Histocytological examination on organogenesis and somatic embryogenesis of HBsAg-transgenic cherry tomato mutant

Abstract

The initiation and development of organogenic buds and somatic embryos in HBsAg-transgenic cherry tomato (Lycopersicum esculentum var. cerasiforme) mutant were studied histologically. The leaf explants of the mutant were cultured on Murashige & Skoog (MS) basal medium supplemented with 6-BA 1.0 mg/L and IAA 0.05 mg/L for callus induction. Histological studies on the leaf explants of the mutant at various developmental stages revealed that organogenic buds first appeared in the axillary position of explants on the 14th cultured day, and then somatic embryos formed in the same mutant explants after 35 days of culture. Transmission electron microscopy and scanning electron microscopy indicated that there were significant changes in morphology and quantity of some organelles in the mutant callus cells compared with the control. On the 7th day of culture, embryogenic callus cells of the control showed dense cytoplasm and abundant organelles; at the same time, there was little cytoplasm or less organelles, except for a great number of dense lipid bodies in the mutant callus cells. In the later stage, the chloroplasts, Golgi bodies and mitochondria in the mutant cells also had obvious differences. These findings demonstrated that the regeneration pathway in vitro of the HBsAg-transgenic cherry tomato mutant showed variation, which was useful for the regeneration and gene transfer protocol.