Study of proline accumulation and gene expression of P5CS at vegetative and flowering stages of Dracocephalum kotschyi under drought stress

Dracochephalum kotschyi is an endemic medicinal plant in iran belonging to Lamiaceae family known as Zarin-Giah. Under osmotic stresses, proline accumulation is an important response of plants to these conditions. Proline is a compatible osmolyte which affects many cellular and molecular aspects of a plant in both normal and stressful situations. Proline is shown to be involved in plant development in normal conditions and in conferring resistance to a plant under biotic and abiotic stresses. Δ1-pyrroline-5-carboxylate synthetase )P5CS), one of the two main enzymes in the proline biosynthesis pathway of the glutamate precursor, has been demonstrated to play a significant role in proline accumulation in plants under drought stresses. In this research, the effect of different levels of drought stress was investigated on the relative water content, chlorophyll content, proline accumulation and P5CS gene expression in Dracocephalum kotschyi at two growth stages. This experiment was conducted as a factorial experiment with two factors including drought stress and growth stages in a completely randomized design with three replications. Drought stress treatments includes severe (25% FC), moderate (50% FC), low (75%FC) drought stress and control (100%FC). Growth stage includes vegetative and flowering stages. Analysis of variance showed that drought stress significantly increased P5CS gene expression and proline content while decreased chlorophyll a, b, total and relative water content. The highest expression level of P5CS gene and maximum amount of proline were observed at flowering stage under moderate drought stress (50% FC) conditions.