Strategies for psbA gene expression in cyanobacteria, green algae and higher plants: From transcription to PSII repair

Abstract

The Photosystem (PS) II of cyanobacteria, green algae and higher plants is prone to light-induced inactivation, the D1 protein being the primary target of such damage. As a consequence, the D1 protein, encoded by the psbA gene, is degraded and re-synthesized in a multistep process called PSII repair cycle. In cyanobacteria, a small gene family codes for the various, functionally distinct D1 isoforms. In these organisms, the regulation of the psbA gene expression occurs mainly at the level of transcription, but the expression is fine-tuned by regulation of translation elongation. In plants and green algae, the D1 protein is encoded by a single psbA gene located in the chloroplast genome. In chloroplasts of Chlamydomonas reinhardtii the psbA gene expression is strongly regulated by mRNA processing, and particularly at the level of translation initiation. In chloroplasts of higher plants, translation elongation is the prevalent mechanism for regulation of the psbA gene expression. The pre-existing pool of psbA transcripts forms translation initiation complexes in plant chloroplasts even in darkness, while the D1 synthesis can be completed only in the light. Replacement of damaged D1 protein requires also the assistance by a number of auxiliary proteins, which are encoded by the nuclear genome in green algae and higher plants. Nevertheless, many of these chaperones are conserved between prokaryotes and eukaryotes. Here, we describe the specific features and fundamental differences of the psbA gene expression and the regeneration of the PSII reaction center protein D1 in cyanobacteria, green algae and higher plants. This article is part of a Special Issue entitled Photosystem II.

Photoprotective Non-photochemical Quenching Does Not Prevent Kleptoplasts From Net Photoinactivation

“…In particular FTSH, a quality control protease forming heteroor homo-oligomers (Janska et al, 2013) that removes damaged D1 from the PSII reaction center (Mulo et al, 2012), came into focus as a factor enabling kleptoplast longevity in Sacoglossa (de Vries et al, 2013). However, it is still unknown whether FTSH in kleptoplasts can function, because the M41 domain, needed for proteolysis of damaged D1 (Zhang et al, 2010), is missing in plastid encoded FTSH of the food source of one LtR Sacoglossa (de Vries et al, 2013).…”

“…Nevertheless, under any given light intensity, damage to D1 occurs, independently of the presence or absence of photoprotection mechanisms. Once damaged, D1 needs to be pulled out from the reaction center and newly incorporated (Mulo et al, 2012). This so-called D1 turnover is crucial for photosynthetic organisms and largely nuclear controlled, although several tools, including psbA, tufA, and ftsH, are plastid encoded in the food sources of Sacoglossa (de Vries et al, 2013;Leliaert and Lopez-Bautista, 2015).…”

Expression Profiles of <i>psbA, ALS, EPSPS</i>, and Other Chloroplastic Genes in Response to PSII-, ALS-, and EPSPS-Inhibitor Treatments in <i>Kochia scoparia</i>

“…These high Dl protein turnover rates are essential for repair of the photoinhibitory damage caused by PSII-inhibitors. The high D1 protein turnover is also accompanied by corresponding increase in psbA gene transcription [34]. In this study, the high KspsbA gene expression in kochia after atrazine application can be explained by the rapid turnover of the D1 protein.…”

Phylogenetic viewpoints on regulation of light harvesting and electron transport in eukaryotic photosynthetic organisms

“…The molecular mechanisms of photoinhibition and repair of PSII have been extensively studied during the past decades, and despite some controversy surrounding the primary target of photodamage, the replacement of photodamaged D1 protein through a multi-step process regulated by phosphorylation and assisted by a large catalogue of auxiliary proteins has become relatively well understood (Baena-Gonzalez and Aro 2002;Chi et al 2012;Mulo et al 2012).…”