Histone variant H2A.Z is required for plant salt response by regulating gene transcription.

As a well-conserved histone variant, H2A.Z epigenetically regulates plant growth and development as well as the interaction with environmental factors. However, the role of H2A.Z in response to salt stress remains unclear, and whether nucleosomal H2A.Z occupancy work on the gene responsiveness upon salinity is obscure. Here, we elucidate the involvement of H2A.Z in salt response by analysing H2A.Z disorder plants with impaired or overloaded H2A.Z deposition. The salt tolerance is dramatically accompanied by H2A.Z deficiency and reacquired in H2A.Z OE lines. H2A.Z disorder changes the expression profiles of large-scale of salt responsive genes, announcing that H2A.Z is required for plant salt response. Genome-wide H2A.Z mapping shows that H2A.Z level is induced by salt condition across promoter, transcriptional start site (TSS) and transcription ending sites (-1 kb to +1 kb), the peaks preferentially enrich at promoter regions near TSS. We further show that H2A.Z deposition within TSS provides a direct role on transcriptional control, which has both repressive and activating effects, while it is found generally H2A.Z enrichment negatively correlate with gene expression level response to salt stress. This study shed light on the H2A.Z function in salt tolerance, highlighting the complex regulatory mechanisms of H2A.Z on transcriptional activity for yielding appropriate responses to particularly environmental stress.

Transcription Factors and Their Regulatory Roles in the Male Gametophyte Development of Flowering Plants.

Male gametophyte development in plants relies on the functions of numerous genes, whose expression is regulated by transcription factors (TFs), non-coding RNAs, hormones, and diverse environmental stresses. Several excellent reviews are available that address the genes and enzymes associated with male gametophyte development, especially pollen wall formation. Growing evidence from genetic studies, transcriptome analysis, and gene-by-gene studies suggests that TFs coordinate with epigenetic machinery to regulate the expression of these genes and enzymes for the sequential male gametophyte development. However, very little summarization has been performed to comprehensively review their intricate regulatory roles and discuss their downstream targets and upstream regulators in this unique process. In the present review, we highlight the research progress on the regulatory roles of TF families in the male gametophyte development of flowering plants. The transcriptional regulation, epigenetic control, and other regulators of TFs involved in male gametophyte development are also addressed.

Endogenous melatonin involved in plant salt response by impacting auxin signaling.

KEY MESSAGE: The study on melatonin biosynthesis mutant snat1snat2 revealed that endogenous melatonin plays an important role in salt responsiveness by mediating auxin signaling. Melatonin is a pleiotropic signaling molecule, which, besides being involved in multiple growth and developmental processes, also mediates environmental stress responses. However, whether and how endogenous melatonin is involved in salt response has not been determined. In this study, we elucidated the involvement of endogenous melatonin in salt response by investigatiing the impact of salt stress on a double mutant of Arabidopsis (snat1snat2) defective in melatonin biosynthesis genes SNAT1 and SNAT2. This mutant was found to exhibit salt sensitivity, manifested by unhealthy growth, ion imbalance and ROS accumulation under salt stress. Transcriptomic profiles of snat1snat2 revealed that the expression of a large number of salt-responsive genes was affected by SNAT defect, and these genes were closely related to the synthesis of auxin and several signaling pathways. In addition, the salt-sensitive growth phenotype of snat1snat2 was alleviated by the application of exogenous auxin. Our results show that endogenous melatonin may be essential for plant salt tolerance, a function that could be correlated with diverse activity in mediating auxin signaling.

The roles of non-coding RNAs in male reproductive development and abiotic stress responses during this unique process in flowering plants.

Successful male reproductive development is the guarantee for sexual reproduction of flowering plants. Male reproductive development is a complicated and multi-stage process that integrates physiological processes and adaptation and tolerance to a myriad of environmental stresses. This well-coordinated process is governed by genetic and epigenetic machineries. Non-coding RNAs (ncRNAs) play pleiotropic roles in the plant growth and development. The identification, characterization and functional analysis of ncRNAs and their target genes have opened a new avenue for comprehensively revealing the regulatory network of male reproductive development and its response to environmental stresses in plants. This review briefly addresses the types, origin, biogenesis and mechanisms of ncRNAs in plants, highlights important updates on the roles of ncRNAs in regulating male reproductive development and emphasizes the contribution of ncRNAs, especially miRNAs and lncRNAs, in responses to abiotic stresses during this unique process in flowering plants.

