Enantiomer Recognition Based on Chirality Transfer from Chiral Amines to Ternary Dynamic Covalent Systems.

Enantiomer recognition is usually required in organic synthesis and materials and life sciences. This paper describes an enantiomer recognition method based on ternary dynamic covalent systems constructed via the complexation of chiral amines with a chiral boronate derived from 1,4-phenylenediboric acid and an L-DOPA-modified naphthalenediimide. The ternary systems aggregate into chiral assemblies driven by π-π interactions, and the chirality is transferred from the chiral amines to assemblies with high stereospecificity. Consequently, the enantiomer composition of chiral amines and the absolute configuration of the major enantiomer can be determined according to the sign of the Cotton effect of the ternary system by using circular dichroism (CD) spectroscopy. This method offers the advantage of using the long wavelength CD signals of the boronate at around 520 nm, thereby avoiding interference with those of the carbon skeleton. This ternary system provides a novel approach to the design of enantiomer recognition systems.

Low phosphorus promotes NSP1-NSP2 heterodimerization to enhance strigolactone biosynthesis and regulate shoot and root architecture in rice.

Phosphorus is an essential macronutrient for plant development and metabolism, and plants have evolved ingenious mechanisms to overcome phosphate (Pi) starvation. However, the molecular mechanisms underlying the regulation of shoot and root architecture by low phosphorus conditions and the coordinated utilization of Pi and nitrogen remain largely unclear. Here, we show that Nodulation Signaling Pathway 1 (NSP1) and NSP2 regulate rice tiller number by promoting the biosynthesis of strigolactones (SLs), a class of phytohormones with fundamental effects on plant architecture and environmental responses. We found that NSP1 and NSP2 are induced by Oryza sativa PHOSPHATE STARVATION RESPONSE2 (OsPHR2) in response to low-Pi stress and form a complex to directly bind the promoters of SL biosynthesis genes, thus markedly increasing SL biosynthesis in rice. Interestingly, the NSP1/2-SL signaling module represses the expression of CROWN ROOTLESS 1 (CRL1), a newly identified early SL-responsive gene in roots, to restrain lateral root density under Pi deficiency. We also demonstrated that GR244DO treatment under normal conditions inhibits the expression of OsNRTs and OsAMTs to suppress nitrogen absorption but enhances the expression of OsPTs to promote Pi absorption, thus facilitating the balance between nitrogen and phosphorus uptake in rice. Importantly, we found that NSP1p:NSP1 and NSP2p:NSP2 transgenic plants show improved agronomic traits and grain yield under low- and medium-phosphorus conditions. Taken together, these results revealed a novel regulatory mechanism of SL biosynthesis and signaling in response to Pi starvation, providing genetic resources for improving plant architecture and nutrient-use efficiency in low-Pi environments.

Comparative Microscopic, Transcriptome and IAA Content Analyses Reveal the Stem Growth Variations in Two Cultivars Ilex verticillata.

Ilex verticillata is not only an excellent ornamental tree species for courtyards, but it is also a popular bonsai tree. 'Oosterwijk' and 'Red sprite' are two varieties of Ilex verticillata. The former has a long stem with few branches, while the latter has a short stem. In order to explain the stem growth differences between the two cultivars 'Oosterwijk' and 'Red sprite', determination of the microstructure, transcriptome sequence and IAA content was carried out. The results showed that the xylem thickness, vessel area and vessel number of 'Oosterwijk' were larger than in 'Red sprite'. In addition, our analysis revealed that the differentially expressed genes which were enriched in phenylpropanoid biosynthesis; phenylalanine metabolism and phenylalanine, tyrosine and tryptophan biosynthesis in the black and tan modules of the two varieties. We found that AST, HCT and bHLH 94 may be key genes in the formation of shoot difference. Moreover, we found that the IAA content and auxin-related DEGs GH3.6, GH3, ATRP5, IAA27, SAUR36-like, GH3.6-like and AIP 10A5-like may play important roles in the formation of shoot differences. In summary, these results indicated that stem growth variations of 'Oosterwijk' and 'Red sprite' were associated with DEGs related to phenylpropanoid biosynthesis, phenylalanine metabolism and phenylalanine, tyrosine and tryptophan biosynthesis, as well as auxin content and DEGs related to the auxin signaling pathway.

The Welwitschia genome reveals a unique biology underpinning extreme longevity in deserts.

