PLANT PHYSIOLOGY , Vol 107, Issue 3 765-773, Copyright © 1995 by American Society of Plant Biologists
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GENE REGULATION AND MOLECULAR GENETICS |
Differential Accumulation of Sunflower Tetraubiquitin mRNAs during Zygotic Embryogenesis and Developmental Regulation of Their Heat-Shock Response
C. Almoguera, M. A. Coca and J. Jordano
Instituto de Recursos Naturales y Agrobiologia, Consejo Superior de Investigaciones Cientificas, Apartado 1052, 41080 Sevilla, Spain
We have isolated and sequenced Ha UbiS, a cDNA for a dry-seed-stored mRNA
that encodes tetraubiquitin. We have observed differential accumulation of
tetraubiquitin mRNAs during sunflower (Helianthus annuus L.) zygotic
embryogenesis. These mRNAs were up-regulated during late embryogenesis and
reached higher prevalence in the dry seed, where they were found to be
associated mainly with provascular tissue. UbiS mRNA, as confirmed by Rnase
A protection experiments, accumulated also in response to heat shock, but
only in leaves and later during postgerminative development. These novel
observations demonstrate expression during seed maturation of specific
plant polyubiquitin transcripts and developmental regulation of their
heat-shock response. Using ubiquitin antibodies we also detected discrete,
seed-specific proteins with distinct temporal expression patterns during
zygotic embryogenesis. Some of these patterns were concurrent with UbiS
mRNA accumulation in seeds. The most abundant ubiquitin-reacting proteins
found in mature seeds were small (16-22 kD) and acidic (isoelectric points
of 6.1-7.4). Possible functional implications for UbiS expression elicited
from these observations are discussed.
