Hydrogen peroxide mediates spermidine-induced autophagy to alleviate salt stress in cucumber
Creators: name: Zhang, Yuemei
name: Wang, Yu
name: Wen, Wenxu
name: Shi, Zhengrong
name: Gu, Qinsheng
name: Ahammed, Golam Jalal
name: Cao, Kai
name: Jahan, Mohammad Shah
name: Shu, Sheng
name: Wang, Jian
name: Sun, Jin
name: Guo, Shirong
Publisher: name: Taylor & Francis
Year: 2020
Subjects: subject: Biochemistry
subject: Medicine
subject: Microbiology
subject: FOS: Biological sciences
subject: Cell Biology
subject: Physiology
subject: Environmental Sciences not elsewhere classified
subject: Science Policy
subject: Astronomical and Space Sciences not elsewhere classified
subject: Immunology
subject: FOS: Clinical medicine
subject: Biological Sciences not elsewhere classified
subject: Marine Biology
subject: Plant Biology

description: Autophagy, an evolutionally conserved cellular degradation process, plays critical roles in plant development and stress response. Despite the wealth of information on the vital role of autophagy in responses to environmental stresses, little is known about the regulation of autophagy. In this study, we demonstrated that spermidine (Spd), a kind of polyamine, was involved in the regulation of salt tolerance through activating the expression of <i>ATG</i> (autophagy-related) genes and the formation of autophagosomes in cucumber under salt stress. Furthermore, NADPH oxidase-derived apoplastic H<sub>2</sub>O<sub>2</sub>-mediated Spd-induced salt tolerance and autophagy. Exogenous Spd significantly increased the tolerance to salt stress and inhibited the accumulation and ubiquitination of insoluble proteins. Foliar application of Spd promoted the transcript levels of <i>ATG</i> genes and autophagosomes formation. Besides, Spd induced the expression of <i>RBOH</i> (respiratory burst oxidase homolog), and the accumulation of H<sub>2</sub>O<sub>2</sub> both in leaves and roots. However, either pretreatment with dimethylthiourea (DMTU, an H<sub>2</sub>O<sub>2</sub> scavenger) or diphenyleneiodonium chloride (DPI, an inhibitor of NADPH oxidase) reduced Spd-induced accumulation of apoplastic H<sub>2</sub>O<sub>2</sub>. Importantly, Spd-induced salt tolerance and autophagy were compromised when plants were pretreated with DMTU or DPI. Furthermore, the silencing of <i>ATG4</i> and <i>ATG7</i> reduced Spd-induced salt tolerance and autophagosomes formation. Taken together, these results revealed that <i>RBOH</i>-dependent H<sub>2</sub>O<sub>2</sub> mediated the Spd-induced autophagy and salt tolerance in cucumber. <b>Abbreviations</b>: Asat: light-saturated rate of CO<sub>2</sub> assimilation; ATG: autophagy-related; DCF-DA: 2, 7-dichlorofluorescein diacetate; DMTU: dimethylthiourea; DPI: diphenyleneiodonium chloride; DW: dry weight; EL: electrolyte leakage; FW: fresh weight; Fv/Fm: the maximum quantum yield of photosystem II; GFP: green fluorescent protein; MDC: monodansylcadaverine; PDS: phytoene desaturase; PE: phosphatidylethanolamine; PLD: phospholipase D; RBOH: respiratory burst oxidase homolog; ROS: reactive oxygen species; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SIN1: salt induced NAC1; Spd: spermidine; TOR: target of rapamycin; VIGS: virus-induced gene silencing.