The gymnosperm Welwitschia mirabilis belongs to the ancient, enigmatic gnetophyte lineage. It is a unique desert plant with extreme longevity and two ever-elongating leaves. We present a chromosome-level assembly of its genome (6.8 Gb/1 C) together with methylome and transcriptome data to explore its astonishing biology. We also present a refined, high-quality assembly of Gnetum montanum to enhance our understanding of gnetophyte genome evolution. The Welwitschia genome has been shaped by a lineage-specific ancient, whole genome duplication (~86 million years ago) and more recently (1-2 million years) by bursts of retrotransposon activity. High levels of cytosine methylation (particularly at CHH motifs) are associated with retrotransposons, whilst long-term deamination has resulted in an exceptionally GC-poor genome. Changes in copy number and/or expression of gene families and transcription factors (e.g. R2R3MYB, SAUR) controlling cell growth, differentiation and metabolism underpin the plant's longevity and tolerance to temperature, nutrient and water stress.

FOXC2-AS1 stabilizes FOXC2 mRNA via association with NSUN2 in gastric cancer cells.

Long noncoding RNA (lncRNA) FOXC2-AS1 has been reported to act as an oncogene in multiple human cancers. However, the clinical significance, functional role and underlying mechanism of FOXC2-AS1 in gastric cancer (GC) remains largely unknown. Here, we found that FOXC2-AS1 expression was significantly elevated in GC tissues and cells, and overexpression of FOXC2-AS1 indicated advanced TNM stage and shorter overall survival in GC patients. Functionally, knockdown of FOXC2-AS1 attenuated the proliferation, migration and invasion of GC cells, whereas overexpression of FOXC2-AS1 showed the opposite effects. Further investigation revealed that FOXC2-AS1 interacted with FOXC2 mRNA and repressed its degradation. FOXC2-AS1 recruited RNA methyltransferase NSUN2 to FOXC2 mRNA, increasing its m5C level and association with YBX1. Taken together, our findings suggested that FOXC2-AS1 acted as an oncogenic lncRNA by stabilizing FOXC2 mRNA in an m5C-dependent manner, which may provide a novel therapeutic target for GC.

The mechanism for brassinosteroids suppressing climacteric fruit ripening.

The plant hormone ethylene is important for the ripening of climacteric fruit, such as pear (Pyrus ussuriensis), and the brassinosteroid (BR) class of phytohormones affects ethylene biosynthesis during ripening via an unknown molecular mechanism. Here, we observed that exogenous BR treatment suppressed ethylene production and delayed fruit ripening, whereas treatment with a BR biosynthesis inhibitor promoted ethylene production and accelerated fruit ripening in pear, suggesting BR is a ripening suppressor. The expression of the transcription factor BRASSINAZOLE-RESISTANT 1PuBZR1 was enhanced by BR treatment during pear fruit ripening. PuBZR1 interacted with PuACO1, which converts 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, and suppressed its activity. BR-activated PuBZR1 bound to the promoters of PuACO1 and of PuACS1a, which encodes ACC synthase, and directly suppressed their transcription. Moreover, PuBZR1 suppressed the expression of transcription factor PuERF2 by binding its promoter, and PuERF2 bound to the promoters of PuACO1 and PuACS1a. We concluded that PuBZR1 indirectly suppresses the transcription of PuACO1 and PuACS1a through its regulation of PuERF2. Ethylene production and expression profiles of corresponding apple (Malus domestica) homologs showed similar changes following epibrassinolide treatment. Together, these results suggest that BR-activated BZR1 suppresses ACO1 activity and the expression of ACO1 and ACS1, thereby reducing ethylene production and suppressing fruit ripening. This likely represents a conserved mechanism by which BR suppresses ethylene biosynthesis during climacteric fruit ripening.

Multi-analysis of sheath senescence provides new insights into bamboo shoot development at the fast growth stage.

Sheath senescence is an important part of bamboo shoot development during the fast growth stage. However, no information has been reported about this distinctive process until now. Using multiple approaches, we found that sheath senescence is a complex process that occurs sequentially with chloroplast corruption, chlorophyll degradation and water loss. Reactive oxygen species (ROS), salicylic acid and abscisic acid also accumulate in the senescing sheath. Transcriptome analysis showed that NAC and WRKY transcription factors, such as NAC2 and WRKY75, as well as their possible downstream target genes, such as those involved in ROS production, proteolysis and nutrition recycling, constitute the gene network of the bamboo sheath senescence process. Furthermore, the initiation of sheath senescence might be triggered by hexokinase genes, such as HXK6, which is localized to the mitochondrion and could promote leaf senescence when overexpressed in Arabidopsis. Sheath senescence occurs after the growth decrease of the internodes, which provides assimilates. The slowing of internode growth possibly results in sugar accumulation, such as glucose, in the sheath, which finally upregulates hexokinase genes and initiates sheath senescence. These findings reveal that sheath senescence is a multilevel regulation process and has a close link to the corresponding internode growth, which provides new insights into the shoot development of bamboo during the fast growth stage.

