The relative abundance of wheat Rubisco activase isoforms is post-transcriptionally regulated

Abstract

Diurnal rhythms and light availability affect transcription–translation feedback loops that regulate the synthesis of photosynthetic proteins. The CO2-fixing enzyme Rubisco is the most abundant protein in the leaves of major crop species and its activity depends on interaction with the molecular chaperone Rubisco activase (Rca). In Triticum aestivum L. (wheat), three Rca isoforms are present that differ in their regulatory properties. Here, we tested the hypothesis that the relative abundance of the redox-sensitive and redox-insensitive Rca isoforms could be differentially regulated throughout light–dark diel cycle in wheat. While TaRca1-β expression was consistently negligible throughout the day, transcript levels of both TaRca2-β and TaRca2-α were higher and increased at the start of the day, with peak levels occurring at the middle of the photoperiod. Abundance of TaRca-β protein was maximal 1.5 h after the peak in TaRca2-β expression, but the abundance of TaRca-α remained constant during the entire photoperiod. The redox-sensitive TaRca-α isoform was less abundant, representing 85% of the redox-insensitive TaRca-β at the transcript level and 12.5% at the protein level. Expression of Rubisco large and small subunit genes did not show a consistent pattern throughout the diel cycle, but the abundance of Rubisco decreased by up to 20% during the dark period in fully expanded wheat leaves. These results, combined with a lack of correlation between transcript and protein abundance for both Rca isoforms and Rubisco throughout the entire diel cycle, suggest that the abundance of these photosynthetic enzymes is post-transcriptionally regulated.

Temperature-induced changes in Arabidopsis Rubisco activity and isoform expression

“…protein turnover) events, and availability of the SSu ( Berry et al , 1985 , 1986 ; Deng and Gruissem, 1987 ; Shirley and Meagher, 1990 ; Suzuki and Makino, 2012 ; Hanson et al , 2021 ). Recent work demonstrated that the expression of both rbcL and RbcS did not match the diel pattern of Rubisco protein abundance in wheat, supporting the importance of post-transcriptional regulation in Rubisco production ( Perdomo et al , 2021 ). Supporting this, we found that cold-grown Arabidopsis plants produce more Rubisco than 20 °C-grown plants ( Table 1 ), but the total RbcS mRNA does not increase accordingly ( Fig.…”

Turning the Knobs: The Impact of Post-translational Modifications on Carbon Metabolism

“…The Fd/Trx system reduces Rca disulfide bridges, resulting in increased Rca activity ( Zhang and Portis, 1999 ). Activated Rca continuously remodels inhibited active sites of Rubisco by removing inhibitory RuBP to enhance photosynthetic activity ( Carmo-Silva et al, 2015 ; Perdomo et al, 2021 ; Figure 2 ). Moreover, Rca dark-dependent inactivation is putatively regulated by Thr78 and Ser172 phosphorylation ( Boex-Fontvieille et al, 2014 ).…”

Comparative transcriptomics and bioinformatics analysis of genes related to photosynthesis in Eucalyptus camaldulensis

“…Studies showed that limiting carboxylation and regeneration of ribulose 1, 5-bisphosphate (RUBP) could reduce the content and activity of ribulose 1, 5-bisphosphate carboxylation/oxygenase (Rubisco), down-regulate the expression levels of Rubisco proteins RBCL and RBCS, and thus reduced the photosynthetic rate of plants, and caused the imbalance of material and energy metabolism in plants ( Dizengremel, 2001 ; Pellegrini et al, 2017 ). Rubsico activase (RCA) was responsible for the activation of Rubisco in leaves, and Rubisco could show its carboxylation/oxygenation activity only after activation, the activity of Rubisco in plants was therefore dependent on the activation of RCA ( Perdomo, Buchner & Carmo-Silva, 2021 ). In addition, other genes related to photosynthesis were less reported.…”