Iberverin exhibits antineoplastic activities against human hepatocellular carcinoma via DNA damage-mediated cell cycle arrest and mitochondrial-related apoptosis.

Hepatocellular carcinoma (HCC) is one of the malignant tumors with high incidence and mortality rates in the world. Isothiocyanates (ITCs), bioactive substances present primarily in the plant order Brassicales, have been proved to be promising candidates for novel anti-HCC drugs with chemopreventive and anticancer activities. Iberverin, a predominant ITC isolated from the seeds of oxheart cabbage, has been discovered with anticancer property in lung cancer cells. However, the roles of iberverin in HCC remain elusive. In the present study, the effect and potential mechanisms of iberverin against human HCC were dissected. We demonstrated that low concentrations of iberverin inhibited cell proliferation, suppressed migration and induced mitochondrial-related apoptosis in vitro, and hampered tumorigenicity in vivo, with no obvious toxicity. Furthermore, we found that iberverin treatment induced DNA damage and G2/M phase arrest. Iberverin treatment also caused increased intracellular reactive oxygen species formation and glutathione depletion. Taken together, these results suggest that iberverin promotes mitochondrial-mediated apoptosis and induces DNA damage and G2/M cell cycle arrest in HCC by enhancing oxidative stress. Our findings provide better understanding of the anti-HCC mechanisms of ITCs and the potential for the natural product iberverin as a promising new anti-HCC biotherapeutic.

Redox Regulation of Salt Tolerance in Eutrema salsugineum by Proteomics.

Salt stress severely restricts plant growth and crop production, which is accompanied by accumulation of reactive oxygen species (ROS) that disturb cell redox homeostasis and oxidize redox-sensitive proteins. Eutrema salsugineum, a halophytic species closely related to Arabidopsis, shows a high level of tolerance to salinity and is increasingly used as a model plant in abiotic stress biology. To understand redox modifications and signaling pathways under salt stress, we used tandem mass tag (TMT)-based proteomics to quantify the salt-induced changes in protein redox modifications in E. salsugineum. Salt stress led to increased oxidative modification levels of 159 cysteine sites in 107 proteins, which play roles in carbohydrate and energy metabolism, transport, ROS homeostasis, cellular structure modulation, and folding and assembly. These lists of unknown redox reactive proteins in salt mustard lay the foundation for future research to understand the molecular mechanism of plant salt response. However, glutathione peroxidase (GPX) is one of the most important antioxidant enzymes in plants. Our research indicates that EsGPX may be involved in regulating ROS levels and that plants with overexpressed EsGPX have much improved salt tolerance.

Growth promotion of Sargassum fusiforme by epiphytic microbes is dependent on the extent of interspecific interactions of the microbial community.

Profound growth differences such as seedling length and biomass are often observed during the cultivation of Sargassum fusiforme despite the absence of detectable variance in abiotic factors that could have affected this process. This highlights the importance of biotic factors such as epiphytic microbiota in controlling seedling growth. Yet, how, and to what extent microbial activities can affect host growth in the presence of seawater flow and continuous erosion remains debatable. Particularly, the contribution of microbial network interactions to the growth of macroalgae remains poorly understood. This study aimed to compare the physicochemical properties of S. fusiforme seedlings via 16S rRNA gene Illumina sequencing-based profiling of the epiphytic microbial communities of seedlings with different lengths. Significantly different epiphytic bacterial communities were observed among S. fusiforme seedlings of different lengths. The result showed that community from longer seedlings maintained higher bacterial diversity with the taxa Gammaproteobacteria, Burkholderiales, Alteromonadales, Vibrionaceae, Ralstonia, Colwelliaceae, and Thalassotalea being selectively enriched. More importantly, microbial interspecific interactions, which were predominantly positive, were enhanced consistently in communities of the longer seedlings, indicative of reinforced prevalent and mutually cooperative relationships among the microorganisms associated with S. fusiforme seedlings of greater length. Furthermore, longer seedlings also displayed up-regulation of microbial functional potentials involved in N fixation and mineralization, P mineralization and transportation, and ion transportation compared with shorter ones. Lastly, stochastic processes dominated the community assembly of the epiphytic microorganisms. These findings could provide new insights into the relationship between microbial communities and growth in S. fusiforme seedlings and enable us to predict the community diversity and assembly of macroalgae-associated microbial communities. This could have important implications for linking microbial community diversity and network interactions to their host productivity.

