Production of Raphanus sativus (C3)-Moricandia arvensis (C3-C4 intermediate) Monosomic and Disomic Addition Lines with Each Parental Cytoplasmic Background and their Photorespiratory Characteristics

We are maintaining five Moricandia arvensis monosomic addition lines of Raphanus sativus carrying R. sativus cytoplasm (autoplasmic MALs) and twelve M. arvensis MALs of R. sativus carrying M. arvensis cytoplasm (alloplasmic MALs) from BC 6 to BC 8 generation, and newly produced five M. arvensis disomic addition lines of R. sativus (autoplasmic DALs) and seven M. arvensis DALs of R. sativus carrying M. arvensis cytoplasm (alloplasmic DALs) from selfing and sib-crossing of the MALs and DALs in S 3 BC 5 and S 2 BC 6 generations. The structural, biochemical and physiological characteristics related to photorespiration of these MALs and DALs were compared to study the genetic mechanisms of the C 3 -C 4 intermediate photosynthesis in the individual chromosomes of M. arvensis. The CO 2 compensation point of the autoplasmic and alloplasmic DALs (RMa-b and MaR-b DALs) with one pair of M. arvensis 'b' chromosome were 29.4 and 30.1 μmol mol -1 , respectively, which were significantly lower than that of other DALs and MALs as well as R. sativus (34.5 μmol mol -1 ). An immunogold electron microscopic study of the P-protein of glycine decarboxylase (GDC) in photosynthetic cells of the RMa-b DAL revealed that the bundle sheath cell (BSC) mitochondria were more intensively labeled for the protein than the mesophyll cell (MC) mitochondria. The ratio of the labeling density of the BSC mitochondria to that of the MC mitochondria was 1.13, which lies between values in M. arvensis (2.66) and R. sativus (0.76). These data suggest that the 'b' chromosome of M. arvensis genome controls the expression of C 3 -C 4 intermediate characteristics.