PLANT PHYSIOLOGY , Vol 111, Issue 3 877-883, Copyright © 1996 by American Society of Plant Biologists
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GENE REGULATION AND MOLECULAR GENETICS |
Sugar Regulation of Harvest-Related Genes in Asparagus
K. M. Davies, J. F. Seelye, D. E. Irving, W. M. Borst, P. L. Hurst and G. A. King
New Zealand Institute for Crop & Food Research Ltd., Private Bag 4005, Levin, New Zealand
The signals controlling the abundance of transcripts up-regulated (pTIP27,
pTIP31, and pTIP32) or down-regulated (pTIP20 and pTIP21) after harvest in
asparagus (Asparagus officinalis L.) spears were examined. pTIP27 and
pTIP31 are known to encode asparagine synthetase (AS) and a
[beta]-galactosidase ([beta]-gal) homolog, respectively. The nucleotide
sequences of pTIP20, pTIP21, and pTIP32 were determined, and they encode
histone 3, histone 2B, and an unknown product, respectively. Changes in
respiration, soluble sugars, and abundance of the five mRNAs were similar
in the tips stored as 30-mm lengths or as part of 180-mm spears. We
previously hypothesized that sugars may regulate the level of AS
transcripts in asparagus tissue. Asparagus cell cultures were used to test
the role of sugar status in regulating gene expression. Transcript
abundance for AS, [beta]-gal, and pTIP32 was low in cells in
sugar-containing medium but increased within 12 h after transferring cells
to a sugar-free medium. Histone 3 and histone 2B transcripts were, in
general, abundant in cells on sugar-containing medium but declined in
abundance when transferred to sugar-free medium. When cells were returned
to sugar-containing medium the abundance of transcripts for histone 3 and
histone 2B increased, whereas that for AS, [beta]-gal, and pTIP32
decreased. Soluble sugar levels are known to decline rapidly in the tips of
harvested spears. Metabolic regulation by sugar status may have a major
influence on gene expression in asparagus spears and other tissues after
harvest.
