Geochemistry and Genetic Significance of Scheelite in the Nanwenhe Tungsten Deposit, Yunnan Province, Southwestern China

The Nanwenhe tungsten deposit is located in the southeastern Yunnan Laojunshan mineral district and is hosted in the Paleoproterozoic Mengsong Group strata. It can be divided into two periods and four stages: skarn (early and late) and the vein type (feldspar–quartz–scheelite–tourmaline and calcite. There are two types of scheelite occurrences: one in skarn (Sch-1) and the other in feldspar–quartz–scheelite–tourmaline veins (Sch-2). The latter is further divided into two types: Sch-2a and Sch-2b. The REE content and Eu anomaly of skarn scheelite (Sch-1) are affected by early mineral crystallization; Sch-2a in feldspar–quartz–scheelite–tourmaline veins forms in a Na+-rich environment, and Eu2+ released into the fluid through hydrolysis may have largely entered tourmaline, resulting in the weak positive Eu anomaly of Sch-2a; the negative Eu anomaly of Sch-2b is likely inherited from the metamorphic fluid. The mineralization is likely closely related to the metamorphic fluid activity generated by the tensional structural environment at the end and after the regional uplift, forming ore by reducing fluids associated with regional metamorphism. The Laojunshan mineral district hosts several tungsten and tin polymetallic deposits and occurrences that share similar geological characteristics with the Nanwenhe tungsten deposit. No granite bodies related to mineralization have been identified within the mining area. Therefore, research on the genesis of the Nanwenhe tungsten deposit holds significant value for guiding exploration efforts

Overexpression of <i>OsEXPA8</i>, a Root-Specific Gene, Improves Rice Growth and Root System Architecture by Facilitating Cell Extension

<div><p>Expansins are unique plant cell wall proteins that are involved in cell wall modifications underlying many plant developmental processes. In this work, we investigated the possible biological role of the root-specific α-expansin gene <i>OsEXPA8</i> in rice growth and development by generating transgenic plants. Overexpression of <i>OsEXPA8</i> in rice plants yielded pleiotropic phenotypes of improved root system architecture (longer primary roots, more lateral roots and root hairs), increased plant height, enhanced leaf number and enlarged leaf size. Further study indicated that the average cell length in both leaf and root vascular bundles was enhanced, and the cell growth in suspension cultures was increased, which revealed the cellular basis for <i>OsEXPA8</i>-mediated rice plant growth acceleration. Expansins are thought to be a key factor required for cell enlargement and wall loosening. Atomic force microscopy (AFM) technology revealed that average wall stiffness values for <i>35S</i>::<i>OsEXPA8</i> transgenic suspension-cultured cells decreased over six-fold compared to wild-type counterparts during different growth phases. Moreover, a prominent change in the wall polymer composition of suspension cells was observed, and Fourier-transform infrared (FTIR) spectra revealed a relative increase in the ratios of the polysaccharide/lignin content in cell wall compositions of <i>OsEXPA8</i> overexpressors. These results support a role for expansins in cell expansion and plant growth.</p></div

mRNA level analyses for <i>OsEXPA8</i> by quantitative real-time PCR in <i>35S::OsEXPA8</i> transgenic lines.

<p>Mature leaves of eight independent adult transgenic lines harboring <i>35S::OsEXPA8</i> and wild-type (WT) rice plants were used for investigating <i>OsEXPA8</i> expression. L1–L8 (line 1 to line 8) represents eight independent transgenic lines. Values are the means of three biological replications ± standard error. One independent transgenic plant was considered as one biological replication.</p

Effect of <i>OsEXPA8</i> overexpression on the cell length of vascular bundles in the flag leaf and lateral root.

<p>(A) The cell length of flag leaf vascular bundles. (B) The cell length of lateral root vascular bundles. Three independent transgenic line 1 (L1), line 4 (L4) and line 5 (L5) were analyzed. WT: wild-type. n = 100 for metaxylem cells from ten plants. Values are the means of 10 biological replications ± standard error. Asterisks (*) indicate the cell parameters of <i>35S::OsEXPA8</i> transgenic lines were significantly different from that of wild-type cells (<i>t</i>-test, <i>P</i><0.01).</p

Height ratios of characteristic lignin and carbohydrate FTIR peaks in isolated cell walls from wild-type and <i>35S::OsEXPA8</i> transgenic suspension cells.

<p>Suspension cultures on day 10 from three independent <i>35S::OsEXPA8</i> transgenic lines (L1, L4 and L5) were used for preparing cell wall extracts, respectively. Values are the means of three biological replications ± standard error. Asterisks (*) indicate <i>35S::OsEXPA8</i> transgenic suspension cell parameters were significantly different from that of wild-type cells by statistical analysis using the Student’s <i>t</i>-test program (<i>P</i><0.01).</p><p>Peak assignations: 1160 cm⁻¹, C-O-C vibration of the glycosidic link in cellulose, xyloglucan, or pectic polysaccharides; 1425 cm⁻¹, C-H stretch in CH₂ of cellulose; 1540 cm⁻¹, lignin aromatic ring stretching; 1740 cm⁻¹, C = O stretch in ester groups.</p

Effect of overexpression of <i>OsEXPA8</i> on the root system architecture and plant growth.

<p>(A) The length of primary roots of seven-day-old rice seedlings. (B) The number of lateral roots of seven-day-old rice seedlings. (C) The plant height of two -month-old rice plants. (D) The leaf number per plant of two-month-old rice plants. (E) The length of the flag leaf of two-month-old rice plants. (F) The width of the flag leaf of two-month-old rice plants. Three independent transgenic line 1 (L1), line 4 (L4) and line 5 (L5) were analyzed. WT: wild-type. Values are the means of ten biological replications ± standard error. One independent plant was considered as one biological replication. Asterisks (*) indicate parameters of <i>35S::OsEXPA8</i> transgenic plants were significantly different from that of wild-type plants by statistical analysis using the Student’s <i>t</i>-test program (<i>P</i><0.01).</p

Behavior of infrared absorption bands in cell wall isolates.

<p>Cell wall isolates of wild-type and <i>35S::OsEXPA8</i> transgenic line 1 suspension cells on day 10 was used for wall composition analysis. Average and area-normalized Fourier-transform infrared (FTIR) spectra of isolated cell walls from wild-type (lower) and <i>35S::OsEXPA8</i> (upper) line 1 suspension cells.</p

Stiffness-properties imaging by atomic force microscopy (AFM) technology.

<p>(A) Optical image of a typical single rice cell sample. The shadow of the AFM cantilever is visible on the left-hand side of the image. (B) A typical force-distance (FD) curve recorded on a single rice cell sample. The upper line represents the FD curve when the tip indents (or penetrates) the cell wall and the lower line represents the FD curve when the tip retracts from the cell wall.</p