Functional Analysis Of Arabidopsis Spa Proteins In Plant Growth Control

Author : Renshan Zhang
Publisher : Open Dissertation Press
ISBN 13 : 9781361033579
Total Pages : 178 pages
Book Rating : 4.0/5 (335 download)

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Download or read book FUNCTIONAL ANALYSIS OF 2 ARABI written by Renshan Zhang and published by Open Dissertation Press. This book was released on 2017-01-26 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Functional Analysis of Two Arabidopsis Purple Acid Phosphatases: AtPAP2 and AtPAP9" by Renshan, Zhang, 张仁善, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled FUNCTIONAL ANALYSIS OF TWO ARABIDOPSIS PURPLE ACID PHOSPHATASES: ATPAP2 AND ATPAP9 Submitted by ZHANG Renshan for the Degree of Doctor of Philosophy at The University of Hong Kong in May 2015 AtPAP2 is a tail-anchored phosphatase that is dually targeted to the outer membranes of chloroplasts and mitochondria and its biological functions remain elusive. Chloroplasts import assay in Chapter II showed that the chloroplasts of 35 pap2 imported [ S]-AtSSU1B translated in the wheat germ extract (WGE) less efficiently than the chloroplasts from wild type (WT), while the import efficiency of AtPAP2 overexpression line (OE7) was significantly higher than that of WT. Yeast Two-Hybrid assay (Y2H) showed that AtPAP2 can interact with a number of chloroplast proteins. Based on my results, I update the model of preprotein recognition and translocation through the Translocon of Outer Membrane of Chloroplasts (TOC) complex. In this model, AtPAP2 acts as a co-receptor for certain nucleus-encoded chloroplast proteins and dephosphorylate their transit peptides prior to their import into chloroplasts. The overexpression of AtPAP2 promotes the import of certain photosystem proteins including those involved in cyclic electron flow. Higher ATP and carbon outputs from chloroplasts thus results in early bolting, high sugars and high seed yield phenotypes of AtPAP2 OE lines. In most plant genomes, there is only a single AtPAP2-like gene but in the genomes of plants in the Brassicaceae, there are 2-6 AtPAP2-like genes. For example, there is a 73% a. a. sequence identity between AtPAP2 and AtPAP9 proteins in Arabidopsis thaliana. GFP localization and plant transformation study showed that AtPAP9 is also a tail-anchored (TA) protein that is dually targeted to chloroplasts and mitochondria. Unlike AtPAP2 OE lines, no growth promotion effect was observed inAtPAP9 OE lines as well as AtPAP9_K OE lines carrying the glutamic acid (E) to lysine (K) substitution (Chapter III). Chloroplasts import 35 assay showed that the chloroplasts of pap9 imported [ S]-AtSSU1B less efficiently than the chloroplasts from wild type (WT), while the import efficiency of AtPAP9 overexpression line (OE10) was significantly higher than that of WT. As Y2H study suggested a similar ligand binding profiles with the substrates of AtPAP2 between AtPAP2 and AtPAP9, more intensive screening of interacting proteins will be needed to find out their functional differences. The overexpression of AtPAP2 solely in mitochondria (P2Tom) conferred the transgenic lines with an early senescence phenotype (Chapter IV). Proteomics analysis (P2Tom vs WT) showed that the senescence phenotype was associated with suppressed abundance of photosystem components and redox proteins, but with increased abundance of a few components of the mitochondria respiratory chain (Complexes I, III and V, but not II). This suggests an enhanced respiratory activity in mitochondria but an impaired function of photosystems, which is a general phenomenon prior to the onset of plant senescence. AtPAP2 may play a role in the import of nucleus-encoded proteins into mitochondria and its overexpression affects the energy output of mitochondria. Finally, AtPAP2 OE lines were generally more susceptible to pathogens attack, and there is a general trade-offs in biological systems, such as the pros (elevated fitness) and cons