Banana MaNAC1 activates secondary cell wall cellulose biosynthesis to enhance chilling resistance in fruit.

Chilling injury has a negative impact on the quantity and quality of crops, especially subtropical and tropical plants. The plant cell wall is not only the main source of biomass production, but also the first barrier to various stresses. Therefore, improving the understanding of the alterations in cell wall architecture is of great significance for both biomass production and stress adaptation. Herein, we demonstrated that the cell wall principal component cellulose accumulated during chilling stress, which was caused by the activation of MaCESA proteins. The sequence-multiple comparisons show that a cold-inducible NAC transcriptional factor MaNAC1, a homologue of Secondary Wall NAC transcription factors, has high sequence similarity with Arabidopsis SND3. An increase in cell wall thickness and cellulosic glucan content was observed in MaNAC1-overexpressing Arabidopsis lines, indicating that MaNAC1 participates in cellulose biosynthesis. Over-expression of MaNAC1 in Arabidopsis mutant snd3 restored the defective secondary growth of thinner cell walls and increased cellulosic glucan content. Furthermore, the activation of MaCESA7 and MaCESA6B cellulose biosynthesis genes can be directly induced by MaNAC1 through binding to SNBE motifs within their promoters, leading to enhanced cellulose content during low-temperature stress. Ultimately, tomato fruit showed greater cold resistance in MaNAC1 overexpression lines with thickened cell walls and increased cellulosic glucan content. Our findings revealed that MaNAC1 performs a vital role as a positive modulator in modulating cell wall cellulose metabolism within banana fruit under chilling stress.

Understanding the dynamic evolution of hemicellulose during Pinus taeda L. growth.

Pinus taeda L. is a fast-growing softwood with significant commercial value. Understanding structural changes in hemicellulose during growth is essential to understanding the biosynthesis processes occurring in the cell walls of this tree. In this study, alkaline extraction is applied to isolate hemicellulose from Pinus taeda L. stem segments of different ages (1, 2, 3, and 4 years old). The results show that the extracted hemicellulose is mainly comprised of O-acetylgalactoglucomannan (GGM) and 4-O-methylglucuronoarabinoxylan (GAX), with the molecular weights and ratios (i.e., GGM:GAX) of GGM and GAX increasing alongside Pinus taeda L. age. Mature Pinus taeda L. hemicellulose is mainly composed of GGM, and the ratio of (mannose:glucose) in the GGM main chain gradually increases from 2.45 to 3.60 with growth, while the galactose substitution of GGM decreases gradually from 21.36% to 14.65%. The acetylation of GGM gradually increases from 0.33 to 0.45 with the acetyl groups mainly substituting into the O-3 position in the mannan. Furthermore, the contents of arabinose and glucuronic acid in GAX gradually decrease with growth. This study can provide useful information to the research in genetic breeding and high-value utilization of Pinus taeda L.

ULK1-dependent phosphorylation of PKM2 antagonizes O-GlcNAcylation and regulates the Warburg effect in breast cancer.

Pyruvate kinase M2 (PKM2) is a central metabolic enzyme driving the Warburg effect in tumor growth. Previous investigations have demonstrated that PKM2 is subject to O-linked ß-N-acetylglucosamine (O-GlcNAc) modification, which is a nutrient-sensitive post-translational modification. Here we found that unc-51 like autophagy activating kinase 1 (ULK1), a glucose-sensitive kinase, interacts with PKM2 and phosphorylates PKM2 at Ser333. Ser333 phosphorylation antagonizes PKM2 O-GlcNAcylation, promotes its tetramer formation and enzymatic activity, and decreases its nuclear localization. As PKM2 is known to have a nuclear role in regulating c-Myc, we also show that PKM2-S333 phosphorylation inhibits c-Myc expression. By downregulating glucose consumption and lactate production, PKM2 pS333 attenuates the Warburg effect. Through mouse xenograft assays, we demonstrate that the phospho-deficient PKM2-S333A mutant promotes tumor growth in vivo. In conclusion, we identified a ULK1-PKM2-c-Myc axis in inhibiting breast cancer, and a glucose-sensitive phosphorylation of PKM2 in modulating the Warburg effect.

Trifolirhizin protects ovariectomy-induced bone loss in mice by inhibiting osteoclast differentiation and bone resorption.

