Blue-light mediated accumulation of nuclear-encoded transcripts coding for proteins of the thylakoid membrane is absent in the phytochrome-deficient aurea mutant of tomato (original) (raw)
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The Plant Journal, 1997
et al., 1995a; Malhotra et al.,1995), and overexpression of USA CRY1 protein in transgenic plants conferred a blue-light hypersensitive phenotype (Lin et al.,1995b), consistent with its role as photoreceptor. Blue-light-dependent phenotypes Summary shown to be under the control of CRY1 include inhibition Blue-light responses in higher plants are mediated by of hypocotyl elongation and anthocyanin production in specific photoreceptors, which are thought to be flavoseedlings (Ahmad et al., 1995; Jackson and Jenkins, 1995; proteins; one such flavin-type blue-light receptor, CRY1 Koornneef et al., 1980). In spite of its striking homology to (for cryptochrome), which mediates inhibition of hypocotyl the DNA photolyases, CRY1 shows no demonstrable DNA elongation and anthocyanin biosynthesis, has recently binding or photoreactivating activity (Lin et al., 1995a; been characterized. Prompted by classical photobiological Malhotra et al., 1995). The structure of CRY1 suggests a studies suggesting possible co-action of the red/far-red mechanism of action involving electron transfer; the reacabsorbing photoreceptor phytochrome with blue-light tion partners and downstream transduction apparatus photoreceptors in certain plant species, the role of phytoremain to be identified. chrome in CRY1 action in Arabidopsis was investigated. A recurring theme in plant blue-light research has been The activity of the CRY1 photoreceptor can be substantially an involvement of the red/far-red-absorbing photoreceptor altered by manipulating the levels of active phytochrome phytochrome in physiological responses to blue-light treat-(Pfr) with red or far-red light pulses subsequent to bluements. Experiments in a number of monocot and dicot light treatments. Furthermore, analysis of severely phytoplant species have shown that blue-light responses such chrome-deficient mutants showed that CRY1-mediated as inhibition of hypocotyl elongation or anthocyanin accublue-light responses were considerably reduced, even mulation can be partially reversed if the blue-light pulses though Western blots confirmed that levels of CRY1 photoare followed by, or given in the presence of, saturating receptor are unaffected in these phytochrome-deficient pulses of far-red light (Casal, 1994; Gaba et al., 1984; mutant backgrounds. It was concluded that CRY1-medi-Mancinelli et al., 1991; Mohr, 1994). Such far-red reversiated inhibition of hypocotyl elongation and anthocyanin bility had been taken as evidence that phytochrome, or the production requires active phytochrome for full expresphytochrome signal transduction pathway, was somehow sion, and that this requirement can be supplied by low implicated in blue-light responses. However, interpretation levels of either phyA or phyB. of these studies has been complicated by the fact that the phytochrome photoreceptor itself directly absorbs blue light. It is therefore difficult to unequivocally distinguish
Photosynthetica, 2016
The effect of UV-A radiation (365 nm) and the protective effect of preillumination with red light (RL, 664 nm, 10 min) or with a combination of red and far-red light (FRL, 727 nm, 10 min) on the activity of the PSII as well as the expression levels of selected genes, especially those encoding chloroplast proteins (sAPX, tAPX, CAB1, and D1), were studied in leaves of the 26-d-old hy3 mutant of Arabidopsis thaliana, which is deficient in the phytochrome B apoprotein. The effects were compared with corresponding effects observed in the hy2 mutant of A. thaliana, which is deficient in the phytochrome chromophore. Illumination with UV-A decreased the photosynthetic pigment content, the maximum photochemical quantum yield of PSII (Fv/Fm), and the effective quantum yield of PSII (Ф PSII). The reduction of the F v /F m ratio and Ф PSII was more pronounced in the mutants as compared to wild-type plants (WT). The preillumination of the leaves with RL caused a significant reduction in the inhibitory effect of UV-radiation on the PSII activity in the WT plants, but it caused only a small decrease in the hy3 mutant. The preillumination of leaves with RL and FRL combination compensated the protective effect of RL on the UV-induced decrease of the fluorescence parameters in the WT. Such reversibility is typical for involvement of red/far-red reversible phytochromes at low intensity light. The results suggest an important role of red/far-red reversible phytochromes (phytochrome B) in the resistance of PSII to UV-A radiation caused by changes in contents of either carotenoids or other UV-absorbing pigments probably through biosynthesis of these pigments. The data also demonstrated that phytochrome B and other phytochromes can affect the PSII stress resistance by the fast regulation of the expression of genes encoding antioxidant enzymes and transcription factors at the step of gene transcription.
