Decrease of nitrogen cycle gene abundance and promotion of soil microbial-N saturation restrain increases in N2O emissions in a temperate forest with long-term nitrogen addition.

Increases in soil available nitrogen (N) influence N-cycle gene abundances and emission of nitrous oxide (N2O), which is primarily due to N-induced soil acidification in forest. Moreover, the extent of microbial-N saturation could control microbial activity and N2O emission. The contributions of N-induced alterations of microbial-N saturation and N-cycle gene abundances to N2O emission have rarely been quantified. Here, the mechanism underlying N2O emission under N additions (three chemical forms of N, i.e., NO3--N, NH4+-N and NH4NO3-N, and each at two rates, 50 and 150 kg N ha-1 year-1, respectively) spanning 2011-2021 was investigated in a temperate forest in Beijing. Results showed N2O emissions increased at both low and high N rates of all the three forms compared with control during the whole experiment. However, N2O emissions were lower in high rate of NH4NO3-N and NH4+-N treatments than the corresponding low N rates in the recent three years. Effects of N on microbial-N saturation and abundances of N-cycle genes were dependent on the N rate and form as well as experimental time. Specifically, negative effects of N on N-cycle gene abundances and positive effects of N on microbial-N saturation were demonstrated in high N rate treatments, particularly with NH4+ addition during 2019-2021. Such effects were associated with soil acidification. A hump-backed trend between microbial-N saturation and N2O emissions was observed, suggesting N2O emissions decreased with increase of the microbial-N saturation. Furthermore, N-induced decreases in N-cycle gene abundances restrained N2O emissions. In particular, the nitrification process, dominated by ammonia-oxidize archaea, is critical to determination of N2O emissions in response to the N addition in the temperate forest. We confirmed N addition promoted soil microbial-N saturation and reduced N-cycle gene abundances, which restrained the continuous increase in N2O emissions. It is important for understanding the forest-N-microbe nexus under climate change.

Hyperthermia promotes degradation of the acute promyelocytic leukemia driver oncoprotein ZBTB16/RARα.

The acute promyelocytic leukemia (APL) driver ZBTB16/RARα is generated by the t(11;17) (q23;q21) chromosomal translocation, which is resistant to combined treatment of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) or conventional chemotherapy, resulting in extremely low survival rates. In the current study, we investigated the effects of hyperthermia on the oncogenic fusion ZBTB16/RARα protein to explore a potential therapeutic approach for this variant APL. We showed that Z/R fusion protein expressed in HeLa cells was resistant to ATO, ATRA, and conventional chemotherapeutic agents. However, mild hyperthermia (42 °C) rapidly destabilized the ZBTB16/RARα fusion protein expressed in HeLa, 293T, and OCI-AML3 cells, followed by robust ubiquitination and proteasomal degradation. In contrast, hyperthermia did not affect the normal (i.e., unfused) ZBTB16 and RARα proteins, suggesting a specific thermal sensitivity of the ZBTB16/RARα fusion protein. Importantly, we found that the destabilization of ZBTB16/RARα was the initial step for oncogenic fusion protein degradation by hyperthermia, which could be blocked by deletion of nuclear receptor corepressor (NCoR) binding sites or knockdown of NCoRs. Furthermore, SIAH2 was identified as the E3 ligase participating in hyperthermia-induced ubiquitination of ZBTB16/RARα. In short, these results demonstrate that hyperthermia could effectively destabilize and subsequently degrade the ZBTB16/RARα fusion protein in an NCoR-dependent manner, suggesting a thermal-based therapeutic strategy that may improve the outcome in refractory ZBTB16/RARα-driven APL patients in the clinic.

ZmEREB92 interacts with ZmMYC2 to activate maize terpenoid phytoalexin biosynthesis upon Fusarium graminearum infection through jasmonic acid/ethylene signaling.

