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Antagonistic shifting from abscisic acid- to salicylic acid-mediated sucrose accumulation contributes to drought tolerance in Brassica napus

Author:
La, Van Hien, Lee, Bok-Rye, Islam, Md. Tabibul, Park, Sang-Hyun, Lee, Hyo, Bae, Dong-Won, Kim, Tae-Hwan
Source:
Environmental and experimental botany 2019 v.162 pp. 38-47
ISSN:
0098-8472
Subject:
Brassica napus, abscisic acid, biomass, drought, drought tolerance, genes, hexokinase, hormonal regulation, leaves, metabolism, osmotic pressure, pathogenesis-related proteins, phloem, plant stress, salicylic acid, starch, stress response, sucrose, sucrose-phosphate synthase, synergism, water stress
Abstract:
The phytohormone salicylic acid (SA), as an important signaling molecule involved in the regulation of plant stress responses. This study aimed to characterize the hormonal regulation of drought-responsive sugar metabolism, focusing on SA-mediated sucrose modulation with regard to the drought resistance mechanism. The responses of sucrose synthesis, starch degradation, sucrose transport, as well as stress symptom development to SA pretreatment and/or drought imposition were interpreted in relation to the altered endogenous hormonal status and their signaling genes. Drought-induced severe reduction of leaf biomass coincided with the highest endogenous level of abscisic acid (ABA) and expression of SAG12. Under drought-stressed, sugar accumulation was mainly due to the enhanced hexose level with depressed expression of hexokinase gene HXK1 and, in part, to increased sucrose content with the highest expression of ABA-dependent sucrose signaling genes SnRK2.2 and AREB2. In the presence of SA, an additional sucrose accumulation occurred with further enhancement of sucrose phosphate synthase (SPS) activity and starch degradation-related genes BAM1 and AMY3 expression, which coincided with the depression of SnRK2.2 and AREB2. Further, SA-mediated sucrose accumulation was responsible for the induction of phloem sucrose loading with enhanced expression of sucrose transporter genes SUT1 and SUT4. SA-mediated pathogenesis-related protein 2 (PR2) activation reflected a synergistic interaction between SA and sucrose signaling. These results indicate that antagonistic shifting from ABA- to SA-mediated sucrose accumulation is an important process in regulating osmotic potential and leaf senescence.
Agid:
6302870