Induction kinetics of the nuclear proteins encoded by the early indoleacetic acid-inducible genes, PS-IAA4/5 and PS-IAA6, in pea (Pisum sativum L.).
The plant hormone indoleacetic acid (IAA) rapidly induces transcription of two genes, PS-IAA4/5 and PS-IAA6, in pea that encode nuclear proteins. The proteins were expressed in Escherichia coli and polyclonal antibodies were raised. The proteins can neither be detected on immunoblots of pea extracts from IAA-treated epicotyls nor subcellularly localized by immunofluorescence, suggesting that they are of low abundance. However, they can be immunoprecipitated as 35S-methionine-labeled proteins synthesized in vivo from control and IAA-treated tissue segments. Short-term time-course experiments indicate that the amounts of PS-IAA4/5 and PS-IAA6 proteins decrease dramatically in non-IAA-treated tissue. However, the hormone slightly increases the PS-IAA4/5 and significantly enhances the PS-IAA6 proteins compared with the initial amounts present in the tissue, despite a large induction of both mRNAs. A net increase in the amount of the in vivo synthesized PS-IAA6 is observed after a lag period of 30 min after addition of IAA. Little or no PS-IAA4/5 or PS-IAA6 protein is detected after 6 h of induction, even though PS-IAA4/5 and PS-IAA6 mRNAs remain detectable. Immunoprecipitation of in vitro translated polypeptides with mRNAs from various auxin-treated and untreated mono- and dicotyledonous plants reveals that similar proteins are encoded by constitutive or IAA-induced mRNAs. Phylogenetic analysis of 10 PS-IAA4-like proteins from various plant species reveals that the PS-IAA4 and PS-IAA6 proteins belong to different lineages, suggesting that they may have distinct functions. The data suggest that as a primary response to IAA plant tissues produce short-lived nuclear proteins whose synthesis is regulated at the transcriptional and post-transcriptional levels.
Oeller
P W
PW
Plant Gene Expression Center, Albany, CA 94710.
Theologis
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D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004926:Escherichia coli / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D007210:Indoleacetic Acids / Q000494:pharmacology*; D007700:Kinetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics*; D018532:Pisum sativum / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics*; D011233:Precipitin Tests; D013045:Species Specificity
D018076:DNA, Complementary; D007210:Indoleacetic Acids; D009687:Nuclear Proteins; D010940:Plant Proteins; C030737:indoleacetic acid