Varied expression pattern of the small heat shock protein gene encoding HSP17.7 against UVA, UVB, Cu2+ and Zn2+ stresses in sunflower

Today, one of the main objectives of agricultural biotechnology area is to find the responsible genes involved in stress response and engineering these genes to improve the plant response mechanisms. Therefore the current study was conducted to gain an insight on the role of HSP17.7 gene, which is a member of sHsps family, in defence mechanism of sunflower (Helianthus annuus L. cv. Confeta -Turkish cultivar) treated with different doses of UVA and UVB (4, 8, 12 and 20 kJ/m2) and concentrations of copper (Cu2+) and zinc (Zn2+) (80, 160, 320, 640, and 1280 µM) heavy metals. Based on our data, it was observed that different doses of UVA and UVB irradiation resulted in increased levels of HSP17.7 mRNA in sunflower plants. The highest levels of these increases (8 and 12 kJ/m2 of UVA) were seen under UVA stress. In contrast to UV stress, only the Cu2+concentration of 1280 µM led to higher expression levels of HSP17.7 gene compared to the control. Besides this, the 1280 µM concentration of Zn2+ treatment was the peak point of increased HSP17.7 mRNA levels for all stress conditions with nearly 8 times more than in the control sample. Negative correlations were found between malondialdehyde (MDA) levels and expression levels of HSP17.7 gene in sunflower plants subjected to current abiotic stress conditions. This correlation might indicate that an effective defence mechanism was in action and it might be concluded that the HSP17.7 gene can be used for identification of cultivars tolerant to UV and high doses of Cu2+ and Zn2+ for molecular breeding studies in the near future. These findings provide evidence of the HSP17.7 gene contribution to abiotic stress response in sunflower and will be helpful for the next studies about stress tolerance improvement in sunflower plants.