The Fate of Chloroplast Proteins during Photooxidation in Carotenoid-Deficient Maize Leaves

Mayfield, Stephen P.; Nelson, Timothy; Taylor, William C.

doi:10.1104/pp.82.3.760

Cited by 45 publications

(26 citation statements)

References 27 publications

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“…At the same time, Rubisco activity per TSP content did not change significantly. The latter can be explained by indirect effects of NF on the en zyme: 10 -4 M NF solution did not affect Rubisco activity in vitro, which is in line with literature data (Mayfield et al 1986). …”

Section: R E S U L T S a N D Discussionsupporting

confidence: 76%

Effects of norflurazon on СО2 fixation and Rubisco activity in some C3 and C4 plants under different light intensity

Kosogova¹,

Rusinova²,

Karapetyan³

2016

Bot Pac

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A B S T R A C TNorflurazon (NF) is a herbicide that is known to inhibit carotenoid biosynthesis, destroy chlorophylls, desintefrate chloroplasts, and ruin chloroplast ribosome. In this study, we clarify how light intensity modulates effects of NF on СО2 fixation and activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in some C 3 and C4 plants. We investigate effects of NF on maize, barley, triticale, and radish under low light intensity (0.12 and 0.4 W/m 2 ), and on maize, wheat, bean, and radish under high light intensity (100 W/m 2 ). We show that the effects are modulated by light intensity and species peculiarities. Specifically, C3 plants, with no mechanism for CO2 recycling, loose carbon compounds easier compared to C4 plants, resulting in earlier manifestation of photodestruction under NF treat ment. Besides, we show that Rubisco activity increases as far as its content decreases.K e y w o r d s : CO2 fixation, Rubisco activity, light intensity, norflurazon, C3 plants, C4 plants, carotenoids, chlorophylls

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Section: R E S U L T S a N D Discussionsupporting

confidence: 76%

Effects of norflurazon on СО2 fixation and Rubisco activity in some C3 and C4 plants under different light intensity

Kosogova¹,

Rusinova²,

Karapetyan³

2016

Bot Pac

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“…Besides affecting Cab (both RNA and protein), Chl photooxidation was found to cause an alteration in mRNA and protein levels of the small subunit of ribulose 1,5-bisphosphate carboxylase (26,30,31). In maize, the accumulation of several cytosolic mRNAs besides Cab and RbcS was affected (13), although the effect seen on the different mRNA species varied widely.…”

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confidence: 99%

“…In maize, the accumulation of several cytosolic mRNAs besides Cab and RbcS was affected (13), although the effect seen on the different mRNA species varied widely. Similarly, chloroplast proteins exhibited varying degrees of sensitivity to damage caused by photooxidation (26). Cytosolic mRNAs or proteins not associated with the plastid were not affected by this treatment (32).…”

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confidence: 99%

Light Effects on Several Chloroplast Components in Norflurazon-Treated Pea Seedlings

Sagar¹,

Horwitz²,

Elliott³

et al. 1988

Plant Physiol.

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Changes occurring in several chloroplast components during Norflurazon-induced photobleaching of Pisum sativum seedlings were investigated. mRNA steady state levels of the chlorophyll a/b-binding protein of photosystem II, ferredoxin I, the small and large subunits of ribulose 1,5-bisphosphate carboxylase, and pEA214 and pEA207, two other lightresponsive genes, were determined during chlorophyll photooxidation. Relative transcription rates were assayed in isolated nuclei. The results illustrate a complex set of interactions regulating expression of the nuclear and chloroplast genomes. Photobleaching was found to affect the expression of the various genes in different ways. While transcript levels of the chlorophyll a/b-binding protein decreased by more than 80% under photooxidative light conditions in carotenoid-deficient peas, levels of ferredoxin, the small and large subunits of ribulose 1,5-bisphosphate carboxylase, and pEA214 mRNAs were reduced by less than 50%. pEA207 mRNA levels, on the other hand, were resistant to the effects of photobleaching. Analyses of chlorophylls a and b and the chlorophyll al b-binding protein suggest that accumulation of the protein and its mRNA are coordinated with chlorophyll abundance at several steps. In addition to post-transcriptional regulation at the level of mRNA and protein stability, there may exist coordination at the transcriptional stage.Since most (>80%) chloroplast proteins are nuclear encoded (14), the nuclear and chloroplast genomes must coordinate gene expression to bring about normal development of a green plant. The messenger RNAs of the nuclear-encoded chloroplast proteins are translated on cystosolic ribosomes and transported into the plastid where they are incorporated into the photosynthetic machinery. The nuclear-chloroplast interaction can be studied both during greening ofetiolated tissue and by the use ofmutants lacking Chl. In addition, one can study plants that are blocked in carotenoid biosynthesis either because of mutations or due to growth in the presence of herbicides such as Norflurazon [NF4; 4-chloro-5-(methylamino)-2-(a,a,a-trifluoro-m-tolyl)-3(2H)-pyridazinone] (7). In the absence of protecting carotenoids in these plants, high light intensities cause "bleaching" of the green parts(1, 19).

