Cold-hardening results in increased activity of enzymes involved in carbon metabolism in leaves of winter rye (Secale cereale L.)

Abstract

Abstract. Light-and CO2-saturated photosynthesis of nonhardened rye (Secale cereale L. cv. Musketeer) was reduced from 18.10 to 7.17 lamol O2-m 2.s i when leaves were transferred from 20 to 5~ for 30 min. Following cold-hardening at 5~ for ten weeks, photosynthesis recovered to 15.05 ~tmol O2.m 2.s 1, comparable to the nonhardened rate at 20~ Recovery of photosynthesis was associated with increases in the total activity and activation of enzymes of the photosynthetic carbon-reduction cycle and of sucrose synthesis. The total hexose-phosphate pool increase by 30% and 120% for nonhardened and cold-hardened leaves respectively when measured at 5~ The large increase in esterified phosphate in coldhardened leaves occurred without a limitation in inorganic phosphate supply. In contrast, the much smaller increase in esterified phosphate in nonhardened leaves was associated with an inhibition of ribulose-l,5-bisphosphate carboxylase/oxygenase and sucrose-phosphate synthase activation. It is suggested that the large increases in hexose phosphates in cold-hardened leaves compensates for the higher substrate threshold concentrations needed for enzyme activation at low temperatures. High substrate concentrations could also compensate for the kinetic limitations imposed by product inhibition from the accumulation of sucrose at 5~ Nonhardened leaves appear to be unable to compensate in this fashion due to an inadequate supply of inorganic phosphate. Fru 1,6BP = fructose-1,6-bisphosphate; Fru 1,6BPase = fructose-1,6-bisphosphatase; Glc6P = glucose-6-phosphate; PGA=3-phosphoglycerate; PPFD=photosynthetic photon flux density; CH=cold-hardened rye grown at 5~ NH = nonhardened rye grown at 24~ Rubisco = ribulose-1,5-bisphosphate carboxylase/oxygenase; RuBP=ribulose-l,5-bisphosphate; SPS=sucrose-phosphate synthase; UDPGlc=uridine 5'-diphosphoglucose Correspondence to: V.M. Hurry; FAX: 61 (6) 2475896

Cold Hardening of Spring and Winter Wheat and Rape Results in Differential Effects on Growth, Carbon Metabolism, and Carbohydrate Content

“…In contrast to these responses, long-term (months) acclimation of herbaceous plants to low growth temperatures results not only in the accumulation of large pools of soluble carbohydrates (Tognetti et al, 1990;Sagisaka et al, 1991;Koster and Lynch, 1992) but also in the enhancement of pathways involved in photosynthetic carbon metabolism (Guy et al, 1992;Holaday et al, 1992;Hurry et al, 1994Hurry et al, , 1995a. The recovery of photosynthesis at low temperature is supported by increases in the activity of severa1 enzymes of the photosynthetic carbon reduction cycle (Holaday et al, 1992;Hurry et al, 1995a) and by increases in the capacity for RuBP regeneration and in the pool sizes of phosphorylated intermediates (Hurry et al, 1994(Hurry et al, , 1995a.…”

“…The recovery of photosynthesis at low temperature is supported by increases in the activity of severa1 enzymes of the photosynthetic carbon reduction cycle (Holaday et al, 1992;Hurry et al, 1995a) and by increases in the capacity for RuBP regeneration and in the pool sizes of phosphorylated intermediates (Hurry et al, 1994(Hurry et al, , 1995a. The increase in cellular Suc content during cold hardening also coincides with increases in the activity of cFru-1,6-BPase and SI ' S (Holaday et al, 1992;Hurry et al, 1995a) and in SPS protein content (Guy et al, 1992).…”

“…The recovery of photosynthesis at low temperature is supported by increases in the activity of severa1 enzymes of the photosynthetic carbon reduction cycle (Holaday et al, 1992;Hurry et al, 1995a) and by increases in the capacity for RuBP regeneration and in the pool sizes of phosphorylated intermediates (Hurry et al, 1994(Hurry et al, , 1995a. The increase in cellular Suc content during cold hardening also coincides with increases in the activity of cFru-1,6-BPase and SI ' S (Holaday et al, 1992;Hurry et al, 1995a) and in SPS protein content (Guy et al, 1992). Thus, during acclimation of cold-tolerant herbaceous plants to low temperature, the photosynthetic capacity that is normally lost during a shift to lower temperature is recovered, despite the accumulation of large, soluble carbohydrate pools (Hurry et al, 1994(Hurry et al, , 1995a.…”

Contrastive responses of spring and winter wheat cultivars to chilling and acclimation treatments

“…Nevertheless, and in contrast to 'Zagros', total soluble sugars rather increased in chilled 'Sabalan' leaves. It has been assumed that the accumulation of soluble carbohydrates during cold acclimation plays an important role in winter survival and probably results from the differential low-temperature sensitivity of the enzymes of starch and sucrose metabolism (Hurry et al, 1995). Table 2.…”

“…Cold acclimation of cereals results in an increase in photosynthetic capacity following increases in the activities of Rubisco and stromal and cytosolic fructose-1,6-bisphosphatase (Hurry et al, 1995). Winter wheat cultivars can be distinguished from spring cultivars by their ability to adjust their photosynthetic capacity upon cold acclimation which is associated with an increased resistance to photoinhibition (Savitch et al, 1997).…”