Rubisco Activity: Effects of Drought Stress

Abstract

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity is modulated in vivo either by reaction with CO2 and Mg2+ to carbamylate a lysine residue in the catalytic site, or by the binding of inhibitors within the catalytic site. Binding of inhibitors blocks either activity or the carbamylation of the lysine residue that is essential for activity. At night, in many species, 2-carboxyarabinitol-1-phosphate (CA1P) is formed which binds tightly to Rubisco, inhibiting catalytic activity. Recent work has shown that tight-binding inhibitors can also decrease Rubisco activity in the light and contribute to the regulation of Rubisco activity. Here we determine the influence that such inhibitors of Rubisco exert on catalytic activity during drought stress. In tobacco plants, 'total Rubisco activity', i.e. the activity following pre-incubation with CO2 and Mg2+, was positively correlated with leaf relative water content. However, 'total Rubisco activity' in extracts from leaves with low water potential increased markedly when tightly bound inhibitors were removed, thus increasing the number of catalytic sites available. This suggests that in tobacco the decrease of Rubisco activity under drought stress is not primarily the result of changes in activation by CO2 and Mg2+ but due rather to the presence of tight-binding inhibitors. The amounts of inhibitor present in leaves of droughted tobacco based on the decrease in Rubisco activity per mg soluble protein were usually much greater than the amounts of the known inhibitors (CA1P and 'daytime inhibitor') that can be recovered in acid extracts. Alternative explanations for the difference between maximal and total activities are discussed.

Restrição fotossintética de plantas de soja sob variação de disponibilidade hídrica

“…A fluorescência da clorofila é considerada uma ferramenta para determinação de estresse em plantas, pois indica que a energia da radiação solar não está sendo utilizada de forma eficiente (MAXWELL & (BERTOLLI et al, 2012). Ainda, a recuperação limitada da taxa de fotossíntese líquida em soja, submetida à indução lenta e rápida de déficit hídrico, após reidratação, provavelmente, foi causada por fatores bioquímicos (BERTOLLI et al, 2012), tais como decréscimo na síntese de RuBP (BOTA et al, 2004) e na atividade da Rubisco (PARRY et al, 2002).…”

Proteomics Analysis of Drought Stress-Responsive Proteins in Hippophae rhamnoides L.

“…It is well-known that drought can cause the decrease on synthesis of rubisco (Vu et al 1999) and a loss of rubisco activity (Parry et al 2002;Chaitanya et al 2003), and the decline in the rubisco activity is mainly due to the proteolysis of the large subunit (Hajheidari et al 2005;Jorge et al 2006). However, in agreement with our findings, Rizhsky et al (2002) reported that drought greatly increases the number of transcripts encoding the large subunit of rubisco in tobacco and suggested that the large subunit of rubisco, as a protein of the PSI reaction center, may take part in the cyclic electron flow pathway through which some energy can dissipate during stress (Rizhsky et al 2002).…”

Leaf recovery responses during rehydration after water deficit in two bean (Phaseolus vulgarisL.) cultivars

“…During WD, the reduction of photosynthesis has been attributed to reduction of Rubisco activity due to a decrease of Rubisco activase, the energy component of photosynthesis, RuBP regeneration, and severe conditions in the chloroplasts and reactive oxygen species (ROS) generation under limited supply of CO 2 (Lawlor & Tezara 2009). Rubisco activity reduction has generally been found under severe WD (Maroco et al 2002;Parry et al 2002;Flexas et al 2006). Alterations in both stomatal and non-stomatal limitations have been shown during WD periods and rewatering (Costa Franca et al 2000;Singer et al 2003;Efeoglu et al 2009).…”