Mitochondrial mutant MSC cucumber shows impaired somatic

The cucumber MSC16 mutant was obtained by regeneration from cell cultures of the inbred line B and it is associated with complex mitochondrial genome rearrangements causing DNA deletions and duplications. We compared cell suspensions of cucumber MSC16 and the control wild type line B. MSC16 growth intensity in cell cultures was the same as a control line B. There were differences, however, in ability to undergo somatic embryogenesis. In auxin-dependent cell suspension (ADS) the MSC16 formed abnormal embryos not able to convert into the plantlets, however, 14% of MSC16 somatic embryos were normal after application of the cytokinin-dependent cell suspension (CDS) procedure. There were no differences between MSC16 and wild type line B observed in liquid culture of meristematic clumps (LMC). An electron microscopy revealed long fasciated mitochondria present in MSC16 ADS culture and mitochondria organized in clumps present in MSC16 CDS culture, with a control showing typical mitochondria appearance. An accumulation of large starch grains in chloroplasts appeared in cell cultures of the MSC16. These differences are discussed in the context of MSC16 mutant formation and its unique features.