Expression Analysis Of Maize Non-coding RNA In Response To Drought And Salt Stress

In recent years, with the completion of genome projects in human and other organisms, it is becoming clear that the number of non-protein-coding (ncRNA) genes is much larger than protein-coding genes. In addition, the more complex the species is, the greater the proportion of ncRNA genes in genome. Although more and more ncRNAs have been identified, the specific functions of which remain largely unkonwn. ncRNAs are believed to play important roles in various cellular processes, such as participating in chromatin modification, regulation of gene expression at the level of transcription and post-transcription.To overcome biotic and abiotic stress, plants modulate the expression of a large variety of genes to adapt to the harsh environment. In recent years, ncRNAs have been noticed to play essential roles during the stress response in bacteria. However, although many ncRNAs in plants have been found to be induced in response to stress, yet the specific function of which is unclear.Previously, we have characterized a large number of newly identified ncRNAs involved in maize development in our laboratory. To investigate the roles of ncRNAs in the stress responses, we screened the novel ncRNAs in hand, and found that 11of them may function during the stress responses. To analyze the regulatory mechanisms of ncRNAs in early maize development, three simulated stress conditions with 20% PEG6000, 150 mmol·L-1 NaCl, 100μmol·L-1 ABA were implemented to maize root at trefoil stage. Three clearly characterized stress response genes were induced during stess responses, which suggested that our stress treatments are successful. Based on the established stress treatments, we studied the expression profiles of 11 ncRNAs by semi-quantitative RT-PCR and Northern blot at different time points under both drought and salt stress.Results showed that dbf1 was highly expressed after 1 hour under 20% PEG6000; the expression of dhn1 significantly increased after 3 hour under 100μmol·L-1 ABA treatment; while DREB2A began to increase after 3 hour under 150 -mmol·L-1 NaCl treatment.By semi-quantitative RT-PCR and Northern blot, the 11 tested ncRNAs exhibited different response to stress treatments. Under PEG treatment, most of the induced ncRNAs reached the highest expression level at 1 hour; whereas ncRNAs gradually accumulated under ABA stress, with the highest expression level at 6 hour. Under salt stress, the highest expression levels for most ncRNAs appeared at 3 hour after NaCl treatment. In addition, ncRNAs also show distinct expression patterns in responses to different stresses. Zm-17, Zm-28, Zm-60 and Zm-88 were all rapidly induced after PEG or ABA treatment. The expression of Zm-128、Zm-89、Zm-79 and Zm-29 gradually decreased under PEG treatment, while were rapidly induced under ABA stress, with the highest expression level at 6 hour, and subsequently gradually decreased to normal level. The results showed that the four ncRNAs were transcriptionally repressed under PEG treatment, whereas were activated after ABA treatment. The expression of Zm-37 decreased after treatment with PEG, while was rapidly induced after ABA treatment, and subsequently decreased to normal level; as does under NaCl treatment. We found that single ncRNA exhibited similar expression patterns under ABA and NaCl treatment, which differ under PEG stress. Taken together, our results suggested that ncRNAs may play important roles during stress response, and may be dependent on the ABA during maize root response to salt stress.