5'-upstream region of WRKY18 transcription factor from banana is a stress inducible promoter with strong expression in guard cells.

Increasing crop productivity in an ever-changing environmental scenario is a major challenge for maintaining the food supply worldwide. Generation of crops having broad spectrum pathogen resistance with the ability to cope with water scarcity is the only solution to feed the expanding world population. Stomatal closure has implications on pathogen colonization and drought tolerance. Recent studies have provided novel insights into networks involved in stomatal closure which is being used in biotechnological applications for improving crop endurance. Despite that genetic engineering of stomata requires guard cell preferred or specific regulatory regions to avoid undesirable side effects. In the present study, we describe the 5'-upstream regulatory region of the WRKY18 transcription factor of banana and functionally analyzed its stress meditated activation and strong guard cell preferred activity. Expression of MusaWRKY18 is augmented in leaves of banana cultivars Karibale Monthan, Rasthali and Grand Nain under multiple stress conditions suggesting its role in stress responses of banana plants. Transgenic tobacco lines harboring PMusaWRKY18 -GUS were regenerated and GUS staining demonstrated substantial GUS expression in guard cells which corroborates with multiple Dof1 binding cis-elements in PMusaWRKY18 . Fluorescent β-galactosidase assay demonstrated the stress mediated strong induction profiles of PMusaWRKY18 at different time points in transgenic tobacco lines exposed to drought, high-salinity, cold and applications of ABA, SA, MeJA and ethephon. This study sheds novel insights into guard cell preferred expression of WRKY genes under stress and confirm the utility of PMusaWRKY18 for exploring guard cell functions and guard cell engineering. This article is protected by copyright. All rights reserved.