Comparison of the expression of a plastidic chaperonin 60 in different plant tissues and under photosynthetic and non-photosynthetic conditions.
A partial cDNA which codes for the beta-subunit of a plastidic chaperonin 60 (cpn60-beta) from rye (Secale cereale L.) leaves was identified and sequenced, except for 46 amino acids of the N-terminus of the mature protein and the transit sequence. This is the first cpn60-beta sequence determined for a monocotyledonous plant. Specific antibodies against cpn60-beta were affinity-purified from an antiserum raised against the total soluble protein fraction of ribosome-deficient plastids. The localization of cpn60-beta in chloroplasts or non-green plastids was confirmed by immunodetection in Percoll gradient-purified organelles. The expression and occurrence of cpn60-beta was analysed by immunoblotting with the specific antibodies and Northern hybridization. The cpn60-beta protein was constitutively expressed in various green and non-green tissues. It was evenly distributed along the major part of a rye leaf, while highest transcript levels occurred in the youngest and oldest leaf sections. The expression of the cpn60-beta protein was not enhanced by a heat-shock treatment at 42 degrees C. The cpn60-beta transcript and protein were more strongly expressed in various non-green, for instance etiolated, 70S-ribosome-deficient 32 degree C-grown, or herbicide-bleached tissues, than in green leaves of rye. A rapid increase in the cpn60-beta transcript level was also observed when green leaves were transferred from light to darkness while the protein level was not affected. The dark-induced increase in the cpn60-beta transcript was totally suppressed in the presence of 2% sucrose. Inhibitor treatments suggested that the change in cpn60-beta transcript level was not related to changes of the ATP supply of the tissue. While the large subunit of the photosynthetic protein ribulose-1,5-bisphosphate carboxylase was largely degraded during ripening of tomato fruits, high levels of cpn60-beta were detected in tomato chromoplasts and in the yellow flower petals of Narcissus. Low levels of cpn60-beta were detected in root tissue.
Schmitz
G
G
Botanisches Institut, J.W. Goethe-Universität, Frankfurt am Main, Germany.
Schmidt
M
M
Feierabend
J
J
D000595:Amino Acid Sequence; D018834:Chaperonin 60 / Q000096:biosynthesis* / Q000737:chemistry; D003001:Cloning, Molecular; D018076:DNA, Complementary; D003624:Darkness; D004926:Escherichia coli / Q000378:metabolism; D008027:Light; D008969:Molecular Sequence Data; D010788:Photosynthesis; D018515:Plant Leaves; D010944:Plants / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D012434:Secale / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014908:Triticum / Q000378:metabolism
D018834:Chaperonin 60; D018076:DNA, Complementary; D011994:Recombinant Proteins