Application of L-Cysteine Hydrochloride Delays the Ripening of Harvested Tomato Fruit.

Fruit ripening is controlled by internal factors such as hormones and genetic regulators, as well as external environmental factors. However, the impact of redox regulation on fruit ripening remains elusive. Here, we explored the effects of L-cysteine hydrochloride (LCH), an antioxidant, on tomato fruit ripening and elucidated the underlying mechanism. The application of LCH effectively delayed tomato fruit ripening, leading to the suppression of carotenoid and lycopene biosynthesis and chlorophyll degradation, and a delayed respiration peak. Moreover, LCH-treated fruit exhibited reduced hydrogen peroxide (H2O2) accumulation and increased activities of superoxide dismutase (SOD), catalase (CAT), and monodehydroascorbate reductase (MDHAR), compared with control fruit. Furthermore, transcriptome analysis revealed that a substantial number of genes related to ethylene biosynthesis (ACS2, ACS4, ACO1, ACO3), carotenoid biosynthesis (PSY, PDS, ZDS, CRTISO), cell wall degradation (PG1/2, PL, TBG4, XTH4), and ripening-related regulators (RIN, NOR, AP2a, DML2) were downregulated by LCH, resulting in delayed ripening. These findings suggest that the application of LCH delays the ripening of harvested tomato fruit by modulating the redox balance and suppressing the expression of ripening-related genes.

The role of non-coding RNA in lupus nephritis.

Systemic lupus erythematosus (SLE) is a common autoimmune disease with multiple manifestations. The renal implication, also called lupus nephritis (LN) is the most regular type of complication and results in adverse outcomes. Multiple studies revealed the importance of non-coding RNA in diseases, likewise observed in nephropathies, particularly LN. Long-non-coding RNA (lncRNA) is a group of RNA that are more than 200 nucleotides in length. And in circular RNA (circRNA), the head and tail of RNA are connected by a 3' → 5' phosphodiester bond. Both two types of non-coding RNA play important roles in LN pathogenesis through the competitive endogenous RNA (ceRNA) effect. LncRNAs and circRNAs can sponge miRNAs and consequently act on downstream signaling pathways, which are capable to influence various aspects of LN, including cell proliferation, inflammation, and oxidative stress. And lncRNAs and circRNAs have the potential to act as biomarkers to diagnose LN and distinguish whether SLE patients with LN or not. In the future, lncRNAs and circRNAs may be accessible therapeutic targets.

Histone demethylase MaJMJ15 is involved in the regulation of postharvest banana fruit ripening.

Histone methylation plays important roles in plant development. However, the role of histone methylation in fruit ripening remains unclear. Here, a total of 16 Jumonji domain-containing proteins (JMJs) were identified from banana genome. During fruit ripening, expression of MaJMJ15 was significantly upregulated. Exogenous ethylene accelerated the upregulation whereas 1-methylcyclopropene delayed the process, suggesting that MaJMJ15 positively regulates banana fruit ripening. MaJMJ15 is an H3K27me3 site-specific demethylase. Transient overexpression of MaJMJ15 promoted banana fruit ripening. Moreover, the global H3K27me3 was decreased by MaJMJ15. Furthermore, MaJMJ15 directly targeted several key ripening-related genes (RRGs) in banana including NAC transcription factor 1/2 (MaNAC1/2), 1-aminocyclopropane-1-carboxylate synthase 1 (MaACS1), 1-aminocyclopropane-1-carboxylate oxidase 1 (MaACO1) and expansin 2 (MaEXP2), removed H3K27me3 from their chromatin, and activated their expression. Our data suggest that MaJMJ15 is an H3K27me3 demethylase, which is involved in the regulation of banana fruit ripening by activating expression of key RRGs via removal of H3K27me3.

MaMYB13 is involved in response to chilling stress via activating expression of VLCFAs and phenylpropanoids biosynthesis-related genes in postharvest banana fruit.

Fruit chilling injury is the result of physiological dysfunction due to membrane lipid phase change, oxidative damage of biomacromolecules and respiratory metabolism abnormality. However, the involvement of transcription factors in response to fruits chilling tolerance remains largely unclear. Here, MaMYB13 was identified to participate in banana fruit response to chilling stress. MaMYB13 has transcriptional activation activity. When exposed to low temperature, expression of MaMYB13 was enormously induced. Moreover, MaMYB13 promoter was activated by chilling stress. MaMYB13 bound to the promoters of several important very-long-chain fatty acids (VLCFAs) and phenylpropanoids biosynthesis-related genes, including MaKCS11, Ma4CL6 and MaAAE1, and activated their transcription. Furthermore, MaKIN10 X1/3 interacted with MaMYB13 and enhanced MaMYB13-mediated transcriptional activation possibly via phosphorylation. Altogether, our results unravel the mechanism of MaMYB13-MaKIN10 X1/3 interaction regulating banana fruit chilling tolerance through activating the expression of MaKCS11, Ma4CL6 and MaAAE1, providing new insights into the regulatory network of MYB transcription factor.

