Xanthophyll cycle, light energy dissipation and electron transport in transgenic tobacco with reduced carbon assimilation capacity

2000 ◽  
Vol 27 (4) ◽  
pp. 289 ◽  
Author(s):  
Sari A. Ruuska ◽  
Susanne von Caemmerer ◽  
Murray R. Badger ◽  
T. John Andrews ◽  
G. Dean Price ◽  
...  
Keyword(s):  
Electron Transport ◽  
Transgenic Tobacco ◽  
Xanthophyll Cycle ◽  
Co2 Assimilation ◽  
Light Energy ◽  
Pigment Composition ◽  
Wild Type ◽  
Xanthophyll Cycle Pigments ◽  
Leaf Pigment ◽  
Assimilation Capacity

The effects of reduced CO2 assimilation capacity on the leaf pigment composition and the dissipation of light energy were studied using transgenic tobacco (Nicotiana tabacum L. cv. W38). Two plant types were used: anti-SSu plants with reduced amounts of Rubisco and anti-GAPDH plants with reduced activity of chloroplast glycer-aldehyde 3-phosphate dehydrogenase. A moderate reduction in the photosynthetic capacity increased the de-epoxidation state of the xanthophyll-cycle pigments. In contrast, there was no large effect on the leaf pigment composition and the ratio of the xanthophyll cycle pigments to chlorophyll, and total carotenoids increased only in the most severe transgenic plants. The light induction of photosynthesis, fluorescence quenching and de-epoxida ion of the xanthophyll cycle pigments were also followed in wild-type and anti-SSu plants. Anti-SSu plants maintained high nonphotochemical quenching and increased xanthophyll de-epoxidation in the light but the reduction state of QA remained high. For both wild-type and anti-SSu plants, the electron transport rate estimated from chlorophyll a fluorescence appeared to be much higher than that required to support the observed rate of CO2 assimilation and photorespiration during the early phase of photosynthetic induction. However, the two estimates converged with the onset of steady-state photosynthesis.

Xanthophyll cycle, light energy dissipation and photosystem II down-regulation in senescent leaves of wheat plants grown in the field

2001 ◽  
Vol 28 (10) ◽  
pp. 1023 ◽  
Author(s):  
Congming Lu ◽  
Qingtao Lu ◽  
Jianhua Zhang ◽  
Qide Zhang ◽  
Tingyun Kuang
Keyword(s):  
Energy Dissipation ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Xanthophyll Cycle ◽  
Light Energy ◽  
Photochemical Quenching ◽  
Down Regulation ◽  
Psii Efficiency ◽  
Psii Photochemistry ◽  
Assimilation Capacity

Photosynthesis, the xanthophyll cycle, light energy dissipation and down-regulation of photosystem II (PSII) in senescent leaves of wheat plants grown in the field were investigated. With the progress of senescence, maximal efficiency of PSII photochemistry decreased only slightly early in the morning but substantially at midday. Actual PSII efficiency, photochemical quenching, efficiency of excitation capture by open PSII centres, and the I–P phase of fluorescence induction curves decreased significantly and such decreases were much more evident at midday than in the morning. At the same time, non-photochemical quenching, thermal dissipation and de-epoxidation status of the xanthophyll cycle increased, with much greater increases at midday than in the morning. These results suggest that the xanthophyll cycle played a role in photoprotection of PSII in senescent leaves by dissipating excess excitation energy. Taking into account the substantial decrease in photosynthetic capacity in senescent leaves, our data seem to support the view that the decrease in actual PSII efficiency in senescent leaves may represent a mechanism to down-regulate photosynthetic electron transport to match the decreased CO2 assimilation capacity and avoid photodamage of PSII from excess excitation energy.

