MicroRNAs (miRNAs) have important roles in the regulation of genes; however, for trees few studies have explored the potential impact of the interactions between miRNAs and their target genes. Here, we performed transcript profiling and association genetics (single-SNP, haplotype-based and multi-SNP associations) to study the genetic regulatory relationship of Pto-miR257 and its 12 target genes in 435 individuals of a natural population of Populus tomentosa. Expression profiling of Pto-miR257 and its targets showed a negative relationship between their expression levels. Of the 61 single-nucleotide polymorphisms (SNPs) detected in Pto-miR257, 6 in the pre-mature region strongly affected its secondary stability and 1 in the mature region could alter its target spectrum. Among the 1029 SNPs in the targets, 3 were located in target sites that could change the binding affinity of Pto-miR257. Single-SNP association analysis revealed that SNPs in Pto-miR257 and target genes associated with both growth and wood property traits, in agreement with haplotype-based identifications. Multi-SNP association found that 10 targets shared at least one common trait with Pto-miR257, with phenotypic variance from 0.5 to 8.5%, suggesting a possible internal genetic interaction between them. Epistasis analysis showed significant epistatic interactions among Pto-miR257 and its targets. Therefore, our study demonstrated Pto-miR257 and its 12 targets had roles in wood formation and revealed the genetic interaction network between the miRNA and its targets under additive, dominant and epistatic models. Thus, association genetics can be used to decipher the interactions between miRNAs and their target genes and to help understand the genetic architecture of complex traits.

The prevention and control of invasive of alien species is an important work for nature reserves. This study analyzes the development trend of the alien species sika deer in Liancheng National Nature Reserve. From October 2019 to June 2020, 3523 valid photos and videos of terrestrial animals were acquired from 130 camera traps, and sika deer were recorded in 21 photos from 13 traps. The survival of the sika deer population was investigated by means of morphological identification, population structure analysis, species relative abundance indices, and species spatial association analysis. A total of 13 sika deer individuals were identified by camera trapping, including two kids and three subadults representing the reproductive capacity of the population. Spatially, sika deer is not associated with any local species and was outside the spatial association network of terrestrial animals in Liancheng National Nature Reserve, indicating that the sika deer population has not been integrated into the local community and has failed to perform its ecological function. It is worth noting that the reserve provides habitat suitable for sika deer and that the population has adequate reproductive capacity. Due to the lack of large apex predators in the reserve, the population size of ungulates such as sika deer, red deer, and Siberian roe deer may expand and lead to population outbreaks and the associated problems for the ecosystem. To restore large-and medium-sized carnivores and avoid the population outbreak of the species, the present challenges require immediate attention in Liancheng National Nature Reserve.