Role of Temperature Stress on Chloroplast Biogenesis and Protein Import in Pea

Abstract

Modulation of photosynthesis and chloroplast biogenesis, by low and high temperatures, was studied in 12-d-old pea (Pisum sativum) plants grown at 25°C and subsequently exposed to 7°C or 40°C up to 48 h. The decline in variable chlorophyll a fluorescence/maximum chlorophyll a fluorescence and estimated electron transport rate in temperature-stressed plants was substantially restored when they were transferred to room temperature. The ATP-driven import of precursor of small subunit of Rubisco (pRSS) into plastids was down-regulated by 67% and 49% in heat-stressed and chill-stressed plants, respectively. Reduction in binding of the pRSS to the chloroplast envelope membranes in heat-stressed plants could be due to the downregulation of Toc159 gene/protein expression. In addition to impaired binding, reduced protein import into chloroplast in heat-stressed plants was likely due to decreased gene/protein expression of certain components of the TOC complex (Toc75), the TIC complex (Tic20, Tic32, Tic55, and Tic62), stromal Hsp93, and stromal processing peptidase. In chill-stressed plants, the gene/protein expression of most of the components of protein import apparatus other than Tic110 and Tic40 were not affected, suggesting the central role of Tic110 and Tic40 in inhibition of protein import at low temperature. Heating of intact chloroplasts at 35°C for 10 min inhibited protein import, implying a low thermal stability of the protein import apparatus. Results demonstrate that in addition to decreased gene and protein expression, down-regulation of photosynthesis in temperaturestressed plants is caused by reduced posttranslational import of plastidic proteins required for the replacement of impaired proteins coded by nuclear genome.Temperature has a profound effect on plant development (Xin and Browse, 1998;Guy, 1999; Allen and Ort, 2001;Browse and Xin, 2001). Plants exposed to chill stress, or heat stress, have impaired chlorophyll (Chl) biosynthesis due to down-regulation of gene expression and protein abundance of several enzymes involved in tetrapyrrole metabolism Tripathy, 1998, 1999;Mohanty et al., 2006). Impaired Chl biosynthesis and chloroplast development leads to reduced photosynthesis beyond the optimum temperature, resulting in substantial loss of plant productivity. The reduced photosynthesis affected by temperature stress is attributed to decline in PSII, F v /F m (variable Chl fluorescence/maximal Chl fluorescence), inhibition of electron transport, perturbation of thylakoid membrane fluidity, and consequent decline in photophosphorylation and CO 2 assimilation

Effects of a simulated heat wave on photophysiology and gene expression of high- and low-latitude populations of Zostera marina

“…chaperones and antioxidants. Photosynthesis is among the first processes to be affected by elevated temperatures (Sharkey 2005), with photosystem II (PSII) and its components shown to be particularly sensitive to thermal stress (Havaux 1993, Dutta et al 2009). Thus, photophysiological measurements have become an important tool in studying thermal stress in plants in general (Larcher 1994) and in marine primary producers in particular (Masini & Manning 1997, Ralph et al 1998, Campbell et al 2006.…”

Alterations in Chlorophyll a Fluorescence and Pigments Concentration in the Leaves of Cauliflower and Broccoli Transplants Subjected to Chilling

“…Exposure to low temperature may lead to overproduction of ROS, affects cellular components through damage to nucleic acids, protein oxidation, and lipid peroxidation (Sharma et al, 2012), ultimately results in oxidative stress, often requiring the involvement of several antioxidant enzymes or lowmolecular antioxidants (Turan and Ekmekci, 2011). Excessive 18 fluorescence parameters which was frequently reported and widely discussed (Strauss et al, 2006;Dutta et al, 2009, Oliveira et al, 2009Gorbe and Calatayud, 2012;Guidi and Degl'Innocenti, 2012). The Fv/Fm value is a measure of the maximum efficiency of PSII.…”

“…Low temperature slows down the metabolism of the transplants, impairing the biosynthesis of main photosynthetic pigments as well as chloroplast development (Yadegari et al, 2007;Dutta et al, 2009). Plants subjected to low-temperature conditions may optimize their photosynthetic apparatus, since the activity of the enzymes of the main metabolic pathways is significantly down-regulated.…”

Phylogenetic analysis and photoregulation of siroheme biosynthesis genes: uroporphyrinogen III methyltransferase and sirohydrochlorin ferrochelatase of Arabidopsis thaliana

“…Semiquantitative RT-PCR was performed as described by Dutta et al (2009). Actin was used as internal control.…”