Evaluation of proline, soluble sugar and ABA content in soybean Glycine max (L.) under drought stress memory

Drought stress memory in plant can alter their physiological, biochemical and molecular to a subsequent stress. An experiment was conducted to determine biochemical parameters of soybean seedlings under drought stress memory. 14-days-old soybean seedlings were subjected to three consecutive water deficit phases (D1, D2, D3), each phase recovered by re-watering (R1, R2, R3), and control plant watering daily (R0). Leave of seedlings from these phases were collected and analyzed. Significantly increasing contents of soluble sugar and proline observed at the first drought stress. After the first re-water and continuous stress phases, these indicator contents decreased and maintained at a relatively stable level. Expression level of two memory genes encoded to transcription factor (NAC09 and NAC109) and one gene encoded enzyme Δ1-pyrroline-5-carboxylate synthetase (P5CS1) were increased in the first stress and decreased in third stress. Our results demonstrate that changing of biochemical parameters of soybean seedlings can be seen as the strong indications of “drought stress memory”. This result may serve as a reference platform to study advanced researches at molecular and genetic levels.