The effect of heat stress on expression alternation of miR398 on Helianthus annuus L.

microRNAs are small non-coding RNAs approximately 21-22 nucleotides long and have been identified as negative regulators of gene expression in the post-transcriptional level in plants and animals. Temperature is one of the most important climate change factors and higher temperatures affect agriculture and crop production adversely. In this study، the expression pattern of miR398 and its target gene NtGT5b were measured in root and leaf tissues of sunflower (Helianthus annuus) in various heat stress conditions (0h، 1. 5h، 3h، 6h) at 42 °C by qRT-PCR. The results showed different pattern of miRNA expression in both root and leaf tissues during mild، moderate and severe heat stress، respectively. miR398 was highly up regulated and its target gene down regulated in leaf tissue that showed thermo tolerance of this tissue in term of heat stress. There is a different miRNA expression patterns in leaf and root tissues under various stress conditions which is an indication of induced signal transmission after heat stress. Investigating miR398 network shows that this miRNA through presences of important genes and transcription factors such as AFO and INO has the ability to change the pattern of gene expression of many processes such as growth، development and response to stress.