Heterotrimeric guanine-nucleotide-binding proteins (G-proteins) play key roles in responses to various abiotic stress responses and tolerance in plants. However, the detailed mechanisms behind these roles remain unclear. Mulberry (Morus alba L.) can adapt to adverse abiotic stress conditions; however, little is known regarding the associated molecular mechanisms. In this study, mulberry G-protein genes, MaGα, MaGβ, MaGγ1, and MaGγ2, were independently transformed into tobacco, and the transgenic plants were used for resistance identification experiments. The ectopic expression of MaGα in tobacco decreased the tolerance to drought and salt stresses, while the overexpression of MaGβ, MaGγ1, and MaGγ2 increased the tolerance. Further analysis showed that mulberry G-proteins may regulate drought and salt tolerances by modulating reactive oxygen species’ detoxification. This study revealed the roles of each mulberry G-protein subunit in abiotic stress tolerance and advances our knowledge of the molecular mechanisms underlying G-proteins’ regulation of plant abiotic stress tolerance.

The endosomal-type Na⁺, K⁺/H⁺ antiporters (NHXs) play important roles in K⁺, vesicle pH homeostasis, and protein trafficking in plant. However, the structure governing ion transport mechanism and the key residues related to the structure–function of the endosomal-type NHXs remain unclear. Here, the structure-function relationship of the only endosomal-type NHX from mulberry, MnNHX6, was investigated by homology modeling, mutagenesis, and localization analyses in yeast. The ectopic expression of MnNHX6 in arabidopsis and Nhx1 mutant yeast can enhance their salt tolerance. MnNHX6’s three-dimensional structure, established by homology modeling, was supported by empirical, phylogenetic, and experimental data. Structure analysis showed that MnNHX6 contains unusual 13 transmembrane helices, but the structural core formed by TM5-TM12 assembly is conserved. Localization analysis showed that MnNHX6 has the same endosomal localization as yeast Nhx1/VPS44, and Arg402 is important for protein stability of MnNHX6. Mutagenesis analysis demonstrated MnNHX6 contains a conserved cation binding mechanism and a similar charge-compensated pattern as NHE1, but shares a different role in ion selectivity than the vacuolar-type NHXs. These results improve our understanding of the role played by the structure–function related key residues of the plant endosomal-type NHXs, and provide a basis for the ion transport mechanism study of endosomal-type NHXs.

Rapid urbanization has led to a large-scale loss of cropland to non-agricultural uses. To avoid losses caused by abandonment, farmers working in cities have converted part of their farmland into economic forests (Primarily poplar). To assess how converting cropland to forest land negatively impacts neighboring grain production, we selected five agroforestry interfaces in humid and semi-humid regions of China. We investigated the effects of long-term poplar planting on the production process of summer maize in neighboring fields. Eight sampling points (d1-d8) were established at 1-meter intervals along the agroforestry interface extending into the maize field, at each interface. During the maize maturity stage, morphological structure, yield, and dry matter distribution were measured. The results showed that long-term planting of poplar trees had a significant effect on the growth and harvest parameters of neighboring summer maize. Compared to the farthest distance (control), the maize plants closest to the poplar trees exhibited reductions in plant height, stem diameter, and leaf area by 46.4%, 34.9%, and 60.2%, respectively. Compared to control, root, stem, leaf, tassel, bract, and corncob dry weight at d1 were reduced by 47.2%, 28.7%, 42.6%, 27.5%, 35.3%, and 40.5%, respectively, and the yield per spike and total dry weight at d1 were reduced by 94.9% and 58.0%, respectively. Furthermore, trend analysis revealed that these parameters exhibited logarithmic growth trends with increasing distance (All R ² > 0.80). Structural equation modeling demonstrated that summer maize morphological structure and dry matter distribution directly and indirectly influenced yield per spike and total dry weight through distinct pathways. These findings provide management implications for mitigating the negative impacts of agroforestry systems on agricultural production in humid regions, while also providing a parameter basis for accurately assessing the grain yield reduction effect resulting from the large-scale conversion of agricultural land to forestry.