| Summary: | 碩士 === 國立中興大學 === 生命科學系所 === 106 === In recent years, global warming becomes increasingly serious problems, causing negative impacts on plant. Hence, the responsive mechanism and countermeasures of heat stress in plants are important issues. MicroRNAs are small noncoding RNAs with important regulatory plays in plant growth and development, and also participate in stress. Heat stress increased the performance of miR828, which could trigger the cleavage of TAS4 transcripts to produce ta-siRNA. Then, ta-siRNA repressed MYB75, MYB90, and MYB113. To study the plays of miR828 under heat stress, transgenic plants overexpressing miR828 (miR828OE) and T-DNA insertion mutants of miR828 (mir828), and TAS4 (tas4) were used. Results presented that survival rates and chlorophyll contents were better in mir828 mutants than in wild type (WT) under heat stress. Moreover, heat-caused ion leakage of mir828 is lower than WT. These results might reveal that reduction of miR828 abundances enhanced abilities of heat-tolerance in plants. In addition, transcriptome analyses were used to figure out miR828/MYB downstream regulated genes. Expression of heat-related genes, HSP20, HSFA7B, and HTT4, in miR828 mutants were higher than WT. Also, expression of MYB and bHLH genes participated in the synthesis of secondary metabolites and responses of stress were affected in mir828 mutant. The mir828 mutant had higher anthocyanin content and lower H2O2 content compared to WT. In addition, several drought-related genes, such as ERF and DOR, were regulated by miR828 according to transcriptome analyses. Under drought stress, mir828 mutants presented better adaptive abilities compared to WT. Collectively, miR828 might alter the expression of MYB, bHLH, and ERF genes to affect contents of anthocyanin and H2O2. Further, plants enhanced adaptation to heat stress and drought stress.
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