AUTHOR=Li Zhou , Zhang Yan , Peng Dandan , Wang Xiaojuan , Peng Yan , He Xiaoshuang , Zhang Xinquan , Ma Xiao , Huang Linkai , Yan Yanhong TITLE=Polyamine regulates tolerance to water stress in leaves of white clover associated with antioxidant defense and dehydrin genes via involvement in calcium messenger system and hydrogen peroxide signaling JOURNAL=Frontiers in Physiology VOLUME=6 YEAR=2015 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2015.00280 DOI=10.3389/fphys.2015.00280 ISSN=1664-042X ABSTRACT=

Endogenous polyamine (PA) may play a critical role in tolerance to water stress in plants acting as a signaling molecule activator. Water stress caused increases in endogenous PA content in leaves, including putrescine (Put), spermidine (Spd), and spermine (Spm). Exogenous application of Spd could induce the instantaneous H₂O₂ burst and accumulation of cytosolic free Ca²⁺, and activate NADPH oxidase and CDPK gene expression in cells. To a great extent, PA biosynthetic inhibitor reduced the water stress-induced H₂O₂ accumulation, free cytosolic Ca²⁺ release, antioxidant enzyme activities and genes expression leading to aggravate water stress-induced oxidative damage, while these suppressing effects were alleviated by the addition of exogenous Spd, indicating PA was involved in water stress-induced H₂O₂ and cytosolic free Ca²⁺ production as well as stress tolerance. Dehydrin genes (Y₂SK, Y₂K, and SK₂) were showed to be highly responsive to exogenous Spd. PA-induced antioxidant defense and dehydrin genes expression could be blocked by the scavenger of H₂O₂ and the inhibitors of H₂O₂ generation or Ca²⁺ channels blockers, a calmodulin antagonist, as well as the inhibitor of CDPK. These findings suggested that PA regulated tolerance to water stress in white clover associated with antioxidant defenses and dehydrins via involvement in the calcium messenger system and H₂O₂ signaling pathways. PA-induced H₂O₂ production required Ca²⁺ release, while PA-induced Ca²⁺ release was also essential for H₂O₂ production, suggesting an interaction between PA-induced H₂O₂ and Ca²⁺ signaling.