Maize (Zea mays) terpenoid phytoalexins (MTPs) induced by multiple fungi display extensive antimicrobial activities, yet how maize precisely regulates MTP accumulation upon pathogen infection remains elusive. In this study, pretreatment with jasmonic acid (JA)/ethylene (ET)-related inhibitors significantly reduced Fusarium graminearum-induced MTP accumulation and resulted in enhanced susceptibility to F. graminearum, indicating the involvement of JA/ET in MTP regulatory network. ZmEREB92 positively regulated MTP biosynthetic gene (MBG) expression by correlation analysis. Knockout of ZmEREB92 significantly compromised maize resistance to F. graminearum with delayed induction of MBGs and attenuated MTP accumulation. The activation of ZmEREB92 on MBGs is dependent on the interaction with ZmMYC2, which directly binds to MBG promoters. ZmJAZ14 interacts both with ZmEREB92 and with ZmMYC2 in a competitive manner to negatively regulate MBG expression. Altogether, our findings illustrate the regulatory mechanism for JA/ET-mediated MTP accumulation upon F. graminearum infection with the involvement of ZmEREB92, ZmMYC2, and ZmJAZ14, which provides new insights into maize disease responses.

Maize WRKY Transcription Factor ZmWRKY79 Positively Regulates Drought Tolerance through Elevating ABA Biosynthesis.

Drought stress causes heavy damages to crop growth and productivity under global climatic changes. Transcription factors have been extensively studied in many crops to play important roles in plant growth and defense. However, there is a scarcity of studies regarding WRKY transcription factors regulating drought responses in maize crops. Previously, ZmWRKY79 was identified as the regulator of maize phytoalexin biosynthesis with inducible expression under different elicitation. Here, we elucidated the function of ZmWRKY79 in drought stress through regulating ABA biosynthesis. The overexpression of ZmWRKY79 in Arabidopsis improved the survival rate under drought stress, which was accompanied by more lateral roots, lower stomatal aperture, and water loss. ROS scavenging was also boosted by ZmWRKY79 to result in less H2O2 and MDA accumulation and increased antioxidant enzyme activities. Further analysis detected more ABA production in ZmWRKY79 overexpression lines under drought stress, which was consistent with up-regulated ABA biosynthetic gene expression by RNA-seq analysis. ZmWRKY79 was observed to target ZmAAO3 genes in maize protoplast through acting on the specific W-boxes of the corresponding gene promoters. Virus-induced gene silencing of ZmWRKY79 in maize resulted in compromised drought tolerance with more H2O2 accumulation and weaker root system architecture. Together, this study substantiates the role of ZmWRKY79 in the drought-tolerance mechanism through regulating ABA biosynthesis, suggesting its broad functions not only as the regulator in phytoalexin biosynthesis against pathogen infection but also playing the positive role in abiotic stress response, which provides a WRKY candidate gene to improve drought tolerance for maize and other crop plants.

Maize transcription factor ZmEREB20 enhanced salt tolerance in transgenic Arabidopsis.

Soil salinity severely limits agricultural crop production worldwide. As one of the biggest plant specific transcription factor families, AP2/ERF members have been extensively studied to regulate plant growth, development and stress responses. However, the role of AP2/ERF family in maize salt tolerance remains largely unknown. In this study, we identified a maize AP2-ERF family member ZmEREB20 as a positive salinity responsive gene. Overexpression of ZmEREB20in Arabidopsis enhanced ABA sensitivity and resulted in delayed seed germination under salt stress through regulating ABA and GA related genes. ZmEREB20 overexpression lines also showed higher survival rates with elevated ROS scavenging toward high salinity. Furthermore, root hair growth inhibition by salt stress was markedly rescued in ZmEREB20 overexpression lines. Auxin transport inhibitor TIBA drastically enhanced root hair growth in ZmEREB20 overexpression Arabidopsis under salt stress, together with the increased expression of auxin-related genes, ion transporter genes and root hair growth genes by RNA-seq analysis. ZmEREB20 positively regulated salt tolerance through the molecular mechanism associated with hormone signaling, ROS scavenging and root hair plasticity, proving the potential target for crop breeding to improve salt resistance.

