Effect of Zn deficiency stress on expression pattern of genes encoding bZIP4, bZIP79 and bZIP97 transcription factors in bread wheat (Triticum aestivum L.) cultivars

A factorial experiment (based on completely randomized design) with three replications was conducted in faculty of agriculture of Urmia University, Iran in 2016 to investigate the effect of soil Zn deficiency on the expression of genes encoding bZIP4, bZIP79 and bZIP97 transcription factors in Zn-efficient and Zn-inefficient bread wheat cultivars. Cv. Bayat (Zn-efficient) and cv. Hirmand (Zn-inefficient) were grown under soil Zn deficient and Zn sufficent conditions. The expression levels of three above-mentioned transcription factors were measured using Real time PCR technique in leaf and root of the cultivars at two growth stages; beginning of stem elongation (vegetative) and 30% of heading (reproductive). Analysis of variance showed that the interaction effect of cultivar × tissue × sampling time was significant on the expression of three studied genes. The mean comparison revealed that the highest expression level of bZIP4 (more than 65 fold change) in the leaf of Zn-efficient cultivar (Bayat) at vegetative stage under Zn deficiency conditions. The highest expression of bZIP79 and bZIP97 genes (more than 31 and 60 fold change, respectively) observed in the root of Bayat cultivar at vegetative stage under Zn deficiency conditions. No significant difference was found between Zn-efficient and Zn-inefficient cultivars for the expression level of three studied genes at the vegetative stage. Considering the significant increase in expression of all studied genes at vegetative stages, it may be concluded that the mRNA transcription of the transporter genes involved in Zn uptake and translocation (ZIP genes), are activated at the heading stage of the two bread wheat cultivars. Moreover, according to the increased expression of bZIP4 in leaf, and bZIP79 and bZIP97 in root, the possible role of bZIP4 and bZIP79, and bZIP97 might be the transcriptional activation of ZIP genes involved in Zn translocation within the plant and Zn uptake from soil, respectively, under soil Zn deficiency conditions.