M. Ghoreishi - Biology Department, Faculty of Sciences, Urmia University, Urmia, Iran. Institute of Biotechnology, Urmia University, Urmia, Iran.
F. Rahmani - Biology Department, Faculty of Sciences, Urmia University, Urmia, Iran. Institute of Biotechnology, Urmia University, Urmia, Iran.
B. Abdollahi Mandoulakani - Institute of Biotechnology, Urmia University, Urmia, Iran. Department of Plant Breeding and Biotechnology, Urmia University, Urmia, Iran.
A. Hassanzadeh Ghorttapeh - Horticulture Crop Science Research Department, West Azarbaijan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization, Urmia, Iran.

Environmental stresses such as cold and heat are adversely affecting all aspects of crop plants including yield. In this study, the contents of fourteen amino acids and expression levels of four transcription factor genes including MYB۱-۱, KRP۲, ERF and WRKY۴۰ were analyzed in TN-۹۷-۲ (cold sensitive) and TN-۹۷-۲۹۰ (cold tolerant) local flax varieties under cold and heat stresses conditions. Seeds of two local flax varieties were grown in growth chamber of Biotechnology Institute of Urmia University, Urmia, Iran, under control conditions for ۳۰ days. Then, plants were subjected to three different thermal regimes including control (۲۵± ۱°C), cold (۴ ± ۱°C) and heat (۳۷ ± ۱ °C) for three consecutive days.  Cold stress significantly increased the Asp, His, Ala and Met amino acids contents in both varieties. TN-۹۷-۲۹۰ variety exhibited less decline in His, Val, Phe, Iso and Leu contents than TN- ۹۷- ۲ variety under heat stress. Cold stress increased expression of ERF and WRKY۴۰ mRNAs while heat stress elevated transcript levels of KRP۲ and MYB۱-۱ genes in TN-۹۷-۲۹۰ variety. In summary, Asp, Glu, His, Ala and Met amino acids could be exogenously applied to flax plants by either foliar spray or root supplement to tolerate cold stress conditions. In addition, application of Ser and Pro amino acids may aid conferring heat tolerance to cold sensitive flax plants. The positive response of ERF and WRKY۴۰ genes (cold stress) and KRP۲ and MYB۱-۱ (heat stress) in TN-۹۷-۲۹۰ variety suggests their over-expression assist protecting flax plants under cold and heat stresses.

Flax, Cold stress, Heat stress, thermal tolerance, transcription factor