La, Van HienLee, Bok-RyeIslam, Md TabibulAl Mamun, MdPark, Sang-HyunBae, Dong-WonKim, Tae-Hwan2020-09-022020-09-022020-04512http://hdl.handle.net/10919/99892Proline metabolism influences the metabolic and/or signaling pathway in regulating plant stress responses. This study aimed to characterize the physiological significance of glutamate (Glu)-mediated proline metabolism in the drought stress responses, focusing on the hormonal regulatory pathway. The responses of cytosolic Ca2+ signaling, proline metabolism, and redox components to the exogenous application of Glu in well-watered or drought-stressed plants were interpreted in relation to endogenous hormone status and their signaling genes. Drought-enhanced level of abscisic acid (ABA) was concomitant with the accumulation of ROS and proline, as well as loss of reducing potential, which was assessed by measuring NAD(P)H/NAD(P)(+) and GSH/GSSG ratios. Glu application to drought-stressed plants increased both salicylic acid (SA) and cytosolic Ca2+ levels, with the highest expression of calcium-dependent protein kinase (CPK5) and salicylic acid synthesis-related ICS1. The SA-enhanced CPK5 expression was closely associated with further enhancement of proline synthesis-related genes (P5CS1, P5CS2, and P5CR) expression and a reset of reducing potential with enhanced expression of redox regulating genes (TRXh5 and GRXC9) in a SA-mediated NPR1- and/or PR1-dependent manner. These results clearly indicate that Glu-activated interplay between SA- and CPK5-signaling as well as Glu-enhanced proline synthesis are crucial in the amelioration of drought stress in Brassica napus.application/pdfenCreative Commons Attribution 4.0 Internationalcalcium signalingglutamateproline synthesisredoxsalicylic acidArticle - Refereedhttps://doi.org/10.3390/plants904051294323161092223-7747