PLANT PHYSIOLOGY , Vol 101, Issue 1 171-177, Copyright © 1993 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Characterization of Three Related Low-Temperature-Regulated cDNAs from Winter Brassica napus
E. Weretilnyk, W. Orr, T. C. White, B. Iu and J. Singh
Plant Research Centre, Agriculture Canada, Ottawa, Ontario, Canada, K1A 0C6
A cDNA clone, pBN115, encoding a low-temperature-regulated transcript in
winter Brassica napus has been isolated. Northern blot analyses show that
levels of transcripts hybridizing to pBN115 increase within 24 h of
exposure of B. napus to low temperature, peak at 3 d, and then remain at an
elevated level for the duration of the cold treatment (up to 10 weeks).
Transferring plants from 2[deg]C to room temperature results in the loss of
detectable transcripts hybridizing to pBN115 within 1 d. The transcript was
not detected in RNA isolated from roots of cold-acclimated B. napus.
Results of in vivo labeling of nascent RNA in leaf discs of B. napus with
thiouridine suggest that regulation of expression may be transcriptional,
at least at the onset of cold temperature. Although drought stress leads to
a slight increase in transcript level at room temperature, neither a brief
exposure to elevated temperatures nor exogenous application of abscisic
acid resulted in the appearance of the transcript represented by pBN115.
Furthermore, transcripts hybridizing to pBN115 were present at the same
levels whether the plants were acclimated in the light or dark.
Hybridization experiments show that pBN115 hybridizes strongly to
cold-regulated transcripts in Arabidopsis thaliana, Descurania sophia, and
spring B. napus, all of which are cruciferous plants capable of cold
acclimation. No hybridizing transcript could be detected in cold-acclimated
Spinacea oleracea, winter Secale cereale, or cold-grown Nicotiana tabacum.
DNA sequence analysis of pBN115 reveals a single open reading frame that
potentially encodes a protein of 14.8 kD. This size closely approximates
that of a polypeptide produced by in vitro transcription/translation
experiments. Two additional cDNA clones, pBN19 and pBN26, with divergent
5[prime]- and 3[prime]-untranslated regions, were also isolated and found
to encode similar, but not identical, polypeptides.