Vascular endothelial S1pr1 ameliorates adverse cardiac remodelling via stimulating reparative macrophage proliferation after myocardial infarction.

AIMS: Endothelial cell (EC) homoeostasis plays an important role in normal physiological cardiac functions, and its dysfunction significantly influences pathological cardiac remodelling after myocardial infarction (MI). It has been shown that the sphingosine 1-phosphate receptor 1 (S1pr1) was highly expressed in ECs and played an important role in maintaining endothelial functions. We thus hypothesized that the endothelial S1pr1 might be involved in post-MI cardiac remodelling. METHODS AND RESULTS: Our study showed that the specific loss of endothelial S1pr1 exacerbated post-MI cardiac remodelling and worsened cardiac dysfunction. We found that the loss of endothelial S1pr1 significantly reduced Ly6clow macrophage accumulation, which is critical for the resolution of inflammation and cardiac healing following MI. The reduced reparative macrophages in post-MI myocardium contributed to the detrimental effects of endothelial S1pr1 deficiency on post-MI cardiac remodelling. Further investigations showed that the loss of endothelial S1pr1-reduced Ly6clow macrophage proliferation, while the pharmacological activation of S1pr1-enhanced Ly6clow macrophage proliferation, thereby ameliorated cardiac remodelling after MI. A mechanism study showed that S1P/S1pr1 activated the ERK signalling pathway and enhanced colony-stimulating factor 1 (CSF1) expression, which promoted Ly6clow macrophage proliferation in a cell-contact manner. The blockade of CSF1 signalling reversed the enhancing effect of S1pr1 activation on Ly6clow macrophage proliferation and worsened post-MI cardiac remodelling. CONCLUSION: This study reveals that cardiac microvascular endothelium promotes reparative macrophage proliferation in injured hearts via the S1P/S1PR1/ERK/CSF1 pathway and thus ameliorates post-MI adverse cardiac remodelling.

Ginsenoside Rg1 protects against cigarette smoke-induced airway remodeling by suppressing the TGF-ß1/Smad3 signaling pathway.

Chronic obstructive pulmonary disease (COPD) is a devastating and common respiratory disease characterized by chronic inflammation and progressive airway remodeling. Ginsenoside Rg1 (GRg1), a major active component of Panax ginseng, has been found to possess beneficial properties against acute lung injury and respiratory diseases. However, the effects of GRg1 on airway remodeling in COPD remain unclear. In this study, we aimed to investigate the potential protective effects of GRg1 on airway remodeling induced by cigarette smoke (CS) and the underlying mechanism. A rat model of COPD was established in which the animals were subjected to CS and GRg1 daily for 12 weeks. Subsequently, we evaluated lung function, inflammatory responses, along with airway remodeling and associated signaling factors. GRg1 treatment was found to improve pulmonary function, reduce airway collagen volume fraction, and markedly reduce the expression of IL-6, TNF-α, α-SMA, and collagen I. Moreover, GRg1 treatment decreased the expression of TGF-ß1, TGF-ßR1, and phosphorylated-Smad3. In vitro, pretreatment of MRC5 human lung fibroblasts with GRg1 prior to exposure to cigarette smoke extract (CSE) reversed the cell ultrastructure disorder, decreased the expression of IL-6 and TNF-α, and significantly attenuated transdifferentiation of MRC5 cells by suppressing α-SMA and collagen I expression. Additionally, GRg1 suppressed the TGF-ß1/Smad3 signaling pathway in CSE-stimulated MRC5 cells, whereas Smad3 over-expression abolished the anti-transdifferentiation effect of GRg1. In conclusion, the results of our study demonstrated that GRg1 improves lung function and protects against CS-induced airway remodeling, in part by down-regulating the TGF-ß1/Smad3 signaling pathway.

Transcriptional Factors Regulate Plant Stress Responses through Mediating Secondary Metabolism.

