Functional Investigation Of Wheat(Triticum Aestivum L.)Gene TaMYB13in Stress Response

Wheat is one of the most important food crops for humans in both growing and production, and it is also serving as an essential source for energy supply in our daily lives. However, wheat is extremely sensitive to the environmental stresses including both bio-and abio-stresses, such as salinity, drought, extreme temperature, light radiation, mechanical damage, electromagnetic damage, wind damage, pathogen, and so on. Therefore, functional investigation of wheat stress responsive genes and the breeding of the new wheat cultivars with better stress tolerance and higher yield is essential for modern agriculture development.Transcription factors can combine with specific DNA sequences to activate or inhibit transcription of target genes, so they play a pivotal role in cell signal transduction process. The plant transcription factors are divided into more than one family and the MYB transcription factor family is one of the largest families in plants. The members of MYB family usually contain a SANT domain, and play multifaceted roles in the transcriptional regulation. Previously, based on the gene expression chip of Jinan177and SR3root SSH cDNA library upon NaCl stress, TaMYB13expression was down regulated. This work, based on the previous results, was mainly to investigate its deeper function to get more scientific understanding of wheat MYB gene family in stress tolerance.By using EST sequences from NCBI website, we obtained the whole sequence of the TcMYB13gene. This gene has no intron, and its cDNA contains556bp5’UTR,543bp ORF and265bp3’UTR. By amino acid sequence database analysis, we found that this gene contains the SANT structural domain that MYB transcription factor family conserved.To determin if the gene expression of TaMYB13is regulated by environmental stresses, Realtime RT-PCR analyses were performed by using both leaves and roots.The results turned out that the expression of TaMYB13is higher in the root, and its expression is down regulated by drought (18%PEG), high salt (200mM NaCl) and ABA (100μM), and suggesting that these abiotic stresses are negative regulators for TaMYB13expression, and this gene may play significant role in root.To better understand the physiological function of the TaMYB13in abiotic stresses, the gene was heterogenetically over-expressed in Arabidopsis, and the transgenetic OE plants were screened and physiologically analyzed with transgenic lines expressiing vector control. These data showed that, compared with the control plants, the transgenic lines are hypo-sensitive to ABA and high salt stresses.To clarify the signaling network of TaMYB13in plant stress responses, Realtime-PCR was used to check the expression alteration of a series of representative stress responsive Marker genes. We found that the expression of genes involved in both ABA dependent-and independent-pathways are raised, suggesting that this gene is participated in both pathways. The expression level of ABI1and ABI2was increased in TaMYB13overexpression lines of transgene’ic Arabidopsis, and these two genes are involved as negative signaling factors in ABA signal transduction pathway, indicating that TaMYB13may be a negative regulator as well. The expression of RD29A, CBF3and DREB2A are also raised in OE plants, indicating that TaMYB13may be involved in ABA-independent osmotic stress pathway and play a positive regulatory role to improve salt tolerance by increasing expression of RD29A, CBF3and DREB2A. A lot of stress responsive genes in ABA-dependent and ABA-independent pathway are highly expressed in OE Arabidopsis transgenetic plants, and this also confirmed that the gene is hypo-sensitive to ABA and high salt.In summary, high salt, drought and ABA negatively regulate the expression of TaMYB13, and this gene is hyposensitive to ABA and high salt. TaMYB13functions in stress responses through ABA dependent and ABA independent pathways.