Chemistry: molecular biology and microbiology – Process of mutation – cell fusion – or genetic modification – Introduction of a polynucleotide molecule into or...
Reexamination Certificate
1999-09-28
2003-06-17
McGarry, Sean (Department: 1635)
Chemistry: molecular biology and microbiology
Process of mutation, cell fusion, or genetic modification
Introduction of a polynucleotide molecule into or...
C435S006120, C435S091100, C435S419000, C536S023100, C536S023600
Reexamination Certificate
active
06579716
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains, in general, to the production of seedlings which demonstrate better emergence characteristics and improved seedling growth when grown under low light conditions. In particular, the present invention pertains to modifying the genotypes of plant cells to include a sequence coding for the Coil domain of the COP1 protein.
BACKGROUND OF THE INVENTION
All publications and patent applications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
Through photosynthesis, light provides the energy source for plants and, ultimately, for all living organisms. The light environment plays a crucial role in plant growth and development. Besides serving as a source of energy, light provides signals to regulate many complex developmental processes. At least three photoreceptor families—pytochromes (red and far-red light), blue light receptors, and UV light receptors—mediate these light-regulated developmental processes. Light signals perceived by specific photoreceptors are transduced via signaling components to bring about the diverse downstream physiological responses, including seed germination, stem elongation, chloroplast and leaf development, floral induction, and coordinated expression of many light-regulated nuclear- and chloroplast-encoded genes.
In response to a fluctuating environment, the nonmobile plant must be able to sense varying light signals and to optimize growth and development. Higher plants possess sophisticated photosensory and signal transduction systems to monitor the direction, quantity, and quality of the light signal and to adjust their growth and development through regulated gene expression at every stage of their life cycle, such as germination, seedling development, and flowering. These light-regulated developmental processes are collectively termed photomorphogenesis.
Plant development is a highly malleable process that is strongly influenced by environmental factors, especially light. The effects of light on plant development are especially prominent at the seedling stage (Kendrick and Kronenberg, 1994; McNellis and Deng, 1995). As compared with plants grown in light, those grown in darkness are white or yellow in color, the internodes are long, the leaves are very much reduced in size, and the root systems are poorly developed. This condition is known as etiolation. Of course, etiolated seedlings cease growth when their reserve food supply is exhausted. While the effect is less dramatic than when plants are grown in darkness, the etiolation effect also occurs under low light levels as well.
The light environment in nature is complex. Unobstructed sunlight consists of a wide continuum of photon wavelengths that is conveniently divided into three large spectral domains: UV (<400 nm), visible (400 to 700 nm) and far-red (>700 nm) light. The spectral quality, or relative photon distribution, at different wavelengths can vary greatly, depending on the location and the time of day. For example, within the canopy, the light available is essentially depleted in the visible and UV regions, and far-red light is highly represented. Furthermore, twilight normally has a higher far-red to red ratio than daylight. Although higher plants effectively utilize only visible light for photosynthesis, they have the capability to sense and respond to a much wider range of the spectrum, including UV and far-red light.
In a photochemical process such as photosynthesis, the end product depends upon the number of quanta absorbed rather than the total light energy absorbed. A single red photon has the same effect in photosynthesis as a single blue photon, for example, although the blue photon has more energy. Hence, in the recent literature it has become common to refer to the number of photons per unit area per unit time. Einsteins (for photosynthesis) or microEinsteins (for low light responses) are used. While an open field during a mid-summer day may receive as much as 2,000 microEinsteins per square meter per second, the same area in an indoor room with fluorescent lamps may only receive 50 to 100 microEinsteins per square meter per second. When the open field has its light blocked by smog, clouds or rain, it may actually register less photons per unit area per unit time than the indoor room.
In general, absence of light increases, and presence of light decreases, the rate at which the stems elongate. Thus, the features associated with etiolation ensure, under natural conditions, that the shoot is carried towards the light as rapidly as possible. Such a physiological and morphological response to the complete lack of light is critical for the growth and eventual emergence of the seedling from the position where the seed is planted in the soil or other growth media.
The etiolation process does not necessarily cease once the seedlings successfully emerge from the soil or other growth media. In many plants, there is a rhythmic night-and-day growth rate of the shoot—greater at night than during the day, provided that the temperature at night does not fall too low. Plants grown in full light have shorter and sturdier stems and somewhat thicker leaves than those grown in the shade. One result of crowding plants is a reduction in the light intensity to which they are exposed. In an effort to reach higher light levels, the shaded plants develop longer and more spindly stems than those grown under less crowded conditions. Thus, in some circumstances, the etiolation process can be viewed as a survival tactic.
However, under some conditions of low natural light, such as would result from a succession of smoggy, cloudy or rainy days or from an inability to supply high levels of artificial light in the greenhouse, etiolation can cause plant husbandry problems. For example, etiolated seedlings tend to fall over easily and to produce weaker plants which are more susceptible to pests, such as aphids and spider mites, and to other environmental challenges, such as wind or water-logged pots or fields. Under such conditions, the etiolated seedlings may develop into less vigorous adult plants, produce less reproductive structures and fewer offspring, or even perish. If a sufficient number of seedlings or plants are adversely affected by the etiolation effect, this may result in reduced production of a particular plant product on a per surface area yield basis. For example, the yield of tomato fruits on a per hectare or per acre basis may be dramatically reduced if severe seedling etiolation results in the formation of spindly tomato plants which lodge. Such lodging can reduce fruit size through decreased photosynthetic activity of the collapsed shoot, greatly increase fruit rotting through contact of the fruit with the soil, and lead to greater pest access and pest damage of the fruits. While the spindly tomato plants could be supported on trellises, stakes or cages, such rescue attempts are very labor intensive and can be prohibitively costly for large-production operations. In addition, such increased “man-handling” of the plants can also result in further plant breakage and fruit droppage.
Plant responses to light are especially evident in the young seedling, although they occur throughout the life of the plant. Early seedling development in Arabidopsis (
Arabidopsis thaliana
) provides an excellent model system to dissect the light signal transduction pathway in plants. As a typical dicotyledonous plant, Arabidopsis seedlings follow two distinct strategies of development, skotomorphogenesis in darkness or photomorphogenesis in light. Thus, Arabidopsis seedlings display contrasting developmental patterns in the presence or absence of light. In selecting for and characterizing late germinating mutants of Arabidopsis, Michelle Stopper and James J. Campanella (
Arabidopsis thaliana
Database, http://genome.www.stanford.edu/Arabidopsis) used high-intensity light conditions of approximately 450 microEinsteins p
Deng Xing Wang
McNellis Timothy
Torii Keiko
McGarry Sean
Morgan & Lewis & Bockius, LLP
Yale University
Zara Joe
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