Addition of ionophore A23187 increases the efficiency of Cocos nucifera somatic embryogenesis

Abstract

The present study reports the effect of treatment of coconut embryogenic structure explants (derived from embryogenic callus) with the calcium ionophore A23187 (0, 1, 5, 10 µM) to promote somatic embryogenesis under in vitro conditions. The results showed no significant increase in the percentage of explants forming embryogenic callus, but with 1 µM ionophore there were significant increases in the formation of embryogenic structures per callus (2.8-fold), of somatic embryos per callus (1.5-fold) and also a greater absolute number (1.5-fold) of developing plantlets per callus. The ionophore treatment also promoted a change of pattern of the expression of the CnSERK gene during embryogenic callus formation. It is proposed that if the use of ionophore A23187 treatment is coupled with an embryogenic callus multiplication process there could be a potentially greater increase in the efficiency of the formation of somatic embryos and plantlets of coconut.

Keywords: Calcium ionophore A23187; Cn SERK; Coconut; Somatic embryogenesis.

Fig. 1

Alignment of sequences reported at GenBank with the highest identity percentage to CnSERK. The region between the nucleotides on position 230 and 241 was used to design the corresponding TaqMan probe for CnSERK

Fig. 2

Developmental stages during embryogenic callus formation from embryogenic structures explants (a) after 30, 60 days; (b) fully formed embryogenic calli formed at day 90 of culture without (control) and with 1 µM ionophore A23187; and (c) corresponding globular somatic embryos. TS translucent structures, ES embryogenic structures, SE somatic embryos

Fig. 3

Effect of treatment of embryogenic structures explants with ionophore A23187 (0, 1, 5 and 10 µM) on the rate of embryogenic callus formation. Different letters represent statistical differences among groups

Fig. 4

Histological sections of embryogenic calli obtained after 90 days of culture without (a) and with 1 µM ionophore A23187 treatment (b); and corresponding magnified areas (×40) within squares shown in (c) and (d). ES embryogenic structures

Fig. 5

Postgerminative development within 2 months of culture in ionophore-free medium 4. a Tissues were previously cultured in ionophore-free media. b Tissues were previously cultured in 1 µM ionophore A23187-containing medium 1 (calli induction) and medium 2 (embryo formation), and ionophore-free medium 3 (embryo germination)

Fig. 6

Relative expression profiles of CnSERK during embryogenic callus development from of Cocos nucifera embryogenic structure explants with and without 1 µM ionophore A23187 treatment