Rescue of early cell death phenotype in Arabidopsis old3-1 mutant plants in short-day condition

The mutant plants old3-1 (onset of leaf death 3-1) have a point mutation in the AT4G14880 gene. This gene encodes the cytosolic cysteine ​​synthase enzyme (OASTL-A1). Cysteine ​​is a sulfur-containing organic compound and a precursor of defense compounds, and the OASTL-A1 enzyme plays a role in the last step of its synthesis. The old3-1 mutation causes a change in the structure and activity of the cysteine ​​synthase enzyme, and the old3-1 mutant plants suffer premature cell death after 14 days under 21°C long-day conditions. In this research, the old3-1 mutant was compared with mutants B40-12, old3-2 and wild type Ler-0, Col-0 under short-day conditions and 21°C. Based on the phenotypic and physiological results, old3-1 plants did not suffer premature cell death and went through different stages of growth and development until flowering and seed production. Examining the activity of catalase and peroxidase enzymes under short day conditions showed that the activity of these enzymes in the leaves of old3-1 is higher than that of Ler-0 and B40-12, which means that in short-day conditions the activity of the enzymes increased. Examining the relative expression of immune system marker genes including GST1, DEFL and PR1 in 22-day-old seedlings old3-1 and Ler-0 under the same conditions (short day and 21˚C) following transferring to long day showed that the expression of the above genes in short day significantly increased, resulting in the survival of old3-1 mutant plants. According to the obtained results, short days improve growth and development conditions and save old3-1 seedlings from premature cell death.