Abstract
The multi-subunit enzyme complex I of the mitochondrial respiratory chain is an assembly
of nuclear and organellar encoded proteins with distinct roles and functions. The
nuclear encoded 28.5 kDa iron-sulfur protein is located at the centre of electron
transfer to ubiquinone. Functional importance and regulatory tolerance of this subunit
were investigated in transgenic tobacco plants carrying antisense constructs driven
by the CaMV 35S promoter. In all of the regenerated transgenics vegetative growth
is undisturbed, while in many transformants flower development is abnormal and pollen
fertility is reduced. Maximal observed suppression of the steady-state 28.5 kDa mRNA
level reaches only about 30%. Apparently, further reduction is lethal to the vegetative
tobacco plants, suggesting that the 28.5 kDa subunit is regulated from the steady-state
level onwards with little tolerance and no additional possibilities for compensation.
This contrasts with the higher flexibility of the NADH-binding subunit of complex
I, which vegetatively survives a 70% reduction of its mRNA level.
Key words
Plant mitochondria - complex I subunit -
Nicotiana tabacum
- antisense suppression
