Transgenic plants that exhibit enhanced nitrogen assimilation

Abstract

Transgenic plants containing free amino acids, particularly at least one amino acid selected from among glutamic acid, asparagine, aspartic acid, serine, threonine, alanine and histidine accumulated in a large amount, in edible parts thereof, and a method of producing them are provided. In this method, glutamate dehydrogenase (GDH) gene is introduced into a plant together with a regulator sequence suitable for over expressing the sequence encoding GDH gene in plant cells.

Description

[0001] This application is a continuation-in-part of co-pending application Ser. No. 08 / 132,334 filed Oct. 6, 1993, which is hereby incorporated by reference in its entirety.1. INTRODUCTION[0003] The present invention relates generally to genetic-engineering plants to display enhanced nitrogen assimilatory and utilization capacities, grow larger, more efficiently or rapidly, and / or have enriched nitrogen contents in vegetative and / or reproductive plant parts and / or increased biomass. More particularly, this invention relates to producing transgenic plants engineered to have altered expression of key enzymes in the nitrogen assimilation and utilization pathways. The engineered plants may be productively cultivated under conditions of low nitrogen fertilizer input or in nitrogen poor soils. Alternatively, the engineered plants may be used to achieve faster growing or maturing crops, higher crop yields and / or more nutritious products under ideal cultivation conditions.2. BACKGROUND OF ...

AI Technical Summary

Benefits of technology

0032] The present invention is based, in part, on the surprising finding that enhancing the expression of nitrogen assimilation or utilization enzymes in plants resulted in enhanced growth characteristics, or improved vegetative or reproductive yields. The invention is illustrated herein by the way of working examples in which tobacco plants were engineered with recombinant constructs encoding a strong, constitutive ant promoter, the cauliflower mosaic virus (CaMV) 35S promoter, operably linked with sequences encoding a pea glutamine synthetase (GS) gene or a pea asparagine synthetase (AS) gene. RNA and protein analyses showed that a majority of the engineered plants exhibited ectopic, overexpression of GS or AS. The GS or AS overexpressing lines have higher nitrogen contents, more vigorous growth characteristics, increased vegetative yields or better seed yields and quality than the control, wild-type plant.

Problems solved by technology

Nitrogen is often the rate-limiting element in plant growth and all field crops have a fundamental dependence on inorganic nitrogenous fertilizer.

There are, however, considerable difficulties associated with the screening of extensive populations in conventional breeding programs for traits which are difficult to assess under field conditions, and such selection strategies have been largely unsuccessful.

By contrast, numerous studies examining overexpression of glutamine synthetase (GS) have failed to report any positive effect of the overexpression on plant growth.

Moreover, it is unclear whether the faster growth produce mature plants with greater biomass or reproductive yield.

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