Title : Investigating the role of Bowman-Birk serine protease inhibitor in Arabidopsis plants under drought stress
Serine protease inhibitors (SPIs) play an important role in cell survival, development and host defense. In plants, serine protease inhibitors such as the Kunitz-type inhibitor (KTI) and Bowman-Birk inhibitor (BBI) have been shown to be induced in response to abiotic stress such as salinity and drought resulting in tolerance to these stresses. In this study, Arabidopsis thaliana (T3) plants overexpressing the BBI gene from maize were generated and identified by PCR and subjected to drought stress in order to study the role of BBI protease inhibitor in drought tolerance. Drought treatment of four-week-old Arabidopsis plants was performed by withholding water from plants for nine days and harvested plant material was used for physiological and biochemical analysis. The transgenic lines exhibited normal growth after nine days of drought as compared to the wild-type. The results also showed a higher leaf relative water content (RWC) in transgenic lines when compared to the wild-type, with line 2 having the highest RWC of 72%. Trypsin-inhibitor activity indicated that the total protein of the positive transgenic plants had stronger inhibitory activity than the wild-type. Transgenic lines overexpressing BBI also showed reduced lipid peroxidation (MDA content) as well as the enhancement of glutathione transferase (GST) antioxidant enzyme activity. These results suggest a potential role for BBI in modulating serine protease activities during drought stress and a possible regulator of stress tolerance through reactive oxygen species (ROS) regulation.