Plants are adapted to sense numerous stress stimuli and mount efficient defense responses by directing intricate signaling pathways. They respond to undesirable circumstances to produce stress-inducible phytochemicals that play indispensable roles in plant immunity. Extensive studies have been made to elucidate the underpinnings of defensive molecular mechanisms in various plant species. Transcriptional factors (TFs) are involved in plant defense regulations through acting as mediators by perceiving stress signals and directing downstream defense gene expression. The cross interactions of TFs and stress signaling crosstalk are decisive in determining accumulation of defense metabolites. Here, we collected the major TFs that are efficient in stress responses through regulating secondary metabolism for the direct cessation of stress factors. We focused on six major TF families including AP2/ERF, WRKY, bHLH, bZIP, MYB, and NAC. This review is the compilation of studies where researches were conducted to explore the roles of TFs in stress responses and the contribution of secondary metabolites in combating stress influences. Modulation of these TFs at transcriptional and post-transcriptional levels can facilitate molecular breeding and genetic improvement of crop plants regarding stress sensitivity and response through production of defensive compounds.

ZmMYC2 exhibits diverse functions and enhances JA signaling in transgenic Arabidopsis.

KEY MESSAGE: ZmMYC2 was identified as the key regulator of JA signaling in maize and exhibited diverse functions through binding to many gene promoters as well as enhanced JA signaling in transgenic Arabidopsis. The plant hormone jasmonate (JA) extensively coordinates plant growth, development and defensive responses. MYC2 is the master regulator of JA signaling and has been widely studied in many plant species. However, little is known about this transcription factor in maize. Here, we identified one maize transcription factor with amino acid identity of 47% to the well-studied Arabidopsis AtMYC2, named as ZmMYC2. Gene expression analysis demonstrated inducible expression patterns of ZmMYC2 in response to multiple plant hormone treatments, as well as biotic and abiotic stresses. The yeast two-hybrid assay indicated physical interaction among ZmMYC2 and JA signal repressors ZmJAZ14, ZmJAZ17, AtJAZ1 and AtJAZ9. ZmMYC2 overexpression in Arabidopsis myc2myc3myc4 restored the sensitivity to JA treatment, resulting in shorter root growth and inducible anthocyanin accumulation. Furthermore, overexpression of ZmMYC2 in Arabidopsis elevated resistance to Botrytis cinerea. Further ChIP-Seq analysis revealed diverse regulatory roles of ZmMYC2 in maize, especially in the signaling crosstalk between JA and auxin. Hence, we identified ZmMYC2 and characterized its roles in regulating JA-mediated growth, development and defense responses.

Endothelial S1pr1 regulates pressure overload-induced cardiac remodelling through AKT-eNOS pathway.

Cardiac vascular microenvironment is crucial for cardiac remodelling during the process of heart failure. Sphingosine 1-phosphate (S1P) tightly regulates vascular homeostasis via its receptor, S1pr1. We therefore hypothesize that endothelial S1pr1 might be involved in pathological cardiac remodelling. In this study, heart failure was induced by transverse aortic constriction (TAC) operation. S1pr1 expression is significantly increased in microvascular endothelial cells (ECs) of post-TAC hearts. Endothelial-specific deletion of S1pr1 significantly aggravated cardiac dysfunction and deteriorated cardiac hypertrophy and fibrosis in myocardium. In vitro experiments demonstrated that S1P/S1pr1 praxis activated AKT/eNOS signalling pathway, leading to more production of nitric oxide (NO), which is an essential cardiac protective factor. Inhibition of AKT/eNOS pathway reversed the inhibitory effect of EC-S1pr1-overexpression on angiotensin II (AngII)-induced cardiomyocyte (CM) hypertrophy, as well as on TGF-ß-mediated cardiac fibroblast proliferation and transformation towards myofibroblasts. Finally, pharmacological activation of S1pr1 ameliorated TAC-induced cardiac hypertrophy and fibrosis, leading to an improvement in cardiac function. Together, our results suggest that EC-S1pr1 might prevent the development of pressure overload-induced heart failure via AKT/eNOS pathway, and thus pharmacological activation of S1pr1 or EC-targeting S1pr1-AKT-eNOS pathway could provide a future novel therapy to improve cardiac function during heart failure development.