Calcium-Mediated Signaling during Sandalwood Somatic Embryogenesis. Role for Exogenous Calcium as Second Messenger

Anil, Veena S and Rao, Sankara K (2000) Calcium-Mediated Signaling during Sandalwood Somatic Embryogenesis. Role for Exogenous Calcium as Second Messenger. In: PLANT PHYSIOLOGY, 123 (04). pp. 1301-1311.

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Abstract

The possible involvement of $Ca{^2^+}$-mediated signaling in the induction/regulation of somatic embryogenesis from proembryogenic cells of sandalwood (Santalum album) has been investigated. ${^4}$${^5}$ $Ca{^2^+}$-uptake studies and fura-2 fluorescence ratio photometry were used to measure changes in $[Ca{^2^+}$]$_{cyt}$ of pro-embryogenic cells in response to culture conditions conducive for embryo development. Sandalwood pro-embryogenic cell masses (PEMs) are obtained in the callus proliferation medium that contains the auxin 2,4-dichlorophenoxyacetic acid. Subculture of PEMs into the embryo differentiation medium, which lacks 2,4-dichlorophenoxyacetic acid and has higher osmoticum, results in a 4-fold higher${^4}$${^5}$ $Ca{^2^+}$ incorporation into the symplast. Fura-2 ratiometric analysis corroboratively shows a 10- to 16-fold increase in the $[Ca{^2^+}]$$_{cyt}$ of PEMs, increasing from a resting concentration of 30 to 50 nm to 650 to 800 nm. Chelation of exogenous $Ca{^2^+}$ with ethyleneglycolbis(aminoethyl ether)-N,N9-tetraacetic acid arrests such an elevation in $[Ca{^2+}]$$_{cyt}$. Exogenous $Ca{^2^+}$ when chelated or deprived also arrests embryo development and inhibits the accumulation of a sandalwood $Ca{^2^+}$-dependent protein kinase. However, such culture conditions do not cause cell death as the PEMs continue to proliferate to form larger cell clumps. Culture treatment with N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide reduced embryogenic frequency by 85%, indicating that blockage of $Ca{^2^+}$-mediated signaling pathway(s) involving sandalwood $Ca{^2^+}$-dependent protein kinase and/or calmodulin causes the inhibition of embryogenesis. The observations presented are evidence to suggest a second messenger role for exogenous $Ca{^2^+}$ during sandalwood somatic embryogenesis.

Item Type:	Journal Article
Publication:	PLANT PHYSIOLOGY
Publisher:	American Society of Plant Physiologists
Additional Information:	Copyright of this article belongs to American Society of Plant Physiologists
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	10 Dec 2008 11:27
Last Modified:	19 Sep 2010 04:53
URI:	http://eprints.iisc.ac.in/id/eprint/16624

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