Background: Osteoporosis is a debilitating condition characterized by reduced bone density and microstructure, leading to increased susceptibility to fractures and increased mortality, particularly among older individuals. Despite the availability of drugs for osteoporosis treatment, the need for targeted and innovative agents with fewer adverse effects persists. Trifolirhizin, a natural pterostalin derived from the root of Sophora flavescens, has been previously studied for its effects on certain anticancer and antiinflammatory. The impact of trifolirhizin on the formation and function of osteoclasts remain unclear. Purpose: Herein, the possible roles of trifolirhizin the formation and function of osteoclasts and the underlying mechanism were explored. Methods: Bone marrow-derived macrophages (BMMs) were employed to evaluate the roles of trifolirhizin on steoclastogenesis, bone absorption and the underlying mechanism in vitro. Bone loss model was established by ovariectomy(OVX) in mice in vivo. Results: Trifolirhizin repressed osteoclastogenesis, bone resorption induced by receptor activator of nuclear factor kappa B ligand (RANKL) in vitro. Mechanistically, trifolirhizin inhibits RANKL-induced MAPK signal transduction and NFATc1 expression. Moreover, trifolirhizin inhibited osteoclast marker gene expression, including NFATc1, CTSK, MMP9, DC-STAMP, ACP5, and V-ATPase-D2. Additionally, trifolirhizin was found to protect against ovariectomy(OVX)-induced bone loss in mice. Conclusion: Trifolirhizin can effectively inhibit osteoclast production and bone resorption activity. The results of our study provide evidence for trifolirhizin as a potential drug for the prevention and treatment of osteoporosis and other osteolytic diseases.

RAD18 O-GlcNAcylation promotes translesion DNA synthesis and homologous recombination repair.

RAD18, an important ubiquitin E3 ligase, plays a dual role in translesion DNA synthesis (TLS) and homologous recombination (HR) repair. However, whether and how the regulatory mechanism of O-linked N-acetylglucosamine (O-GlcNAc) modification governing RAD18 and its function during these processes remains unknown. Here, we report that human RAD18, can undergo O-GlcNAcylation at Ser130/Ser164/Thr468, which is important for optimal RAD18 accumulation at DNA damage sites. Mechanistically, abrogation of RAD18 O-GlcNAcylation limits CDC7-dependent RAD18 Ser434 phosphorylation, which in turn significantly reduces damage-induced PCNA monoubiquitination, impairs Polη focus formation and enhances UV sensitivity. Moreover, the ubiquitin and RAD51C binding ability of RAD18 at DNA double-strand breaks (DSBs) is O-GlcNAcylation-dependent. O-GlcNAcylated RAD18 promotes the binding of RAD51 to damaged DNA during HR and decreases CPT hypersensitivity. Our findings demonstrate a novel role of RAD18 O-GlcNAcylation in TLS and HR regulation, establishing a new rationale to improve chemotherapeutic treatment.

Brevilin A inhibits RANKL-induced osteoclast differentiation and bone resorption.

Brevilin A (BA) is the primary component of Centipeda minima, which is widely used in Chinese traditional medicine. The anti-inflammatory and anti-tumor properties of BA have been established; however, its function in bone metabolism is not well understood. This study revealed that concentrations of BA below 1.0 µM did not inhibit the proliferation of bone marrow macrophages but did impede the differentiation and bone resorption activity of osteoclasts. Furthermore, BA suppressed the expression of osteoclast-specific genes Mmp9, Acp5, Dc-stamp, Ctsk, and Atp6v0d2. In addition, mTOR, ERK, and NFATc1 activation in bone marrow macrophages were suppressed by BA. As a whole, BA blocks the mTOR and ERK signaling pathways, which is responsible for the development and activity of osteoclasts, and the resorption of bone.

Antidepressant duloxetine hydrochloride protects against ovariectomy-induced bone loss in mice by inhibiting osteoclast differentiation.

BACKGROUND: Several studies have reported the association between osteoporosis and major depressive disorder (MDD) as well as the use of antidepressants. However, it remains to be elucidated whether these associations are related to exposure to antidepressants, a consequence of a disease process, or a combination of both. METHODS: This study investigates the independent effect of the antidepressant duloxetine hydrochloride (DH) on ovariectomy-induced bone loss in mice. One week after ovariectomy, the treated mice received DH. To explore the mechanism underlying the rescue of bone loss, bone marrow cells were isolated from mouse femurs and tibias, and macrophages extracted from them were induced to become osteoclasts in vitro while being treated with DH. Subsequently, the osteoclasts underwent Bulk RNA-Seq to reveal the involved signaling pathways. The results of the bioinformatic analysis were then validated through in vitro experiments. RESULTS: The in vivo experiments demonstrated that DH treatment compromised ovariectomy-induced bone loss after 7 weeks. The in vitro experiments suggested that DH treatment attenuated osteoclast differentiation via the MAPKs/NFATc1 signaling pathway. CONCLUSION: The findings from this study suggest that DH, instead of causing bone mass loss, may assist in alleviating postmenopausal osteoporosis. These results can serve as a reference for the clinical treatment of patients with perimenopausal or postmenopausal depression using antidepressants.