Hyperhydricity in pepper plants regenerated in vitro: involvement of BiP (Binding Protein) and ultrastructural aspects

Hyperhydricity in regenerated pepper plants was monitored by the induction of the ER-luminal resident protein, as observed by immunoblotting. Immunobl otting of total protein using an anti-soybean BiP serum indicated that the induction and accumulation of an 80-kDa protein was related to BiP (Binding protein), a 78-kDa ER-resident molecular chaperone. The anti-BiP serum cro ss-reacted with an 80-kDa protein which was significantly induced by hyperh ydricity. Based on similar molecular weight and immunological reactivity we concluded that the 80-kDa protein induced in hyperhydric plants is a BiP h omologue. The ultrastructural organisation of leaves in non-hyperhydric and hyperhydric pepper (Capsicum annuum L.) plants was investigated with the a im of identifying the subcellular changes associated with this phenomenon. In non-hyperhydric leaves the chloroplasts of the palisade cells had normal ly developed thylakoids and grana and a low accumulation or absence of star ch grains and plastoglobules. In the hyperhydric plants, however, the chlor oplasts exhibited thylakoid disorganisation, low grana number, an accumulat ion of large starch grains and a low accumulation or absence of plastoglobu les. Although the structure of mitochondria and peroxisomes did not change in hyperhydric plants, the number of peroxisomes did increase.