Marker proteins for embryogenic differentiation patterns in pea callus

Polypeptide pattern alterations during somatic embryogenesis were investigated using callus cultures of two Pisum sativum genotypes. Both genotypes show the formation of two different callus lines from the same explant after six to eight weeks in culture: a nodular yellowish callus line, which forms somatic embryoids in suspension cultures (e(+)) and a white compact callus line with no regenerative capacity (e(-)). The cytosol proteins of the two different callus lines were separated in a semi-preparative two-dimensional system and the polypeptide patterns were compared. Two protein bands were found (P1: Mr=45000 D, pI=7.0-7.1; P2: Mr=7000 D, pI=<4.5), which were characteristic of the putatively embryogenic (e(+)) callus line in all tissues investigated (two genotypes × two explant sources). These proteins found in nodular (e(+)) pea cultures are very similar to two proteins found in Daucus carota suspension cultures preceding the formation of somatic embryos.