Defensive strategies against high light stress in wild and D1 protein mutant biotypes of Erigeron canadensis

2000 ◽  
Vol 27 (4) ◽  
pp. 325 ◽  
Author(s):  
Éva Darkó ◽  
Gyula Váradi ◽  
Yves Lemoine ◽  
Endre Lehoczki
Keyword(s):  
Electron Transport ◽  
Xanthophyll Cycle ◽  
D1 Protein ◽  
High Light ◽  
Wild Type ◽  
Mutant Plant ◽  
Defensive Strategies ◽  
Erigeron Canadensis ◽  
Intact Leaves

The Ser264ÆGly substitution on the D1 protein is accompanied by a higher photosensitivity of the mutant plant. This may be due to an increased D1 protein turnover and/or to a lower xanthophyll cycle activity in vivo. The relative importance of these two photoprotective mechanisms in wild and D1 protein mutant biotypes of Erigeron canadensis L. was established by using dithiothreitol and streptomycin. Moreover, the interconversion of violaxan-thin to zeaxanthin via antheraxanthin was studied in isolated thylakoids and in intact leaves treated with paraquat. Streptomycin caused a more severe decrease in the optimal quantum yield (Fv/Fm) of PS II and a large increase in the initial fluorescence yield (Fo) in the mutant compared to the wild biotype. In the fluorescence-quenching parameters of the wild-type leaves, dithiothreitol caused alterations similar to those observed in the mutant plant without dithiothreitol. A lowered activity of the xanthophyll cycle was detected in the mutant biotype compared to the wild-type in vivo. However, under in vitro, conditions which were optimal for violaxanthin de-epoxidation, or when paraquat was used on intact leaves to accelerate the electron transport, violaxanthin could readily be converted to zeaxanthin even in the mutant plants. This demonstrates that neither the decrease in the enzymatic activity of violaxanthin de-epoxidase nor the low availability of violaxanthin is responsible for the low zeaxanthin formation under in vivo conditions. It is presumed that, in vivo, the D1 protein mutation results in slower electron transport, a smaller DpH and lower zeaxanthin formation, and thereby in alterations in the defensive strategies against high light illumination.

CO2 assimilation, xanthophyll cycle pigments and PSII efficiency in pumpkin plants as affected by ozone fumigation

1997 ◽  
Vol 101 (4) ◽  
pp. 881-889 ◽  
Author(s):  
Stefania Ciompi ◽  
Antonella Castagna ◽  
Annamaria Ranieri ◽  
Cristina Nali ◽  
Giacomo Lorenzini ◽  
...  
Keyword(s):  
Xanthophyll Cycle ◽  
Co2 Assimilation ◽  
Psii Efficiency ◽  
Xanthophyll Cycle Pigments

CO2 assimilation, xanthophyll cycle pigments and PSII efficiency in pumpkin plants as affected by ozone fumigation

1997 ◽  
Vol 101 (4) ◽  
pp. 881-889 ◽  
Author(s):  
Stefania Ciompi ◽  
Antonella Castagna ◽  
Annamaria Ranieri ◽  
Cristina Nali ◽  
Giacomo Lorenzini ◽  
...  
Keyword(s):  
Xanthophyll Cycle ◽  
Co2 Assimilation ◽  
Psii Efficiency ◽  
Xanthophyll Cycle Pigments

Photosynthesis is strongly reduced by antisense suppression of chloroplastic cytochrome bf complex in transgenic tobacco

1998 ◽  
Vol 25 (4) ◽  
pp. 445 ◽  
Author(s):  
G. Dean Price ◽  
Susanne von Caemmerer ◽  
John R. Evans ◽  
Katharina Siebke ◽  
Jan M. Anderson ◽  
...  
Keyword(s):  
Protein Content ◽  
Transgenic Tobacco ◽  
Co2 Assimilation ◽  
High Light ◽  
Cytochrome F ◽  
Assimilation Rate ◽  
Wild Type ◽  
Co2 Assimilation Rate ◽  
Cytochrome Bf Complex ◽  
Rieske Fes Protein

