Sucrose Metabolism in Plastids1

• Published in: Plant physiology (Bethesda) Vol. 125; no. 2; pp. 926 - 934
• Main Authors: Gerrits, Nathalie, Turk, Stefan C.H.J., van Dun, Kees P.M., Hulleman, Stephan H.D., Visser, Richard G.F., Weisbeek, Peter J., Smeekens, Sjef C.M.
• Format: Journal Article
• Language: English
• Published: American Society of Plant Physiologists 01-02-2001
• ISSN: 0032-0889; 1532-2548

The question whether sucrose (Suc) is present inside plastids has
been long debated. Low Suc levels were reported to be present inside
isolated chloroplasts, but these were argued to be artifacts of the
isolation procedures used. We have introduced Suc-metabolizing enzymes
in plastids and our experiments suggest substantial Suc entry into
plastids. The enzyme levansucrase from
Bacillus subtilis
efficiently synthesizes fructan from Suc. Targeting of this enzyme to
the plastids of tobacco (
Nicotiana tabacum
) and potato
(
Solanum tuberosum
) plants leads to high-level fructan
accumulation in chloroplasts and amyloplasts, respectively. Moreover,
introduction of this enzyme in amyloplasts leads to an altered starch
structure. Expression of the yeast invertase in potato tuber
amyloplasts results in an 80% reduction of total Suc content, showing
efficient hydrolysis of Suc by the plastidic invertase. These
observations suggest that Suc can enter plastids efficiently and they
raise questions as to its function and metabolism in this
organelle.