Expression pattern of in vitro organogenesis-associated genes as transcriptional marker in Indian Sandalwood ( Santalum album L.).

Abstract

Indian sandalwood (Santalum album L.) is an expensive wood that requires reproducible method for mass propagation to ensure consistent production and sustainable use of sandalwood. For mass propagation of sandalwood, plant organogenesis requires different combinations of the tissue culture medium. The media is composed of exogenous phytohormones which decides the explant's morphological stages such as shooting or rooting induction. Early prediction of morphological stage from explant can potentially help in selecting the exogenous phytohormones combinations thereby saving time and resources for mass sandalwood propogation. An efficient protocol for the direct and indirect organogenesis (up to shooting development phase) of sandalwood were developed using Woody Plant Media (WPM). WPM supplemented with various concentrations of 6-Bezylaminopurine (BAP) and 1-Naphthaleneacetic acid (NAA) were tested for direct organogenesis, while different treatments consisting of various levels of 2,4-dichlorophenoxyacetic acid (2,4-D), NAA, BAP, Adenine sulphate (ADS), glycine and potassium nitrate were tested for indirect organogenesis. Three stages of leaf development were selected viz., the leaf just after inoculation in WPM media, initial stage of callus formation from leaf and shoot formation for expression pattern analysis. The targeted genes were Alternative oxidase (ao), Late embryogenesis abundant (lea), Cytochrome P450 (cyt-p450), ABC transporter (abct), and Serine-threonine phosphatase (stp) which are associated with in vitro organogenesis. The expression patterns were evaluated to identify a transcription marker. During the initial stages of organogenesis, ao, cyt-p450 and abct showed no/little change in expression in the direct pathway but up-regulation of ao and abct and downregulation of cyt-p450 were observed in the indirect pathway. Expression of lea was increased up to 70-fold during direct and dropped to half during indirect organogenesis.