Hartmut E. Schroeder

Bean [alpha]-Amylase Inhibitor Confers Resistance to the Pea Weevil (Bruchus pisorum) in Transgenic Peas (Pisum sativum L.)

Bruchid larvae cause major losses of grain legume crops through-out the world. Some bruchid species, such as the cowpea weevil and the azuki bean weevil, are pests that damage stored seeds. Others, such as the pea weevil (Bruchus pisorum), attack the crop growing in the field. We transferred the cDNA encoding the [alpha]-amylase inhibitor ([alpha]-AI) found in the seeds of the common bean (Phaseolus vulgaris) into pea (Pisum sativum) using Agrobacterium-mediated transformation. Expression was driven by the promoter of phytohemagglutinin, another bean seed protein. The [alpha]-amylase inhibitor gene was stably expressed in the transgenic pea seeds at least to the T5 seed generation, and [alpha]-AI accumulated in the seeds up to 3% of soluble protein. This level is somewhat higher than that normally found in beans, which contain 1 to 2% [alpha]-AI. In the T5 seed generation the development of pea weevil larvae was blocked at an early stage. Seed damage was minimal and seed yield was not significantly reduced in the transgenic plants. These results confirm the feasibility of protecting other grain legumes such as lentils, mungbean, groundnuts, and chickpeas against a variety of bruchids using the same approach. Although [alpha]-AI also inhibits human [alpha]-amylase, cooked peas should not have a negative impact on human energy metabolism.

Transformation and Regeneration of Two Cultivars of Pea (Pisum sativum L.)

A reproducible transformation system was developed for pea (Pisum sativum L.) using as explants sections from the embryonic axis of immature seeds. A construct containing two chimeric genes, nopaline synthase-phosphinothricin acetyl transferase (bar) and cauliflower mosaic virus 35S-neomycin phosphotransferase (nptII), was introduced into two pea cultivars using Agrobacterium tumefaciens-mediated transformation procedures. Regeneration was via organogenesis, and transformed plants were selected on medium containing 15 mg/L of phosphinothricin. Transgenic peas were raised in the glasshouse to produce flowers and viable seeds. The bar and nptII genes were expressed in both the primary transgenic pea plants and in the next generation progeny, in which they showed a typical 3:1 Mendelian inheritance pattern. Transformation of regenerated plants was confirmed by assays for neomycin phosphotransferase and phosphinothricin acetyl transferase activity and by northern blot analyses. Transformed plants were resistant to the herbicide Basta when sprayed at rates used in field practice.

The Expression of an Ovalbumin and a Seed Protein Gene in the Leaves of Transgenic Plants

Many major hurdles in the genetic engineering of plants have been overcome in recent years. These hurdles include the availability of characterized genes for transfer, systems for gene integration into a plant cell nucleus and regeneration of whole plants from cells carrying the integrated DNA. Apart from its value as a tool for unravelling the control of gene expression, genetic engineering has great potential as a means of introducing agronomically useful characters into crop and pasture plants. Although the number of crop and pasture plants that can be transformed and regenerated is still fairly small, the list is increasing rapidly (Gasser and Fraley, 1989).

Retardation of soybean leaf senescence and associated effects on seed composition

Soybean leaf senescence, leaf abscission, and pod yellowing were markedly delayed by sprays of 10−4 M 6-benzylamino-9-(tetrahydropyran-2-yl)purine plus 5×10−5 M α-naphthalene acetic acid. The pods on the sprayed plants turned yellow 5–7 days later than those on the control plants, and the treated leaves remained dark green even when the pods had already desiccated. The antisenescence spray did not change pod numbers, seed numbers, seed size, or the yield. By retarding senescence, seed nitrogen content was increased in both TCA-soluble and TCA-insoluble fractions. Seed total protein, buffer-extractable total protein, and globulin were increased by 26, 28, and 33 mg/g of seed flour, respectively, and albumin was decreased by 6 mg/g. The overall increase in seed protein caused by spray treatment is confined to the globulin portion.