrate proteins by ubiquitin ligase. Plant U-box (PUB) proteins are a class of ubiquitin ligases, multiple members of which have shown to participate in water-deficit stress in Arabidopsis and rice. U-box gene family and large-scale profiling of the ubiquitome in potato has not been reported to date, although it is one of the most important food crops. The identified 66 U-box genes from the potato genome database were unevenly distributed on 10 chromosomes. These StPUBs have a large number of tandem repeat sequences. Analysis of gene expression characteristics revealed that many StPUBs responded to abiotic stress. Three hundred and fourteen lys modification sites were identified under PEG-induced drought stress, which were distributed on 200 proteins, with 25 differential ubiquitination modification sites, most of which were up-regulated. The ubiquitination modification in potato protein was enhanced under PEG-induced drought stress, and U-box ubiquitin ligase was involved. This study provides an overall strategy and rich data set to clarify the effects of ubiquitination on potatoes under PEG-induced drought stress and the ubiquitination modification involved in potato U-box genes in response to PEG-induced drought stress.

Identification and expression analysis of PUB genes in tea plant exposed to anthracnose pathogen and drought stresses

The plant U-box (PUB) gene family, one of the major ubiquitin ligase families in plants, plays important roles in multiple cellular processes including environmental stress responses and resistance. The function of U-box genes has been well characterized in Arabidopsis and other plants. However, little is known about the tea plant (Camellia sinensis) PUB genes. Here, 89 U-box proteins were identified from the chromosome-scale referenced genome of tea plant. According to the domain organization and phylogenetic analysis, the tea plant PUB family were classified into ten classes, named Class I to X, respectively. Using previously released stress-related RNA-seq data in tea plant, we identified 34 stress-inducible CsPUB genes. Specifically, eight CsPUB genes were expressed differentially under both anthracnose pathogen and drought stresses. Moreover, six of the eight CsPUBs were upregulated in response to these two stresses. Expression profiling performed by qRT-PCR was consistent with the RNA-seq analysis, and stress-related cis-acting elements were identified in the promoter regions of the six upregulated CsPUB genes. These results strongly implied the putative functions of U-box ligase genes in response to biotic and abiotic stresses in tea plant.

Molecular and Functional Analysis of U-box E3 Ubiquitin Ligase Gene Family in Rice (Oryzasativa)

Proteins encoded by U-box type ubiquitin ligase (PUB) genes in rice are known to play an important role in plant responses to abiotic and biotic stresses. Functional analysis has revealed a detailed molecular mechanism involving PUB proteins in relation to abiotic and biotic stresses. In this study, characteristics of 77 OsPUB genes in rice were identified. Systematic and comprehensive analyses of the OsPUB gene family were then performed, including analysis of conserved domains, phylogenetic relationships, gene structure, chromosome location, cis-acting elements, and expression patterns. Through transcriptome analysis, we confirmed that 16 OsPUB genes show similar expression patterns in drought stress and blast infection response pathways. Numerous cis-acting elements were found in promoter sequences of 16 OsPUB genes, indicating that the OsPUB genes might be involved in complex regulatory networks to control hormones, stress responses, and cellular development. We performed qRT-PCR on 16 OsPUB genes under drought stress and blast infection to further identify the reliability of transcriptome and cis-element analysis data. It was confirmed that the expression pattern was similar to RNA-sequencing analysis results. The transcription of OsPUB under various stress conditions indicates that the PUB gene might have various functions in the responses of rice to abiotic and biotic stresses. Taken together, these results indicate that the genome-wide analysis of OsPUB genes can provide a solid basis for the functional analysis of U-box E3 ubiquitin ligase genes. The molecular information of the U-box E3 ubiquitin ligase gene family in rice, including gene expression patterns and cis-acting regulatory elements, could be useful for future crop breeding programs by genome editing.