Analysis of N6-methyladenosine reveals a new important mechanism regulating the salt tolerance of sugar beet (Beta vulgaris).

Salinity is an important environmental factor in crop growth and development. N6-methyladenosine (m6A) is an essential epigenetic modification that regulates plant-environment interaction. Sugar beet is a major sugar-yielding crop that has a certain tolerance to salt, but the dynamic response elicited by the m6A modification of transcripts under salt stress remains unknown. In this study, sugar beet was exposed to 300 mM NaCl to investigate its physiological response to high salinity and transcriptome-wide m6A modification profile. After the salt treatment, 7737 significantly modified m6A sites and 4981 differentially expressed genes (DEGs) were identified. Among the 312 m6A-modified DEGs, 113 hypomethylated DEGs were up-regulated and 99 hypermethylated DEGs were down-regulated, indicating a negative correlation between m6A modification and gene expression. Well-known salt tolerance genes (e.g., sodium/hydrogen exchanger 1, choline monooxygenase, and nucleoredoxin 2) and phospholipid signaling pathway genes (phosphoinositol-specific phospholipase C, phospholipase D, diacylglycerol kinase 1, etc.) were also among the m6A-modified genes. Further analysis showed that m6A modification may regulate salt-tolerant related gene expression by controlling mRNA stability. Therefore, changes in m6A modification may negatively regulate the expression of the salt-resistant genes in sugar beet, at least in part by modulating the stability of the mRNA via demethylase BvAlkbh10B. These findings could provide a better understanding of the epigenetic mechanisms of salt tolerance in sugar beets and uncover new candidate genes for improving the production of sugar beets planted in high-salinity soil.

First Report of Exserohilum rostratum Causing Leaf Blight on Broccoli (Brassica oleracea var. italica) in China.

Broccoli (Brassica oleracea var. italica) is not only an important crop worldwide with a large amount of production and consumption annually, but also rich in biologically active compounds (Surh et al., 2021). In November 2022, an unknown leaf blight was observed in the Broccoli planting area, Wenzhou City of Zhejiang Province (28.05 °N, 120.31 °E). Symptoms initially occurred at the leaf margin with yellow to gray lesions that were irregular and wilting. Approximately 10% of the surveyed plants were affected. To determine the pathogen, leaves with blight were collected randomly from five B. oleracea plants. Tissue blocks (3×3 mm) from diseased leaf portions were disinfected with 75% ethanol, rinsed three times with sterilized water, placed aseptically onto potato dextrose agar (PDA) medium, and incubated for 5 days at 28℃ in darkness. Seven fungal isolates with the same morphology were obtained using the spore method. The observed colonies were circular, taupe, pewter in color with light gray edging and many cottony aerial mycelia. Conidia were straight, curved or slightly bent, ellipsoidal to fusiform, and septate (typically 4-8 septa per conidium), with the size of 50.0-90.0 µm × 10.0-20.0 µm (n=30). The conidia had a slightly protruding and truncate hilum. These morphological characteristics were consistent with Exserohilum rostratum (Sharma et al., 2014). To further identify the pathogen, isolate WZU-XLH1 was chosen as a representative and the internal transcribed spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase-like (GAPDH) gene were amplified and sequenced using primer pairs ITS1/ITS4 (White et al., 1990) and Gpd1/Gpd2 (Berbee et al., 1999), respectively. The ITS and gpd gene sequences of isolate WZU-XLH1 were deposited in the GenBank database with accession numbers OQ750113 and OQ714500, respectively. BLASTn analysis showed matches of 568/571 (MH859108) and 547/547 (LT882549) with Exserohilum rostratum CBS 188.68. A neighbor-joining phylogenetic tree was constructed by combining the two sequenced loci, this isolate in the E. rostratum species complex clade at 71% bootstrap support.To verify the pathogenicity of the isolate, ten healthy Broccoli (cultivar 'You Xiu') seedlings with at least five leaves were divided into two groups: one group was inoculated with the isolate, while the other group served as a control. After surface disinfection with 75% ethanol and wiping with sterile water, tiny wounds were made on two leaves (two wounds in one leaf) using an inoculation needle. Fungal culture plugs cut from the isolate were placed on the wounds, while sterile PDA plugs served as the control. The leaves were sealed in wet airtight bags to retain moisture at room temperature with natural light (Cao et al., 2022). After five days, all leaves inoculated with isolate WZU-XLH1 showed symptoms identical to those observed in the field, with no symptoms present in the control group. The pathogenicity was confirmed by repeating the test in triplicate, and fungi re-isolated from symptomatic leaves were identified as E. rostratum by the morphological and molecular methods described above. To the best of our knowledge, this is the first report of E. rostratum causing leaf blight on broccoli in China. This study contributes to our understanding of B. oleracea leaf blight and establishes a basis for future studies on E. rostratum to develop management strategies.

