Isolation of a cDNA clone for a cytokinin-repressed gene in excised cucumber cotyledons.
Rapid changes in gene expression were studied during incubation of cucumber (Cucumis sativus L.) cotyledons with cytokinins in darkness. Complementary-DNA clones for mRNAs whose levels decreased within 4 h of treatment with N6-benzyladenine (BA) were isolated by differential hybridization. One of them (CR9) was sequenced. It is 588 bp long, and would encode a protein consisting of 137 amino-acid residues and having a molecular mass of 15 kDa. The sequence shows a high homology with a light-induced gene from rice. Northern blot analysis of the CR9 transcript showed the level of the mRNA (0.7 kb) to decrease tenfold within 4 h of BA treatment, i.e. well before BA-induced cotyledon expansion was observed. The repression became greater with increasing concentration of BA (10(-8)-10(-5) M). The expression of the CR9 gene was repressed specifically by cytokinins (BA, isopentenyladenine and t-zeatin), but not by adenine or 2,4-dichlorophenoxyacetic acid (auxin). The results are discussed in relation to the primary action of cytokinin.
Teramoto
H
H
Department of Botany, Faculty of Science, Kyoto University, Japan.
Momotani
E
E
Takeba
G
G
Tsuji
H
H
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000595:Amino Acid Sequence; D001483:Base Sequence; D001593:Benzyl Compounds; D003583:Cytokinins / Q000502:physiology*; D018076:DNA, Complementary; D005786:Gene Expression Regulation; D017343:Genes, Plant; D007701:Kinetin; D009693:Nucleic Acid Hybridization; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics*; D011687:Purines; D012333:RNA, Messenger / Q000235:genetics; D013997:Time Factors; D014675:Vegetables / Q000235:genetics*
D001593:Benzyl Compounds; C088308:CR9 protein, Cucumis sativus; D003583:Cytokinins; D018076:DNA, Complementary; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011687:Purines; D012333:RNA, Messenger; D000225:Adenine; C480551:benzylaminopurine; D007701:Kinetin