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The rise of the photosynthetic rate when light intensity increases is delayed in ndh gene-defective tobacco at high but not at low CO2 concentrations.

Martín M, Noarbe DM, Serrot PH, Sabater B - Front Plant Sci (2015)

Bottom Line: We have compared the photosynthetic activity of tobacco (Nicotiana tabacum, cv.Petit Havana) with five transgenic lines (ΔndhF, pr-ΔndhF, T181D, T181A, and ndhF FC) and found that photosynthetic performance is impaired in transgenic ndhF-defective tobacco plants at rapidly fluctuating light intensities and higher than ambient CO2 concentrations.Hence, ndh genes could be dispensable at low but not at high atmospheric concentrations of CO2.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, University of Alcalá, Alcalá de Henares Spain.

ABSTRACT
The 11 plastid ndh genes have hovered frequently on the edge of dispensability, being absent in the plastid DNA of many algae and certain higher plants. We have compared the photosynthetic activity of tobacco (Nicotiana tabacum, cv. Petit Havana) with five transgenic lines (ΔndhF, pr-ΔndhF, T181D, T181A, and ndhF FC) and found that photosynthetic performance is impaired in transgenic ndhF-defective tobacco plants at rapidly fluctuating light intensities and higher than ambient CO2 concentrations. In contrast to wild type and ndhF FC, which reach the maximum photosynthetic rate in less than 1 min when light intensity suddenly increases, ndh defective plants (ΔndhF and T181A) show up to a 5 min delay in reaching the maximum photosynthetic rate at CO2 concentrations higher than the ambient 360 ppm. Net photosynthesis was determined at different CO2 concentrations when sequences of 130, 870, 61, 870, and 130 μmol m(-2) s(-1) PAR sudden light changes were applied to leaves and photosynthetic efficiency and entropy production (Sg) were determined as indicators of photosynthesis performance. The two ndh-defective plants, ΔndhF and T181A, had lower photosynthetic efficiency and higher Sg than wt, ndhF FC and T181D tobacco plants, containing full functional ndh genes, at CO2 concentrations above 400 ppm. We propose that the Ndh complex improves cyclic electron transport by adjusting the redox level of transporters during the low light intensity stage. In ndhF-defective strains, the supply of electrons through the Ndh complex fails, transporters remain over-oxidized (specially at high CO2 concentrations) and the rate of cyclic electron transport is low, impairing the ATP level required to rapidly reach high CO2 fixation rates in the following high light phase. Hence, ndh genes could be dispensable at low but not at high atmospheric concentrations of CO2.

No MeSH data available.


Related in: MedlinePlus

Genetic identification and fluorescence properties of pr-ΔndhF tobacco. (A) PCR amplification products of plastid DNAs of wt, pr-ΔndhF, and ΔndhF tobacco plants using primers F2/F4 (Serrot et al., 2012) for the ndhF gene sequence (bottom map). Sizes of the main amplified fragments and of some markers are indicated on the left and right, respectively. (B) Chlorophyll fluorescence traces of wt, pr-ΔndhF, and ΔndhF tobacco plants after relative high to minimum light transition. Assays were performed with intact tobacco leaves as described Martín et al. (2009). The traces shown are of fluorescence readings every 0.1 s during the final 9 min of minimum light. Vertical axes show the relative fluorescence readings.
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Figure 1: Genetic identification and fluorescence properties of pr-ΔndhF tobacco. (A) PCR amplification products of plastid DNAs of wt, pr-ΔndhF, and ΔndhF tobacco plants using primers F2/F4 (Serrot et al., 2012) for the ndhF gene sequence (bottom map). Sizes of the main amplified fragments and of some markers are indicated on the left and right, respectively. (B) Chlorophyll fluorescence traces of wt, pr-ΔndhF, and ΔndhF tobacco plants after relative high to minimum light transition. Assays were performed with intact tobacco leaves as described Martín et al. (2009). The traces shown are of fluorescence readings every 0.1 s during the final 9 min of minimum light. Vertical axes show the relative fluorescence readings.

