The Expression of Light-Regulated Genes in the High-Pigment-1 Mutant of Tomato (original) (raw)
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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/
Overexpression of homologous phytochrome genes in tomato: exploring the limits in photoperception
Journal of Experimental Botany, 2007
Transgenic tomato [Lycopersicon esculentum (=Solanum lycopersicum)] lines overexpressing tomato PHYA, PHYB1, or PHYB2, under control of the constitutive double-35S promoter from cauliflower mosaic virus (CaMV) have been generated to test the level of saturation in individual phytochrome-signalling pathways in tomato. Western blot analysis confirmed the elevated phytochrome protein levels in dark-grown seedlings of the respective PHY overexpressing (PHYOE) lines. Exposure to 4 h of red light resulted in a decrease in phytochrome A protein level in the PHYAOE lines, indicating that the chromophore availability is not limiting for assembly into holoprotein and that the excess of phytochrome A protein is also targeted for light-regulated destruction. The elongation and anthocyanin accumulation responses of plants grown under white light, red light, far-red light, and end-of-day far-red light were used for characterization of selected PHYOE lines. In addition, the anthocyanin accumulation response to different fluence rates of red light of 4-d-old dark-grown seedlings was studied. The elevated levels of phyA in the PHYAOE lines had little effect on seedling and adult plant phenotype. Both PHYAOE in the phyA mutant background and PHYB2OE in the double-mutant background rescued the mutant phenotype, proving that expression of the transgene results in biologically active phytochrome. The PHYB1OE lines showed mild effects on the inhibition of stem elongation and anthocyanin accumulation and little or no effect on the red light high irradiance response. By contrast, the PHYB2OE lines showed a strong inhibition of elongation, enhancement of anthocyanin accumulation, and a strong amplification of the red light high irradiance response.
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 Molecular Biology, 1989
Polyclonal antibodies against pea phytochrome detect 2 protein bands (about 116 and 120 kDa) on blots of crude protein extracts and protein of microsomal preparations of dark-grown tomato seedlings. Both protein bands are undetectable in Western blots of the aurea mutant extracts. Neither protein band is detectable after isogenic wild-type seedlings are illuminated with 3 h of red light, either in the crude extract or in the membrane fraction of the irradiated seedlings; this result is consistent with the hypothesis that both bands are phytochrome. When dark-grown wild-type seedlings are illuminated with 3 h of red light or blue light against a red light background, the transcript levels for chlorophyll a/b-binding proteins of photosystem I and II, plastocyanin, and the subunit II of photosystem I increase. In all cases, the same fluence rate of blue light is much more effective than red light alone, a result that indicates the involvement of a blue/UV-A light photoreceptor in addition to the involvement of the far-red-absorbing form of phytochrome, Pfr. The aurea mutant responds neither to red light nor to blue light. Thus, no Pfrindependent induction of the four transcripts by a blue/UV-A fight photoreceptor can be measured in the aurea mutant.
A temporarily red light-insensitive mutant of tomato lacks a light-stable, B-like phytochrome
We have selected four recessive mutants in tomato (Lycopersicon esculentum Mill.) that, under continuous red light (R), have long hypocotyls and small cotyledons compared to wild type (WT), a phenotype typical of phytochrome B (phyl) mutants of other species. These mutants, which are allelic, are only insensitive to R during the first 2 days upon transition from darkness to R, and therefore we propose the gene symbol tri (temporarily ied light insensitive). White light-grown mutant plants have a more elongated growth habit than that of the WT. An immunochemically and spectrophotometrically detectable phyl-like polypeptide detectable in the WT is absent or below detection limits in the fri' mutant.
Overexpression of homologous phytochrome genes in tomato: exploring the limits
2015
Transgenic tomato [Lycopersicon esculentum (=Solanum lycopersicum)] lines overexpressing tomato PHYA, PHYB1, or PHYB2, under control of the constitutive double-35S promoter from cauliflower mosaic virus (CaMV) have been generated to test the level of saturation in individual phytochrome-signalling pathways in tomato. Western blot analysis confirmed the elevated phytochrome protein levels in dark-grown seedlings of the respective PHY overexpressing (PHYOE) lines. Exposure to 4 h of red light resulted in a decrease in phytochrome A protein level in the PHYAOE lines, indicating that the chromophore availability is not limiting for assembly into holoprotein and that the excess of phytochrome A protein is also targeted for light-regulated destruction. The elongation and anthocyanin accumulation responses of plants grown under white light, red light, far-red light, and end-of-day far-red light were used for characterization of selected PHYOE lines. In addition, the anthocyanin accumulation response to different fluence rates of red light of 4-d-old dark-grown seedlings was studied. The elevated levels of phyA in the PHYAOE lines had little effect on seedling and adult plant phenotype. Both PHYAOE in the phyA mutant background and PHYB2OE in the double-mutant background rescued the mutant phenotype, proving that expression of the transgene results in biologically active phytochrome. The PHYB1OE lines showed mild effects on the inhibition of stem elongation and anthocyanin accumulation and little or no effect on the red light high irradiance response. By contrast, the PHYB2OE lines showed a strong inhibition of elongation, enhancement of anthocyanin accumulation, and a strong amplification of the red light high irradiance response.
