Abstract
MicroRNAs are important regulators in plant developmental processes and stress responses. In this study, we generated a series of maize STTM166 transgenic plants. Knock-down of miR166 resulted in various morphological changes, including rolled leaves, enhanced abiotic stress resistance, inferior yield-related traits, vascular pattern and epidermis structures, tassel architecture, as well as abscisic acid (ABA) level elevation and indole acetic acid (IAA) level reduction in maize. To profile miR166 regulated genes, we performed RNA-seq and qRT-PCR analysis. A total of 178 differentially expressed genes (DEGs) were identified, including 118 up-regulated and 60 down-regulated genes. These DEGs were strongly enriched in cell and intercellular components, cell membrane system components, oxidoreductase activity, single organism metabolic process, carbohydrate metabolic process, and oxidation reduction process. These results indicated that miR166 plays important roles in auxin and ABA interaction in monocots, yet the specific mechanism may differ from dicots. The enhanced abiotic stress resistance is partly caused via rolling leaves, high ABA content, modulated vascular structure, and the potential changes of cell membrane structure. The inferior yield-related traits and late flowering are partly controlled by the decreased IAA content, the interplay of miR166 with other miRNAs and AGOs. Taken together, the present study uncovered novel functions of miR166 in maize, and provide insights on applying short tandem target mimics (STTM) technology in plant breeding.
Highlights
MicroRNAs are a class of endogenous small, single-stranded non-coding RNA molecules
Our study provided the preliminary evidence of miR166 functions in plant development and abiotic stresses resistance in maize
Kyoto encyclopedia of genes and genomes (KEGG) analysis indicated that those down-regulated genes were strongly enriched in and associated with RNA transport, purine metabolism, glycolysis or gluconeogenesis, and carbon metabolism (Figure 9). Those up-regulated genes were largely enriched in and associated with starch and sucrose metabolism, phenylpropanoid biosynthesis, peroxisome, and glycolysis or gluconeogenesis. These results revealed that miR166 primarily regulates cell component biogenesis and organization, stress resistance, and carbohydrate metabolism, thereby defining the leaf polarity defect, abiotic stress tolerance, and inferior yield-related traits
Summary
MicroRNAs (miRNA) are a class of endogenous small, single-stranded non-coding RNA molecules. Those up-regulated genes were largely enriched in and associated with starch and sucrose metabolism, phenylpropanoid biosynthesis, peroxisome, and glycolysis or gluconeogenesis These results revealed that miR166 primarily regulates cell component biogenesis and organization, stress resistance, and carbohydrate metabolism, thereby defining the leaf polarity defect, abiotic stress tolerance, and inferior yield-related traits. Most auxin biogenesis, signaling, and responsive protein encoding genes were greatly increased, only an auxin transporter encoding gene showed decreased expression level These results are consistent with those corresponding gene expression alterations in Arabidopsis STTM165/166 plants, which further implied miR166 mediated ABA and auxin homeostasis to involve complicated regulatory mechanisms. The diameter and number of metaxylem vessels was significantly decreased in stems and leaf veins of STTM166 plants Such alterations were consistent with the down-regulated expression of cell and intercellular components related genes that greatly enriched in GO analysis. MiR166 is probably in the interaction with other miRNAs, which is largely unknown
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