Singlet oxygen- and EXECUTER1-mediated signaling is initiated in grana margins and depends on the protease FtsH2

Abstract

Formation of singlet oxygen ( 1 O 2 ) has been implicated with damaging photosystem II (PSII) that needs to undergo continuous repair to maintain photosynthetic electron transport. In addition to its damaging effect, 1 O 2 has also been shown to act as a signal that triggers stress acclimation and an enhanced stress resistance. A signaling role of 1 O 2 was first documented in the fluorescent (flu) mutant of Arabidopsis. It strictly depends on the chloroplast protein EXECUTER1 (EX1) and happens under nonphotoinhibitory light conditions. Under severe light stress, signaling is initiated independently of EX1 by 1 O 2 that is thought to be generated at the acceptor side of active PSII within the core of grana stacks. The results of the present study suggest a second source of 1 O 2 formation in grana margins close to the site of chlorophyll synthesis where EX1 is localized and the disassembly of damaged and reassembly of active PSII take place. The initiation of 1 O 2 signaling in grana margins depends on EX1 and the ATP-dependent zinc metalloprotease FtsH. As FtsH cleaves also the D1 protein during the disassembly of damaged PSII, EX1-and 1 O 2 -mediated signaling seems to be not only spatially but also functionally associated with the repair of PSII.

Production of Reactive Oxygen Species by Photosystem II as a Response to Light and Temperature Stress

“…Even if EX1 and EX2 are located in chloroplast, it was proposed that jasmonic acid formed by 1 O 2 -initiated lipid peroxidation mediates genetically controlled programmed cell death response via these two plastid proteins (Przybyla et al, 2008). The initiation of 1 O 2 signaling has been recently demonstrated close to EX1 in the grana margins nearby the site of chlorophyll synthesis and 1 O 2 formation (Wang et al, 2016). As 1 O 2 signaling depends on the FstH protease, the authors proposed that 1 O 2 signaling is linked to D1 repair cycle.…”

FtsH2-Dependent Proteolysis of EXECUTER1 Is Essential in Mediating Singlet Oxygen-Triggered Retrograde Signaling in Arabidopsis thaliana

“…Protein immunoprecipitation (IP) coupled with mass spectrometry (MS) unveiled a group of proteins potentially forming the EXECUTER complex in grana margin, including enzymes involved in chlorophyll biosynthesis, PSII RC proteins and FtsH proteases (Wang et al, 2016). Because EX1 is associated with PSII and FtsH protease, upon 1 O 2 generation, EX1 possibly undergoes similar oxidative post-translational modification as PSII RC proteins including D1 and CP43 (Dreaden et al, 2012).…”

Enhanced tolerance to a combination of heat stress and drought in Arabidopsis plants deficient in ICS1 is associated with modulation of photosynthetic reaction center proteins

“…turnover) is therefore essential to maintain the photosynthetic apparatus (Kim et al , Roose and Pakrasi ). In this study, sid2‐1 plants showed higher level of FtsH2 and FtsH8 transcripts, encoding proteases that might be involved in the degradation of damaged D1 protein (Wagner et al , Wang et al ), under a combination of heat stress and drought (Fig. ).…”

“…'H + D' represents a combination of heat stress and drought. transcripts, encoding proteases that might be involved in the degradation of damaged D1 protein (Wagner et al 2012, Wang et al 2016, under a combination of heat stress and drought (Fig. 6).…”