Functional characterization of a novel cell-wall annotated PELPK1 gene in Arabidopsis thaliana

  • Author / Creator
    Rashid, Abdur
  • Abstract In silico analysis showed that Arabidopsis thaliana gene AT5G09530 encodes a uniquely repetitive, proline-enriched protein that is conserved across species, and is likely secreted to the cell wall. Based on its most common amino acid repeat motif, I named the gene PELPK1 and its putative paralog PELPK2 (AT5G09520). Reporter (GUS) expression showed that the PELPK1 upstream genomic region is sufficient for expression in the aleurone layer during seed germination, and is induced throughout the plant by biotic factors (especially Pseudomonas syringae infection), defense chemicals (MeJa, salicylic acid), and mechanical wounding, consistent with the presence of conserved regulatory elements. Sub-cellular localization of a translational fusion of PELPK1 with GFP showed that the protein was secreted into seed-coat aleurone cells and to the cell walls of other tissues. Based on these results, it was concluded that the PELPK1 is a cell wall-associated protein and is most actively transcribed during radicle penetration of the seed coat and during pathogen and wounding responses. A proteomic survey of aleurone proteins failed to identify PELPK1, although several proteins not previously associated with this tissue were identified. Mutational analysis demonstrated that RNAi silencing significantly down-regulated the transcript abundance of PELPK1. Phenotypic analysis showed that RNAi plants exhibited significantly slower germination and root growth when the medium was supplemented with sucrose (100mM). Conversely, constitutive overexpression (OX) of PELPK1 enhanced seed germination and root elongation as compared to wild-type (WT). Analysis of soil-grown plants showed slower emergence and slower vegetative growth for RNAi lines, while OX plants exhibited faster emergence and enhanced vegetative growth and flowering as compared to WT. However, PELPK1 RNAi and OX lines did not differ from WT in response to treatment with pathogens. These results show that the abundance of PELPK1 is positively correlated with plant growth rate under some conditions. PELPK1 may influence growth through CW modification or other independent pathways.

  • Subjects / Keywords
  • Graduation date
    Spring 2011
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.