The biochemical and molecular basis for photosynthetic acclimation to elevated atmospheric CO₂

Abstract

There have been many recent exciting advances in our understanding of the cellular processes that underlie photosynthetic acclimation to rising atmospheric CO 2 concentration. Of particular interest have been the molecular processes that modulate photosynthetic gene expression in response to elevated CO 2 and the biochemical processes that link changes in atmospheric CO 2 concentration to the production of a metabolic signal. Central to this acclimation response is a reduction in ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) protein content. Studies indicate that this reduction results from species-dependent variation in the differential use and temporal control of molecular processes. We present a model for the control of Rubisco protein accumulation that emphasizes the role of subunit message translation as well as the abundance of subunit messages as components of the acclimation response. Many studies indicate that photosynthetic acclimation to elevated CO 2 results from adjustments in leaf carbohydrate signalling. The repression of photosynthetic gene expression is considered to occur primarily by hexokinase functioning as a hexose flux sensor that ultimately affects transcription. Leaf hexoses may be produced as potential sources of signals primarily by sucrose cycling and secondarily by starch hydrolysis. An increased rate of sucrose cycling is suggested to occur at elevated CO 2 by enhanced provision of sucrose to leaf acid invertases. Additionally, sink limitations that accentuate photosynthetic acclimation may result from a relative decrease in the export of leaf sucrose and subsequent increase in cellular sucrose levels and sucrose cycling.

Carbon balance, partitioning and photosynthetic acclimation in fruit-bearing grapevine (Vitis vinifera L. cv. Tempranillo) grown under simulated climate change (elevated CO2, elevated temperature and moderate drought) scenarios in temperature gradient greenhouses

“…There are two basic 14 mechanisms by which Rubisco down-regulation occurs. The first mechanism 15 hypothesizes that the reduction in Rubisco content occurs as a consequence of the leaf C 16 build-up (Moore et al, 1999;Aranjuelo et al, 2008;. According to this 17 theory, when plants exposed to elevated CO 2 have limitations for increasing C sink 18 strength, plants decrease their photosynthetic rates to balance C source activity and sink 19 capacity (Aranjuelo et al, 2008;.…”

Elevated CO2 and water-availability effect on gas exchange and nodule development in N2-fixing alfalfa plants

“…3A and B). Since there was no change in the enzyme activation state, our data revealed that the decreased initial and total Rubisco activity was the result of a depleted Rubisco protein content (Moore et al, 1999). The fact that WD plants exposed to elevated CO 2 had depleted Rubisco and TSP contents, and a larger TSS value suggests that those plants had problems to increase sink strength (reflected by the lack of CO 2 effect on DM production).…”

“…TSS data (Table 3) confirmed that plants exposed to elevated CO 2 , especially in WD plants, had a massive production and build-up of carbohydrates. Carbon sink/source imbalance induced photosynthetic acclimation caused by depletions in the expression of Calvin cycle enzymes (Moore et al, 1999;Stitt and Krapp, 1999;Aranjuelo et al, 2005b;Reich et al, 2006;Rogers et al, 2006). However, it should also be noted that all the enzymes involved in the photosynthetic processes may not be equally affected by enhanced CO 2 (Moore et al, 1999).…”

“…Carbon sink/source imbalance induced photosynthetic acclimation caused by depletions in the expression of Calvin cycle enzymes (Moore et al, 1999;Stitt and Krapp, 1999;Aranjuelo et al, 2005b;Reich et al, 2006;Rogers et al, 2006). However, it should also be noted that all the enzymes involved in the photosynthetic processes may not be equally affected by enhanced CO 2 (Moore et al, 1999). Nie et al (1995) observed that, although transcripts for Rubisco subunits and phosphoglycerate kinase are particularly sensitive to moderate increases in CO 2 , sedoheptulose-1,7-bisphosphatase (SBP) and phosphoribulosekinase (PRK) mRNAs are not.…”

Effects of Elevated CO2Concentration on Photosynthetic Carbon Metabolism in Flag-Leaf Blades of Rice before and after Heading

“…Rapid development of plant molecular techniques aided our understanding of the acclimatization of plants to elevated [C0 2 ] (Moore et al, 1999 Abbreviations: CA, carbonic anhydrase; [C0 2 J, CO 2 concentration; control leaves, flag-leaf blades of control plants; cFBP, cytosolic fructose-l,6-bisphosphatase; DAT, days after transplanting; high-C0 2 -grown leaves, flag-leaf blades of rice plants grown under elevated CO 2 concentration; P=probability level; rubisco, ribulose-l,5-bisphosphate carboxylase/oxygenase; SDS, sodium dodecyl sulfate; SLA, specific leaf area; SPS, sucrose-phosphate synthase; SSU, small subunit of ribulose-l,5-bisphosphate carboxylase/oxygenase; stems, culms and leaf sheaths.…”