Zh. Miao et Jj. Gaynor, MOLECULAR-CLONING, CHARACTERIZATION AND EXPRESSION OF MN-SUPEROXIDE DISMUTASE FROM THE RUBBER TREE (HEVEA-BRASILIENSIS), Plant molecular biology, 23(2), 1993, pp. 267-277
A genomic clone encoding manganese-containing superoxide dismutase (SO
D; EC 1.15.1.1) was isolated from a Hevea brasiliensis genomic library
made in A phage EMBL3 by using a heterologous cDNA probe of MnSOD fro
m Nicotiana plumbaginifolia. The nucleotide sequence of 4968 bp from t
he genomic clone was determined. Based on the putative translation ini
tiation codon and stop codon, PCR primers were design ed and utilized
for cloning the full-length cDNA from total mRNA. Of the two distinct
cDNAs of MnSOD isolated, MnSOD-A has a perfect match with exons of the
nuclear gene, while MnSOD-B has a 90.2% homology and is 6 nucleotides
longer than MnSOD-A in the putative transit peptide region. The nucle
ar gene comprises 6 exons and 5 introns, giving a total length of 3211
bp. The sequences of 1400 bp upstream of the initiation codon and 320
bp downstream of the stop codon were also determined. Southern analys
is of genomic DNA from Hevea probed with a genomic fragment indicated
there are at least two genes of MnSOD in Hevea. Northern blot analysis
showed that MnSOD transcripts were present in all tissues examined (l
eaf, petiole, root, latex, callus) with young leaves showing the highe
st levels in intact plants. The transcript level in embryogenic callus
was nearly 50-fold higher than in mature leaves. In addition, transcr
ipts of MnSOD could be induced 3- to 5-fold in response to sucrose, et
hephon and Murashige-Skoog salts.