E3 ubiquitin ligases: styles, structures and functions

E3 ubiquitin ligases are a large family of enzymes that join in a three-enzyme ubiquitination cascade together with ubiquitin activating enzyme E1 and ubiquitin conjugating enzyme E2. E3 ubiquitin ligases play an essential role in catalyzing the ubiquitination process and transferring ubiquitin protein to attach the lysine site of targeted substrates. Importantly, ubiquitination modification is involved in almost all life activities of eukaryotes. Thus, E3 ligases might be involved in regulating various biological processes and cellular responses to stress signal associated with cancer development. Thanks to their multi-functions, E3 ligases can be a promising target of cancer therapy. A deeper understanding of the regulatory mechanisms of E3 ligases in tumorigenesis will help to find new prognostic markers and accelerate the growth of anticancer therapeutic approaches. In general, we mainly introduce the classifications of E3 ligases and their important roles in cancer progression and therapeutic functions.

Genome-wide identification and expression analysis of U-box gene family in wild emmer wheat (Triticum turgidum L. ssp. dicoccoides)

In this study, 82 U-box genes were identified in wild emmer wheat (TdPUBs) through a genome-search method. Phylogenetic analysis classified them into seven groups and the genes belonging to the same group shared the similar exon-intron structure, motif organization and cis-element compositions. Synteny analysis of the U-box genes between different species revealed that segmental duplication and polyploidization mainly contributed to the expansion of TdPUBs. Furthermore, the genetic variations of U-box were investigated in wild emmer, domesticated emmer and durum wheat. Results showed that significant genetic bottleneck has occurred during domestication process of tetraploid emmer wheat. Meanwhile, 12 TdPUBs were co-located with known domestication related QTLs. Finally, the tissue-specific and stress-responsive TdPUB genes were identified through RNA-seq analysis. Combined with qPCR validation of 19 salt-responsive TdPUBs, the candidates involving in salt response were obtained. It lays the foundation to better understand the regulatory roles of U-box family in emmer wheat and beyond.

OsPUB41, a U-box E3 ubiquitin ligase, acts as a negative regulator of drought stress response in rice (Oryza Sativa L.)

OsPUB41 plays a negative role in drought stress response through the mediation of OsUBC25 and interacts with OsCLC6, suggesting a putative substrate. The notable expansion of Plant U-Box E3 ligases (PUB), compared with those in mammals, implies that PUB proteins have evolved to perform plant-specific functions. OsPUB41, a potential ortholog of CMPG1, was recently reported to regulate the cell wall degrading enzyme (CWDE)-induced innate immune response in rice. Here, we characterized the OsPUB41 gene, which encodes a dual-localized cytosolic and nuclear U-box E3 ligase in rice. OsPUB41 expression was specifically induced by dehydration among various abiotic stresses and abscisic acid (ABA) treatments. Furthermore, we revealed that the core U-box motif of OsPUB41 possesses the E3 ligase activity that can be activated by OsUBC25 in rice. The Ubi:RNAi-OsPUB41 knock-down and ospub41 suppression mutant plants exhibited enhanced tolerance to drought stress compared with the wild-type rice plants in terms of transpirational water loss, long-term dehydration response, and chlorophyll content. Moreover, the knock-down or suppression of the OsPUB41 gene did not cause adverse effect on rice yield-related traits. Yeast two-hybrid and an in vitro pull-down analyses revealed that OsCLC6, a chloride channel, is a putative substrate of OsPUB41. Overall, these results suggest that OsPUB41 acts as a negative regulator of dehydration conditions and interacts with OsCLC6, implying that it is a substrate of OsPUB41.

Genome Wide Analysis of U-Box E3 Ubiquitin Ligases in Wheat (Triticum aestivum L.)

