Expression of a yeast-derived invertase in the cell wall of tobacco and Arabidopsis plants leads to accumulation of carbohydrate and inhibition of photosynthesis and strongly influences growth and phenotype of transgenic tobacco plants.

Abstract

Chimeric genes consisting of the coding sequence of the yeast invertase gene suc 2 and different N‐terminal portions of the potato‐derived vacuolar protein proteinase inhibitor II fused to the 35S CaMV promoter and the poly‐A site of the octopine synthase gene were transferred into tobacco and Arabidopsis thaliana plants using Agrobacterium based systems. Regenerated transgenic plants display a 50‐ to 500‐fold higher invertase activity compared to non‐transformed control plants. This invertase is N‐glycosylated and efficiently secreted from the plant cell leading to its apoplastic location. Whereas expression of the invertase does not lead to drastic changes in transgenic Arabidopsis thaliana plants, transgenic tobacco plants show dramatic changes with respect to development and phenotype. Expression of the invertase leads to stunted growth due to reduction of internodal distances, to development of bleached and/or necrotic regions in older leaves and to suppressed root formation. In mature leaves, high levels of soluble sugars and starch accumulate. These carbohydrates do not show a diurnal turnover. The accumulation of carbohydrate is accompanied by an inhibition of photosynthesis, and in tobacco, by an increase in the rate of respiration. Measurements in bleached versus green areas of the same leaf show that the bleached section contains high levels of carbohydrates and has lower photosynthesis and higher respiration than green sections. It is concluded that expression of invertase in the cell wall interrupts export and leads to an accumulation of carbohydrates and inhibition of photosynthesis.

In situ effects of elevated CO2 on the carbon and nitrogen status of alpine plants

“…However, as our data indicate, this effect can not be attributed to N dilution by accumulating TNC as has been proposed by Wong (1979) but is rather the result of a decrease in Rubisco, an effect frequently observed under elevated CO 2 (Sage, Sharkey & Seemann 1989). Thus, TNC accumulation may have a regulatory effect on Rubisco (Von Schaewen et al 1990;Stitt 1991) and the observed decrease in leaf nitrogen most likely reflects a downward adjustment of photosynthesis under conditions of an imbalance between carbon supply and demand. We have evidence that such downregulation of photosynthetic capacity has taken place (Diemer 1994;Sage, Schäppi & Körner 1997) similar to what had been observed in arctic tundra (Grulke et al 1990).…”

Systemic Acquired Resistance Mediated by the Ectopic Expression of Invertase: Possible Hexose Sensing in the Secretory Pathway.

“…Transgenic tobacco plants expressing yeast invertase in the apoplast and vacuole may develop necrotic lesions spontaneously on their source leaves, in contrast to transgenic tobacco plants in which the yeast invertase is located in the cytosol (von Schaewen et al, 1990;Sonnewald et al, 1991). Formation of necroses starts at the tip and develops to the leaf base as individual necrotic lesions, which in the end may coalesce.…”

“…Frommer, submitted manuscript) are characterized by a metabolic disturbance similar to that seen in cwlnv plants. In both cases, phloem loading of sucrose is inhibited, and as a consequence, leaves accumulate carbohydrates (von Schaewen et al, 1990; L. Burkle, J.…”

“…They have been designated cwlnv, vaclnv, and cytlnv, respectively (von Schaewen et al, 1990;Sonnewald et al, 1991). Apoplastic and vacuolar invertases give rise to stunted growth and to development of bleached and/or necrotic regions in older leaves (von Schaewen et al, 1990;Sonnewald et al, 1991).…”

“…These symptoms are reminiscent of disease lesion-mimic mutants. Biochemically, the plants are characterized by limited sucrose export, resulting in accumulation of photoassimilates and inhibition of photosynthesis in their leaves (von Schaewen et al, 1990;Sonnewald et al, 1991). Stimulated by the observation that vaclnv and cwlnv plants develop necroses like those of lesionmimic mutants, we studied defense-related responses and SAR in the transgenic plants.…”