Summary
Rice is able to accumulate high concentrations of silicon (Si) in the shoots, and this ability is required for the mitigation of abiotic and biotic stresses. Although transporters for Si ...uptake have been identified, a transporter for the xylem loading of Si has not been found.
We functionally characterized a Si transporter, OsLsi3, in terms of tissue‐specific localization, knockout line phenotype and mathematic simulation.
OsLsi3 was shown to be an efflux Si transporter. OsLsi3 was mainly expressed in the mature root region, and its expression was downregulated by Si. Immunostaining with a specific antibody showed that OsLsi3 was localized to the pericycle in the roots, without polarity. However, when it was expressed under the control of the OsLsi2 promoter, OsLsi3 became polarly localized to the proximal side of both the exodermis and endodermis. Knockout of this gene resulted in decreased Si uptake and concentration in the xylem sap under low Si supply, but not under high Si supply. Mathematical modeling showed that localization of OsLsi3 to the pericycle accounts for c. 30% of the total Si loading to the xylem under low Si concentrations.
In summary, OsLsi3 was involved in the xylem loading of Si in rice roots, which is required for the efficient root‐to‐shoot translocation of Si.
The genesis of intermediate intrusions is highly controversial, and one of the hot topics is whether they represent frozen melts or cumulates in the evolution of magmatic systems. Distinguishing ...accumulation from crystallization melt differentiated along the liquid line of descent is the key issue. The Paleoproterozoic intermediate intrusions in southern North China Craton provide an excellent case to decipher this issue. Multiple lines of evidence, including mineral textures, geochemistry as well as alphaMELTS modeling, indicate disequilibrium between whole‐rock and minerals, with melt extraction occurring at temperatures of 760°–820°C and with 10–40 wt.% of trapped melts. Effective water storage, revealed by amphibole and clinopyroxene hygrometers, plays a crucial role in promoting crystal‐melt segregation in pluton‐sized reservoirs in the upper crust. This study demonstrates that the accumulation in intermediate magmas can be identified even without evident complementary initial and extracted melts and provides deep insights into the genesis of intermediate continental crust.
Plain Language Summary
The genesis of intermediate rocks has long been controversial since they are analogs of the average composition of continental upper crust. The key topic is whether intermediate rocks represent frozen melts of intermediate magmas or crystal residues after melt extraction in the evolution of felsic magmatic systems. Here we carried out a comprehensive study on the Paleoproterozoic intermediate intrusions in the southern North China Craton, which is considered to have recorded the process of crystal accumulation and melt segregation in the shallow crust. Upon mineral texture, geochronologic, whole‐rock and mineral geochemical, and thermodynamic investigation, we propose that crystal accumulation and crystal‐melt segregation processes can be identified in intermediate magmas with the melt extraction temperatures and proportions of trapped melts recorded by zircon trace elements. Amphibole and clinopyroxene hygrometers revealed high water content of the melts, which likely decreased the viscosity of melts and facilitated effective cumulate‐melt segregation. This study provides a powerful reference to see through the accumulation in intermediate magmas, record the processes of crystal‐melt segregation, and definitively resolve the debate concerning the genesis of intermediate intrusions.
Key Points
Crystal accumulation in intermediate magmas can be identified by mineral texture and geochemistry
The effective water storage system in the reservoirs is key to promoting crystal‐melt segregation
Crystal‐melt segregation and accumulation are fundamental processes to form evolved continental upper crust
In response to diverse environmental conditions, rice (
) roots have developed one Casparian strip (CS) at the exodermis and one CS at the endodermis. Here, we functionally characterized OsCASP1 ...(Casparian strip domain protein 1) in rice.
was mainly expressed in the root elongation zone, and the protein encoded was first localized to all sides of the plasma membrane of endodermal cells without CS, followed by the middle of the anticlinal side of endodermal cells with CS. Knockout of
resulted in a defect of CS formation at the endodermis and decreased growth under both soil and hydroponic conditions. Mineral analysis showed that the
mutants accumulated more Ca, but less Mn, Zn, Fe, Cd, and As in the shoots compared with the wild type. The growth inhibition of the mutants was further aggravated by high Ca in growth medium. The polar localization of the Si transporter Low Si 1 at the distal side of the endodermis was not altered in the mutant, but the protein abundance was decreased, resulting in a substantial reduction in silicon uptake. These results indicated that
is required for CS formation at the endodermis and that the CS in rice plays an important role in root selective uptake of mineral elements, especially Ca and Si.
