MSc

The study entitled " Induction of embryogenic calli from immature ovaries
in coconut (Cocos nucifera L.)" was conducted at the Department of Molecular
Biology and Biotechnology, College of Agriculture, Vellayani,
Thiruvananthapuram during 2022-23. The objective of the study was induction
of embryogenic calli from immature ovary in coconut variety West Coast Tall
(WCT) and effect of sodium butyrate in callus induction through histone
deacetylation.
In the present study, immature ovaries from explants of maturity indices -
4 to -6 were extracted and surface sterilized using 3% sodium hypochlorite, 0.2%
mercuric chloride, and 70% ethanol. They were inoculated into basal Y3 medium
containing different plant growth regulators such as 2,4-D, TDZ, and picloram.
The results showed that out of all the maturity indices tried (-4 to -6), inflorescence
of maturity index -4 showed a maximum response in callus induction, and among
different callus induction medium (CIM) tried CIM with 100 μM 2,4-D showed
maximum response (47.28%) to embryogenic calli initiation. The time taken for
embryogenic calli-like structure development was 45 days.
To analyze the effect of sodium butyrate (SB) in callus initiation, the excised
immature ovaries were inoculated into standardized CIM (Y3 + 100 μM 2,4-D)
with different concentrations of SB. The results displayed that, compared with the
CIM, the induction rates of embryogenic calli were significantly increased (66%)
and the time taken for embryogenic calli-like structure development was
significantly reduced (20 days) with the addition of 100 μM SB. The gene
expression analysis shows that gene expression of the HDA6 gene was reduced in
CIM with SB when compared to CIM. The increased embryogenic response of
immature ovaries to CIM with SB as well as the reduced time taken for the
embryogenic response can be correlated with the downregulation of the HDAC
gene.
To conclude, induction of embryogenic calli and the time taken for
embryogenic response of immature ovary in coconut variety West Coast Tall
(WCT) has improved by adding SB in CIM. This may be due to the downregulation
of the HDAC gene. Reduced activity of histone deacetylase can accumulate
acetylated histone and thereby increase gene expression. The preliminary data
showed that SB at a lower concentration (100 μM) can improve the embryogenic
calli response of immature ovaries of coconut in callus induction medium. The
mechanism of action of SB on coconut embryogenesis and the regulated genes must
be investigated further

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