Cryptochrome 1 controls tomato development in response to blue light
The Plant Journal, 1999
Cryptochrome genes (CRY) are a novel class of plant genes encoding proteins that bear a strong resemblance to photolyases, a rare class of flavoproteins that absorb light in the blue (B) and UV-A regions of the spectrum and utilise it for photorepair of UV-damaged DNA. In Arabidopsis, both CRY1 and CRY2 are implicated in numerous blue light-dependent responses, including inhibition of hypocotyl elongation, leaf and cotyledon expansion, pigment biosynthesis, stem growth and internode elongation, control of flowering time and phototropism. No information about the in vivo function of CRY genes is available in other plant species. The tomato CRY1 gene (TCRY1) encodes a protein of 679 amino acids, which shows 78% identity and 88% similarity to Arabidopsis CRY1. In order to verify the in vivo function of TCRY1, we constructed antisense tomato plants using the C-terminal portion of the gene. Partial repression of both mRNA and protein levels was observed in one of the transformants. The progeny from this transformant showed an elongated hypocotyl under blue but not under red light. This character co-segregated with the transgene and was dependent on transgene dosage. An additional, partially elongated phenotype was observed in adult plants grown in the greenhouse under dim light and short days with no artificial illumination. This phenotype was suppressed by artificial illumination of both short and long photoperiods. The synthesis of anthocyanins under blue light was reduced in antisense seedlings. In contrast, carotenoid 551 and chlorophyll levels and second positive phototropic curvature were essentially unaltered.
Plant and Cell Physiology, 2005
To investigate the mechanism of phytochrome action in vivo, NtPHYB, AtPHYB and phyD:green fluorescent protein (GFP) were overexpressed in Nicotiana plumbaginifolia and Arabidopsis thaliana. The expression of 35S: NtPHYB:GFP and 35S:AtPHYB:GFP complemented the tobacco hgl2 and Arabidopsis phyB-9 mutations, whereas the 35S:AtPHYD:GFP only rescued the hgl2 mutant. All three fusion proteins are transported into the nucleus in all genetic backgrounds. These data indicate that AtPHYD: GFP is biologically active and functions as the main red light receptor in transgenic tobacco, and establish an experimental system for the functional analysis of this elusive photoreceptor in vivo.
Plant Physiology, 1990
Phytochrome and the blue ultraviolet-A photoreceptor control light-induced expression of genes encoding the chlorophyll a/b binding protein of photosystem 11 and photosystem I and the genes for the small subunit of the ribulose-1,5-bisphosphate carboxylase in etiolated seedlings of Lycopersicon esculentum (tomato) and Nicotiana tabacum (tobacco). A 'high irradiance response' also controls the induction of these genes. Gernes encoding photosystem 11-and I-associated chlorophyll a/b binding proteins both exhibit a transient rapid increase in expression in response to light pulse or to continuous irradiation. In contrast, genes encoding the small subunit exhibit a continuous increase in expression in response to light. These distinct expression characteristics are shown to reflect differences at the level of transcription. Higher plants have several photoreceptors which detect light quality and intensity. The major photoreceptors are phytochrome (26), which control induction and 'high irradiance responses' (HIR2) (10), a blue/UV-A photoreceptor (27), and a UV-B photoreceptor (34). Studies of expression of nuclear genes encoding CAB, SSU, and CHS proteins revealed that photoregulation of gene expression in higher plants occurs at transcriptional and posttranscriptional levels (33). The dependence ofgene expression on light quality and intensity varies for different genes and different species. For instance, in parsley cell suspension cultures excitation of the UV-B photoreceptor is essential for maximal expression of CHS, while the excitation of the blue/
Photochemistry and Photobiology, 2000
The plant receptor phytochrome A (phyA) mediates responses like hypocotyl growth inhibition and cotyledon unfolding that require continuous far-red (FR) light for maximum expression (high-irradiance responses, HIR), and responses like seed germination that can be induced by a single pulse of FR (very-low-fluence responses, VLFR). It is not known whether this duality results from either phyA interaction with different end-point processes or from the intrinsic properties of phyA activity. Etiolated seedlings of Arabidopsis thaliana were exposed to pulses of FR (3 min) separated by dark intervals of different duration. Hypocotyl-growth inhibition and cotyledon unfolding showed two phases. The first phase (VLFR) between 0.17 and 0.5 pulses•h Ϫ1 , a plateau between 0.5 and 2 pulses•h Ϫ1 and a second phase (HIR) at higher frequencies. Reciprocity between fluence rate and duration of FR was observed within phases, not between phases. The fluence rate for half the maximum effect was 0.1 and 3 mol•m Ϫ2 •s Ϫ1 for hourly pulses of FR (VLFR) and continuous FR (HIR), respectively. Overexpression of phytochrome B caused dominant negative suppression under continuous but not under hourly FR. We conclude that phyA is intrinsically able to initiate two discrete photoresponses even when a single end-point process is considered.
