Virus induction of heat shock protein 70 reflects a general response to protein accumulation in the plant cytosol.
Different cytoplasmically replicating RNA viruses were shown to induce a specific subset of heat-inducible heat shock protein 70 (HSP70) genes in Arabidopsis (Arabidopsis thaliana). To identify the inducing principle, a promoterreporter system was developed for the facile analysis of differentially responding Arabidopsis HSP70 genes, by infiltration into Nicotiana benthamiana leaves. Through transient expression of individual viral cistrons or through deletion analysis of a viral replicon, we were unable to identify a unique inducer of HSP70. However, there was a positive correlation between the translatability of the test construct and the differential induction of HSP70. Since these data implied a lack of specificity in the induction process, we also expressed a random series of cytosolically targeted Arabidopsis genes and showed that these also differentially induced HSP70. Through a comparison of different promoterreporter constructs and through measurements of the steady-state levels of the individual proteins, it appeared that the HSP70 response reflected the ability of the cytosol to sense individual properties of particular proteins when expressed at high levels. This phenomenon is reminiscent of the unfolded protein response observed when the induced accumulation of proteins in the endoplasmic reticulum also induces a specific suite of chaperones.
Aparicio
Frederic
F
John Innes Centre, Norwich NR4 7UH, United Kingdom.
Thomas
Carole L
CL
Lederer
Carsten
C
Niu
Yan
Y
Wang
Daowen
D
Maule
Andrew J
AJ
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000235:genetics; D001483:Base Sequence; D003600:Cytosol / Q000378:metabolism*; D017931:DNA Primers; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic
D029681:Arabidopsis Proteins; D017931:DNA Primers; D018840:HSP70 Heat-Shock Proteins