Heterotrophic tobacco nicotiana tabacum cultivar xanthi cell cultures during greening 2. physiological and biochemical aspects

Nato, A.; Mathieu, Y.; Brangeon, J.

Physiologia Plantarum 53(3): 335-341

1981


ISSN/ISBN: 0031-9317
DOI: 10.1111/j.1399-3054.1981.tb04509.x
Accession: 005567540

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Abstract
N. tabacum L. (cv. Xanthi) suspension cultures initially grown in the dark and then exposed to continuous light followed a developmental pattern divided into a lag phase (T0-T2), a growth phase (T3 .fwdarw. T9) and a stationary phase (T10 .fwdarw. T21). The onset of chloroplast differentiation during the active cell division phase was associated with a rapid chlorophyll synthesis, a high rate of respiratory activity (400 .mu.mol h-1 g-1 dry wt) and a 4-fold increase in soluble protein content compared to that of the initial inoculum. O2 evolution was zero until T3. It increased regularly up to a value of 30 .mu.mol h-1 g-1 dry weight at the beginning of the stationary phase, higher values (80 .mu.mol) being reached later in this phase. An inverse relationship between phosphoenolpyruvate carboxylase (PEPCase) and ribulose 1,5-bisphosphate carboxylase (RUBPCase) was shown during cell growth. The PEPCase capacity expressed on a soluble protein basis rose from an initial day 0 value of 3.5 .mu.mol to a maximum of 7.0 .mu.mol at T5 and then returned to the initial value during the post-exponential and stationary phases. In contrast, RUBPCase activity was minimal (0.1 .mu.mol) from T0-T3 of greening, increasing to a maximum (1.7-2.0 .mu.mol) at T8. The 20-fold stimulation of this enzyme capacity was related to a de novo protein synthesis. Immunodiffusion tests revealed the presence of RUBPCase molecules in soluble crude extract of dark-grown cells. The SDS polypeptide co-migrating with the large subunit (LSU) of RUBPCase appeared reduced in dark-grown cells compared to the peak height of the same polypeptide present in green cells. In both preparations, the 13,000 D polypeptide co-migrating with the small subunit (SSU) was equally present. The current hypothesis is that the synthesis of RUBPCase at the time of greening would concern the preferential synthesis of the LSU of the enzyme.

Heterotrophic tobacco nicotiana tabacum cultivar xanthi cell cultures during greening 2. physiological and biochemical aspects