Publications (80) View all
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Article: Stem transcriptome reveals mechanisms to reduce the energetic cost of shade-avoidance responses in tomato.
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ABSTRACT: While the most conspicuous response to low red/far-red ratios (R:FR) of shade light perceived by phytochrome is the promotion of stem growth, additional, less obvious effects may be discovered by studying changes in the stem transcriptome. Here, we report rapid and reversible stem transcriptome responses to R:FR in tomato (Solanum lycopersicum). As expected, low R:FR promoted the expression of growth-related genes, including those involved in the metabolism of cell wall carbohydrates and in auxin responses. In addition, genes involved in flavonoid synthesis, isoprenoid metabolism, and photosynthesis (dark reactions) were overrepresented in clusters showing reduced expression in the stem of low R:FR-treated plants. Consistent with these responses, low R:FR decreased the levels of flavonoids (anthocyanin, quercetin, kaempferol) and selected isoprenoid derivatives (chlorophyll, carotenoids) in the stem and severely reduced the photosynthetic capacity of this organ. However, lignin contents were unaffected. Low R:FR reduced the stem levels of jasmonate, which is a known inducer of flavonoid synthesis. The rate of stem respiration was also reduced in low R:FR-treated plants, indicating that by downsizing the stem photosynthetic apparatus and the levels of photoprotective pigments under low R:FR, tomato plants reduce the energetic cost of shade-avoidance responses.Plant physiology 08/2012; 160(2):1110-9. · 6.53 Impact Factor -
Article: COP1 re-accumulates in the nucleus under shade.
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ABSTRACT: Shade-avoider plants typically respond to shade-light signals by increasing the rate of stem growth. CONSTITTUTIVE PHOTOMORPHOGENESIS 1 (COP1) is an E3 ligase involved in ubiquitin labelling of proteins targeted for degradation. In dark-grown seedlings, COP1 accumulates in the nucleus and light exposure causes COP1 migration to the cytosol. Here we show that in Arabidopsis thaliana, COP1 accumulates in the nucleus under natural or simulated shade, despite the presence of far-red light. In plants grown under white light, transfer to shade-light conditions triggers an unexpectedly rapid re-accumulation of COP1 in the nucleus. Partial simulation of shade by lowering either blue or red light (maintaining far-red light) caused COP1 nuclear re-accumulation. Hypocotyl growth of wild-type seedlings is more sensitive to afternoon than morning shade events. A residual response to shade was observed in the cop1 mutant background but these seedlings showed inverted sensitivity as they responded to morning and not to afternoon shade events. COP1 overexpression exaggerated the wild-type pattern by enhancing afternoon sensitivity and making morning shade events inhibitory of growth. COP1 nuclear re-accumulation also responded more strongly to afternoon than morning shade events. These results are consistent with a signalling role of COP1 in shade avoidance. We propose a function of COP1 in setting the daily patterns of sensitivity to shade events in the fluctuating light environments of plant canopies. This article is protected by copyright. All rights reserved.The Plant Journal 05/2013; · 6.16 Impact Factor -
Article: cry1 and GPA1 signaling genetically interact in hook opening and anthocyanin synthesis in Arabidopsis.
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ABSTRACT: While studying blue light-independent effects of cryptochrome 1 (cry1) photoreceptor, we observed premature opening of the hook in cry1 mutants grown in complete darkness, a phenotype that resembles the one described for the heterotrimeric G-protein α subunit (GPA1) null mutant gpa1. Both cry1 and gpa1 also showed reduced accumulation of anthocyanin under blue light. These convergent gpa1 and cry1 phenotypes required the presence of sucrose in the growth media and were not additive in the cry1 gpa1 double mutant, suggesting context-dependent signaling convergence between cry1 and GPA1 signaling pathways. Both, gpa1 and cry1 mutants showed reduced GTP-binding activity. The cry1 mutant showed wild-type levels of GPA1 mRNA or GPA1 protein. However, an anti-transducin antibody (AS/7) typically used for plant Gα proteins, recognized a 54 kDa band in the wild type but not in gpa1 and cry1 mutants. We propose a model where cry1-mediated post-translational modification of GPA1 alters its GTP-binding activity.Plant Molecular Biology 08/2012; 80(3):315-24. · 4.15 Impact Factor -
Article: Phototropins but not cryptochromes mediate the blue light-specific promotion of stomatal conductance, while both enhance photosynthesis and transpiration under full sunlight.
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ABSTRACT: Leaf epidermal peels of Arabidopsis (Arabidopsis thaliana) mutants lacking either phototropins 1 and 2 (phot1 and phot2) or cryptochromes 1 and 2 (cry1 and cry2) exposed to a background of red light show severely impaired stomatal opening responses to blue light. Since phot and cry are UV-A/blue light photoreceptors, they may be involved in the perception of the blue light-specific signal that induces the aperture of the stomatal pores. In leaf epidermal peels, the blue light-specific effect saturates at low irradiances; therefore, it is considered to operate mainly under the low irradiance of dawn, dusk, or deep canopies. Conversely, we show that both phot1 phot2 and cry1 cry2 have reduced stomatal conductance, transpiration, and photosynthesis, particularly under the high irradiance of full sunlight at midday. These mutants show compromised responses of stomatal conductance to irradiance. However, the effects of phot and cry on photosynthesis were largely nonstomatic. While the stomatal conductance phenotype of phot1 phot2 was blue light specific, cry1 cry2 showed reduced stomatal conductance not only in response to blue light, but also in response to red light. The levels of abscisic acid were elevated in cry1 cry2. We conclude that considering their effects at high irradiances cry and phot are critical for the control of transpiration and photosynthesis rates in the field. The effects of cry on stomatal conductance are largely indirect and involve the control of abscisic acid levels.Plant physiology 12/2011; 158(3):1475-84. · 6.53 Impact Factor -
Article: Shade avoidance.
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ABSTRACT: The presence of neighboring vegetation modifies the light environment experienced by plants, generating signals that are perceived by phytochromes and cryptochromes. These signals cause large changes in plant body form and function, including enhanced growth of the hypocotyl and petioles, a more erect position of the leaves and early flowering in Arabidopsis thaliana. Collectively, these so-called shade-avoidance responses tend to reduce the degree of current or future shade by neighbors. Shade light signals increase the abundance of PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF5 proteins, promote the synthesis and redirection of auxin, favor the degradation of DELLA proteins and increase the expression of auxin, gibberellins and brassinosteroid-promoted genes, among other events downstream the photoreceptors. Selectively disrupting these events by genetic or pharmacological approaches affects shade-avoidance responses with an intensity that depends on the developmental context and the environment. Shade-avoidance responses provide a model to investigate the signaling networks used by plants to take advantage of the cues provided by the environment to adjust to the challenges imposed by the environment itself.The Arabidopsis Book 01/2012; 10:e0157.