DFT-based analysis of siderophore-metal ion interaction for efficient heavy metal remediation.

Siderophores have great application potential in metal pollutant remediation because of their effective cost and friendly impact on the environment. However, the practical use of siderophores in the remediation of specific metals is rather limited because of the weak nonspecific interactions between the siderophores and different metals. Thus, screening for a siderophore with optimal interaction with a specific metal would be necessary. In this study, the interaction between metal ions and moieties that donate the oxygen ligands for the coordination of four types of siderophore (hydroxamates, catecholates, phenolates, and carboxylates) was modeled and analyzed. As revealed by DFT-based analysis, the four types of siderophore generally exhibited selection preference for different metal ions in the order Ga3+ > Al3+ > Fe3+ > Cr3+ > Ni2+ > Cu2+ > Zn2+ > Co2+ > Mn2+ > Hg2+ > Pb2+ > Cd2+, which was determined mainly by the electronegativity of the siderophore functional groups, the electronegativity of the metals, and the ionic radius of the metals, as well as the interaction between the siderophores and the metals. Moreover, the effect of linear or nonlinear (cyclic) structure on the affinity of each siderophore for different metal ions was evaluated. In most situations, metal-bound cyclic siderophores were found to be more stable than their linear counterparts. Thus, proper siderophores for the remediation of metal pollution may be rapidly screened using this model.

Unique Features of the m6A Methylome and Its Response to Salt Stress in the Roots of Sugar Beet (Beta vulgaris).

Salt is one of the most important environmental factors in crop growth and development. N6-methyladenosine (m6A) is an epigenetic modification that regulates plant-environment interaction at transcriptional and translational levels. Sugar beet is a salt-tolerant sugar-yielding crop, but how m6A modification affects its response to salt stress remains unknown. In this study, m6A-seq was used to explore the role of m6A modification in response to salt stress in sugar beet (Beta vulgaris). Transcriptome-wide m6A methylation profiles and physiological responses to high salinity were investigated in beet roots. After treatment with 300 mM NaCl, the activities of peroxidase and catalase, the root activity, and the contents of Na+, K+, and Ca2+ in the roots were significantly affected by salt stress. Compared with the control plants, 6904 differentially expressed genes (DEGs) and 566 differentially methylated peaks (DMPs) were identified. Association analysis revealed that 243 DEGs contained DMP, and 80% of these DEGs had expression patterns that were negatively correlated with the extent of m6A modification. Further analysis verified that m6A methylation may regulate the expression of some genes by controlling their mRNA stability. Functional analysis revealed that m6A modifications primarily affect the expression of genes involved in energy metabolism, transport, signal transduction, transcription factors, and cell wall organization. This study provides evidence that a post-transcriptional regulatory mechanism mediates gene expression during salt stress by affecting the stability of mRNA in the root.

Variation in Glucosinolate Accumulation among Different Sprout and Seedling Stages of Broccoli (Brassica oleracea var. italica).

