Poly-γ-glutamic acid induces system tolerance to drought stress by promoting abscisic acid accumulation in Brassica napus L.

As a new plant biostimulant, poly-gamma-glutamic acid (gamma-PGA) may be an effective anti-drought agent that can efficiently alleviate the damage to plants under drought stress. In this study, the effects of gamma-PGA on the physiological responses of oilseed rape (Brassica napus L.) seedlings under drought stress were investigated using hydroponics. Growth and development of the rape seedlings were significantly inhibited in a polyethylene glycol-simulated drought environment. However, 12 d after application of gamma-PGA under drought stress, the fresh weight, chlorophyll content, and relative water content of rape seedlings all markedly increased. Moreover, proline content and antioxidant enzyme activity were all markedly enhanced, and the malondialdehyde content was significantly reduced in rape seedlings treated with gamma-PGA. Furthermore, the content of the important anti-drought response hormone, abscisic acid (ABA), as well as the expression levels of the ABA metabolism regulation genes BnNCED3, BnZEP, and BnAAO4, significantly increased. These results indicate that gamma-PGA may induce elements of a tolerance system to drought stress by promoting ABA accumulation in B. Napus.