The auxin-induced maize gene ZmSAUR2 encodes a short-lived nuclear protein expressed in elongating tissues.
By differential screening of a cDNA library from auxin-induced maize coleoptiles we have isolated and characterized a SAUR gene, designated ZmSAUR2, belonging to a not yet characterized subtype of the SAUR family. ZmSAUR2 encodes a 15.3-kDa protein and is specifically induced by auxin in elongating coleoptile tissue but not in primary leaves or in roots. The transcript level rapidly increased within minutes and preceded auxin-stimulated elongation of coleoptile segments. Cycloheximide also induced ZmSAUR2 transcription, as has been shown for other early auxin-induced genes, whereas abscisic acid, brassinolide, ethylene, gibberellic acid, kinetin, and methyl jasmonate did not provoke an increase in ZmSAUR2 mRNA abundance. In pulse-chase experiments using auxin-induced coleoptiles and an anti-ZmSAUR2 antibody we were able to precipitate a protein of the expected molecular mass and to determine a half-life of about 7 min, which is among the shortest known in eukaryotes. In gel shift assays binding of calmodulin to ZmSAUR2 was demonstrated, suggesting the possibility of post-transcriptional regulation. Upon transformation of onion epidermal cells with a ZmSAUR2::GUS construct the corresponding chimeric protein was detected in the nucleus. The results suggest that ZmSAUR2 encodes a short-lived nuclear protein that might be involved in auxin-mediated cell elongation.
Knauss
Stefan
S
Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Universität Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
Rohrmeier
Thomas
T
Lehle
Ludwig
L
D001483:Base Sequence; D002147:Calmodulin / Q000378:metabolism; D018548:Cotyledon / Q000166:cytology; D018076:DNA, Complementary / Q000302:isolation & purification; D005786:Gene Expression Regulation / Q000187:drug effects*; D006207:Half-Life; D007210:Indoleacetic Acids / Q000494:pharmacology*; D007700:Kinetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development
D002147:Calmodulin; D018076:DNA, Complementary; D007210:Indoleacetic Acids; D009687:Nuclear Proteins