A1 Journal article – refereed

A chloroplast-targeted DnaJ protein AtJ8 is negatively regulated by light and has rapid turnover in darkness

List of Authors: Chen KM, Piippo M, Holmstrom M, Nurmi M, Pakula E, Suorsa M, Aro EM


Publication year: 2011

Journal: Journal of Plant Physiology

Journal name in source: JOURNAL OF PLANT PHYSIOLOGY

Journal acronym: J PLANT PHYSIOL

Number in series: 15

Volume number: 168

Issue number: 15

Number of pages: 4

ISSN: 0176-1617

DOI: http://dx.doi.org/10.1016/j.jplph.2011.04.001

The DnaJ proteins (also called as J proteins, J domain proteins or HSP40 proteins) function as molecular co-chaperones for the HSP70 proteins. We assessed the expression of the small chloroplast-targeted DnaJ protein, the AtJ8 protein, by subjecting the wild type Arabidopsis plants to different illumination conditions. It is shown that the expression of the transcripts and proteins of the ATJ8 gene is primarily regulated at the level of transcription. When plants were incubated under high light for 3 h, both the transcripts and proteins were completely abolished. Upon transfer of plants to darkness, the transcripts started rapidly accumulating, and subsequently, the AtJ8 protein became visible after 2 h in darkness. Conversely, incubation of plants in darkness or under low light intensities induced expression of the ATJ8 transcripts and proteins. Feeding plants with sugars clearly decreased the transcript and protein levels, and incubation with cycloheximide revealed a rapid turnover for AtJ8 in darkness. Moreover, the AtJ8 protein was found to be nearly missing from the van l mutant, which lacks the FTSH5 protease. It is concluded that AtJ8 is expressed mainly in darkness, is prone to a rapid turnover but is partially stabilized by the FTSH proteases. (C) 2011 Elsevier GmbH. All rights reserved.

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