Characterization of CDKA gene expressed during in vitro regeneration from pepper (Capsicum annuum L.) cotyledon explants

Adventitious bud-like structures were directly regenerated from pepper (Capsicum annuum L. cv. Baklouti) cotyledon explants taken from 14 days-old seedlings and cultivated on MS medium supplemented with 5.7 μM IAA and 8.8 μM BAP. Histological and molecular studies were performed at different stages of the in vitro culture process in order to follow the regeneration pathway. Histological study revealed that a cell dedifferentiation process took place at the periphery of the excised petiolar side of cotyledon after 4 days of culture. It led to the formation of teratological protuberances resulting in the development of disorganized apical shoot meristem. In order to follow the regeneration process at the molecular level, the study was based on CDKA gene expression analysis. This gene was chosen because of its major role in the regulation of eukaryotic cell cycle. The CDKA mRNA transcription rate study revealed a steady-state transcript level during all the developmental phases except at the dedifferentiation step where an increase was noticed. The Western blot analysis showed that CDKA protein was particularly expressed in initial cotyledons of 14 days-old seedlings, declined until dedifferentiation stage and tended to reincrease during the subsequent stages. All these results suggest that CDKA expression may be linked to dedifferentiation during adventitious organogenesis in pepper tissues cultivated in vitro. It can therefore be used as a molecular marker for in vitro regeneration in this recalcitrant species.