ISSN:
1573-9368
Keywords:
C4-plant
;
maize
;
phosphoenolpyruvate carboxylase
;
quantum yield
;
transgenic tobacco
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The expression of maize (Zea mays) phosphoenolpyruvate carboxylase (PEPC) gene constructs in transgenic tobacco plants (Nicotiana tabacum) was studied. Where transcription was under the control of a CaMV 35S promoter, maize PEPC transcripts of the correct size were detected. Western blot analysis indicated that the transgenic plants contained about twice as much PEPC as non-transformed plants. Furthermore, the enzymatic activity of PEPC in the leaves of these transgenic plants was up to twice as high as that in non-transformed plants. Two forms of PEPC with different kinetic properties were identified in leaf extracts of the transgenic plants: one form (the maize isoform) gave a high apparentK m value for phosphoenolpyruvate (PEP) and a high maximum activity, and the other (the tobacco isoform) exhibited a low apparentK m value for PEP and a low maximum activity. These biochemical differences resulted in several significant physiological changes in the transgenic plants: (1) the growth rate of the transgenic plants was lower than that of non-transgenic plants: (2) chlorophyll content per leaf area was relatively lower in the transgenic plants; and (3) the quantum yield of photosynthesis in the transgenic plants was not affected by changes in leaf temperature.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01973588
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