The Phytochromes, a Family of Red/Far-red Absorbing Photoreceptors
Journal of Biological Chemistry, 2001
Because plants are photo-auxotrophic they are particularly sensitive to their light environment. To fine-tune their development according to light intensity, direction, spectral quality, and periodicity they possess a multiplicity of light sensors (1). In Arabidopsis there are eight identified photoreceptors, but this list is still incomplete. It includes three UV-A/blue light receptors (phototropin, a photoreceptor to sense light direction, and two cryptochromes that mediate many photomorphogenic responses (2, 3)) and five phytochromes (phy) 1 named phyA-phyE that absorb mainly red/far-red light, with phyA also responding to broad-spectrum light (UV-A to far-red) of very low intensity (4). All these photoreceptors bind to a chromophore, which for the phytochromes is a linear tetrapyrrole (phytochromobilin) (5). Because many light effects are induced by the co-action of several photoreceptors and because some photoreceptors regulate multiple aspects of photomorphogenesis, a genetic approach was instrumental for dissecting the specific roles of individual photoreceptors (1). As a consequence, research has concentrated on a few species that are particularly well suited for molecular genetic studies, in particular Arabidopsis (6). Multiple Phytochromes Have Overlapping and Distinct Functions Phytochromes were originally defined as the receptors responsible for red, far-red reversible, plant responses (7-9). Photobiological experiments led to the proposal that phy exists in two spectral forms: the inactive Pr form (red light absorbing) phototransforms into the active Pfr form (far-red light absorbing) upon absorption of red light. This reaction can be reversed when Pfr is converted to Pr upon absorption of far-red light. Purification of phy from plants confirmed the existence of those two spectrally interconvertible forms (10). phy are classified into two groups; type I (phyA in Arabidopsis) is light-labile and type II (phyB-phyE in Arabidopsis) is light-stable (11). Numerous recent reviews cover phy-mediated photomorphogenesis in detail (12-19). Photobiological and genetic studies have revealed that this small gene family plays important roles in seed germination, seedling de-etiolation, neighbor perception and avoidance, and the transition from vegetative to reproductive growth (induction of flowering). At the molecular and cellular level phy responses include: development of the chloroplast, inhibition or promotion of cell growth (depending on the organ), ion fluxes at the plasma membrane, and gene expression responses (1). Genetic screens to identify loci implicated in phy responses have yielded four apoprotein mutants (phyA, phyB, phyD, and phyE), two chromophore mutants (hy1 and hy2), and numerous mutants implicated in phy-mediated * This minireview will be reprinted in the 2001 Minireview Compendium, which will be available in December, 2001. This is the second article of three in the "Light Minireview Series.
Planta, 2015
Main conclusion Light quality has various effects on photochemistry and protein phosphorylation in Zea mays and Arabidopsis thaliana thylakoids due to different degrees of light penetration across leaves and redox status in chloroplasts. The effect of the spectral quality of light (red, R and far red, FR) on the function of thylakoid proteins in Zea mays and Arabidopsis thaliana was investigated. It was concluded that red light stimulates PSII activity in A. thaliana thylakoids and in maize bundle sheath (BS) thylakoids, but not in mesophyll (M) thylakoids. The light quality did not change PSI activity in M thylakoids of maize. FR used after a white light period increased PSI activity significantly in maize BS and only slightly in A. thaliana thylakoids. As shown by blue native (BN)-PAGE followed by SDS-PAGE, proteins were differently phosphorylated in the thylakoids, indicating their different functions. FR light increased dephosphorylation of LHCII proteins in A. thaliana thylakoids, whereas in maize, dephosphorylation did not occur at all. The rate of phosphorylation was higher in maize BS than in M thylakoids. D1 protein phosphorylation increased in maize and decreased in A. thaliana upon irradiation with both R and growth light (white light, W). Light variations did not change the level of proteins in thylakoids. Our data strongly suggest that response to light quality is a species-dependent phenomenon. We concluded that the maize chloroplasts were differently stimulated, probably due to different degrees of light penetration across the leaf and thereby the redox status in the chloroplasts. These acclimation changes induced by light quality are important in the regulation of chloroplast membrane flexibility and thus its function. Keywords Acclimation to light quality Á Bundle sheath chloroplasts Á Mesophyll chloroplasts Á PSI Á PSII Á Protein phosphorylation Á Red and far red light Á Thylakoids Abbreviations BS Bundle sheath BN-PAGE Blue native electrophoresis CET Cyclic electron transport FR Far red light LHCII Chlorophyll a/b-binding protein of photosystem II M Mesophyll R Red light W White light & El_ zbieta Romanowska