Purified plant expansion proteins and DNA encoding same

Details Purified plant expansion proteins and DNA encoding same Purified plant expansion proteins and DNA encoding same

1998-06-05

2001-07-03

Nashed, Nashaat T. (Department: 1652)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carbohydrates or derivatives

C536S023200, C536S023500, C536S023600, C530S350000, C435S069100, C435S252300, C435S320100

Reexamination Certificate

active

06255466

ABSTRACT:

INTRODUCTION
The present invention relates to a new class of proteins, known as expansins, and their isolation, sequencing, genesis by expression systems, and utilization. These proteins have been identified in a wide variety of plant and other materials and have a variety of applications, including but not limited to agricultural and/or food applications and industrial uses such as their use in the paper industry as a catalyst for weakening the strength of paper products. For example, they can prove especially useful in the recycling of paper.
By the way of background, for many years wall “loosening enzymes” have been implicated in the control of plant cell enlargement (growth), largely on the basis of rapid biophysical and biochemical changes in the wall during auxin-induced growth (reviewed by Cleland and Rayle, Bot. Mag. Tokyo, 1:125-139, 1978; Taiz,
Annu. Rev. Plant Physiol.,
35:585-657, 1984). Plant walls contain numerous hydrolytic enzymes, which have been viewed as catalysts capable of weakening the wall to permit turgor-driven expansion (reviewed by Fry,
Physiol. Plantarum,
75:532-536, 1989). In support of this hypothesis, Huber and Nevins (
Physiol. Plant.,
53:533-539, 1981) and Inoue and Nevins (
Plant Physiol.,
96:426-431, 1991) found that antibodies raised against wall proteins could inhibit both auxin-induced growth and wall autolysis of corn coleoptiles. In addition, isolated walls from many species extend irreversibly when placed under tension in acid conditions in a manner consistent with an enzyme-mediated process (Cosgrove D. J.
Planta,
177:121-130, 1989). Despite these results and other evidence in favor of “wall-loosening” enzymes, a crucial prediction of this hypothesis has never been demonstrated, namely, that exogenously added enzymes or enzyme mixtures can induce extension of isolated walls. To the contrary, Ruesink (
Planta,
89:95-107, 1969) reported that exogenous wall hydrolytic enzymes could mechanically weaken the wall without stimulating expansion. Similarly, autolysis of walls during fruit ripening does not lead to cell expansion. Thus a major piece of evidence in favor of wall-loosening enzymes as agents of growth control has been lacking.
Once identified, expansins—proteins capable of inducing cell wall extension—would have utility not only in the engineered extension of cell walls in living plants but foreseeably in commercial applications where their chemical reactivity could prove useful. If expansins can disrupt noncovalent associations of cellulose, as they have been shown to do, then they would have particular utility in the paper recycling industry. Paper recycling is a growing concern and will prove more important as the nation's landfill sites become more scarce and more expensive. Paper derives its mechanical strength from hydrogen bonding between paper fibers, which are composed primarily of cellulose. During paper recycling, the hydrogen bonding between paper fibers is disrupted by chemical and mechanical means prior to re-forming new paper products. Proteins which cause cell expansion are thus intrinsically well suited to paper recycling, especially when the proteins are nontoxic and otherwise innocuous, and when the proteins can break down paper products which are resistant to other chemical and enzymatic means of degradation. Use of proteins of this type could thus expand the range of recyclable papers.
Other modes of application of expansins, once they are found, include production of virgin paper. Pulp for virgin paper is made by disrupting the bonding between plant fibers. For the reasons identified above, expansins are useful in the production of paper pulp from plant tissues. Use of expansins can substitute for harsher chemicals now in use and thereby reduce the financial and environmental costs associated with disposing of these harsh chemicals. The use of expansins can also result in higher quality plant fibers because they would be less degraded than fibers currently obtained by harsher treatments.
Thus, a need remains for the identification, characterization and purification of expansins—proteins which can be characterized as catalysts of the extension of plant cell walls and the weakening of the hydrogen bonds in the pure cellulose paper—and the incorporation of DNA sequences which give rise to such proteins in appropriate expression systems.
SUMMARY OF THE INVENTION
In accordance with the present invention, a new class of proteins and methods related thereto are presented. The proteins, which can be characterized as catalysts of the extension of plant cell walls and the weakening of the hydrogen bonds in pure cellulose, are referred to as expansins. Two proteins have been isolated by fractionation techniques from washed wall fragments of cucumber hypocotyls, referred to as “cucumber expansin-29” and “cucumber expansin-30” (abbreviated cEx-29 and cEx-30). Moreover, three peptide fragments from the purified cEx-29 protein were sequenced, then oligonucleotide primers were designed to amplify a portion of the expansin cDNA using polymerase chain reaction with a cDNA template derived from cucumber seedlings, and then the PCR fragment was used to screen a cDNA library to identify full length clones. Another expansin protein has been isolated from oat coleoptiles (oat expansin oEx-29), while three additional expansin sequences have been identified in Arabidopsis and an additional two in rice. Expansins appear to be broadly distributed throughout the plant kingdom and can be identified in stem and leaf vegetables (i.e., broccoli, cabbage), fruit and seed vegetables (i.e., tomato), fiber crops and cereals (i.e., corn), and forest and ornamental crops (i.e., cotton). Also, expansin-like protein has been found in proteins obtained from the digestive tract of snail and its feces (sEx). These novel proteins can find use in a variety of applications including the paper industry in production of paper pulp in preparation of virgin paper and in paper recycling as a preferred way of disruption of paper fibers due to their nontoxic and environmentally innocuous nature in contrast with the harsh chemical treatments applied today, which are environmentally noxious and in many cases completely unacceptable.


REFERENCES:
Shcherban et. al, PNAS (Sep. 26, 1995), 92 (20) : 9245-9.

Affiliated with

Also associated with

Rating

Purified plant expansion proteins and DNA encoding same does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Purified plant expansion proteins and DNA encoding same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Purified plant expansion proteins and DNA encoding same will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2553079