The Function Of MiR165/166 Mediated Tomato Morphological Formation And Arabidopsis Abiotic Stress Response

MicroRNAs (miRNAs), a major class of 21-24 nt endogenous non-coding RNAs, regulate the expression of protein-coding genes by affecting the mRNA stability or translation of the target genes in plants and animals, even viruses. MiRNAs are conserved in evolution and play important roles in plant growth and development. Increasing data showed that miR165/166 regulate a number of plant developmental processes, such as shoot apical meristem (SAM) and lateral meristem formation, leaf adaxial/abaxial polarity, vascular patterning, and floral development. MiR165/166 has been characterized to down-regulate the expressions of five members of class Ⅲ homeodomain-leucine zipper (HD-ZIPIII) transcription factor genes. In this study, we have discovered the function of miR165/166 in organs formation in tomato plant, and the function of miR165/166 in abiotic stress, including drought stress and salt stress. The mainly result include,1. Tissue-specific expression of miR165/166 showed that miR165/166 has the highest expression level in flower bud, followed by red fruit, green fruit, orange fruit, root, leaf, stem, and flower.2. In STTM165/166 transgenic tomato, the expression of miR165/166 is decreased by 90%, and its target genes, Sly-REV and Sly-HOX32, are increased by 2 times and 2.5 times, respectively.3. STTM165/166 transgenic tomato showed some abnormal morphological formations, including up-curling cotyledons, the abnormal numbers of sepal, and disrupting development.4. By PlantCARE analysis, all Arabidopsis miR165/166 family members and their target genes have cis-elements related to abiotic stress in their promoters.5. qRT-PCR analysis showed that the expression of miR165/166 was induced by 26% in wild type Arabidopsis, but STTM165/166 transgenic Arabidopsis no obvious change after PEG treatment. The relative expression of PHB, PHV and REV are reduced in defference level in both wild type and transgenic Arabidopsis.6. After PEG treatment, POD enzyme activity was increased by 28% and MDA content had no change in STTM165/166 transgenic Arabidopsis. However, POD enzyme activity was decreased by 11.6%, and MDA content increased 22% after PEG treatment.7. After the soil drought treatment, wild type Arabidopsis showed growth delay, leaf yellow and white, while drought has no obvious effection on STTM165/166 transgenic Arabidopsis. The content of chlorophyll is reduced by 20% in wild type, but 9% in STTM165/166.8. After salt treatment, both wild type and STTM165/166 transgenic Arabidopsis occurred growth delay, inhibited root development. And the albino rate of wild type is much higher than that of STTM165/166. The number of survival STTM 165/166 seedling is more than that of wild type.In conclusion, miR165/166 and their target genes HD-ZIPIII are involved in regulating leaf formation and flower development in tomato, and play important roles in abiotic stress in Arabidopsis. All of results suggest that miR165/166 are an inhibitor in defending abiotic stress, while HD-ZIPIII are activator of defending abiotic stress.