Differential Expression Gene During Root Development in Tomato

Genome wide expression analysis using SSH led to the identification of 161 unique ESTs for root development and root system architecture in tomato. A total of 36 ESTs were selected on the basis of their putative involvement in hormonal regulations, transport processes and other accessory attributes of root development. Among the expression profile of nine selected genes pertaining to root development were analysed in tomato (cv. Pusa Ruby) by quantitative real time (qRT) PCR analysis. These nine genes showed wide variation in their expression pattern during different stages of growth and development of roots as well as shoots in the genotype Pusa Ruby. All the nine genes showed higher expression in roots as compared to shoots, either at the end of eight days or 40 days or both. Six genes (AAT, NRT, HSP90.2, ADC1, TUB8 and EF-1A) showed higher expression (2 to 8 fold) in 8 days old root in comparison 8 days old shoots. Similarly, eight genes (AAT, HSP 90.2, ADC1, NAP1, TUB8, EF-1A, FLV, JMJ) showed higher expression (1.5 to 8 fold) in 40 days old root. Among nine genes tested, seven genes showed differential expression in tomato genotypes with contrasting root biomass such as, high rooting (ArkaMeghali, IIHR 2624) and low rooting(IIHR 2615, IIHR 2613) phenotype. All the seven genes (AAT, NAP, ADC1, HSP90.2, TUB8, NRT and EF-1A) showed 3-20 fold higher level expression in 40 days old roots of high rooting genotypes as compared to that of low rooting genotypes (IIHR2613 as low rooting control). Differential expressions of these genes in roots of the contrasting genotypes suggests theri role in root development and root system architecture. Furthur their functional characterization in root developemnt and root biomass accumulation is being studied by transgenic approach.