BZS1, a B-box Protein, Promotes Photomorphogenesis Downstream of Both Brassinosteroid and Light Signaling Pathways
ABSTRACT Photomorphogenesis is controlled by multiple signaling pathways, including the light and brassinosteroid (BR) pathways. BR signaling activates the BZR1 transcription factor, which is required for suppressing photomorphogenesis in the dark. We identified a suppressor of the BR hypersensitive mutant bzr1-1D and named it bzr1-1D suppressor1-Dominant (bzs1-D). The bzs1-D mutation was caused by overexpression of a B-box zinc finger protein BZS1, which is transcriptionally repressed by BZR1. Overexpression of BZS1 causes de-etiolation in the dark, short hypocotyls in the light, reduced sensitivity to BR treatment, and repression of many BR-activated genes. Knockdown of BZS1 by co-suppression partly suppressed the short hypocotyl phenotypes of BR-deficient or insensitive mutants. These results support that BZS1 is a negative regulator of BR response. BZS1 overexpressors are hypersensitive to different wavelengths of light and loss of function of BZS1 reduces plant sensitivity to light and partly suppresses the constitutive photomorphogenesis 1 (cop1) mutant in the dark, suggesting a positive role in light response. BZS1 protein accumulates at an increased level after light treatment of dark-grown BZS1-OX plants and in the cop1 mutants, and BZS1 interacts with COP1 in vitro, suggesting that light regulates BZS1 through COP1-mediated ubiquitination and proteasomal degradation. These results demonstrate that BZS1 mediates the crosstalk between BR and light pathways.
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ABSTRACT: We explored the interaction between radiation of different wavelength and jasmonic acid or brassinosteroids (BR) on leaf senescence-induced oxidative stress. Three approaches were used: 1) jasmonic acid insensitive1-1 (jai1-1) and brassinosteroid-deficient [dumpy (dpy)] mutants were treated with red (R) or far-red (FR) radiation; 2) phytochromedeficient aurea (au) and high pigment-1 (hp-1) (radiation exaggerated response) mutants were treated with methyl jasmonate (MeJA) or epibrassinolide (epiBL); and 3) double mutants au jai1-1 and au dpy were produced. Leaf chlorophyll content, lipid peroxidation, and antioxidant enzyme activities were determined. After senescence induction in detached leaves, we verified that the patterns of chlorophyll degradation of hormonal and photomorphogenic mutants were not significantly different in comparison with original cv. Micro-Tom (MT). Moreover, there was no significant change in lipid peroxidation measured as malondialdehyde (MDA) production, as well as catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities in the hormonal mutants. Exogenous BR increased CAT and APX activities in MT, au, and hp-1. As concerns the double mutants, severe reduction in H2O2 production which was not accompanied by changes in MDA content, and CAT and APX activities was observed during senescence in au dpy. The results suggest that JA and BR do not participate in light signaling pathway during leaf senescence-induced oxidative stress.Biologia Plantarum 12/2013; 57(4). DOI:10.1007/s10535-013-0333-1 · 1.74 Impact Factor
Article: Brassinosteroid signalling[Show abstract] [Hide abstract]
ABSTRACT: The brassinosteroid (BR) class of steroid hormones regulates plant development and physiology. The BR signal is transduced by a receptor kinase-mediated signal transduction pathway, which is distinct from animal steroid signalling systems. Recent studies have fully connected the BR signal transduction chain and have identified thousands of BR target genes, linking BR signalling to numerous cellular processes. Molecular links between BR and several other signalling pathways have also been identified. Here, we provide an overview of the highly integrated BR signalling network and explain how this steroid hormone functions as a master regulator of plant growth, development and metabolism.Development 04/2013; 140(8):1615-20. DOI:10.1242/dev.060590 · 6.27 Impact Factor
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ABSTRACT: Any two people on Earth may be connected by a chain of 'a friend of a friend' in six steps or less, dubbed as the 'six degrees of separation'. In the world of plant systems, the degree of separation between the signaling 'pathways' of photoreceptor phytochromes and growth regulator phytohormones is smaller than previously expected, according to the recent studies. Plants control their growth by simultaneously sensing and responding to both the external environmental signals and the internal developmental signals. Taking the well-studied light inhibition of hypocotyl elongation of young seedlings as an example, this response is controlled by both the red/far-red light receptor phytochromes and phytohormones, including auxin, cytokinins (CK), gibberellins (GA), brassinosteriods (BR), ethylene, and Abscisic acid (ABA). How phytochromes and phytohormones interact to control growth has been a subject of plant physiology studies for decades (Neff et al., 2006), and it appears to be a favored subject for the systems biology studies nowadays.Molecular Plant 09/2012; 6(1). DOI:10.1093/mp/sss102 · 6.61 Impact Factor