Biochemical changes in embryogenic and non-embryogenic callus of Bambusa nutans Wall. during somatic embryogenesis

Abstract

Abstract Bambusa nutans Wall. is a clump-forming, evergreen bamboo species that is most often found in Southeast Asian forests. Comparative activities of nitrate reductase (NR), glutamine synthetase (GS) and peroxidase (POX) as well as expression of peroxidase isozymes during somatic embryogenesis (SE) were investigated in the segregated embryogenic callus (EC) and non-embryogenic callus (NEC) from the same genotype (CPC-648) of B. nutans Wall. The EC was compact, with large prominent nuclei and dense cytoplasm, while the NEC was fragile, with rudimentary nuclei and hyaline cytoplasm. SE in EC encompassed induction, maturation and germination stages each of 30 days on MS medium supplemented with ascorbic acid 50mg/l, citric acid 25mg/l, cysteine 25mg/l and glutamine 100mg/l + 2, 4-D-2 mg/l + coconut water 10%. EC exhibited dedifferentiation and growth leading to SE, while NEC remained amorphous loose lump throughout. EC had lower NR and POX activities and less number of peroxidase isozymes but higher GS activity than NEC during three stages of SE. NR activity followed a trend as induction > germination > maturation (EC and NEC); GS activity, maturation > germination >induction (EC) and induction >germination >maturation (NEC) and POX activity, maturation > induction > germination (EC) and induction > germination > maturation (NEC). Compared to NEC, EC exhibited less peroxidase isozymes. SE is an epigenetically regulated process that leads to the expression of enzymes involved in primary metabolism in EC and secondary metabolism in NEC. GS activity corresponding to SE process may be developed as biochemical marker. A chaotic scenario, rather from being a marker of SE, is indicated by high levels of peroxidase activity and isozyme expression.