Lotus is one of the most popular aquatic plants cultivated in Asia for its high ornamental, edible and medicinal value. It is becoming an emerging horticultural model for studying flower color coloration, rhizome development, species phylogeny and primary and secondary metabolite biosynthesis. It is, however, a severe recalcitrant species, with no viable regeneration and transgenic system available to date.  

Dr. DENG Xianbao, together with his coauthors from the Lotus Resources and Genetic Improvement Group of the Wuhan Botanical Garden, reported the establishment of a highly efficient callus induction system in lotus.  

A series of key factors that affect callus formation were optimized. The best callus induction was achieved using immature cotyledon and embryo explants grown on Murashige and Skoog basal medium supplemented with the combination of 3 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg/L 6-benzylaminopurine (6-BA). 

According to the researchers, other factors, such as plant genotypes, explant sources, auxin/cytokinin ratios, light, the developmental stages of explants, and the time of explant sampling also affected lotus callus induction. 

Notably, high quality callus was also observed in explants of immature embryo derived aseptic seedlings. Benzylisoquinoline alkaloids (BIAs) accumulation and obvious expression of BIA biosynthetic genes were detected in lotus callus.    

"This efficient lotus callus induction system provides a useful starting point for the development of an integrated lotus transformation system based on somatic embryogenesis, and is valuable for building a cell culture system aiming to in vitro production of medicinal BIAs", said Dr. DENG. 

Relevant results entitled "The Establishment of an Efficient Callus Induction System for Lotus (Nelumbo nucifera)" have been published online on Plants.  

This research was supported by funds received from the Key Research Program of Frontier Science of the Chinese Academy of Sciences and the National Science Foundation of China. 

Schematic diagram showing the system of lotus callus induction. Both embryo and cotyledon explants (B) taken from immature seeds at 12-15 days after pollination (A) developed good quality callus (C and D). Lotus aseptic seedlings (E) developed from immature embryo were also excellent explants in induction high quality callus (F, G, and H) (Image by WBG)