ISSN:
1617-4623
Keywords:
Thioredoxins
;
Cell growth
;
Protoplast
;
Nicotina tabacum
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract A Nicotiana tabacum thioredoxin h gene (EMBL Accession No. Z11803) encoding a new thioredoxin (called h2) was isolated using thioredoxin h1 cDNA (X58527), and represents the first thioredoxin h gene isolated from a higher plant. It encodes a polypeptide of 118 amino acids with the conserved thioredoxin active site Trp-Cys-Gly-Pro-Cys. This gene comprises two introns which have lengths of 1071 and 147 by respectively, and three exons which encode peptides of 29, 41 and 48 amino acids, respectively. This thioredoxin h shows 66% identity with the amino acid sequence of thioredoxin h1 (X58527) and only around 35% with the choroplastic thioredoxins. The two thioredoxins, h1 and h2, do not have any signal peptides and are most probably cytoplasmic. Using the 3′ regions of the mRNAs, two probes specific for thioredoxins h1 and h2 have been prepared. Southern blot analysis shows that thioredoxin sequences are present in only two genomic EcoRI fragments: a 3.3 kb fragment encodes h1 and a 4.5 kb fragment encodes h2. Analysis of the ancestors of the allotetraploid N. tabacum shows that thioredoxin h2 is present in N. sylvestris and N. tomentosiformis but that thioredoxin h1 is absent from both putative ancestors. Thus, the thioredoxin h1 gene has probably been recently introduced in to N. tabacum as a gene of agronomic importance, or linked to such genes. Northern blot analysis shows that both genes are expressed in N. tabacum, mostly in organs or tissues that contain growing cells. Thioredoxin h1 is always expressed at a lower level than h2 in tobacco plants. In contrast, the thioredoxin hl gene is abundantly expressed in freshly isolated protoplasts, while h2 mRNAs are not detectable.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00279557
Permalink