Mentions: In addition to previously described wt, ndhF FC, ΔndhF, T181A, and T181D tobacco plants (Martín et al., 2009), we assayed partially reverted phenotypes of ΔndhF (pr-ΔndhF) that we have found among descendants of the ndh-deficient ΔndhF tobacco transgenic, as identified by the increase of the 515 bp PCR-amplified band (Figure 1A, lane pr-ΔndhF) characteristic (Martín et al., 2004; Zapata et al., 2005) of the non-transformed plastid DNA of wt (Figure 1A, lane wt). The relative intensities of the amplified 1,928 and 515 bp bands should approximate and respectively mirror the relative abundance of transformed (ΔndhF) and non-transformed (wt) plastid DNA molecules among the 100s of DNA copies contained in a single mesophyll cell. The presumably low proportion of the functional ndhF gene in pr-ΔndhF only slightly permitted the recovery of the clear post-illumination fluorescence increase characteristic of wt (Figure 1B) that is absent in ndh deficient plants (Burrows et al., 1998; Martín et al., 2004). Accordingly, pr-ΔndhF phenotypes showed a thylakoid Ndh-dependent NADH dehydrogenase activity which was lower than in wt but higher than in ΔndhF transgenic (not shown). In contrast to the clearly delayed leaf senescence phenotype of ΔndhF (Zapata et al., 2005), pr-ΔndhF showed only slight delayed leaf senescence in comparison to wt tobacco (Figure S1). The frequency of pr-ΔndhF phenotype is increasing in successive offspring derived from the original ΔndhF tobacco (despite the presence of spectinomycin during the initial culture of ΔndhF). Conceivably, unknown factors favor the replication of the few remaining copies of wt plastid DNA in ΔndhF tobacco over the transformed molecules defective in the ndhF gene. Although we are not yet able to control its emergence or its inheritance, the finding of pr-ΔndhF phenotype provides an additional retro-mutant control that confirms the involvement of ndh genes in photosynthesis and other processes. In the future, the ability to control (and determine by quantitative PCR) the wt to ΔndhF plastid DNA ratio will provide a deeper understanding of the influence of the copy proportion of the plastid ndh gene in different processes.


The rise of the photosynthetic rate when light intensity increases is delayed in ndh gene-defective tobacco at high but not at low CO2 concentrations.

Martín M, Noarbe DM, Serrot PH, Sabater B - Front Plant Sci (2015)

Genetic identification and fluorescence properties of pr-ΔndhF tobacco. (A) PCR amplification products of plastid DNAs of wt, pr-ΔndhF, and ΔndhF tobacco plants using primers F2/F4 (Serrot et al., 2012) for the ndhF gene sequence (bottom map). Sizes of the main amplified fragments and of some markers are indicated on the left and right, respectively. (B) Chlorophyll fluorescence traces of wt, pr-ΔndhF, and ΔndhF tobacco plants after relative high to minimum light transition. Assays were performed with intact tobacco leaves as described Martín et al. (2009). The traces shown are of fluorescence readings every 0.1 s during the final 9 min of minimum light. Vertical axes show the relative fluorescence readings.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4321573&req=5

