Chloroplast biogenesis at cold-hardening temperatures. Development of photosystem I and photosystem II activities in relation to pigment accumulation

Abstract

Chloroplast biogenesis during continuous illumination at either low, cold-hardening temperatures (5°C) or non-hardening temperatures (20°C) was examined by monitoring the etioplast-chloroplast transformation with respect to pigment accumulation and the development of PSI- and PSII-associated electron transport activities in winter rye (Secale cereale L. cv Puma). Generally, chlorophyll and carotenoid accumulation during greening at 20°C were characterized by rapid initial rates in contrast to pronounced, initial lag times during biogenesis at 5°C. Although greening temperature had no effect on the sequential appearance of PSI relative to PSII, greening temperature significantly altered the pattern of appearance of PSI relative to chlorophyll accumulation. Thylakoid biogenesis under continuous illumination at 20°C imposed a pattern whereby the development of PSI activity was antiparallel to chlorophyll accumulation. In contrast, the development of PSI activity under continuous illumination at 5°C was paralllel to chlorophylll accumulation. These developmental patterns were independent of the temperature experienced during etiolation. However, rye seedlings etiolated at 20°C and subsequently subjected to continuous illumination at 5°C exhibited a 70% reduction in the maximum PSII activity (100 μmol DCPIP reduced.mg Chl(-1).h(-1)) attained relative to that observed for similar etiolated seedlings greened at 20°C (300 μmol DCPIP reduced.mg Chl(-1).h(-1)). This low temperature-induced inhibition could be alleviated by an initial 2 h exposure to continuous light at 20°C prior to greening to 5°C. Rye seedlings etiolated at 5°C attained similar maximal PSII activities (300 μmol DCPIP reduced.mg Chl(-1).h(-1)) regardless of the greening temperature. We suggest that the altered kinetics for pigment accumulation, the low temperature-induced change in the pattern for the appearance of PSI activity relative to chlorophyll accumulation and the differential sensitivity of 20° and 5° etiolated seedlings to greening temperature reflect an alteration in membrane organization incurred as a consequence of thylakoid assembly at low temperature.

Photosynthetic Redox Imbalance Governs Leaf Sectoring in theArabidopsis thalianaVariegation Mutantsimmutans,spotty,var1, andvar2

“…First, although greening at low irradiance indicated minimal differences in chloroplast biogenesis based on the disappearance of PORA and the appearance of Lhcb2 in the wild type and im (Figure 9C), the accumulation of Lhcb2, PsaB, and PsbA were delayed and the relative abundance of these thylakoid proteins was reduced in im cotyledons relative to the wild type during greening at 150 mmol photons m 22 s 21 ( Figure 9C; see Supplemental Figure 5 online). Furthermore, the observed kinetics for the disappearance of PORA and the appearance of PsaB, PsbA, and and Lhcb2 during the greening of wild-type Arabidopsis cotyledons are consistent with those published for chloroplast biogenesis in other photoautotrophs (Krol et al, 1987;Biswal et al, 2003;Philippar et al, 2007;Sakamoto et al, 2008).…”

Overwintering Periwinkle (Vinca minor L.) Exhibits Increased Photosystem I Activity

“…Thus, the increased capacity for PSI electron transport under cold-hardening conditions appears to be a general phenomenon observed under natural and controlled environment conditions. Krol et al (9) recently suggested that the increased PSI activity observed after growth of winter rye, an annual, at cold-hardening conditions was a consequence of thylakoid biogenesis at low temperature. Although periwinkle thylakoids exhibit a twofold increase in PSI activity upon exposure to winter conditions, the overwintering leaves had developed and become fully expanded during the warm spring and summer months.…”

“…They suggested that this altered assembly pattern at 5°C results in a change in the organization of PSI which, in turn gives rise to the increased capacity for PSI electron transport (9). In contrast, the pattern for development of PSII electron transport was similar at both 5 and 20°C (9). Low temperature growth did not affect the apparent quantum efficiencies of whole chain, PSI, or PSII electron transport (7).…”

“…Krol et al (9) reported that the assembly pattern for PSI during rye chloroplast biogenesis at 5°C was distinct from the assembly pattern for PSI during chloroplast biogenesis at 20C. They suggested that this altered assembly pattern at 5°C results in a change in the organization of PSI which, in turn gives rise to the increased capacity for PSI electron transport (9).…”

“…Thus, an increased capacity to process electrons through PSI may be a general characteristic of cold-tolerant plant species grown at low, nonfreezing temperatures under control environment conditions. In winter rye, this low temperature-induced increase in PSI activity has been shown to occur with no change in the following thylakoid characteristics: Chl/P700 (6,9), Chl a/b, CPl/CPa, Chl/lipid, Chl/protein, lipid/protein (8)(9)(10), polypeptide and lipid complements (8,10). The only compositional change observed in isolated thylakoids from low temperature-grown rye was a 72% decrease in the trans-16:1 content of PG (8).…”