A NAC transcriptional factor BrNAC029 is involved in cytokinin-delayed leaf senescence in postharvest Chinese flowering cabbage.

Both cytokinin and NAC transcription factors were reported to involve in leaf senescence. However, the mechanism of NAC transcription factors how to regulate cytokinin-delayed leaf senescence is still unknown. In this study, application of N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU), a cytokinin analogue, significantly delayed leaf senescence and maintained cytokinin content of Chinese flowering cabbage during storage. Meanwhile, the expression of an NAC transcriptional activator (BrNAC029) was increased but suppressed by CPPU treatment. Furthermore, BrNAC029 activated the expressions of chlorophyll catabolic genes BrPAO and BrSGR2, cytokinin oxidase gene BrCKX1 and senescence maker gene BrSAG113 by binding to their promoters. Additionally, overexpressions of BrNAC029 in tobacco and Arabidopsis accelerated leaf senescence and up-expressed the related genes. Taken together, it was suggested that BrNAC029 may serve as a transcriptional activator to activate the transcriptions of these related genes to eventually accelerate leaf senescence of Chinese flowering cabbage by promoting chlorophyll degradation and reducing endogenous cytokinin level.

Proteome-wide identification of non-histone lysine methylation in tomato during fruit ripening.

INTRODUCTION: Histone and non-histone methylations are important post-translational modifications in plants. Histone methylation plays a crucial role in regulating chromatin structure and gene expression. However, the involvement of non-histone methylation in plant biological processes remains largely unknown. METHODS: The methylated substrates and methylation sites during tomato fruit ripening were identified by LC-MS/MS. Bioinformatics of lysine methylated proteins was conducted to analyze the possible role of methylated proteins. The effects of methylation modification on protein functions were preliminarily investigated by site-directed mutation simulation. RESULTS: A total of 241 lysine methylation (mono-, di- and trimethylation) sites in 176 proteins were identified with two conserved methylation motifs: xxxxxxExxx_K_xxxExxxxxx and xxxxxxExxx_K_xxxxxxxxxx. These methylated proteins were mainly related to fruit ripening and senescence, oxidation reduction process, signal transduction, stimulus and stress responses, and energy metabolism. Three representative proteins, thioredoxin (Trx), glutathione S-transferase T1 (GST T1), and NADH dehydrogenase (NOX), were selected to investigate the effect of methylation modifications on protein activity. Mimicking demethylation led to decreased Trx activity but increased GST T1 and NOX activities. In addition, RT-qPCR exhibited that the expression of many genes that encode proteins subjected to methylation was upregulated during fruit ripening. CONCLUSION: Our study suggests that tomato fruit ripening undergo non-histone lysine methylation, which may participate in the regulation of fruit ripening. It is the first report of methyl proteome profiling of non-histone lysine in horticultural crops.

Structure-Based Design of 2-Aminopurine Derivatives as CDK2 Inhibitors for Triple-Negative Breast Cancer.

Cyclin-dependent kinase 2 (CDK2) regulates the progression of the cell cycle and is critically associated with tumor growth. Selective CDK2 inhibition provides a potential therapeutic benefit against certain tumors. Purines and related heterocycle (e.g., R-Roscovitine) are important scaffolds in the development of CDK inhibitors. Herein, we designed a new series of 2-aminopurine derivatives based on the fragment-centric pocket mapping analysis of CDK2 crystal structure. Our results indicated that the introduction of polar substitution at the C-6 position of purine would be beneficial for CDK2 inhibition. Among them, compound 11l showed good CDK2 inhibitory activity (IC50 = 19 nM) and possessed good selectivity against other CDKs. Further in vitro tests indicated that compound 11l possesses anti-proliferation activity in triple-negative breast cancer (TNBC) cells. Moreover, molecular dynamics simulation suggested the favorable binding mode of compound 11l, which may serve as a new lead compound for the future development of CDK2 selective inhibitors.

Histone H3K27 demethylase SlJMJ4 promotes dark- and ABA- induced leaf senescence in tomato.

