Loss of peripheral polypeptides in the stromal side of photosystem I by light-chilling in cucumber leaves

Abstract

Photosystem I (PSI) is severely damaged by chilling at 4 degrees C in low light, especially in the chilling sensitive plant cucumber. To investigate the early events in PSI photoinhibition, we examined structural changes in the level of pigment-protein complexes in cucumber leaves in comparison with pea leaves. The complexes were separated on a native green gel and an increase in the intensity of a band was observed only in light-chilled cucumber leaves. The 77 K fluorescence emission spectrum of this green band indicated that the band was mainly composed of PSI with light-harvesting complex I. Each lane was cut from the green gel and separated on a fully denaturing SDS-PAGE in the second dimension. The new green gel band observed after light-chilling in cucumber leaves lacked 19, 18, and 16.5 kDa polypeptides. These results suggest that light-chilling facilitates the release of three peripheral polypeptides as an early event of chilling stress in vivo, which results in the inactivation of PSI in intact cucumber leaves.

The Plastid Genome-Encoded Ycf4 Protein Functions as a Nonessential Assembly Factor for Photosystem I in Higher Plants

“…One possibility could be that some components of the PSI complexes in mature and old leaves suffer photooxidative damage and need to be exchanged by newly synthesized molecules through the action of Ycf3 in a Y3IP1-and Ycf4-independent fashion. Indications for photoinhibition of the PSI acceptor side (Kudoh and Sonoike, 2002;Scheller and Haldrup, 2005;Sonoike, 2011) and a repair cycle replacing the stromal ridge subunits, which are most sensitive to oxidative damage, have recently been reported (Oh et al, 2009). Interestingly, Ycf3 has been specifically implicated in the assembly of PsaD into PSI (Naver et al, 2001) and therefore might also play an important role in the repair of the stromal ridge.…”

Production of superoxide from photosystem II-light harvesting complex II supercomplex in STN8 kinase knock-out rice mutants under photoinhibitory illumination

“…Thylakoid membranes were isolated as described previously [20], using a mortar and pestle to grind leaf samples with liquid nitrogen in a grinding buffer [ Sucrose density gradient ultracentrifugation (SDGU) was performed to isolate different CP complexes, including PSI and PSII complexes, as described previously [23]. An aliquot of the thylakoid membrane extract containing 500 µg of chlorophyll was re-suspended in a buffer containing 0.88% octylglucoside, 0.22% sodium dodecyl sulfate (SDS), 15 mM NaCl, 5 mM MgCl 2 , and 2 mM Tris-maleate (pH 8.0).…”

Photoinhibition of photosystem I

“…The addition of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), an inhibitor of PSII, or 2,5‐dibromo‐3‐methyl‐6‐isopropyl‐ p ‐benzoquinone (DBMIB), an inhibitor of plastoquinone (PQ) oxidation, completely suppresses the PSI photoinhibition in intact leaves or in isolated thylakoid membranes (Sonoike 1996b). The reaction center subunits of PSI were also degraded upon photoinhibition of PSI (Ivanov et al 1998, Oh et al 2009, Sonoike 1996b, Sonoike and Terashima 1994, Tjus et al 1999). Fragmentation of the PsaB subunit, one of the heterodimer subunits constituting the PSI reaction center, was observed as well as the PsaA and other small subunits of PSI.…”