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作者 Vadnais, Dave Allen
書名 Carbohydrate metabolism and freezing tolerance of alfalfa (Medicago sativa L.) expressing an invertase transgene
國際標準書號 0612658384
book jacket
說明 191 p
附註 Source: Dissertation Abstracts International, Volume: 63-01, Section: B, page: 0122
Adviser: Stephen R. Bowley
Thesis (Ph.D.)--University of Guelph (Canada), 2002
The soluble carbohydrate levels in the taproot and crown of alfalfa ( Medicago sativa L.) contribute to freezing tolerance and the regrowth of new shoots. To evaluate further the role of carbohydrates, alfalfa was transformed using Agrobacterium tumefaciens with the binary vector pV-INV containing the CaMV35S promoter and the invertase suc-2 gene from yeast with a transit peptide targeting the enzyme to the vacuole. PCR and Southern analyses confirmed the presence of the transgene. Invertase activities of transgenic plants were between 2 to 10 times greater than controls
The TSC levels ranged from 26 to 78% higher in plants containing the invertase transgene. There were also changes in sugar profile, the monosaccharide and raffinose levels ranged from 10 to 43% and 0.7 to 2.5% higher, respectively and sucrose levels ranged from 19 to 62% lower. Furthermore, the roots of the transgenic plants were smaller than in the non-transformed control. Because of increased soluble carbohydrates and raffinose, it was expected that the transgenic plants would be more tolerant of freezing stresses due to the increased osmotic potential. However, these changes did not confer any protection in controlled environment studies as indicated by shoot regrowth following a freezing event in acclimated plants
In contrast to the greenhouse, root size in the field was relatively unaffected by invertase activity, presumably due to higher photosynthate supply from source tissues. In transgenic plants with high invertase activity concentrations of starch and TSC where higher than in non-transgenic controls. As in the greenhouse, the transgenics also had an altered sugar profile, with monosaccharide and raffinose pools larger and sucrose pools smaller. Because of the two extremes of winter experienced during the two field trials, it was not possible to determine conclusively if altered invertase activity affected persistence, as indicated by winter survival and spring regrowth vigour
Because suc-2 expression was regulated by a constitutive CaMV35S promoter, it was impossible to separate the effects of reduced photosynthate supply from the effects of increased invertase activity in the storage sinks. Using transformation vectors with shoot or root specific promoters to control suc-2 expression would allow a more precise evaluation of these effects
School code: 0081
DDC
Host Item Dissertation Abstracts International 63-01B
主題 Biology, Plant Physiology
0817
Alt Author University of Guelph (Canada)
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