Characterization, chromosomal mapping, and expression of different polyubiquitin genes in tissues from control and heat-shocked maize seedlings.
Polyubiquitin transcripts accumulate in plant and animal cells following a heat shock. Most species have a few to several polyubiquitin genes; within a species, the genes may differ in nucleotide (nt) sequence and (or) the number of 228-nt repeats encoding the ubiquitin monomer. This study examines three maize (inbred Oh43) polyubiquitin genes. Two of the genes, MubG9 and MubG5, possess five repeats; the third, MubG1 possesses seven repeats. Sequence analyses of the genomic clones, MubG9 and MubG1 and a cDNA clone, MubG5, reveal that they differ primarily from each other in their nt sequences 5' and 3' to their open reading frames. MubG1 contains a 1004-base pair (bp) intron in its 5' untranslated region. Using gene-specific probes, we show that the amount of polyribosome-associated mRNA transcripts from MubG9 isolated from 2- and 5-day old plumules and radicles is unchanged by heat shock. While the amount of transcript from MubG1 and MubG5 on the polyribosomes in plumules and radicles of 2-day-old seedlings is also unchanged by heat shock, the levels of these transcripts are elevated considerably in similar tissues from heat-shocked 5-day-old seedlings. Similar or identical gene-specific probes were employed to map the genes using the recombinant inbred method. MubG9 maps to chromosome 4L position 186; MubG1 maps to 5L104 and MubG5 to 4L188. The opportunity to use gene-specific probes extends the evidence for distinct modulation (time and tissue) of polyubiquitin gene expression in maize and provides the basis for locus assignment within the genome.
Liu
L
L
Department of Zoology, University of Western Ontario, London, Canada.
Maillet
D S
DS
Frappier
J R
JR
Walden
D B
DB
Atkinson
B G
BG
D001483:Base Sequence; D001704:Biopolymers / Q000096:biosynthesis / Q000235:genetics*; D002874:Chromosome Mapping; D015342:DNA Probes; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D017343:Genes, Plant / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics*; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry; D011132:Polyribosomes / Q000737:chemistry; D025821:Polyubiquitin; D018749:RNA, Plant / Q000032:analysis / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D014452:Ubiquitins / Q000096:biosynthesis / Q000235:genetics*; D003313:Zea mays / Q000235:genetics*
D001704:Biopolymers; D015342:DNA Probes; D018076:DNA, Complementary; D018744:DNA, Plant; D006360:Heat-Shock Proteins; D018749:RNA, Plant; D014452:Ubiquitins; D025821:Polyubiquitin