Leaf senescence is a highly-programmed developmental process during the plant life cycle. ABA plays an important role in leaf senescence. However, the mechanism underlying ABA-mediated leaf senescence, particularly the upstream epigenetic regulatory network, remains largely unclear. Here, we identified that SlJMJ4, a Jumonji C (jmjC) domain-containing protein in tomato, specifically demethylates di- and tri-methylations of lysine 27 of histone H3 (H3K27) in vitro and in vivo. Overexpression of SlJMJ4 results in premature senescence phenotype and promotes dark- and ABA-induced leaf senescence in tomato. Under dark condition, SlJMJ4-promoted leaf senescence is associated with upregulated expression of transcription factors (SlORE1 and SlNAP2) and senescence-associated genes (SlSAG113, SlSAG12) via removal of H3K27me3. In responses to ABA, overexpression of SlJMJ4 increases its binding at the loci of SlORE1, SlNAP2, SlSAG113, SlSAG12, SlABI5 and SlNCED3 and decreases their H3K27me3 levels, and therefore activates their expression and mediates ABA-induced leaf senescence in tomato. Taken together, these results demonstrate that SlJMJ4 plays a positive role in leaf senescence in tomato and is implicated in ABA-induced leaf senescence by binding to many key genes related to ABA synthesis and signaling, transcription regulation and senescence and hence promoting their H3K27me3 demethylation.

Alternative splicing of MaMYB16L regulates starch degradation in banana fruit during ripening.

The alternative splicing of select genes is an important mechanism to regulate responses to endogenous and environmental signals in plants. However, the role of alternative splicing in regulating fruit ripening remains unclear. Here, we discovered that MaMYB16L, an R1-type MYB transcription factor, undergoes alternative splicing and generates two transcripts, the full-length isoform MaMYB16L and a truncated form MaMYB16S, in banana fruit. During banana fruit ripening, the alternative splicing process intensifies with downregulated MaMYB16L and upregulated MaMYB16S. Moreover, MaMYB16L is a transcriptional repressor that directly binds with the promoters of many genes associated with starch degradation and MaDREB2, a positive ripening regulator, and represses their expression. In contrast, MaMBY16S lacks a DNA-binding domain but competitively combines and forms non-functional heterodimers with functional MaMYB16L. MaMYB16L-MaMYB16S heterodimers decrease the binding capacity and transrepression activity of MaMYB16L. The downregulation of MaMYB16L and the upregulation of MaMYB16S, that is, a decreased ratio of active to non-active isoforms, facilitates the activation of ripening-related genes and thereby promotes fruit ripening. Furthermore, the transient overexpression of MaMYB16S promotes banana fruit ripening, whereas the overexpression of MaMYB16L delays this process. Therefore, the alternative splicing of MaMYB16L might generate a self-controlled regulatory loop to regulate banana fruit ripening.

Recent progress in development of cyclin-dependent kinase 7 inhibitors for cancer therapy.

Introduction: Cyclin-dependent kinase 7 (CDK7) is a part of the CDK-activating kinase family (CAK) which has a key role in the cell cycle and transcriptional regulation. Several lines of evidence suggest that CDK7 is a promising therapeutic target for cancer. CDK7 selective inhibitors such as SY-5609 and CT7001 are in clinical development. Areas covered: We explore the biology of CDK7 and its role in cancer and follow this with an evaluation of the preclinical and clinical progress of CDK7 inhibitors, and their potential in the clinic. We searched PubMed and ClinicalTrials to identify relevant data from the database inception to 14 October 2020. Expert opinion: CDK7 inhibitors are next generation therapeutics for cancer. However, there are still challenges which include selectively, side effects, and drug resistance. Nevertheless, with ongoing clinical development of these inhibitors and greater analysis of their target, CDK7 inhibitors will become a promising approach for treatment of cancer in the near future.

Redox regulation of glutathione peroxidase by thioredoxin in longan fruit in relation to senescence and quality deterioration.

Thioredoxins (Trxs) are important redox regulators in organisms. However, their involvement in fruit senescence and quality deterioration remains unclear. In this study, one Trx (DlTrx1) and one NADPH-dependent Trx reductase (DlNRT1) cDNAs, were cloned from longan fruit. The DlTrx1 could be effectively reduced by the DlNTR1. Expression of DlTrx1 and DlNTR1 were up-regulated during fruit senescence and quality deterioration. We further identified 33 potential Trx target proteins in longan, including one glutathione peroxidase (DlGpx). DlTrx1 could physically interact with DlGpx. DlTrx1 in combination with DlNTR1 effectively activated DlGpx activity by regulating its redox state. Cys90 in DlGPx could form a disulfide bond with either Cys42 or Cys71, which were the sites of redox modulation. Furthermore, DlGpx exhibited a higher ratio of disulfide bonds to sulfhydryl groups in senescent or deteriorative fruit. We propose that Trx-mediated redox regulation of DlGpx is involved in senescence or quality deterioration of harvested longan fruit.

Shoot organogenesis and somatic embryogenesis from leaf and root explants of Scaevola sericea.