U-box E3 ligase genes play specific roles in protein degradation by post-translational modification in plant signaling pathways, developmental stages, and stress responses; however, little is known about U-box E3 genes in wheat. We identified 213 U-box E3 genes in wheat based on U-box and other functional domains in their genome sequences. The U-box E3 genes were distributed among 21 chromosomes and most showed high sequence homology with homoeologous U-box E3 genes. Synteny analysis of wheat U-box E3 genes was conducted with other plant species such as Brachypodium distachyon, barley, rice, Triricum uratu, and Aegilops tauschii. A total of 209 RNA-seq samples representing 22 tissue types, from grain, root, leaf, and spike samples across multiple time points, were analyzed for clustering of U-box E3 gene expression during developmental stages, and the genes responded differently in various tissues and developmental stages. In addition, expression analysis of U-box E3 genes under abiotic stress, including drought, heat, and both heat and drought, and cold conditions, was conducted to provide information on U-box E3 gene expression under specific stress conditions. This analysis of U-box E3 genes could provide valuable information to elucidate biological functions for a better understanding of U-box E3 genes in wheat.

Exogenous phytohormone application and transcriptome analysis of Mikania micrantha provides insights for a potential control strategy

Effective and complete control of the invasive weed Mikania micrantha is required to avoid increasing damages. We exogenously applied indole 3-acetic acid (IAA), gibberellin (GA), and N-(2-Chloro-4-pyridyl)-N'-phenylurea (CPPU), and their combinations i.e. IAA + CPPU (IC), GA + CPPU (GC), and GA + IAA + CPPU (GIC), at 5, 10, 25, 50, and 75 ppm against distilled water as a control (CK), to examine their effects on the weed. The increasing concentrations of these hormones when applied alone or in combination were fatal to M. micrantha and led towards the death of inflorescences and/or florets. CPPU and GIC were found as the most effective phytohormones. Transcriptome analysis revealed differential regulation of genes in auxin, cytokinin, gibberellin and abscisic acid signaling pathways, suggesting their role in the prohibition of axillary bud differentiation. Collectively, CPPU and GIC at a high concentration (75 ppm) could be used as a control measure to protect forests and other lands from the invasion of M. micrantha.

Overexpression of a novel E3 ubiquitin ligase gene from Coptis chinensis Franch enhances drought tolerance in transgenic tobacco

Drought stress has a significant effect on the growth, physiology and biochemistry of medicinal plants. SDIR1 (Salt- and Drought-Induced Ring Finger1), a C3H2C3-type RING-finger E3 ubiquitin ligase gene plays an important role in the stress response of various plants. However, the role of this gene is not clear in Coptis chinensis. In this study, the CcSDIR1 gene was cloned from C. chinensis using RACE and RT-PCR. Sequence analysis revealed that CcSDIR1 had an open reading frame of 840 bp that encodes 279 amino acids with a theoretical molecular weight about 31 kDa and pI value of 5.65 and shared conserved domains with other plants. On comparison with the wild-type plants, overexpression of CcSDIR1 in transgenic tobaccos increased drought tolerance and showed better growth performance. However, lower malondialdehyde contents and high antioxidant enzyme activities were observed in transgenic tobacco plants compared to wild-type plants. In addition, Evans blue staining showed high cell viability of transgenic lines under drought stress. These results suggest that CcSDIR1 regulates various responses to drought stress by increasing antioxidant enzyme activities and reducing oxidative damage. From the study results, the CcSDIR1 gene will be very useful for drought stress research in plants.

Molecular dissection of two homoeologous wheat genes encoding RING H2-type E3 ligases: TaSIRFP-3A and TaSIRFP-3B