The Plant Journal, 2001
Several novel allelic groups of tomato (Solanum lycopersicum L.) mutants with impaired photomorphogenesis have been identi®ed after g-ray mutagenesis of phyA phyB1 double-mutant seed. Recessive mutants in one allelic group are characterized by retarded hook opening, increased hypocotyl elongation and reduced hypocotyl chlorophyll content under white light (WL). These mutants showed a speci®c impairment in response to blue light (BL) resulting from lesions in the gene encoding the BL receptor cryptochrome 1 (cry1). Phytochrome A and cry1 are identi®ed as the major photoreceptors mediating BL-induced de-etiolation in tomato, and act under low and high irradiances, respectively. Phytochromes B1 and B2 also contribute to BL sensing, and the relative contribution of each of these four photoreceptors differs according to the light conditions and the speci®c process examined. Development of the phyA phyB1 phyB2 cry1 quadruple mutant under WL is severely impaired, and seedlings die before¯owering. The quadruple mutant is essentially blind to BL, but experiments employing simultaneous irradiation with BL and red light suggest that an additional non-phytochrome photoreceptor may be active under short daily BL exposures. In addition to effects on de-etiolation, cry1 is active in older, WL-grown plants, and in¯uences stem elongation, apical dominance, and the chlorophyll content of leaves and fruit. These results provide the ®rst mutant-based characterization of cry1 in a plant species other than Arabidopsis.
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.
Physiological interactions of phytochromes A, B1 and B2 in the control of development in tomato
The Plant Journal, 2000
The role of phytochrome B2 (phyB2) in the control of photomorphogenesis in tomato (Solanum lycopersicum L.) has been investigated using recently isolated mutants carrying lesions in the PHYB2 gene. The physiological interactions of phytochrome A (phyA), phytochrome B1 (phyB1) and phyB2 have also been explored, using an isogenic series of all possible mutant combinations and several different phenotypic characteristics. The loss of phyB2 had a negligible effect on the development of white-lightgrown wild-type or phyA-de®cient plants, but substantially enhanced the elongated pale phenotype of the phyB1 mutant. This redundancy was also seen in the control of de-etiolation under continuous red light (R), where the loss of phyB2 had no detectable effect in the presence of phyB1. Under continuous R, phyA action was largely independent of phyB1 and phyB2 in terms of the control of hypocotyl elongation, but antagonized the effects of phyB1 in the control of anthocyanin synthesis, indicating that photoreceptors may interact differently to control different traits. Irradiance response curves for anthocyanin synthesis revealed that phyB1 and phyB2 together mediate all the detectable response to high-irradiance R, and, surprisingly, that the phyA-dependent low-irradiance component is also strongly reduced in the phyB1 phyB2 double mutant. This is not associated with a reduction in phyA protein content or responsiveness to continuous far-red light (FR), suggesting that phyB1 and phyB2 speci®cally in¯uence phyA activity under low-irradiance R. Finally, the phyA phyB1 phyB2 triple mutant showed strong residual responsiveness to supplementary daytime FR, indicating that at least one of the two remaining phytochromes plays a signi®cant role in tomato photomorphogenesis.
Journal of Experimental Botany, 2010
Fruits of tomato plants carrying the high pigment-1 mutations hp-1 and hp-1 w are characterized by an increased number of plastids coupled with enhanced levels of functional metabolites. Unfortunately, hp-1 mutant plants are also typified by light-dependent retardation in seedling and whole-plant growth and development, which limits their cultivation. These mutations were mapped to the gene encoding UV-DAMAGED DNA BINDING PROTEIN 1 (DDB1) and, recently, fruit-specific RNA interference studies have demonstrated an increased number of plastids and enhanced carotenoid accumulation in the transgenic tomato fruits. However, whole-plant overexpression of DDB1, required to substantiate its effects on seedling and plant development and to couple them with fruit phenotypes, has heretofore been unsuccessful. In this study, five transgenic lines constitutively overexpressing normal DDB1 in hp-1 mutant plants were analysed. Eleven-day-old seedlings, representing these lines, displayed up to ;73-and ;221fold overexpression of the gene in hypocotyls and cotyledons, respectively. This overexpression resulted in statistically significant reversion to the non-mutant developmental phenotypes, including more than a full quantitative reversion. This reversion of phenotypes was generally accompanied by correlated responses in chlorophyll accumulation and altered expression of selected light signalling genes: PHYTOCHROME A, CRYPTO-CHROME 1, ELONGATED HYPOCOTYL 5, and the gene encoding CHLOROPHYLL A/B-BINDING PROTEIN 4. Cumulatively, these results provide the missing link between DDB1 and its effects on tomato plant development.