Figure 1: Genetic identification and fluorescence properties of pr-ΔndhF tobacco. (A) PCR amplification products of plastid DNAs of wt, pr-ΔndhF, and ΔndhF tobacco plants using primers F2/F4 (Serrot et al., 2012) for the ndhF gene sequence (bottom map). Sizes of the main amplified fragments and of some markers are indicated on the left and right, respectively. (B) Chlorophyll fluorescence traces of wt, pr-ΔndhF, and ΔndhF tobacco plants after relative high to minimum light transition. Assays were performed with intact tobacco leaves as described Martín et al. (2009). The traces shown are of fluorescence readings every 0.1 s during the final 9 min of minimum light. Vertical axes show the relative fluorescence readings.
Mentions: In addition to previously described wt, ndhF FC, ΔndhF, T181A, and T181D tobacco plants (Martín et al., 2009), we assayed partially reverted phenotypes of ΔndhF (pr-ΔndhF) that we have found among descendants of the ndh-deficient ΔndhF tobacco transgenic, as identified by the increase of the 515 bp PCR-amplified band (Figure 1A, lane pr-ΔndhF) characteristic (Martín et al., 2004; Zapata et al., 2005) of the non-transformed plastid DNA of wt (Figure 1A, lane wt). The relative intensities of the amplified 1,928 and 515 bp bands should approximate and respectively mirror the relative abundance of transformed (ΔndhF) and non-transformed (wt) plastid DNA molecules among the 100s of DNA copies contained in a single mesophyll cell. The presumably low proportion of the functional ndhF gene in pr-ΔndhF only slightly permitted the recovery of the clear post-illumination fluorescence increase characteristic of wt (Figure 1B) that is absent in ndh deficient plants (Burrows et al., 1998; Martín et al., 2004). Accordingly, pr-ΔndhF phenotypes showed a thylakoid Ndh-dependent NADH dehydrogenase activity which was lower than in wt but higher than in ΔndhF transgenic (not shown). In contrast to the clearly delayed leaf senescence phenotype of ΔndhF (Zapata et al., 2005), pr-ΔndhF showed only slight delayed leaf senescence in comparison to wt tobacco (Figure S1). The frequency of pr-ΔndhF phenotype is increasing in successive offspring derived from the original ΔndhF tobacco (despite the presence of spectinomycin during the initial culture of ΔndhF). Conceivably, unknown factors favor the replication of the few remaining copies of wt plastid DNA in ΔndhF tobacco over the transformed molecules defective in the ndhF gene. Although we are not yet able to control its emergence or its inheritance, the finding of pr-ΔndhF phenotype provides an additional retro-mutant control that confirms the involvement of ndh genes in photosynthesis and other processes. In the future, the ability to control (and determine by quantitative PCR) the wt to ΔndhF plastid DNA ratio will provide a deeper understanding of the influence of the copy proportion of the plastid ndh gene in different processes.

Bottom Line: We have compared the photosynthetic activity of tobacco (Nicotiana tabacum, cv.Petit Havana) with five transgenic lines (ΔndhF, pr-ΔndhF, T181D, T181A, and ndhF FC) and found that photosynthetic performance is impaired in transgenic ndhF-defective tobacco plants at rapidly fluctuating light intensities and higher than ambient CO2 concentrations.Hence, ndh genes could be dispensable at low but not at high atmospheric concentrations of CO2.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, University of Alcalá, Alcalá de Henares Spain.

ABSTRACT
The 11 plastid ndh genes have hovered frequently on the edge of dispensability, being absent in the plastid DNA of many algae and certain higher plants. We have compared the photosynthetic activity of tobacco (Nicotiana tabacum, cv. Petit Havana) with five transgenic lines (ΔndhF, pr-ΔndhF, T181D, T181A, and ndhF FC) and found that photosynthetic performance is impaired in transgenic ndhF-defective tobacco plants at rapidly fluctuating light intensities and higher than ambient CO2 concentrations. In contrast to wild type and ndhF FC, which reach the maximum photosynthetic rate in less than 1 min when light intensity suddenly increases, ndh defective plants (ΔndhF and T181A) show up to a 5 min delay in reaching the maximum photosynthetic rate at CO2 concentrations higher than the ambient 360 ppm. Net photosynthesis was determined at different CO2 concentrations when sequences of 130, 870, 61, 870, and 130 μmol m(-2) s(-1) PAR sudden light changes were applied to leaves and photosynthetic efficiency and entropy production (Sg) were determined as indicators of photosynthesis performance. The two ndh-defective plants, ΔndhF and T181A, had lower photosynthetic efficiency and higher Sg than wt, ndhF FC and T181D tobacco plants, containing full functional ndh genes, at CO2 concentrations above 400 ppm. We propose that the Ndh complex improves cyclic electron transport by adjusting the redox level of transporters during the low light intensity stage. In ndhF-defective strains, the supply of electrons through the Ndh complex fails, transporters remain over-oxidized (specially at high CO2 concentrations) and the rate of cyclic electron transport is low, impairing the ATP level required to rapidly reach high CO2 fixation rates in the following high light phase. Hence, ndh genes could be dispensable at low but not at high atmospheric concentrations of CO2.

No MeSH data available.


Related in: MedlinePlus