Translational downregulation of RBCL is operative in the coordinated expression of Rubisco genes in senescent leaves in rice

Abstract

Rubisco gene expression was examined in detail in rice (Oryza sativa L.) leaves at different positions, i.e. expanding, mature, and senescent leaves. Rubisco small subunit (RBCS) synthesis and RBCS mRNA levels were maximal in expanding leaves and gradually became lower in mature and senescent leaves, with declines in those of the large subunit (RBCL) being relatively slower. The amount of synthesized RBCL per unit level of RBCL mRNA and polysome loading of RBCL mRNA declined in senescent leaves, whereas such phenomena were not observed for RBCS. These results suggested that gene expression of RBCL is downregulated at the level of its translation when a balance between RBCL and RBCS expression is disturbed by leaf senescence. It has been suggested that RBCS protein is a positive regulator for RBCL mRNA level in expanding rice leaves, as judged from their stoichiometric relationship in RBCS transgenic rice plants. However, the ratio of the RBCL mRNA level to the amount of synthesized RBCS in senescent leaves was significantly higher than that in expanding leaves. Therefore, it is suggested that the decline in RBCL mRNA level in senescent leaves is not fully accounted for by that in the amount of synthesized RBCS. Effects of other factors such as the stability of RBCL mRNA may come into play.

Expression of an Engineered Heterologous Antimicrobial Peptide in Potato Alters Plant Development and Mitigates Normal Abiotic and Biotic Responses

“…We therefore quantified changes in the expression of a medley of gene transcripts in the leaves of the WT and the two msrA3- transgenic lines including anti-senescence gene marker (large subunit of Rubisco which promotes growth) [70-72] versus pro-senescence gene markers [ senescence associated gene 12 ( sag12 ) and glutamine synthetase-1 ( gs-1 )] [73]. To that end, expression of genes not only associated with senescence [( sag12 ) , γ - vacuolar processing enzyme (vpe), ( gs-1 )] and carbon fixation [ rubisco large subunit ( rbcL )] but also those associated with oxidative stress [ ascorbate peroxidese ( apx ) , catalase (cat) , Cu/Zn superoxide dismutase (sod)] and HR [ pathogenesis-related protein ( pr-1 ) , osmotin (osm) , longevity assurance gene1 ( lag1 )] were analyzed by northern analysis of RNA from leaves exposed to dark induced senescence (Figure 2c).…”

Effects of Overproduction of Rubisco Activase on Rubisco Content in Transgenic Rice Grown at Different N Levels

“…This assembly-dependent translational regulation mechanism is termed control by epistasy of synthesis (CES) [48]. In our previous studies of rice plants [49,50], the amount of RBCL loading on polysomes was decreased in senescent leaves, although regulation at the transcription level principally controls RBCL protein synthesis. This suggests that CES regulation is also effective in controlling RBCL synthesis in a senescent rice leaf.…”

New insights into the impacts of elevated CO2, nitrogen, and temperature levels on the regulation of C and N metabolism in durum wheat using network analysis

“…Transcript levels for RCA were closely correlated with transcript levels for enzymes involved in Calvin-Benson cycle and photorespiration. Rubisco catalyzes the first and key step of both pathways [38]. Therefore, the activation of Rubisco by RCA could play a significant role, with a special emphasis on future climate conditions, due to the observed changes in RCA expression reported under heat stress [37].…”