Due to rapid urbanization and industrialization, many soils for crop production are contaminated by cadmium (Cd), a heavy metal highly toxic to many organisms. Cereal crops such as rice, wheat, ...maize, and barley are the primary dietary source of Cd for humans, and reducing Cd transfer from soil to their grains is therefore an important issue for food safety. During the last decade, great progress has been made in elucidating the molecular mechanisms of Cd transport, particularly in rice. Inter- and intraspecific variations in Cd accumulation have been observed in cereal crops. Transporters for Cd have been identified in rice and other cereal crops using genotypic differences in Cd accumulation and mutant approaches. These transporters belong to different transporter families and are involved in the uptake, vacuolar sequestration, root-to-shoot translocation, and distribution of Cd. Attempts have been made to reduce Cd accumulation in grains by manipulating these transporters through overexpression or knockout of the transporter genes, as well as through marker-assisted selection breeding based on genotypic differences in Cd accumulation in the grains. In this review, we describe recent progress on molecular mechanisms of Cd accumulation in cereal crops and compare different molecular strategies for minimizing Cd accumulation in grains.
Angiogenesis is an essential event in tumor growth and metastasis, and immune system also contributes to the tumor evasion. Emerging evidences have suggested the bidirectional link between ...angiogenesis and immunosuppression. Myeloid‐derived suppressor cell (MDSC) is a kind of immunosuppressive cells and plays an important role in this process. However, the actual regulatory mechanisms of angiogenesis and MDSCs in head and neck squamous cell carcinoma (HNSCC) were unclear. In this study, through analyzing the immunohistochemistry staining of human HNSCC tissue microarray, we found that the microvascular density (MVD) was significantly increased in HNSCC patients. We also characterized angiogenic factors p‐STAT3, VEGFA, CK2, and MDSCs marker CD11b in HNSCC tissue array, and found the close expression correlation among these markers. To determine the role of JAK2/STAT3 pathway in tumor microenvironment of HNSCC, we utilized AG490 (an inhibitor of JAK2/STAT3) for further research. Results showed that inhibition of JAK2/STAT3 suppressed angiogenesis by decreasing VEGFA and HIF1‐α both in vitro and vivo. Moreover, in HNSCC transgenic mouse model, inhibiting JAK2/STAT3 not only suppressed angiogenesis but also reduced MDSCs in the tumor microenvironment through suppressing VEGFA and CK2. Our findings demonstrated the close relationship between angiogenesis and MDSCs in HNSCC, and inhibition of JAK2/STAT3 could reduce tumor‐induced angiogenesis and decrease MDSCs.
SUMMARY
The essential micronutrient manganese (Mn) in plants regulates multiple biological processes including photosynthesis and oxidative stress. Some Natural Resistance‐Associated Macrophage ...Proteins (NRAMPs) have been reported to play critical roles in Mn uptake and reutilization in low Mn conditions. NRAMP6 was demonstrated to regulate cadmium tolerance and iron utilization in Arabidopsis. Nevertheless, it is unclear whether NRAMP6 plays a role in Mn nutrition. Here, we report that NRAMP6 cooperates with NRAMP1 in Mn utilization. Mutation of NRAMP6 in nramp1 but not in a wild‐type background reduces root growth and Mn translocation from the roots to shoots under Mn deficient conditions. Grafting experiments revealed that NRAMP6 expression in both the roots and shoots is required for root growth and Mn translocation under Mn deficiency. We also showed that NRAMP1 could replace NRAMP6 to sustain root growth under Mn deficiency, but not vice versa. Mn deficiency does not affect the transcript level of NRAMP6, but is able to increase and decrease the protein accumulation of NRAMP6 in roots and shoots, respectively. Furthermore, NRAMP6 can be localized to both the plasma membrane and endomembranes including the endoplasmic reticulum, and Mn deficiency enhances the localization of NRAMP6 to the plasma membrane in Arabidopsis plants. NRAMP6 could rescue the defective growth of the yeast mutant Δsmf2, which is deficient in endomembrane Mn transport. Our results reveal the important role of NRAMP6 in Mn nutrition and in the long‐distance signaling between the roots and shoots under Mn deficient conditions.
Significance Statement
The essential micronutrient manganese (Mn) plays important roles in multiple biological processes. It is unknown whether the Natural Resistance‐Associated Macrophage Protein family member NRAMP6 plays a role in Mn nutrition. We demonstrate that NRAMP6 cooperates with NRAMP1 in the regulation of root growth and Mn translocation from roots to shoots and that NRAMP6 is involved in long‐distance signaling between the roots and shoots under Mn deficiency.
