Consequences of intergeneric chloroplast transfers on photosynthesis and sensitivity to high light

Plants with alien chloroplasts (cybrids) were investigated to identify spec ies-specific nucleus-chloroplast interactions which affect the organisation and the functionality of the photosynthetic apparatus. The cybrids had nuc lei of Nicotiana tabacum L. and chloroplasts of Atropa belladonna L. (cybri d Nt(Ab)) or Salpiglossis sinuata R. et P. (cybrid Nt(Ss)). Despite the exc hange of the chloroplast genome the morphology of the cybrids was similar t o their nuclear parent. Also the PSI/PSII ratio was comparable. In Nt(Ab) m odified LHCII proteins could be detected which were absent in the parental plants. The trimerisation of LHCII, the chlorophyll contents and the chloro phyll fluorescence parameters were not affected by this modification, but t he portion of trimeric LHCII was slightly reduced. In Nt(Ss) the formation of the antenna system was disturbed, and impaired PSII centres could be det ected in older leaves. These cybrid-specific features suggest that nucleus- chloroplast interactions are involved in the processing of LHCII and in chl oroplast development. High light sensitivity was considerably increased in the cybrids and this risk should be considered when cybridisation is used i n crop breeding.