Site News  |   Monitor Keywords  |   Monitor Archive  |   Organizer  |   Account Info  |

Compositions and methods for regulating abscisic acid-induced closure of plant stomata

This application claims priority to U.S. Provisional Application Nos. 60/142,039, filed Jul. 1, 1999, 60/176,245, filed Jan. 14, 2000 and 60/192,499, filed Mar. 28, 2000, the entireties of which are incorporated by reference herein.

Pursuant to 35 U.S.C. §202(c), it is acknowledged that the U.S. Government has certain rights in the invention described herein, which was made in part with funds from the National Science Foundation, Grant Nos. MCB-9316319 and MCB-9874438.

The present invention relates to the field of molecular biology of plants. More specifically, it relates to the regulation of gas exchange and transpirational water loss in plants possessing stomata.

Various scientific and scholarly articles are referred to throughout the specification. These articles are incorporated by reference herein to describe the state of the art to which this invention pertains.

In terrestrial plants, water is transported, from the roots to the leaves, down a water potential gradient from the soil to the air. Transpiration, or loss of water from the leaves, helps create lowered osmotic potential in the leaves, effectively drawing water from the xylem to the mesophyll cells into the air spaces in the leaves. Estimates are that 90% or more of the water taken up by plants is lost to the air via transpiration.

Transpirational loss of water by evaporation occurs mainly through the pores, called stomata, primarily located in the lower epidermis of the leaves. Each stoma is surrounded by two guard cells, which control the opening and closure of the stomata by their relative turgor pressure. The cell wall properties of guard cells allow them to deform such that when the guard cells develop turgor pressure, the stoma is opened, but when the guard cells lose turgor, the stoma closes.

The rate of evaporation of water from the air spaces of the leaf to the outside air depends on the water potential gradient between the leaf and the outside air. Environmental factors which directly influence the aperture of the plant's stomata affect its transpiration rate. Such factors include light conditions, relative humidity of the air, temperature, water status of the plant, CO2 concentration, relative concentration of certain ions, and concentration of abscisic acid (ABA).

Abscisic acid is a multifunctional phytohormone involved in a variety of important protective functions including bud dormancy, seed dormancy and/or maturation, abscission of leaves and fruits, and response to a wide variety of biological stressors (e.g. cold, heat, salinity, and drought). It is also responsible for regulating stomatal closure by a mechanism independent of CO2 concentration.

ABA is synthesized rapidly in response to water stress in plants, and is stored in the guard cells. During drought, ABA alteration of guard cell ion transport promotes stomatal closure and also prevents stomatal opening, thus reducing transpirational water loss. At the biochemical level, it is believed that the hormone sets off a variety of biological messages that require or include a protein phopsphorylation cascade. One member of this cascade was identified in guard cells of Vicia faba as an ABA-activated, calcium-independent protein kinase. (Li & Assmann, Plant Cell 8: 2359-2368, 1996; Mori & Muto, Plant Physiol. 113: 833-839, 1997). The kinase was identified by SDS polyacrylamide gel electrophoresis as a 48 kDa protein, but was not further isolated or characterized. It exhibited ABA-activated autophosphorylation and kinase activity.

Stomata simultaneously regulate both the transpiration of water and the exchange of gases for photosynthesis. Open stomata allow for maximum gas exchange rate so that photosynthetic reactions may proceed more quickly, however under these conditions, water loss will be maximal. On the other hand, closed stomata minimize transpirational water loss but also substantially reduce photosynthetic reaction rates. Paradoxically, the plant undergoes a continual trade-off between maximizing CO2 uptake for carbon fixation, and minimizing desiccating water loss. Thus, the ability to control stomatal opening and closure could be of tremendous agronomic significance.

Several studies in the literature provide examples of the benefits of selecting for increased stomatal conductance under certain conditions. One system that has been studied extensively comprises eight lines of Pima cotton (Gossypium barbadense) obtained over 40 years of selection and showing a 3-fold range in yield. These and additional studies have confirmed the association of higher conductance with higher yield, and its genetic basis, in both Pima and Upland (Gossypium hirsutum) cotton. A similar correlation of increased yield, increased stomatal conductance, and decreased canopy temperatures has also been observed in a historical series of bread wheat cultivars. Taken collectively, this body or research suggests that selection or genetic engineering of plants to achieve increased stomatal conductance may be of widespread utility for crop plants grown under irrigation under supra-optimal temperatures.

The plant hormone abscisic acid (ABA) causes stomatal closure during periods of reduced water availability by reducing the ion and water content of the pair of guard cells that flanks each stoma. However, even when plants are well-watered, ABA still limits stomatal aperture, as shown by the fact that mutants of tomato and Arabidopsis that are deficient in either ABA-production or ABA-sensing have larger stomatal apertures than wild-type plants, even when water is plentiful. In other words, the ABA response is protective; always somewhat limiting to water loss, but thus unavoidably, also limiting to CO2 uptake. This ABA-mediated limitation of water loss is of no benefit however, to the grower who irrigates crops so that they are always well-watered. For those crops, such as many of the agricultural crops that are grown in arid or semi-arid regions, if this endogenous ABA-response of the stomata were “turned off”, crop yield could be increased, or the time for the plant to reach maturity decreased by removing the limits on increased CO2 uptake and fixation.

Many crops, for example feed corn and wheat, are dried in the field before harvest. Other crops, such as tobacco and dried fruits such as raisins and prunes, are dried immediately post-harvest. It would be advantageous to growers to be able to accelerate or control the rate of crop drying.

For example, at the end of the growing season, it might be advantageous to dry the plants as quickly as possible, to minimize exposure to adverse weather conditions. However, water stress inevitably triggers ABA production/redistribution in the plant, leading to stomatal closure, which slows the rate of water loss, thus slowing the rate of crop drying. Therefore, it would be advantageous to growers if this ABA-triggered stomatal closure response could be prevented or controlled.

In other cases, post-harvest, for many fruits, vegetables, and for cut-flowers, it is advantageous for the produce to dry out as slowly as possible, to retain freshness during transport, distribution, and purchase of the product. In these situations, it would be advantageous if the ABA-induced stomatal closure response could be enhanced. This could significantly extend the shelf life of the product.

The theoretical solution to the problems posed above is for growers to be able to precisely control the plant's transpiration via ABA-responsiveness of the guard cells/stomata. Ideally this control should be:

Continue reading...
Full patent description for Compositions and methods for regulating abscisic acid-induced closure of plant stomata

Brief Patent Description - Full Patent Description - Patent Application Claims
Click on the above for other options relating to this Compositions and methods for regulating abscisic acid-induced closure of plant stomata patent application.

Patent Applications in related categories:

20080235821 - Nucleotide sequences encoding ramosa3 and sister of ramosa3 and methods of use for same - The invention relates to the isolation and characterization of a maize gene, RAMOSA3 (RA3), responsible for meristem development and inflorescence development including branching. The gene, gene product, and regulatory regions may be used to manipulate branching, meristem growth, inflorescence development and arrangement, and ultimately to improve yield of plants. The ...


###


How KEYWORD MONITOR works... a FREE service from FreshPatents
1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored.
3. Each week you receive an email with patent applications related to your keywords.  
Start now! - Receive info on patent apps like Compositions and methods for regulating abscisic acid-induced closure of plant stomata or other areas of interest.
###


Previous Patent Application:
Methods and compositions for providing sa-independent pathogen resistance in plants
Next Patent Application:
Herbicide-tolerant plants through bypassing metabolic pathway
Industry Class:
Multicellular living organisms and unmodified parts thereof and related processes

###