We have used transgenic tobacco (Nicotiana tabacum L. cv. W38) plants expressing an antisense gene directed against the transcript of the Rieske FeS protein of the chloroplast bf complex to examine the effect a reduction in chloroplast Rieske FeS content on leaf gas exchange and photosynthetic metabolite pools. Plants with chloroplast Rieske FeS protein content ranging from 5 to 80% of wild-type were analysed. CO2 assimilation rate declined linearly with the reduction in Rieske FeS content when expressed on a leaf area basis. In contrast to photosynthesis, there was no change in stomatal conductance except for plants with less than 10% of wild-type Rieske FeS content. There was a close correlation between Rieske FeS content and cytochrome f content, showing that the reduction in Rieske FeS content lead to a similar reduction in other components of the cytochrome bf complex. While lower Rieske FeS content was associated with declines in chlorophyll content, ATPδ subunit and ribulosebisphosphate carboxylase–oxygenase (Rubisco) contents, these declines were considerably smaller than the reduction in cytochrome bf content. As Rieske FeS content was reduced, there was a slight lowering of the chlorophyll a/b ratio. Lower CO2 assimilation rates at ambient CO2 and high light were associated with dramatic reductions in ribulose bisphosphate (RuBP) and modest declines in 3- phosphoglycerate (PGA). Rubisco carbamylation declined to 40–50% in plants with Rieske FeS content lower than 20% of wild-type. We conclude that, at high light, a reduction in chloroplast Rieske FeS protein content leads to inhibition of CO2 assimilation rate via reductions in the rate of RuBP regeneration caused by a restriction in electron transport and via effects on in vivo Rubisco activity.

The Relationship Between CO2 Transfer Conductance and Leaf Anatomy in Transgenic Tobacco With a Reduced Content of Rubisco

1994 ◽  
Vol 21 (4) ◽  
pp. 475 ◽  
Author(s):  
JR Evans ◽  
SV Caemmerer ◽  
BA Setchell ◽  
GS Hudson
Keyword(s):  
Gas Exchange ◽  
Leaf Area ◽  
Transgenic Tobacco ◽  
Surface Area ◽  
Leaf Anatomy ◽  
Co2 Assimilation ◽  
Wild Type ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Transfer Conductance

The CO2 transfer conductance in leaves quantifies the ease with which CO2 can diffuse from sub-stomatal cavities to sites of carboxylation within the chloroplast. The aim of this work was to test the hypothesis that the CO2 transfer conductance is proportional to the surface area of chloroplasts exposed to intercellular airspaces. We compared two genotypes, wild-type and transgenic tobacco, that had been transformed with an antisense gene directed at the mRNA of the Rubisco small subunit. Transgenic tobacco had lower rates of CO2 assimilation than wild-type but similar chlorophyll contents. Leaf anatomy was altered by growing plants in two different environments: a high daily irradiance in a growth cabinet (12 h photoperiod of 1 mmol quanta m-2 s-1) and a sunlit glasshouse. The growth cabinet gave at least twice the daily irradiance compared to the glasshouse. The CO2 transfer conductance was calculated from combined measurements of gas exchange and carbon isotope discrimination measured in 2% oxygen. Following gas exchange measurement, leaves were sampled for biochemical and anatomical measure- ment. In transgenic tobacco plants, Rubisco content was 35% of that found in the wild-type tobacco, the CO2 assimilation rate was 50% of the wild-type rate and the chlorophyll content was unaltered. While leaf mass per unit leaf area of transgenic tobacco was 82% of that of the wild-type, differences in leaf thickness and surface area of mesophyll cells exposed to intercellular airspace per unit leaf area (Smes) were small (92 and 87% of wild-type, respectively). Leaves grown in the growth cabinet under high daily irradiance were thicker (63%), had a greater Smes (41%) due to the development of thicker palisade tissue, had higher photosynthetic capacity (27%) and contained more chlorophyll (58%) and Rubisco (77%), than leaves from plants grown in the glasshouse. Irrespective of genotype or growth environment, CO2 transfer conductance varied in proportion to surface area of chloroplasts exposed to intercellular airspaces. While the method for calculating CO2 transfer conductance could not distinguish between limitations due to the gas or liquid phases, there was no reduction in CO2 transfer conductance associated with more closely packed cells, thicker leaves, nor with increasing chloroplast thickness in tobacco.

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