Participation of ABA Metabolism and ROS Generation in Sugar Starvation-Induced Senescence of Rice Flag Leaves
Both sucrose and abscisic acid (ABA) play pivotal role in the regulation of plant leaf senescence. However, the exact mechanism by which sugar starvation , ABA, and reactive oxygen species (ROS) interact with each other during leaf senescence remains largely unknown. In this study, the genotype-dependent alteration in temporal patterns of sugar concentration during leaf senescence and its relation to ABA metabolism and ROS generation were investigated by using the premature senescence of flag
... enescence of flag leaf ( psf ) mutant and its wild type. Results: Results showed that sugar starvation-induced leaf senescence was closely associated with the endogenous ABA concentration and ROS level in senescent leaves. Sugar starvation accelerated leaf senescence, concomitantly with the marked increase in ABA concentration and malonaldehyde (MDA) accumulation in detached leaves. Conversely, exogenous sugar treatment significantly suppressed the ABA concentration ad ROS level in detached leaves, thus leaf senescence was delayed by exogenous sugar supply. Pharmacological tests revealed that ABA biosynthesis inhibitor (NDGA) delayed the sugar starvation-induced leaf senescence, while ABA catabolism inhibitor (DNCZ) accelerated leaf senescence and significantly increased the endogenous ABA content in senescent leaves. For the expression patterns of ABA synthesis and catabolism related genes induced by sugar starvation, exogenous sucrose supply, NDGA and DNCZ. sugar starvation up-regulated the OsABA8ox1 transcript, while exogenous sucrose and NDGA down-regulated the transciptional expressions of OsNCED1 , OsNCED4 and OsNCED5 and OsABA8ox2 and OsABA8ox3 e by sugar starvation and DNCZ, while the transcript of was increased. Conclusion: Together, our results demonstrated that the rise in endogenous ABA content during sugar starvation-induced leaf senescence is mostly caused by the suppression of ABA catabolism, rather than the enhancement of ABA biosynthesis, and the expression of ABA metabolic genes determines the equilibrium between ABA biosynthesis and catabolism that eventually influence cross-talk between endogenous factors. The breaking for the equilibrium between ABA biosynthesis and catabolism was strongly responsible for sugar starvation-induced leaf senescence, which was resulted from the suppression of ABA catabolism, rather than the enhancement of ABA biosynthesis . 2. Gan S, Amasino RM: Making sense of senescence (molecular genetic regulation and manipulation of leaf senescence). Plant physiology 1997, 113(2):313. 3. Woo HR, Kim HJ, Nam HG, Lim PO: Plant leaf senescence and death-regulation by multiple layers of control and implications for aging in general. J Cell Sci 2013:jcs. 109116. 4. Watanabe M, Balazadeh S, Tohge T, Erban A, Giavalisco P, Kopka J, Mueller-Roeber B, Fernie AR, Hoefgen R: Comprehensive dissection of spatio-temporal metabolic shifts in primary, secondary and lipid metabolism during developmental senescence in Arabidopsis thaliana. Plant physiology 2013:pp. 113.217380. 5. Lim PO, Woo HR, Nam HG: Molecular genetics of leaf senescence in Arabidopsis. Trends in plant science 2003, 8(6):272-278. 6. environmental signals during the regulation of leaf senescence. Journal of experimental botany 2005, 57(2):391-399. 9. Chen D, Wang S, Xiong B, Cao B, Deng X: Carbon/nitrogen imbalance associated with drought-induced leaf senescence in Sorghum bicolor. PloS one 2015, 10(8):e0137026.