Glucosinolates (GLs) are plant secondary metabolites that may act against different types of cancers. Broccoli (Brassica oleracea var. italica) is rich in GLs which makes it an excellent source of these nutraceuticals. The composition and concentration of GLs vary among broccoli cultivars and throughout the developmental stages of the plant. To obtain the GL profiles of broccoli, GL compositions and contents in four early developmental stages (seeds, 3-day sprouts, 11-day and 17-day seedlings) were determined for nine cultivars of broccoli in this study. A total of 12 GLs including 9 aliphatic GLs and 3 indole GLs were identified from the nine broccoli cultivars using LC-QTOF-MS. UPLC results showed that aliphatic GLs concentrations decreased with broccoli sprouts and seedling growth for most cultivars. Interestingly, indole GLs amounts increased after germination and reached the highest level in 3-day sprouts or 11-day seedlings, and they fell back to a low level in 17-day seedlings. The GL profiles of nine cultivars documented in this study will provide useful information for high quality germplasm selection for cultivation or genetic engineering, and further understanding of the GL metabolic pathways.

Arbuscular mycorrhizal fungi improve the growth and performance in the seedlings of Leymus chinensis under alkali and drought stresses.

Alkali and drought stresses are increasing severe environmental problems throughout the world, especially in the Songnen grassland of northern China. Leymus chinensis is the dominant grass species in the Songnen grassland of northern China and the most promising species for grassland restoration. Arbuscular mycorrhizal fungi (AMF) can colonize 80% of vascular plants, which can enhance the growth of host plants and provide extrinsic protection against abiotic stresses. However, little is known about the interaction effect of alkali and drought stresses on plant-AM symbionts. Here, seedlings of Leymus chinensis inoculated with or without mycorrhizae were cultivated in soil with 0, 100 or 200 mM NaHCO3 under 0, 5 or 10% (w/v) PEG treatment, and the changes in growth, osmotic adjustment substances and ions were measured. The results showed that the interaction of alkali and drought stresses caused greater seedling growth inhibition than either single alkali or drought stress due to ion toxicity and oxidative damage. Mycorrhizae could alleviate the growth inhibition of seedlings under alkali or drought stress. The interaction of alkali and drought stresses did not affect the alleviating effect of mycorrhizae on seedling growth but improved the osmotic regulation ability and ionic balance of the seedlings. Our results clearly show different effects of the interaction of alkali and drought stresses versus a single stress (alkali or drought) on plant development and provide new insights into the positive effect of arbuscular mycorrhizal fungi on host plants under such stress conditions.

[The physiology of plant seed aging: a review].

Seed quality plays an important role in the agricultural and animal husbandry production, the effective utilization of genetic resources, the conservation of biodiversity and the restoration and reconstruction of plant communities. Seed aging is a common physiological phenomenon during storage. It is a natural irreversible process that occurs and develops along with the extension of seed storage time. It is not only related to the growth, yield and quality of seed and seedling establishment, but also has an important effect on the conservation, utilization and development of plant germplasm resources. The physiological mechanisms of seed aging are complex and diverse. Most studies focus on conventional physiological characterization, while systematic and comprehensive in-depth studies are lacking. Here we review the recent advances in understanding the physiology of seed aging process, including the methods of seed aging, the effect of aging on seed germination, and the physiological and molecular mechanisms of seed aging. The change of multiple physiological parameters, including seed vigor, electrical conductivity, malondialdehyde content and storage material in the seed, antioxidant enzyme activity and mitochondrial structure, were summarized. Moreover, insights into the mechanism of seed aging from the aspects of transcriptome, proteome and aging related gene function were summarized. This study may facilitate the research of seed biology and the conservation and utilization of germplasm resources.

A Type III Polyketide Synthase (SfuPKS1) Isolated from the Edible Seaweed Sargassum fusiforme Exhibits Broad Substrate and Catalysis Specificity.

