Quantitative expression analysis of TaMPK4 and TaTIP1 genes in drought tolerant and non- tolerant wheat (Triticum aestivum L.) cultivars

The regulation of plant responsive genes to drought stress comprises very complex mechanisms. Plant signal transduction cascades are stimulated by the sensing of water stress signals, and then expression of different genes and signaling molecules. Expression patterns of these genes are different; some of them respond to drought very rapidly, while others are induced slowly after the accumulation of ABA. The mitogen-activated protein kinase (MPK) cascade elements and tonoplast intrinsic proteins (TIPs) take place in abiotic signaling pathway and water movement regulation, respectively. We aim to show the expression patterns of MPK4 and TIP1 mRNA in drought tolerant and non-tolerant T. aestivum cultivars treated with two different shock dehydration stresses using qRT-PCR technique. The patterns of MPK4 and TIP1 mRNA accumulation was different in non-tolerant wheat cultivar, upregulated in 4h and 8h drought-stressed root and leaf tissues. The reason for early response to drought stress in the cultivar Atay might be related to drought sensitivity. Drought tolerant cultivars showed MPK4 up-regulation in 8h stressed roots implying that, increased expression of MPK4 might play an important role in drought tolerance of T.aestivum by regulating the stress signaling. There was no significant difference in TIP1 mRNA expression level between drought stressed and control root tissues in both tolerant cultivars. Although down-regulation was observed in TIP1 transcript level under 4h drought stress, an induction was found under 8h drought stress in two drought tolerant cultivar leaves. Similar results were obtained from RNAseq data performed with the same cultivars and stress applications. These results suggest that ABA-dependent MPK4 and TIP genes are also involved in ABAindependent pathway and there might be some relationships between TIP1 and MPK4 gene expresion in wheat under drought stress. Since the functions of TIP1 and MPK genes have not been completely identified yet, detailed protein expression analyses will allow us to get a better idea about the possible role of these genes in drought-response mechanism in plants.