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| Strategic placement of catalytic residues in ferredoxin-dependent bilin reductases for synthesizing phytochrome chromophores. (11-11-2008) |
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| Photosynthetic organisms depend on light as the energy source. For sensing light, these organisms have evolved photoreceptor systems that respond to light quality, quantity, direction and duration in the environment. Phytochrome, the red and far-red photoreceptor, requires a covalently linked tetrapyrrole chromophore. In plants, this chromophore is called phytochromobilin (PFB). Light absorption by the phytochrome-bound PFB induces a structural rearrangement of the chromophore itself, triggering a protein conformational change that subsequently initiates light signaling. Biosynthesis of PFB is fundamentally important for plants as mutations in chromophore biosynthesis enzymes lead to a lack of functional phytochromes and severe defects in light-mediated plant growth and development. The ferredoxin-dependent bilin reductases (FDBRs) are an enzyme family known to participate in the chromophore biosynthesis of many photosynthetic organisms. The research team of Shih-Long Tu has analyzed a plant-specific FDBR, PFB synthase (HY2) from Arabidopsis and reports new insights on the catalytic mechanism of this key enzyme (Journal of Biological Chemistry. 2008, Vol. 283, 27555-27564). Using spectroscopic analysis and site-directed mutagenesis, they proposed that FDBRs synthesize different tetrapyrrole chromophores through a radical mechanism. However, the double bond specificity of HY2 is decided by strategic placement of different proton donating residues surrounding the bilin substrate in the active sites. |
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LZF1 is a new component of light signaling (10-14-2008) |
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| Plants, unable to flee from their habitat, have developed distinct strategies to cope with an ever-changing environment and to achieve optimal growth and development. ¡§Light¡¨ is one eminent environmental cue that influences almost every developmental stage in plants. Shu-Hsing Wu¡¦s group has been focusing on identification and functional characterization of light responsive genes and their gene products. A survey of differential gene expression patterns during early photomorphogenesis in both wild-type and the hy5 mutant identified light-regulated zinc finger protein 1, LZF1 (CS Chang, YH Li, LT Chen, WC Chen, WP Hsieh, J Shin, WN Jane, SJ Chou, G Choi, JM Hu, S Somerville, SH Wu: LZF1, a HY5-regulated transcriptional factor, functions in Arabidopsis de-etiolation. Plant J. 54, 205-219, 2008). These results indicate that LZF1 functions as a positive regulator and works in concert with HY5 during de-etiolation in Arabidopsis. LZF1 is also involved in anthocyanin accumulation and early chloroplast development, possibly via regulation of PAP1/MYB75 and genes encoding chloroplast proteins as shown above. |
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Avid arborist evocated to save trees by Wei-chin Chang(07-27-2008) |
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Oh, our residential tree hugger, TH Chen, stirred a big brouhaha again. The impact of his strike was so strong on shaking big wigs¡¦ glass windows with his complaints on the priority of landscape policy at Sinica national park. What our residential avid arborist sincerely want is to protect the trees around. Every trees that he and his colleagues desire to hug after 20 or 30 years, remembering the cherished moments they had together in the campus. Sinica people should not forget to turn on their heart and brain while making far-reaching decisions on saving the campus green trees and the antique edifices. What nuts, and a sample of endangered species, that struggle to survive in such a concrete-loving community... Read more |
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Honesty-the emperor's seed by Wei-chin Chang (8-22-2008) |
¡§An honest man can feel no pleasure in the exercise of power over his fellow citizens¡¨ Thomas Jefferson
Several colleagues told me about the recent soap opera on picking a new emperor for IPMB and asked my comment. I decline as a retiree now I am not qualify to give any comment on such plays. But I sincerely hope hard working people at IPMB deserve to have someone as the next emperor or empress that appreciate Jefferson¡¦s thought ... Read more |
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