Toxic aluminum enters the root cells rapidly, therefore internal detoxification is required. However, the molecular mechanisms underlying this process are poorly understood. Here we functionally ...characterized a rice gene, Os03g0755100 (OsALS1), that is regulated by ART1, a C2H2‐type zinc finger transcription factor. OsALS1 encodes a half‐size ABC transporter that is a member of the TAP (transporter associated with antigen processing) sub‐group. Expression of OsALS1 was rapidly and specifically induced by Al in the roots, but not by other metals or low pH. OsALS1 was localized at all cells of the roots. Furthermore, OsALS1 is localized to the tonoplast. These expression patterns and cell specificity of localization are different from those of the homologous gene AtALS1 in Arabidopsis. Knockout of OsALS1 in three independent lines resulted in significant increased sensitivity to Al, but did not affect the sensitivity to other metals and low pH. Comparison of Al accumulation patterns between wild‐type and osals1 mutants showed that there was no difference in Al levels in the cell sap of root tips between wild‐type and the mutants, but the mutants accumulated more Al in the cytosol and nucleus than the wild‐type. Expression of OsALS1 in yeast resulted in increased Al sensitivity due to mis‐localization. These results indicate that OsALS1 localized at the tonoplast is responsible for sequestration of Al into the vacuoles, which is required for internal detoxification of Al in rice.
• Plants have evolved two strategies to acquire ferrous (Strategy I) or ferric (Strategy II) iron from soil. The iron-related bHLH transcription factor 2 (IRO2) has been identified as a key regulator ...of iron acquisition (Strategy II) in rice. However, its mode of action, subcellular localisation and binding partners are not clearly defined.
• Using RNA-seq analyses, we identified a novel bHLH-type transcription factor, OsbHLH156. The function of OsbHLH156 in Fe homeostasis was analysed by characterisation of the phenotypes, elemental content, transcriptome, interaction and subcellular localisation of OsbHLH156 and IRO2.
• OsbHLH156 is primarily expressed in the roots and transcript abundance is greatly increased by Fe deficiency. Loss of function of OsbHLH156 resulted in Fe-deficiency-induced chlorosis and reduced Fe concentration in the shoots under upland or Fe(III) supplied conditions. Transcriptome analyses revealed that the expression of most Fe-deficiency-responsive genes involved in Strategy II were not induced in the osbhlh156-1 mutant. Furthermore, OsbHLH156 was required for nuclear localisation of IRO2.
• We conclude that OsbHLH156 is required for a Strategy II uptake mechanism in rice, partnering with a previously identified ‘master’ regulator IRO2. Mechanistically it is required for the nuclear localisation of IRO2.
Zinc (Zn) is an important essential micronutrient for plants and humans; however, the exact transporter responsible for root zinc uptake from soil has not been identified. Here, we found that OsZIP9, ...a member of the ZRT-IRT-related protein, is involved in Zn uptake in rice (
) under Zn-limited conditions. OsZIP9 was mainly localized to the plasma membrane and showed transport activity for Zn in yeast (
). Expression pattern analysis showed that
was mainly expressed in the roots throughout all growth stages and its expression was upregulated by Zn-deficiency. Furthermore,
was expressed in the exodermis and endodermis of root mature regions. For plants grown in a hydroponic solution with low Zn concentration, knockout of
significantly reduced plant growth, which was accompanied by decreased Zn concentrations in both the root and shoot. However, plant growth and Zn accumulation did not differ between knockout lines and wild-type rice under Zn-sufficient conditions. When grown in soil, Zn concentrations in the shoots and grains of knockout lines were decreased to half of wild-type rice, whereas the concentrations of other mineral nutrients were not altered. A short-term kinetic experiment with stable isotope
Zn showed that
Zn uptake in knockout lines was much lower than that in wild-type rice. Combined, these results indicate that OsZIP9 localized at the root exodermis and endodermis functions as an influx transporter of Zn and contributes to Zn uptake under Zn-limited conditions in rice.
Summary
Quercus dentata Thunb., a dominant forest tree species in northern China, has significant ecological and ornamental value due to its adaptability and beautiful autumn coloration, with color ...changes from green to yellow into red resulting from the autumnal shifts in leaf pigmentation. However, the key genes and molecular regulatory mechanisms for leaf color transition remain to be investigated.
First, we presented a high‐quality chromosome‐scale assembly for Q. dentata. This 893.54 Mb sized genome (contig N50 = 4.21 Mb, scaffold N50 = 75.55 Mb; 2n = 24) harbors 31 584 protein‐coding genes. Second, our metabolome analyses uncovered pelargonidin‐3‐O‐glucoside, cyanidin‐3‐O‐arabinoside, and cyanidin‐3‐O‐glucoside as the main pigments involved in leaf color transition. Third, gene co‐expression further identified the MYB‐bHLH‐WD40 (MBW) transcription activation complex as central to anthocyanin biosynthesis regulation.
Notably, transcription factor (TF) QdNAC (QD08G038820) was highly co‐expressed with this MBW complex and may regulate anthocyanin accumulation and chlorophyll degradation during leaf senescence through direct interaction with another TF, QdMYB (QD01G020890), as revealed by our further protein–protein and DNA–protein interaction assays.
Our high‐quality genome assembly, metabolome, and transcriptome resources further enrich Quercus genomics and will facilitate upcoming exploration of ornamental values and environmental adaptability in this important genus.
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