A Comprehensive Analysis of Transcriptomics and Metabolomics Revealed Key Pathways Involved in Saccharum spontaneum Defense against Sporisorium scitamineum.

Sugarcane smut, caused by Sporisorium scitamineum, poses a severe threat to sugarcane production. The genetic basis of sugarcane resistance to S. scitamineum remains elusive. A comparative transcriptomic and metabolomic study was conducted on two wild Saccharum species of S. spontaneum with contrast smut resistance. Following infection, the resistant line exhibited greater down-regulation of genes and metabolites compared to the susceptible line, indicating distinct biological processes. Lignan and lignin biosynthesis and SA signal transduction were activated in the resistant line, while flavonoid biosynthesis and auxin signal transduction were enhanced in the susceptible line. TGA2.2 and ARF14 were identified as playing positive and negative roles, respectively, in plant defense. Exogenous auxin application significantly increased the susceptibility of S. spontaneum to S. scitaminum. This study established the significant switching of defense signaling pathways in contrast-resistant S. spontaneum following S. scitamineum infection, offering a hypothetical model and candidate genes for further research into sugarcane smut disease.

Climatic and edaphic controls over soil δ15N in temperate grassland of northern China: A PLS-PATH analysis.

Identifying the impact path of climate and soil factors on soil δ15N is very crucial for better understanding the N turnover in soils and the integrated information about ecosystem N cycling. Many studies have showed that climate and soil variables influence the change of soil δ15N. However, most of the existing studies focused on the overall impact of factor on soil δ15N, without distinguishing between the direct and indirect effect. Although scholars have studied the relationships among temperature, precipitation, soil N, soil pH, and soil δ15N rather than estimating all the causal relationships simultaneously. To answer the above-mentioned questions, a regional-scale soil collection was conducted across a temperate grassland in northern China. Meanwhile, a PLS-PATH analysis was utilized to evaluate the direct and indirect effects of various factors on soil δ15N and to explore the causal relationships among variables. The results showed that along the transect, mean annual precipitation (MAP) and mean annual temperature (MAT) directly and significantly reduced soil δ15N, and indirectly affected soil δ15N through their effects on soil pH, soil clay, soil N and soil C/N. Soil C/N ratio has a significant direct impact on soil δ15N with a negative correlation. Soil clay, soil N content, and soil pH have a total positive effect on soil δ15N, but the total positive impact of soil pH is very weak because it has a negative indirect impact on soil δ15N by affecting soil clay, soil N and soil C/N ratio. The total influence is, in order, MAP > MAT > soil C/N > soil clay > soil N > soil pH (in absolute value). The above results will provide valuable information about ecosystem N cycle in temperate grassland of northern China.