Abstract
Proline metabolism influences metabolic and 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 abscisic acid (ABA) were concomitant with ROS and proline accumulation, accompanied by decreased NAD(P)H/NAD(P)+ and GSH/GSSG ratios. Exogenous Glu-feeding under drought resulted in an increase of salicylic acid (SA) with an antagonistic decrease of ABA. Glu-enhanced SA coincided with the highest expression of SA synthesis related gene ICS1 and Ca2+-dependent protein kinase CPK5. SA-enhanced CPK5 expression was closely associated with further enhancement of proline synthesis-related genes (P5CS1, P5CS2, and P5CR) expression. The Glu-activated proline synthesis was responsible for the 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 and Glu-enhanced proline synthesis are crucial in the amelioration of drought stress in B. napus.
Highlight
Drought-induced oxidative stress and symptom are developed by ABA-dependent manner
Glu-application increases endogenous SA level with an antagonistic decrease of ABA
Drought-induced proline accumulation was further enhanced by exogenous Glu-application
Glu-enhanced proline synthesis accompanied with SA-mediated regulatory pathway
Glu-enhanced SA-modulated proline metabolism is an integrated process of redox control
Footnotes
Contact of other authors: Van Hien La: hiencnsh87{at}gmail.com, Bok-Rye Lee: turfphy{at}hotmail.com, Md. Tabibul Islam: tabib_pha{at}hotmail.com, Sang-Hyun Park: ghost1284{at}nave.com, Dong-Won Bae: bdwon{at}gnu.ac.kr