Publications (48) View all
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Article: Ethylene promotes hyponastic growth through interaction with ROTUNDIFOLIA3/CYP90C1 in Arabidopsis.
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ABSTRACT: Upward leaf movement, called hyponastic growth, is employed by plants to cope with adverse environmental conditions. Ethylene is a key regulator of this process and, in Arabidopsis thaliana, hyponasty is induced by this phytohormone via promotion of epidermal cell expansion in a proximal zone of the abaxial side of the petiole. ROTUNDIFOLIA3/CYP90C1 encodes an enzyme which was shown to catalyse C-23 hydroxylation of several brassinosteroids (BRs) - phytohormones involved in, for example, organ growth, cell expansion, cell division, and responses to abiotic and biotic stresses. This study tested the interaction between ethylene and BRs in regulating hyponastic growth. A mutant isolated in a forward genetic screen, with reduced hyponastic response to ethylene treatment, was allelic to rot3. The cause of the reduced hyponastic growth in this mutant was examined by studying ethylene-BR interaction during local cell expansion, pharmacological inhibition of BR synthesis and ethylene effects on transcription of BR-related genes. This work demonstrates that rot3 mutants are impaired in local cell expansion driving hyponasty. Moreover, the inhibition of BR biosynthesis reduces ethylene-induced hyponastic growth and ethylene increases sensitivity to BR in promoting cell elongation in Arabidopsis hypocotyls. Together, the results show that ROT3 modulates ethylene-induced petiole movement and that this function is likely BR related.Journal of Experimental Botany 12/2012; · 5.36 Impact Factor -
Article: Genetical Genomics Reveals Large Scale Genotype-By-Environment Interactions in Arabidopsis thaliana.
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ABSTRACT: One of the major goals of quantitative genetics is to unravel the complex interactions between molecular genetic factors and the environment. The effects of these genotype-by-environment interactions also affect and cause variation in gene expression. The regulatory loci responsible for this variation can be found by genetical genomics that involves the mapping of quantitative trait loci (QTLs) for gene expression traits also called expression-QTL (eQTLs). Most genetical genomics experiments published so far, are performed in a single environment and hence do not allow investigation of the role of genotype-by-environment interactions. Furthermore, most studies have been done in a steady state environment leading to acclimated expression patterns. However a response to the environment or change therein can be highly plastic and possibly lead to more and larger differences between genotypes. Here we present a genetical genomics study on 120 Arabidopsis thaliana, Landsberg erecta × Cape Verde Islands, recombinant inbred lines (RILs) in active response to the environment by treating them with 3 h of shade. The results of this experiment are compared to a previous study on seedlings of the same RILs from a steady state environment. The combination of two highly different conditions but exactly the same RILs with a fixed genetic variation showed the large role of genotype-by-environment interactions on gene expression levels. We found environment-dependent hotspots of transcript regulation. The major hotspot was confirmed by the expression profile of a near isogenic line. Our combined analysis leads us to propose CSN5A, a COP9 signalosome component, as a candidate regulator for the gene expression response to shade.Frontiers in genetics. 01/2012; 3:317. -
Article: Photoreceptors CRYTOCHROME2 and phytochrome B control chromatin compaction in Arabidopsis.
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ABSTRACT: Development and acclimation processes to the environment are associated with large-scale changes in chromatin compaction in Arabidopsis (Arabidopsis thaliana). Here, we studied the effects of light signals on chromatin organization. A decrease in light intensity induces a large-scale reduction in chromatin compaction. This low light response is reversible and shows strong natural genetic variation. Moreover, the degree of chromatin compaction is affected by light quality signals relevant for natural canopy shade. The photoreceptor CRYPTOCHROME2 appears a general positive regulator of low light-induced chromatin decompaction. Phytochrome B also controls light-induced chromatin organization, but its effect appears to be dependent on the genetic background. We present a model in which chromatin compaction is regulated by the light environment via CRYPTOCHROME2 protein abundance, which is controlled by phytochrome B action.Plant physiology 10/2010; 154(4):1686-96. · 6.53 Impact Factor -
Article: Ethylene-induced differential petiole growth in Arabidopsis thaliana involves local microtubule reorientation and cell expansion.
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ABSTRACT: • Hyponastic growth is an upward petiole movement induced by plants in response to various external stimuli. It is caused by unequal growth rates between adaxial and abaxial sides of the petiole, which bring rosette leaves to a more vertical position. The volatile hormone ethylene is a key regulator inducing hyponasty in Arabidopsis thaliana. Here, we studied whether ethylene-mediated hyponasty occurs through local stimulation of cell expansion and whether this involves the reorientation of cortical microtubules (CMTs). • To study cell size differences between the two sides of a petiole in ethylene and control conditions, we analyzed epidermal imprints. We studied the involvement of CMT orientation in epidermal cells using the tubulin marker line as well as genetic and pharmacological means of CMT manipulation. • Our results demonstrate that ethylene induces cell expansion at the abaxial side of the- petiole and that this can account for the observed differential growth. At the abaxial side, ethylene induces CMT reorientation from longitudinal to transverse, whereas, at the adaxial side, it has an opposite effect. The inhibition of CMTs disturbed ethylene-induced hyponastic growth. • This work provides evidence that ethylene stimulates cell expansion in a tissue-specific manner and that it is associated with tissue-specific changes in the arrangement of CMTs along the petiole.New Phytologist 01/2012; 193(2):339-48. · 6.64 Impact Factor -
Article: Modulation of ethylene- and heat-controlled hyponastic leaf movement in Arabidopsis thaliana by the plant defence hormones jasmonate and salicylate.
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ABSTRACT: Upward leaf movement (hyponastic growth) is adopted by several plant species including Arabidopsis thaliana, as a mechanism to escape adverse growth conditions. Among the signals that trigger hyponastic growth are, the gaseous hormone ethylene, low light intensities, and supra-optimal temperatures (heat). Recent studies indicated that the defence-related phytohormones jasmonic acid (JA) and salicylic acid (SA) synthesized by the plant upon biotic infestation repress low light-induced hyponastic growth. The hyponastic growth response induced by high temperature (heat) treatment and upon application of the gaseous hormone ethylene is highly similar to the response induced by low light. To test if these environmental signals induce hyponastic growth via parallel pathways or converge downstream, we studied here the roles of Methyl-JA (MeJA) and SA on ethylene- and heat-induced hyponastic growth. For this, we used a time-lapse camera setup. Our study includes pharmacological application of MeJA and SA and biological infestation using the JA-inducing caterpillar Pieris rapae as well as mutants lacking JA or SA signalling components. The data demonstrate that MeJA is a positive, and SA, a negative regulator of ethylene-induced hyponastic growth and that both hormones repress the response to heat. Taking previous studies into account, we conclude that SA is the first among many tested components which is repressing hyponastic growth under all tested inductive environmental stimuli. However, since MeJA is a positive regulator of ethylene-induced hyponastic growth and is inhibiting low light- and heat-induced leaf movement, we conclude that defence hormones control hyponastic growth by affecting stimulus-specific signalling pathways.Planta 10/2011; 235(4):677-85. · 3.00 Impact Factor