An efficient regeneration system via shoot organogenesis and somatic embryogenesis from in vitro leaf and root explants was established for Scaevola sericea for the first time. The highest axillary shoot proliferation coefficient (4.8) was obtained on Murashige and Skoog (MS) medium supplemented with 1.0 mg/L 6-benzyladenine (BA) and 0.1 mg/L α-naphthaleneacetic acid (NAA) every 45 days. Young in vitro leaves and roots, which were used as explants, were cultured onto medium supplemented with different plant growth regulators. Our results showed that only cytokinins BA and thidiazuron (TDZ), could induce adventitious shoots and somatic embryos from leaf and root explants. The optimal medium to achieve this was MS medium supplemented with 2.5 mg/L BA and which induced most adventitious shoots (2.7) and somatic embryos (17.3) from leaf explants within 30 days. From root explants, 1.1 adventitious shoots and 7.6 somatic embryos could be induced on MS medium supplemented with 2.5 mg/L TDZ. Histological observation showed that both somatic embryos and adventitious shoots were originated from homogeneous parenchyma and the development of somatic embryos was visible. Maximum rooting percentage (99.0%) was achieved on half-strength MS medium supplemented with 2.5 mg/L NAA. Well-rooted plantlets, which were transplanted into a substrate of pure river sand, displayed a high survival percentage of 91.7% after transplanting for 45 days while the best substrate for plantlet growth was river sand: coral sand (1:1).

RNA-Seq analysis of Clerodendrum inerme (L.) roots in response to salt stress.

BACKGROUND: Clerodendrum inerme (L.) Gaertn, a halophyte, usually grows on coastal beaches as an important mangrove plant. The salt-tolerant mechanisms and related genes of this species that respond to short-term salinity stress are unknown for us. The de novo transcriptome of C. inerme roots was analyzed using next-generation sequencing technology to identify genes involved in salt tolerance and to better understand the response mechanisms of C. inerme to salt stress. RESULTS: Illumina RNA-sequencing was performed on root samples treated with 400 mM NaCl for 0 h, 6 h, 24 h, and 72 h to investigate changes in C. inerme in response to salt stress. The de novo assembly identified 98,968 unigenes. Among these unigenes, 46,085 unigenes were annotated in the NCBI non-redundant protein sequences (NR) database, 34,756 sequences in the Swiss-Prot database and 43,113 unigenes in the evolutionary genealogy of genes: Non-supervised Orthologous Groups (eggNOG) database. 52 Gene Ontology (GO) terms and 31 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were matched to those unigenes. Most differentially expressed genes (DEGs) related to the GO terms "single-organism process", "membrane" and "catalytic activity" were significantly enriched while numerous DEGs related to the plant hormone signal transduction pathway were also significantly enriched. The detection of relative expression levels of 9 candidate DEGs by qRT-PCR were basically consistent with fold changes in RNA sequencing analysis, demonstrating that transcriptome data can accurately reflect the response of C. inerme roots to salt stress. CONCLUSIONS: This work revealed that the response of C. inerme roots to saline condition included significant alteration in response of the genes related to plant hormone signaling. Besides, our findings provide numerous salt-tolerant genes for further research to improve the salt tolerance of functional plants and will enhance research on salt-tolerant mechanisms of halophytes.

Selection and Validation of Novel RT-qPCR Reference Genes under Hormonal Stimuli and in Different Tissues of Santalum album.

Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) is a widely used technique to investigate gene expression levels due to its high throughput, specificity, and sensitivity. An appropriate reference gene is essential for RT-qPCR analysis to obtain accurate and reliable results. To date, no reliable reference gene has been validated for the economically tropical tree, sandalwood (Santalum album L.). In this study, 13 candidate reference genes, including 12 novel putative reference genes selected from a large set of S. album transcriptome data, as well as the currently used ß-actin gene (ACT), were validated in different tissues (stem, leaf, root and callus), as well as callus tissue under salicylic acid (SA), jasmonic acid methyl ester (MeJA), and gibberellin (GA) treatments using geNorm, NormFinder, BestKeeper, Delta Ct and comprehensive RefFinder algorithms. Several novel candidate reference genes were much more stable than the currently used traditional gene ACT. ODD paired with Fbp1 for SA treatment, CSA and Fbp3 for MeJA treatment, PP2C and Fbp2 for GA treatment, as well as Fbp1 combined with Fbp2 for the total of three hormone treatments were the most accurate reference genes, respectively. FAB1A, when combined with PP2C, was identified as the most suitable reference gene combination for the four tissues tested, while the combination of HLMt, PPR and FAB1A were the most optimal reference genes for all of the experimental samples. In addition, to verify our results, the relative expression level of the SaSSy gene was evaluated by the validated reference genes and their combinations in the three S. album tissues and under MeJA treatment. The evaluated reference genes in this study will improve the accuracy of RT-qPCR analysis and will benefit S. album functional genomics studies in different tissues and under hormone stimuli in the future.