Monitoring Response of a Few bZip Transcription Factors in Response to Osmotic Stress in Sunflower.

Sunflower (Helianthus annuus L.) is one of the important vegetable oil supplies in the world and in Iran, as well. It is classified as a drought semi-tolerant crop; however, its yield is adversely affected by drought stress. Understanding the initial events in sensing stress and the related physiologic and biochemical events thereafter, is crucial in designing drought stress breeding programs. Transcription factors are master molecules directly involved in the plant responses under drought stress, from signal perception and transduction to the regulation of physiologic processes.

The expression pattern of some bZip transcription factors in response to osmotic stress was investigated in sunflower.Employing real-time PCR to monitor, the response of 10 bZIP transcription factors was performed under different osmotic stress conditions including -0.3, 0.9, and 1.2 MPa. Whole seedling was sampled at 6, 12, and 24 h after the osmotic condition application.

Exposure to osmotic potential of 0.9 MPa for 24 h caused a reduction in the fresh weight of the seedling. Among the evaluated genes, eight genes, bz-497, bz-502, bz-485, bz-499, bz-492, bz-504, bz-505, and bz-509 appeared as the osmotic stress responsive transcription factor. Changes in the expression of the genes under 0.3 MPa was observed for four genes. Most of the osmotic responsive genes appeared to be up-regulated. Most of responsiveness in the gene expression was happened under 0.9 MPa of the osmotic stress which is corresponding to fresh weight reduction in the seedlings. Among the investigated genes, two genes was identified to have possible roles in sensitive response of sunflower against drought stress.

It was a focus to have systemic view on the complex response of the plant to abiotic stress, and avoidance of the single gene analysis. Also, the importance of molecular data in molecular breeding procedures toward achievement of the stress tolerant lines was highlighted.