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“…When seedlings, in which carotenoids do not accumulate either due to a mutational or chemical block in the synthesis pathway, are transferred from permissive low light to high light, rapid bleaching occurs in the green leaf tissue (2). Bleaching of leaves in the absence of carotenoids is a symptom of a pleiotropic effect that includes the disappearance of Chl, chloroplast grana stacks, and ribosomes (2,5,30), as well as a decrease in several nuclear-and plastid-encoded chloroplast proteins (15,18,19). Light-dependent decreases in enzyme activity are limited to the chloroplast and peroxisomal compartments (3,5,12).…”

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Regulation of Plastid Gene Expression during Photooxidative Stress

Tonkyn¹,

Deng²,

Gruissem³

1992

Plant Physiol.

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We have used the carotenoid biosynthesis inhibitor norflurazon to study the relationship between chloroplast and nuclear gene expression and the mechanisms by which plastid mRNA accumulation is regulated in response to photooxidative stress. By treating 4-week-old hydroponic spinach plants (Spinacea oleracea), we were able to determine the response at two distinct stages of chloroplast development. For all parameters studied, differences were found between the norflurazon-treated young and mature leaves. Young leaves lost essentially all pigment content in the presence of norflurazon, whereas mature leaves retained more than 60% of their chlorophyll and carotenoids. The accumulation of plastid mRNA was determined for several genes, and we found a decrease in mRNA levels for all genes except psbA in herbicidetreated young leaves. For genes such as atpB, psbB, and psaA, there was a corresponding change in the relative level of transcription, but for psbA and rbcL, transcription and mRNA accumulation were uncoupled. In norflurazon-treated mature leaves, all plastid mRNAs except psaA accumulated to normal levels, and transcription levels were either normal or higher than corresponding controls. This led to the conclusion that plastid mRNA accumulation is regulated both transcriptionally and posttranscriptionally in response to photooxidative stress. Although direct photooxidative damage is confined to the plastid and peroxisome, there is a feedback of information controlling the transcription of nuclearencoded plastid proteins. Considerable evidence has accumulated implicating a "plastid factor" in this control. Therefore, the expression of several nuclear-encoded plastid proteins and the corresponding mRNAs were determined. Although the levels of both the small subunit of ribulose-1,5-bisphosphate carboxylase and the light harvesting chlorophyll a/b-binding protein and corresponding mRNAs were reduced, a 28-kilodalton chloroplast RNA-binding protein and corresponding mRNA were at normal levels in norflurazon-treated plants. Changes in mRNA and protein levels were not the result of a general loss due to photooxidation but rather the result of selective stabilization of certain components. The response of both genomes to photooxidative stress is discussed in terms of the postulated plastid factor.Carotenoids in higher plants protect Chl from photooxidation under normal or high light conditions (1). There is 'This work was supported by the

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The Fate of Chloroplast Proteins during Photooxidation in Carotenoid-Deficient Maize Leaves

Cited by 45 publications

References 27 publications

Effects of norflurazon on СО2 fixation and Rubisco activity in some C3 and C4 plants under different light intensity

Effects of norflurazon on СО2 fixation and Rubisco activity in some C3 and C4 plants under different light intensity

Light Effects on Several Chloroplast Components in Norflurazon-Treated Pea Seedlings

Regulation of Plastid Gene Expression during Photooxidative Stress

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