Enhancing inorganic carbon fixation by photosynthetic organisms

Abstract

A method of enhancing inorganic carbon fixation by a photosynthetic organism. The method is effected by transforming cells of the photosynthetic organism with an expressible polynucleotide encoding a polypeptide having a bicarbonate transporter activity. Preferably, the polynucleotide further includes a plant promoter. Sequences and constructs for implementing the method are also described.

Description

This is a continuation of U.S. patent application Ser. No. 09 / 332,041, filed Jun. 14, 1999.FIELD AND BACKGROUND OF THE INVENTION[0001] The present invention relates to a method of enhancing inorganic carbon fixation by photosynthetic organisms, nucleic acid molecules for effecting the method, and transformed plants characterized by enhanced inorganic carbon fixation.[0002] Photosynthesis is a process executed by photosynthetic organisms by which, inorganic carbon (Ci), such as CO.sub.2 and HCO.sub.3.sup.-, is incorporated into organic compounds using the energy of photon radiation. Photosynthetic organisms, such as, soil grown and aquatic plants and cyanobacteria (blue-green algae), depend on the organic compounds produced via photosynthesis for sustenance and growth.[0003] The rate of photosynthesis is determined by several parameters which include but are not limited to, CO.sub.2 concentration, O.sub.2 concentration, temperature, light intensity, and the water balance in the case ...

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Problems solved by technology

Furthermore, when photosynthesis is rate-limited by the supply of CO.sub.2, the imbalance between the light energy input and its dissipation via CO.sub.2 fixation, leads to photodynamic damage to the photosynthetic reaction centers (photoinhibition).

The abundance of rubisco leads to deleterious effects to the energetic balance of photosynthetic cells since most available resources of these cells must be allocated to the production of rubisco.

C3 plants, to which most of the crop plants belong, are unable to concentrate CO.sub.2 at the site of rubisco and therefore grow poorly (compared to C4 plants) under water-limiting conditions.

Due to the large number of genes involved, and to the complexity of their tight, spatial regulation, in the operation of the C4 mechanism, the introduction of the whole C4 CO.sub.2 concentrating mechanism to C3 plants is presently impossible.

Stomatal closure, in order to minimize water loss under conditions of water stress, generates a significant resistance to CO.sub.2 diffusion leading to a sharp decline in CO.sub.2 fixation.

Although raising the concentration of CO.sub.2 in a closed environment, such as a greenhouse, is commonly practiced in order to raise the diffusional flux of CO.sub.2 and as such, raise plant productivity, such a practice however, is not applicable to outdoor grown plants.

Increasing stomatal conductance can theoretically serve to raise plant productivity, but at present, viable mechanisms for enhancing the stomatal CO.sub.2 conductivity have not been proposed.

Thus, at present, both of the above mentioned approaches are theoretical and as such cannot be applied to render photosynthetic organisms, such as C3 plants, more efficient at fixing CO.sub.2.

Regeneration by seed propagation, however, has the deficiency that due to heterozygosity there is a lack of uniformity in the crop, since seeds are produced by plants according to the genetic variances governed by Mendelian rules.

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