An investigation was conducted to assess proline anabolism and catabolism pathway genes under drought stress. Treatments were irrigation in three levels (25, 50 and 100% field capacity) at 1, 3, 6 and 12 d and two rose species (Rosa canina L. and Rosa damascene Mill.). The results showed that the potential for proline accumulation in R. damascena was higher than R. canina under drought. Simultaneous with proline accumulation, expression of P5CS and P5CR genes increased from 1 to 12 d under 50% FC whereas their expression had an increasing trends from 1 to 6 d at 25% FC and expression of both genes decreased at 12 d in both species. The highest accumulation of proline was observed under 25% FC at 12 d, but expression of genes involved in proline synthesis main pathway decreased on this day. Furthermore, expression of genes (PDH and P5CDH) involved in proline catabolism pathway decreased in 50% FC from 1 to 12 d while their expression remarkably decreased from 1 to 6 d and increased at 12 d under 25% FC. These findings showed that under conditions of 50 and 25% FC, arginine accumulation resulted in the increased expression of the ARG gene, which led to ornithine production. Furthermore, ornithine accumulation increased OAT expression. Therefore, it seems that OAT-induced P5C is transported from the mitochondria to the cytosol and reduced to proline by the P5CR.

Keywords: Abiotic stress; Amino acid; Drought; Expression gene.