Two homoeologous wheat genes, TaSIRFP-3A and TaSIRFP-3B, encode the RING-HC-type E3 ligases that play an inhibitory role in sucrose metabolism in response to cold stress. In higher plants, the attachment of ubiquitin (Ub) and the subsequent recognition and degradation by the 26S proteasome affects a variety of cellular functions that are essential for survival. Here, we characterized the two homoeologous wheat genes encoding the really interesting new gene (RING) HC-type E3 ligases: TaSIRFP-3A and TaSIRFP-3B (Triticum aestivum SINA domain including RING finger protein 1 and 2), which regulate target proteins via the Ub/26S proteasome system. The TaSIRFP-3A gene was highly expressed under cold stress. In contrast, its homoeologous gene, TaSIRFP-3B, showed only a slight increase in expression levels in shoots. Despite these differences, both the proteins exhibited E3 ligase activity with the cytosol- and nucleus-targeted localization, demonstrating their conserved molecular function. Heterogeneous overexpression of TaSIRFP-3A or TaSIRFP-3B in Arabidopsis showed delayed plant growth causing a reduction in sucrose synthase enzymatic activity and photosynthetic sucrose synthesis, by regulating sucrose synthase proteins. TaSIRFP-3A- or TaSIRFP-3B-overexpressing plants showed higher hypersensitivity under cold stress than WT plants with an accumulation of reactive oxygen species (ROS). These results suggest that the negative regulation of TaSIRFP-3A and TaSIRFP-3B in response to cold stress is involved in sucrose metabolism.

The Effect of Drought on Transcriptome and Hormonal Profiles in Barley Genotypes With Contrasting Drought Tolerance

Like many cereal crops, barley is also negatively affected by drought stress. However, due to its simple genome as well as enhanced stress resilient nature compared to rice and wheat, barley has been considered as a model to decipher drought tolerance in cereals. In the present study, transcriptomic and hormonal profiles along with several biochemical features were compared between drought-tolerant (Otis) and drought-sensitive (Baronesse) barley genotypes subjected to drought to identify molecular and biochemical differences between the genotypes. The drought-induced decrease in the leaf relative water content, net photosynthesis, and biomass accumulation was relatively low in Otis compared to Baronesse. The hormonal profiles did not reveal significant differences for majority of the compounds other than the GA20 and the cis-zeatin-o-glucoside (c-ZOG), whose levels were greatly increased in Otis compared to Baronesse under drought. The major differences that emerged from the transcriptome analysis are; (1), the overall number of differentially expressed genes was relatively low in drought-tolerant Otis compared to drought-sensitive Baronesse; (2), a wax biosynthesis gene (CER1), and NAC transcription factors were specifically induced in Otis but not in Baronesse; (3), the degree of upregulation of betaine aldehyde dehydrogenase and a homeobox transcription factor (genes with proven roles in imparting drought tolerance), was greater in Otis compared to Baronesse; (4) the extent of downregulation of gene expression profiles for proteins of the reaction center photosystem II (PSII) (D1 and D2) was low in Otis compared to Baronesse; and, (5), alternative splicing (AS) was also found to differ between the genotypes under drought. Taken together, the overall transcriptional responses were low in drought-tolerant Otis but the genes that could confer drought tolerance were either specifically induced or greatly upregulated in the tolerant genotype and these differences could be important for drought tolerance in barley.

Genome-Wide Identification and Characterization of Long Non-Coding RNAs in Peanut

Long non-coding RNAs (lncRNAs) are involved in various regulatory processes although they do not encode protein. Presently, there is little information regarding the identification of lncRNAs in peanut (Arachis hypogaea Linn.). In this study, 50,873 lncRNAs of peanut were identified from large-scale published RNA sequencing data that belonged to 124 samples involving 15 different tissues. The average lengths of lncRNA and mRNA were 4335 bp and 954 bp, respectively. Compared to the mRNAs, the lncRNAs were shorter, with fewer exons and lower expression levels. The 4713 co-expression lncRNAs (expressed in all samples) were used to construct co-expression networks by using the weighted correlation network analysis (WGCNA). LncRNAs correlating with the growth and development of different peanut tissues were obtained, and target genes for 386 hub lncRNAs of all lncRNAs co-expressions were predicted. Taken together, these findings can provide a comprehensive identification of lncRNAs in peanut.