Underground coal mining in western China causes heavy land subsidence and alters the soil ecology. However, the effects of land subsidence on soil fertility are not currently known, and the key factors governing its impact remain unclear in sandy land. We investigated the effects of land subsidence induced by underground mining on the soil quality in western China. Soil samples were collected at 0–15 cm and 15–30 cm from control and subsidence areas in three coal mines. The results showed that the soil water content (SWC), clay and silt percentage, total nitrogen (TN), dissolved organic carbon (DOC), ammonia nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), available phosphorus (AP), and available potassium (AK) of the subsidence areas were significantly lower than those of the control areas. The saccharase, urease, and alkaline phosphatase activities in the subsidence areas decreased compared to those in the control areas, while the sand percentage of soil tended to increase. Soil nutrient contents, bacterial quantities, and activities of soil enzymes were positively correlated with SWC. Redundancy analysis (RDA) showed that the soil particle size distribution, SWC, and electrical conductivity (EC) were the major environmental factors driving changes in soil properties. These results indicated that land subsidence induced by coal mining caused losses in surface soil water and nutrients, and ultimately led to soil quality degradation. Therefore, the reclamation of mining subsidence land might be necessary, especially in arid and semi-arid areas.

Summary: Currently, there are few studies concerning the function of heavy metal ATPase 2 (HMA2), particularly in monocotyledons, and the potential application of this protein in biofortification and phytoremediation. Thus, we isolated and characterized the TaHMA2 gene from wheat (Triticum aestivum L.). Our results indicate that TaHMA2 is localized to the plasma membrane and stably expressed, except in the nodes, which showed relatively high expression. Zinc/cadmium (Zn/Cd) resistance was observed in TaHMA2‐transformed yeast. The over‐expression of TaHMA2 increased the elongation and decreased the seed‐setting rate in rice (Oryza sativa L.), but not Arabidopsis thaliana, tobacco (Nicotiana tabacum L.) or wheat. TaHMA2 over‐expression also improved root‐shoot Zn/Cd translocation, especially in rice. The seeds of transgenic rice and wheat, not tobacco, showed decreased Zn concentrations. The Zn concentration was decreased in all parts of the transgenic rice seeds, but was decreased only in the ventral endosperm of wheat, which showed an increased Zn concentration in the embryo and aleurone. The over‐expression of TaHMA2 improved plant tolerance under moderate Zn stress and Zn deficiency, but Zn and Cd resistance decreased under high levels of Zn and Cd stress, respectively. The Cd concentration in transgenic rice seedlings was dramatically increased under Zn deficiency. Thus, over‐expression of TaHMA2 showed a more obvious phenotype in monocotyledons than in dicotyledons. These findings provide important information for TaHMA2, and more efforts should be made in the future to characterize the reduced Zn concentration in TaHMA2 transgenic grains and the diversity of TaHMA2 substrate specificity.

Grain size is an important agronomic trait, but our knowledge about grain size determination in crops is still limited. Endoplasmic reticulum (ER)–associated degradation (ERAD) is a special ubiquitin proteasome system that is involved in degrading misfolded or incompletely folded proteins in the ER. Here, we report that SMALL GRAIN 3 (SMG3) and DECREASED GRAIN SIZE 1 (DGS1), an ERAD-related E2–E3 enzyme pair, regulate grain size and weight through the brassinosteroid (BR) signaling pathway in rice (Oryza sativa). SMG3 encodes a homolog of Arabidopsis (Arabidopsis thaliana) UBIQUITIN CONJUGATING ENZYME 32, which is a conserved ERAD-associated E2 ubiquitin conjugating enzyme. SMG3 interacts with another grain size regulator, DGS1. Loss of function of SMG3 or DGS1 results in small grains, while overexpression of SMG3 or DGS1 leads to long grains. Further analyses showed that DGS1 is an active E3 ubiquitin ligase and colocates with SMG3 in the ER. SMG3 and DGS1 are involved in BR signaling. DGS1 ubiquitinates the BR receptor BRASSINOSTEROID INSENSITIVE 1 (BRI1) and affects its accumulation. Genetic analysis suggests that SMG3, DGS1, and BRI1 act together to regulate grain size and weight. In summary, our findings identify an ERAD-related E2–E3 pair that regulates grain size and weight, which gives insight into the function of ERAD in grain size control and BR signaling.