ISSN:
1432-2048
Keywords:
Nicotiana
;
Nutrient deficiency
;
Pyrophosphate:fructose-2-phosphate 1-phosphotransferase
;
Respiration
;
Temperature
;
Transgenic plant
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Transformation of tobacco with the potato gene encoding the subunit of pyrophosphate: fructose-6-phosphate 1-phosphotransferase (PFP) in the antisense orientation under the control of the constitutive CaMV 35S promoter, followed by selfing and crossing of the transformants, generated a line of tobacco (5–37) with up to an 85% reduction in PFP activity in the shoot. Transformants containing a sense construct (4-40-91) contained only 1–3% of wild-type PFP, presumably due to co-suppression. Rates of photosynthesis and partitioning between sucrose and starch in source leaves were identical in 4-40-91 transformants and the wild type. In the dark in sink leaves of 4-40-91 transformants, levels of hexose phosphates were up to 50% higher, glycerate-3-phosphate 30% lower and fructose-2,6-bisphosphate threefold higher than in the wild type; inorganic pyrophosphate, pyruvate and the ATP/ADP ratio were unaltered. Low -PFP and wild-type plants did not differ significantly in their rate of growth at 25° C and 200 μmol quanta · m−2 · s−1 on full nutrient medium. Growth on limiting phosphate and limiting nitrogen was inhibited identically in the wild type and transformants, and transformants adjusted their shoot/root ratio in an identical manner to the wild type. Differences in fructose-2,6-bisphosphate and glycolytic metabolites between the wild type and transformants were no larger in these suboptimal nutrient conditions, than in optimal conditions. Growth of the wild type and 4-40-91 transformants was inhibited identically at 12° C compared to 25° C. Differences in fructose-2,6-bisphosphate were smaller when the genotypes were compared at 12° C than at 25° C. We conclude that PFP does not play an essential role in photosynthate partitioning in source leaves. During respiratory metabolism in sink leaves it catalyzes a net glycolytic flux, as in potato tubers. However, tobacco seedlings are able to compensate for a large decrease in expression of PFP without loss of growth, or the ability to cope with suboptimal phosphate, nitrogen or temperature.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00201385
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