cold, heat, and water deficits. Improved tolerance was documented by demonstrating
improved plant growth rates of transgenic plants relative to their nontransgenic
controls, as measured by plant height. Similar observations were reported with
transgenic maize plants expressing CspA under greenhouse and field conditions.
An across-event analysis demonstrates that the CspA transgenic entries provide a
yield increase of 4.6% under water stress, with the two best performing events
demonstrated advantage of 30.8 and 18.3%. Yield averages of CspB-positive plants
as a group were significantly greater than controls by 7.5%. A number of individual
events exhibited significant yield advantages as well; the best two performing
events, CspB-Zm event 1 and event 2, demonstrated yield improvements of 20.4
and 10.9%, respectively. The action of Csps in plants through a conserved stress
adaptation mechanism common in plants and bacteria is supported by showing a
functional RNA binding motif required for the improved stress tolerance in both
bacteria and plants. Breadth of tolerance across environments and germplasms is the
key element in establishing the value of transgenic strategies for crop stress tolerance
improvement and require indicated the potential benefits of bacterial cold stress gene
in transgenic development.
6.16 Conclusions
Cold tolerant bacteria are widely distributed in the earth and playing a variety of
ecological roles. The most commonly encountered cold tolerance mechanisms
include modification of the cell membrane constituents to maintain cell membrane
fluidity, induction of cold shock proteins (that act as molecular chaperones), synthesis of cold acclimation protein, cryoprotectant-mediated protection, production of ice
nucleation factors or antifreeze proteins and RNA degradosomes. Therefore,
complexities of cold adaptation physiology of microorganisms depend on preponderant temperature of the ecosystem and have the ability to survive and grow in a
“range of temperature” where the lowest, highest, and the optimal points are
different for different organisms. In the past, lot of studies have been carried out
mainly with mesophilic organisms, and now it is the turn of “natives” which has
been given attention to find out the adaptive mechanisms of psychrotrophic bacteria
when subjected to cold temperatures. This would allow one to identify the common
mechanisms and the molecules that are necessary for growth of psychrophiles or
psychrotrophs, which would in turn led to identify the regulatory elements and coldstress response mechanisms that organisms have developed for producing common
molecules/strategies for the respective cold temperatures in the course of evolution.
This would also lead to identification of the unique adaptive features of different
groups of organisms for growing at lower temperatures. However, recent
developments based on cold-adapted organisms and on their biomolecules, such as
those mentioned here, have clearly demonstrated the huge biotechnological potential. This potential appears to be even larger than other extremophiles when considering both the broader psychrophilic biodiversity that encompasses microorganisms,
plants, and animals and the broader fields of application. Most biotechnological
216
P. K. Mishra et al.
improved plant growth rates of transgenic plants relative to their nontransgenic
controls, as measured by plant height. Similar observations were reported with
transgenic maize plants expressing CspA under greenhouse and field conditions.
An across-event analysis demonstrates that the CspA transgenic entries provide a
yield increase of 4.6% under water stress, with the two best performing events
demonstrated advantage of 30.8 and 18.3%. Yield averages of CspB-positive plants
as a group were significantly greater than controls by 7.5%. A number of individual
events exhibited significant yield advantages as well; the best two performing
events, CspB-Zm event 1 and event 2, demonstrated yield improvements of 20.4
and 10.9%, respectively. The action of Csps in plants through a conserved stress
adaptation mechanism common in plants and bacteria is supported by showing a
functional RNA binding motif required for the improved stress tolerance in both
bacteria and plants. Breadth of tolerance across environments and germplasms is the
key element in establishing the value of transgenic strategies for crop stress tolerance
improvement and require indicated the potential benefits of bacterial cold stress gene
in transgenic development.
6.16 Conclusions
Cold tolerant bacteria are widely distributed in the earth and playing a variety of
ecological roles. The most commonly encountered cold tolerance mechanisms
include modification of the cell membrane constituents to maintain cell membrane
fluidity, induction of cold shock proteins (that act as molecular chaperones), synthesis of cold acclimation protein, cryoprotectant-mediated protection, production of ice
nucleation factors or antifreeze proteins and RNA degradosomes. Therefore,
complexities of cold adaptation physiology of microorganisms depend on preponderant temperature of the ecosystem and have the ability to survive and grow in a
“range of temperature” where the lowest, highest, and the optimal points are
different for different organisms. In the past, lot of studies have been carried out
mainly with mesophilic organisms, and now it is the turn of “natives” which has
been given attention to find out the adaptive mechanisms of psychrotrophic bacteria
when subjected to cold temperatures. This would allow one to identify the common
mechanisms and the molecules that are necessary for growth of psychrophiles or
psychrotrophs, which would in turn led to identify the regulatory elements and coldstress response mechanisms that organisms have developed for producing common
molecules/strategies for the respective cold temperatures in the course of evolution.
This would also lead to identification of the unique adaptive features of different
groups of organisms for growing at lower temperatures. However, recent
developments based on cold-adapted organisms and on their biomolecules, such as
those mentioned here, have clearly demonstrated the huge biotechnological potential. This potential appears to be even larger than other extremophiles when considering both the broader psychrophilic biodiversity that encompasses microorganisms,
plants, and animals and the broader fields of application. Most biotechnological
216
P. K. Mishra et al.