Search

Genetically modified potato plants that are resistant to the Colorado potato beetle, plus either the potato leaf roll virus or potato virus Y, have recently been commercialized. As part of the safety assessment for plants produced by modern biotechnology, the composition of the food/feed must be compared to that of the food/feed produced by an equivalent plant variety from a conventional source. The composition of important nutritional and antinutritional factors in tubers produced by virus- and insect-resistant potato plants were compared to tubers produced by conventional potato plants. Key nutritional, quality, and antinutritional components measured were total solids, vitamin C, dextrose, sucrose, soluble protein, and glycoalkaloids. Proximate analyses included fat, ash, calories, total protein, and crude fiber. Minor nutrients measured were vitamin B6, niacin, copper, magnesium, potassium, and amino acids. The results from these analyses confirm that tubers produced by insect- and virus-protected varieties are substantially equivalent to tubers produced by conventional potato varieties.

Light microscope immunofluorescence was used to localize the membrane binding of Bacillus thuringiensis kurstaki 63-kDa δ-endotoxin in Heliothis virescens midgut and Malpighian tubules. Staining was observed along all exposed mucosal (apical microvillar) plasma membranes. Interpretation of the serosal (basal) plasma membrane staining was complicated because the basal lamina also stained. The results suggest that the toxin binds to all exposed plasma membranes without apparent specificity for particular membrane domains.

assay (ELISA) for the Bt protein. A FG is represented by the potatoes harvested from a potato field. These potatoes can be used, whole or in pieces, as vegetative propagules for the next year’s potato field. The FG is sequentially numbered beginning with the first potatoes generated (FG1) from tissue culture derived plants. By beginning new field plots from tissue culture plants in three consecutive years, a sequence of three different FG were generated and they could all be planted in the same season for the expression analysis. This type of experimental design avoided the complication of comparing ELISA results from different years. Results from this work indicated that there was no difference in the Bt protein expression level over three field generations (Table 3). Although the results compare different ELISA assays, there was also no significant difference seen between results obtained in this experiment and those obtained 4 years earlier (Table 3). NewLeaf Plus®. NewLeaf Plus potatoes were created by the insertion of a gene for the replicase protein of the potato leaf roll virus (PLRV) and the gene for a bacterial protein endotoxin (Bt) from Bacillus thuringiensis var. tenebrionis. PLRV is an aphid transmitted virus that can also be transmitted from one growing season to another by the planting of infected potatoes. In the second growing season after infection, yield loss can be as high as 50% to 80% (Banttari et al., 1993). More significant, however, is an internal tuber defect called net necrosis that results in some varieties (e.g., ‘Russet Burbank’) from PLRV infection. Net necrosis can be a major quality defect causing substantial economic loss for potato growers. Typical control of PLRV is through controlling the aphid vector population, planting seed potato in areas with reduced aphid presence, and through the certification of seed potato as virus free (Slack, 1993). NewLeaf Plus, which has been commercially available only since the spring of 1999, provides season-long control against disease development of PLRV in In the United States, potato (Solanum tuberosum L.) is second only to wheat (Triticum aestivum L.) in importance as a crop used primarily for human consumption (as opposed to those crops used primarily for livestock feed or vegetable oil). Potato is the largest vegetable crop, representing 15% of all vegetable cash receipts in 1997. In 1997, the farm value of the potato crop was valued between $2 and $3 billion dollars with 526,000 ha planted and 20.9 billion kg of potato harvested (Evans, 1997). These potatoes were consumed as either fresh-market potatoes or as potatoes processed into chips, fries, frozen products, or dehydrated products (Table 1). Potato is a vegetatively propagated crop which is plagued by numerous disease organisms and pests: Colorado potato beetle (Leptinotarsa decemlineata Say), potato virus Y, and potato leaf roll virus to name a few. These particular pests and pathogens are some of the most devastating in North America, with large expense and effort devoted each year to minimizing their effects on potato production (Banttari et al., 1993; Ferro and Boiteau, 1993). Monsanto has developed, through Agrobacterium tumefaciens–mediated transformation, several genetically modified potato cultivars that provide “built-in” protection from these organisms while maintaining superior agronomic performance. Some of these products have been commercially available since 1995, and in 1998 were planted on 20,000 ha in North America (Table 2). In this paper, we will examine these Monsanto products and present results concerning the stability of their inserted genes.

The gene encoding the coleopteran–specific insect control protein from Bacillus thuringiensis var. tenebrionis was isolated and characterized. When expressed in either E. coli or P. fluorescens the gene directs the production of biologically active insect control protein that is lethal to Colorado potato beetle. The gene contains two functional translational initiation codons in the same reading frame leading to the production of both the full length protein and an N–terminal truncated form. The gene has been engineered to produce each of these two proteins separately, and each is active against Colorado potato beetle. Native crystals from B.t. var. tenebrionis were found to contain five distinct proteins derived from this single gene either as primary translation products or the result of proteolysis. Comparison of this gene to a lepidopteran–specific B.t. gene revealed only limited regions of homology.

The effect of Bacillus thuringiensis kurstaki HD-73 δ-endotoxin was determined on the cytoarchitecture and urine transport in isolated Malpighian tubules from larvae of the skipper butterfly Calpodes ethlius. Endotoxins (134 and 64 kDa) were injected into the tubule lumen or applied externally in the bathing medium of Ileac plexus-rectal lead and Yellow region tubules. Mucosal (lumenal) exposure in both tubule regions with the 63 kDa toxin at 16 μg/ml completely inhibited urine secretion and induced massive cytolysis. Serosal (bathing medium) exposure of the 63 kDa toxin in both tubule regions had variable activity and required a 20-fold higher concentration to inhibit fluid secretion and disrupt cell structure. Mucosal exposure to the 134 kDa endotoxin was without effect on cell structure or fluid secretion in both tubule regions confirming its protoxin status. The 63 kDa toxin induced similar cytological alterations in both Ileac plexus-rectal lead and Yellow region Malpighian tubule primary cells. However, mucosal and serosal exposure had different patterns of membrane disorganization, with those membranes closest to the site of application being disrupted first. After 1 hr exposure mucosally, primary cells exhibited variable cytopathological changes with a progression of severity from low to high toxin concentration. Stage 1 (least severe) changes involved enlargement of spaces in the cytoplasm and basal infolds whereas Stage 2 alterations included microvillar disorganization and lysis, mitochondrial alterations, and continued enlargement of cytoplasmic spaces. Stage 3 (most severe) changes included apical and basal membrane lysis, swelling of the rough endoplasmic reticulum and mitochondria, and leakage of cytoplasmic material into the tubule lumen. These results demonstrate that the 63 kDa B. thuringiensis endotoxin affects a fluid-transporting epithelium other than midgut. The similar patterns of activity in two physiologically distinct Malpighian tubule regions by the 63 kDa toxin is most consistent with the idea that the toxin acts by forming pores in cell membranes rather than by poisoning histospecific membrane proteins.

Beim Erhitzen mit Trifluoressigsaure erhalt man aus dem Epoxy-keton (I) die Diketone (II) und (III) unter Ringverengung sowie das Hydroxyketon (IV).