The studies that expressed fish, mainly winter flounder, AFPs in transgenic plants resulted in the production of plants that were,
at best, approximately 1 ◦ C more freezing tolerant than wild-type
plants. While this was a significant accomplishment, a greater
level of protection is required to provide adequate levels of frost
tolerance in plants. The sequencing and descriptions of insect
AFPs with significantly greater specific thermal hysteresis activity offered an opportunity to improve on
this level of frost protection by making the transgenic plants frost
avoiding.
Holmberg et al. (2001) generated the first transgenic plants
expressing an insect AFP. A synthetic gene, based on the AFP present
in the spruce budworm, Choristoneura fumiferana, was transformed into tobacco with a plant signal peptide and driven by the cauliflower mosaic virus 35S promoter. Success of
the transformation was measured by the presence of appropriately
sized transcripts using RT-PCR, recrystallization inhibition activity
in crude leaf homogenates and apoplastic extracts of the plants,
and most importantly, thermal hysteresis (0.37 ◦ C) in the apoplastic fluid. The freezing response or LT50 of the transgenic tobacco
was not reported.
The studies that expressed fish, mainly winter flounder, AFPs in transgenic plants resulted in the production of plants that were,at best, approximately 1 ◦ C more freezing tolerant than wild-typeplants. While this was a significant accomplishment, a greaterlevel of protection is required to provide adequate levels of frosttolerance in plants. The sequencing and descriptions of insectAFPs with significantly greater specific thermal hysteresis activity offered an opportunity to improve onthis level of frost protection by making the transgenic plants frostavoiding. Holmberg et al. (2001) generated the first transgenic plantsexpressing an insect AFP. A synthetic gene, based on the AFP presentin the spruce budworm, Choristoneura fumiferana, was transformed into tobacco with a plant signal peptide and driven by the cauliflower mosaic virus 35S promoter. Success ofthe transformation was measured by the presence of appropriatelysized transcripts using RT-PCR, recrystallization inhibition activityin crude leaf homogenates and apoplastic extracts of the plants,and most importantly, thermal hysteresis (0.37 ◦ C) in the apoplastic fluid. The freezing response or LT50 of the transgenic tobaccowas not reported.
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