Development and application of qRT-PCR for sugar beet gene expression analysis in response to in vitro induced water deficit

Abstract

Sugar beet is a significant industrial crop, often grown in the areas where summer drought can severely limit root yield and sugar content. In order to improve development of sugar beet cultivars with increased drought tolerance it is necessary to understand plant response to water stress at the genomic level. Since recent research efforts have focused on the molecular response of the plant in order to identify water deficit inducible genes, the aim of this investigation was to develop qRT-PCR methodology for the quantification of gene expression in sugar beet under conditions of water deficiency in vitro. Sugar beet genotypes, selected for different response to water deficit, were grown and multiplied in vitro. Axilary shoots were placed on micropropagation media with 0%, 3% and 5% PEG, for 28 days. To determine reaction of sugar beet genotypes to in vitro induced water deficit changes in number of axillary shoots, shoot fresh weight and dry matter content were measured. Total RNA was extracted from leaves and reverse transcribed into cDNA, which served as matrix in real-time PCR reaction using TaqMan technology. The housekeeping gene for glutamine synthetase was used as endogenous control, while the genes for alpha amylase and osmotin-like protein were target genes. The relative quantification values for each target gene were calculated by the 2-ΔΔCt method. Selected candidate genes differed in relative gene expression among genotypes and applied PEG treatments. The obtained results indicated that qRT-PCR protocol was efficient and accurate, showing the potential to be used in further expression analysis of candidate genes involved in sugar beet reaction to water stress. © 2012 by Pontificia Universidad Católica de Valparaíso, Chile.