A Tailored High-Efficiency Sample Pretreatment Method for Simultaneous Quantification of 10 Classes of Known Endogenous Phytohormones.

One of the hottest topics in plant hormone biology is the crosstalk mechanisms, whereby multiple classes of phytohormones interplay with each other through signaling networks. To better understand the roles of hormonal crosstalks in their complex regulatory networks, it is of high significance to investigate the spatial and temporal distributions of multiple -phytohormones simultaneously from one plant tissue sample. In this study, we develop a high-sensitivity and high-throughput method for the simultaneous quantitative analysis of 44 phytohormone compounds, covering currently known 10 major classes of phytohormones (strigolactones, brassinosteroids, gibberellins, auxin, abscisic acid, jasmonic acid, salicylic acid, cytokinins, ethylene, and polypeptide hormones [e.g., phytosulfokine]) from only 100 mg of plant sample. These compounds were grouped and purified separately with a tailored solid-phase extraction procedure based on their physicochemical properties and then analyzed by LC-MS/MS. The recoveries of our method ranged from 49.6% to 99.9% and the matrix effects from 61.8% to 102.5%, indicating that the overall sample pretreatment design resulted in good purification. The limits of quantitation (LOQs) of our method ranged from 0.06 to 1.29 pg/100 mg fresh weight and its precision was less than 13.4%, indicating high sensitivity and good reproducibility of the method. Tests of our method in different plant matrices demonstrated its wide applicability. Collectively, these advantages will make our method helpful in clarifying the crosstalk networks of phytohormones.

ζ-Carotene Isomerase Suppresses Tillering in Rice through the Coordinated Biosynthesis of Strigolactone and Abscisic Acid.

Rice tillering is an important agronomic trait affecting grain yield. Here, we identified a high-tillering mutant tillering20 (t20), which could be restored to the wild type by treatment with the strigolactone (SL) analog rac-GR24. T20 encodes a chloroplast ζ-carotene isomerase (Z-ISO), which is involved in the biosynthesis of carotenoids and their metabolites, SL and abscisic acid (ABA). The t20 mutant has reduced SL and ABA, raising the question of how SL and ABA biosynthesis is coordinated, and whether they have overlapping functions in tillering. We discovered that rac-GR24 stimulated T20 expression and enhanced all-trans-ß-carotene biosynthesis. Importantly, rac-GR24 also stimulated expression of Oryza sativa 9-CIS-EPOXYCAROTENOID DIOXYGENASE 1 (OsNCED1) through induction of Oryza sativa HOMEOBOX12 (OsHOX12), promoting ABA biosynthesis in shoot base. On the other hand, ABA treatment significantly repressed SL biosynthesis and the ABA biosynthetic mutants displayed elevated SL biosynthesis. ABA treatment reduced the number of basal tillers in both t20 and wild-type plants. Furthermore, while ABA-deficient mutants aba1 and aba2 had the same number of basal tillers as wild type, they had more unproductive upper tillers at maturity. This work demonstrates complex interactions in the biosynthesis of carotenoid, SLs and ABA, and reveals a role for ABA in the regulation of rice tillering.

DROOPY LEAF1 controls leaf architecture by orchestrating early brassinosteroid signaling.

Leaf architecture directly determines canopy structure, and thus, grain yield in crops. Leaf droopiness is an agronomic trait primarily affecting the cereal leaf architecture but the genetic basis and underlying molecular mechanism of this trait remain unclear. Here, we report that DROOPY LEAF1 (DPY1), an LRR receptor-like kinase, plays a crucial role in determining leaf droopiness by controlling the brassinosteroid (BR) signaling output in Setaria, an emerging model for Panicoideae grasses. Loss-of-function mutation in DPY1 led to malformation of vascular sclerenchyma and low lignin content in leaves, and thus, an extremely droopy leaf phenotype, consistent with its preferential expression in leaf vascular tissues. DPY1 interacts with and competes for SiBAK1 and as a result, causes a sequential reduction in SiBRI1-SiBAK1 interaction, SiBRI1 phosphorylation, and downstream BR signaling. Conversely, DPY1 accumulation and affinity of the DPY1-SiBAK1 interaction are enhanced under BR treatment, thus preventing SiBRI1 from overactivation. As such, those findings reveal a negative feedback mechanism that represses leaf droopiness by preventing an overresponse of early BR signaling to excess BRs. Notably, plants overexpressing DPY1 have more upright leaves, thicker stems, and bigger panicles, suggesting potential utilization for yield improvement. The maize ortholog of DPY1 rescues the droopy leaves in dpy1, suggesting its conserved function in Panicoideae. Together, our study provides insights into how BR signaling is scrutinized by DPY1 to ensure the upward leaf architecture.

The challenges of urgent radical sigmoid colorectal cancer resection in a COVID-19 patient: A case report.