A type III polyketide synthase (SfuPKS1) from the edible seaweed Sargassum fusiforme was molecularly cloned and biochemically characterized. The recombinant SfuPKS1 catalyzed the condensation of fatty acyl-CoA with two or three malonyl-CoA using lactone-type intramolecular cyclization to produce tri- and/or tetraketides. Moreover, it can also utilize phenylpropanoyl-CoA to synthesize phloroglucinol derivatives through Claisen-type cyclization, exhibiting broad substrate and catalysis specificity. Furthermore, the catalytic efficiency (kcat/KM) for acetyl-CoA was 11.8-fold higher than that for 4-coumaroyl-CoA. A pathway for the synthesis of naringenin involving SfuPKS1 was also constructed in Escherichia coli by recombinant means, resulting in 4.9 mg of naringenin per liter.

[Advances in the physiological functions of plant lipids in response to stresses].

Lipids are important components of living organisms that participate in and regulate a variety of life activities. Lipids in plants also play important physiological functions in response to a variety of abiotic stresses (e.g. salt stress, drought stress, temperature stress). However, most research on lipids focused on animal cells and medical fields, while the functions of lipids in plants were overlooked. With the rapid development of "omics" technologies and biotechnology, the lipidomics has received much attention in recent years because it can reveal the composition and function of lipids in a deep and comprehensive way. This review summarizes the recent advances in the functions and classification of lipids, the development of lipidomics technology, and the responses of plant lipids against drought stress, salt stress and temperature stress. In addition, challenges and prospects were proposed for future lipidomics research and further exploration of the physiological functions of lipids in plant stress resistance.

A New Lectin from Auricularia auricula Inhibited the Proliferation of Lung Cancer Cells and Improved Pulmonary Flora.

Lectins are widely distributed in the natural world and are usually involved in antitumor activities. Auricularia auricula (A. auricula) is a medicinal and edible homologous fungus. A. auricula contains many active ingredients, such as polysaccharides, melanin, flavonoids, adenosine, sterols, alkaloids, and terpenes. In this study, we expected to isolate and purify lectin from A. auricula, determine the glycoside bond type and sugar-specific protein of A. auricula lectin (AAL), and finally, determine its antitumor activities. We used ammonium sulfate fractionation, ion exchange chromatography, and affinity chromatography to separate and purify lectin from A. auricula. The result was a 25 kDa AAL with a relative molecular mass of 18913.22. Protein identification results suggested that this lectin contained four peptide chains by comparing with the UniProt database. The FT-IR and ß-elimination reaction demonstrated that the connection between the oligosaccharide and polypeptide of AAL was an N-glucoside bond. Analyses of its physical and chemical properties showed that AAL was a temperature-sensitive and acidic/alkaline-dependent glycoprotein. Additionally, the anticancer experiment manifested that AAL inhibited the proliferation of A549, and the IC50 value was 28.19 ± 1.92 µg/mL. RNA sequencing dataset analyses detected that AAL may regulate the expression of JUN, TLR4, and MYD88 to suppress tumor proliferation. Through the pulmonary flora analysis, the bacterial structure of each phylum in the lectin treatment group was more reasonable, and the colonization ability of the normal microflora was improved, indicating that lectin treatment could significantly improve the bacterial diversity characteristics.

Polymorphic tandem DNA repeats activate the human telomerase reverse transcriptase gene.

Multiple independent sequence variants of the hTERT locus have been associated with telomere length and cancer risks in genome-wide association studies. Here, we identified an intronic variable number tandem repeat, VNTR2-1, as an enhancer-like element, which activated hTERT transcription in a cell in a chromatin-dependent manner. VNTR2-1, consisting of 42-bp repeats with an array of enhancer boxes, cooperated with the proximal promoter in the regulation of hTERT transcription by basic helix-loop-helix transcription factors and maintained hTERT expression during embryonic stem-cell differentiation. Genomic deletion of VNTR2-1 in MelJuSo melanoma cells markedly reduced hTERT transcription, leading to telomere shortening, cellular senescence, and impairment of xenograft tumor growth. Interestingly, VNTR2-1 lengths varied widely in human populations; hTERT alleles with shorter VNTR2-1 were underrepresented in African American centenarians, indicating its role in human aging. Therefore, this polymorphic element is likely a missing link in the telomerase regulatory network and a molecular basis for genetic diversities of telomere homeostasis and age-related disease susceptibilities.