Elucidating the biosynthesis of 2-carboxyarabinitol 1-phosphate through reduced expression of chloroplastic fructose 1,6-bisphosphate phosphatase and radiotracer studies with ¹⁴ CO ₂

Abstract

2-Carboxyarabinitol 1-phosphate limits photosynthetic CO2 assimilation at low light because it is a potent, naturally occurring inhibitor of ribulose 1,5-bisphosphate carboxylase͞oxygenase. Evidence is presented that this inhibitor is derived from chloroplastic fructose 1,6-bisphosphate. First, transgenic plants containing decreased amounts of chloroplastic fructose 1,6-bisphosphate phosphatase contained increased amounts of fructose 1,6-bisphosphate and 2-carboxyarabinitol 1-phosphate and greatly increased amounts of the putative intermediates hamamelose and 2-carboxyarabinitol, which in some cases were as abundant as sucrose. Second, French bean leaves in the light were shown to incorporate 14 C from 14 CO2 sequentially into fructose 1,6-bisphosphate, hamamelose bisphosphate, hamamelose monophosphate, hamamelose, and 2-carboxyarabinitol. As shown previously, 14 C assimilated by photosynthesis was also incorporated into 2-carboxyarabinitol 1-phosphate during subsequent darkness.

Elevated CO₂ and temperature differentially affect photosynthesis and resource allocation in flag and penultimate leaves of wheat

“…Decreases in the specific activity of RuBPCO previously observed under similar environmental conditions have been attributed to the presence in wheat and other plants of a day-time inhibitor(s) (Keys et al 1995, Parry et al 1997). An accumulation of precursor metabolites could increase the contents of the RuBPCO inhibitor (Andralojc et al 2002). We have previously found that EC increases, and ET decreases, the contents of metabolites, which also decrease as leaves age .…”

Down-regulation of Rubisco activity under combined increases of CO2 and temperature minimized by changes in Rubisco kcat in wheat

“…It has been speculated that the inhibitor may be formed non-enzymatically from RuBP in the chloroplast, given its favourable conditions for this process (Kane et al 1998). In this case, the levels of the inhibitor could increase in response to an accumulation of precursor metabolites, Plant Growth Regul (2011) 65:439-447 445 as reported for the nocturnal inhibitor of Rubisco, carboxyarabinitol 1-phosphate (Andralojc et al 2002). Consistent with this, we have found that elevated CO 2 increased the levels of carbohydrates and, possibly, of phosphorylated metabolites .…”

Discoveries in Rubisco (Ribulose 1,5-bisphosphate carboxylase/oxygenase): a historical perspective

“…Using classic radio-tracer studies and the analysis of transgenic plants with decreased chloroplastic fructose 1,6-bisphosphate phosphatase expression, Andralojc et al (2002) confirm the biosynthetic pathway for CA1P from newly assimilated carbon. Sage (2002) provides an insightful review of the current understanding of Rubisco control over C 3 and C 4 photosynthesis at different temperature and CO 2 conditions and documents how Rubisco kinetic properties evolved to improve performance in the environment that the plants normally experience.…”