INTRODUCTION: The COVID-19 pandemic presents a unique global health challenge further complicating surgical management of COVID-19 positive patients due to a lack of published literature. CASE: Within we discuss a 48-year-old Chinese man, presenting with acute gastrointestinal obstruction due to sigmoid colonic mass. The patient was screened and tested positive for COVID 19 due to his employment in Wuhan, China at the COVID-19 pandemic epicenter. The patient was subsequently taken for open sigmoid colonic resection, however the case presented multiple challenges due to the patient's COVID-19 positive status. DISCUSSION: The challenges of surgical management of COVID-19 positive patients exist are four-fold. First the unknown efficacy of pre-surgical risk stratification in COVID-19 positive patients, second the risk of aerosolized COVID-19 transmission during intubation for surgery, third the risk of fecal COVID-19 transmission to surgical staff during large bowel resection, and fourth the post-operative challenges of caring for COVID-19 positive patients. CONCLUSION: Further research is needed into these topics, as well as the medical management of COVID-19 surgical patients.

Cysteine protease RD21A regulated by E3 ligase SINAT4 is required for drought-induced resistance to Pseudomonas syringae in Arabidopsis.

Plants can be simultaneously exposed to multiple stresses. The interplay of abiotic and biotic stresses may result in synergistic or antagonistic effects on plant development and health. Temporary drought stress can stimulate plant immunity; however, the molecular mechanism of drought-induced immunity is largely unknown. In this study, we demonstrate that cysteine protease RD21A is required for drought-induced immunity. Temporarily drought-treated wild-type Arabidopsis plants became more sensitive to the bacterial pathogen-associated molecular pattern flg22, triggering stomatal closure, which resulted in increased resistance to Pseudomonas syringae pv. tomato DC3000 (Pst-DC3000). Knocking out rd21a inhibited flg22-triggered stomatal closure and compromised the drought-induced immunity. Ubiquitin E3 ligase SINAT4 interacted with RD21A and promoted its degradation in vivo. The overexpression of SINAT4 also consistently compromised the drought-induced immunity to Pst-DC3000. A bacterial type III effector, AvrRxo1, interacted with both SINAT4 and RD21A, enhancing SINAT4 activity and promoting the degradation of RD21A in vivo. Therefore, RD21A could be a positive regulator of drought-induced immunity, which could be targeted by pathogen virulence effectors during pathogenesis.

A Strigolactone Biosynthesis Gene Contributed to the Green Revolution in Rice.

Plant architecture is a complex agronomic trait and a major factor of crop yield, which is affected by several important hormones. Strigolactones (SLs) are identified as a new class hormoneinhibiting branching in many plant species and have been shown to be involved in various developmental processes. Genetical and chemical modulation of the SL pathway is recognized as a promising approach to modify plant architecture. However, whether and how the genes involved in the SL pathway could be utilized in breeding still remain elusive. Here, we demonstrate that a partial loss-of-function allele of the SL biosynthesis gene, HIGH TILLERING AND DWARF 1/DWARF17 (HTD1/D17), which encodes CAROTENOID CLEAVAGE DIOXYGENASE 7 (CCD7), increases tiller number and improves grain yield in rice. We found that the HTD1 gene had been widely utilized and co-selected with Semidwarf 1 (SD1), both contributing to the improvement of plant architecture in modern rice varieties since the Green Revolution in the 1960s. Understanding how phytohormone pathway genes regulate plant architecture and how they have been utilized and selected in breeding will lay the foundation for developing the rational approaches toward improving crop yield.

LncRNA LINC00470 promotes proliferation through association with NF45/NF90 complex in hepatocellular carcinoma.

Increasing evidence demonstrates that long noncoding RNAs (lncRNAs) play an important role in the development and progression of human cancers. LncRNA LINC00470 has been reported to function as an oncogene in glioblastoma. Until now, the roles and underlying mechanisms of LINC00470 in the progression of hepatocellular carcinoma (HCC) remain unclear. Here, we found that LINC00470 was upregulated in HCC cells and tissues. High-level LINC00470 was significantly correlated with bigger tumor size, advanced TNM stage and poor prognosis in patients with HCC. Functional studies showed that knockdown of LINC00470 expression inhibited HCC cell proliferation and cell cycle progression, while overexpression of LINC00470 showed the opposite effects. Further investigation suggested that LINC00470 was associated with NF45/NF90 complex and increased its interaction with cyclin E1 mRNA, thus inhibiting the degradation of cyclin E1 mRNA. Additionally, knockdown of cyclin E1 in LINC00470-overexpressed cells abolished its promotive effects on HCC cell proliferation. In summary, our findings suggest that targeting LINC00470 could be a potential therapeutic approach in treating HCC patients.