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

Abstract

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