Photosystem II Regulation and Dynamics of the Chloroplast D1 Protein in Arabidopsis Leaves during Photosynthesis and Photoinhibition

Abstract

Arabidopsis fbaliana leaves were examined in short-term (1 h) and long-term (1 O h) irradiance experiments involving growth, saturating and excess light. Changes in photosynthetic and chlorophyll fluorescence parameters and in populations of functional photosystem II (PSII) centers were independently measured. Xanthophyll pigments, 3-(3,4-dichlorophenyI)-l,l-dimethylurea (DCMU)-binding sites, the amounts of D1 protein, and the rates of D1 protein synthesis were determined. These comprehensive studies revealed that under growth or light-saturating conditions, photosynthetic parameters remained largely unaltered. Photoprotection occurred at light saturation indicated by a dark-reversible increase in nonphotochemical quenching accompanied by a 5-fold increase in antheraxanthin and zeaxanthin. No consistent change i n the concentrations of functional PSll centers, DCMU-binding sites, or D1 protein pool size occurred. D1 protein synthesis was rapid. In excess irradiance, quantum yield of O, evolution and the efficiency of PSll were reduced, associated with a 15-to 20-fold increase in antheraxanthin and zeaxanthin and a sustained increase i n nonphotochemical quenching. A decrease in functional PSll center concentration occurred, followed by a decline in the concentration of D1 protein; the latter, however, was not matched by a decrease in DCMU-binding sites. I n the most extreme treatments, DCMUbinding site concentration remained 2 times greater than the concentration of D1 protein recognized by antibodies. D 1 protein synthesis rates remained unaltered at excess irradiances.During the last decade studies of photosynthesis and photoinhibition in higher plants have been driven by many advances in our understanding and by the availability of new techniques for in vivo and in vitro investigations. Following the biochemical studies of Kyle et al. (1984) with photoheterotrophic Chlamydomonas, attention has focused on a central role for the synthesis and degradation of the D1 protein of the heterodimer of the PSII reaction center

From ecophysiology to phenomics: some implications of photoprotection and shade–sun acclimation in situ for dynamics of thylakoids in vitro

“…(f) Acclimation to sunlight in fully expanded avocado shade leaves Recent studies of shade -sun acclimation in avocado shade leaves have focused on short-term issues, similar to those examined in wild-type Arabidopsis [56] and other plants to obtain insights into photoinactivation and photoprotection that are relevant to concepts of thylakoid dynamics discussed at this meeting. We were surprised to discover that although photosynthetic efficiency of old shade leaves of avocado initially declines markedly immediately after transfer to sun, these leaves have a remarkable capacity to reconstruct the photosynthetic apparatus to match the performance of new fully expanded leaves that develop in the sun on the same plant.…”

Mollusc-Algal Chloroplast Endosymbiosis. Photosynthesis, Thylakoid Protein Maintenance, and Chloroplast Gene Expression Continue for Many Months in the Absence of the Algal Nucleus

“…Powdered samples from the monthly collections were aliquoted (200 mg fresh weight) and proteins isolated as described by Russell et al (1995). The powdered tissue was homogenized in a microcentrifuge tube containing 400 L (1:2, w/v) of isolation buffer (330 mm sorbitol, 25 mm HEPES-KOH, pH 7.0, 5 mm MgCl 2 , 10 mm NaCl, 100 mm N-acetyl-l-Cys, and 1 mm phenylmethylsulfonyl fluoride).…”

“…Furthermore, although the gene products D1, D2, PsaA/B, and several other polypeptides that assemble to form the photosynthetic complexes are plastid encoded, they depend on nuclear regulation at either or both the transcriptional and translational levels (Stern et al, 1997;Merchant and Dreyfuss, 1998). In turn this nuclear regulation can be influenced by additional environmental and physiological factors (Aro et al, 1993;Christopher and Mullet, 1994;Russell et al, 1995).…”

Photosynthetic electron transport regulates the expression of cytosolic ascorbate peroxidase genes in Arabidopsis during excess light stress.

“…system. Excess electrons can damage the reaction center of PSII, in particular the D1 protein, and may lead to the perturbation and inhibition of photosynthetic electron transport (Krause, 1988;Andersson and Styring, 1991 ;Andersson et al, 1992;oquist et al, 1992;Aro et al, 1993;Russell et al, 1995). This phenomenon is known as photoinhibition of photosynthesis (Andersson and Styring, 1991 ;Andersson et al, 1992).…”

“…This phenomenon is known as photoinhibition of photosynthesis (Andersson and Styring, 1991 ;Andersson et al, 1992). The mechanisms leading to an inhibition of electron transport through PSll are not known, but the multiple reduction/oxidation (redox) reactions in PSll have a potential to create ROls, and it is known that photoinhibition may lead to D1 protein degradation, probably due to an excess of ROls (Krause, 1988;Andersson and Styring, 1991 ;Andersson et al, 1992;Oquist et al, 1992;Russell et al, 1995). Photoinhibitory stress also has a great potential to damage the LHC.…”