ABSTRACT
MicroRNA (miRNA) is a class of endogenous non-coding single-stranded RNA molecules with a length of about 16 ~ 29 nucleotides. Widely found in eukaryotes, they play important regulatory roles in plant cell proliferation and differentiation, organ formation, metabolism, resistance to salt, temperature, drought, heavy metal stress, etc. Plant miRNA mainly affects plant growth and development by degrading target genes or inhibiting the expression of target genes at the translation level. At present, the research on the production and regulation of miRNA is relatively clear, and the specific roles and regulatory networks of miRNA in plant secondary metabolism and response to abiotic stress have also been identified, which lays the foundation for a full understanding of the molecular regulation of miRNA. In order to better understand the expression and regulation characteristics of miRNA and to interpret the regulatory network of miRNA in plant secondary metabolism and abiotic stress response, we review the molecular mechanisms of plant miRNAs in regulating the biosynthesis of various secondary metabolites(flavonoids, terpenoids, alkaloids) and responding to environmental stress (salt, high temperature, low temperature, drought, heavy metal stress),and summarize the regulatory roles of miRNA in secondary metabolism and abiotic stress, which will provide references for understanding the relationship between environmental stress and plant metabolism, for further studying the regulatory mechanism of miRNA in maintaining plant homeostasis, and for cultivating superior crop varieties.