Rhizoctonia solani infection in two rice lines increases mRNA expression of metabolic enzyme genes in glycolytic, oxidative pentose phosphate pathways and secondary metabolism

Abstract

Using two rice lines, namely 2F 18 -7-32 (32) a Rhizoctonia solani - resistant rice line and one, 2F 21 -21-29 (29) a susceptible rice line, changes in the time course of mRNA expression of 30 metabolic enzyme genes in R. solani- infected samples were examined. These consisted of eight metabolic enzyme genes of the glycolytic pathway; three metabolic enzyme genes of the oxidative pentose phosphate pathway (OPPP), and six metabolic enzyme genes of the reductive pentose phosphate cycle (RPPC); sucrose phosphatase (SPase, EC 3.1.3.24), participating in sucrose synthesis; ADP-glucose pyrophosphorylase (ADPase, EC 2.7.7.9) and starch synthase (SS, EC 2.4.1.21) which are involved in starch synthesis; six metabolic enzyme genes of the tricarboxylic acid (TCA) cycle and four metabolic enzyme genes of the secondary metabolism. The results showed that significant changes in the time course of mRNA expression occurred at 1 dpi and that mRNA expression of glycolytic enzymes; 6-phosphofructokinase, phosphoglycerate kinase, enolase and pyruvate kinase and secondary metabolism enzymes; 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase and phenylalanine ammonialyase was significantly higher ( P < 0.05) in the R. solani- infected samples of the resistant rice line, compared to that of the susceptible rice line. The results suggested that R. solani infection led to activation of the glycolytic pathway, OPPP, TCA cycle and secondary metabolism. Time course of mRNA expression of RPPC genes, ADPase and SS suggested that starch synthesis was low in R. solani- infected samples of both R. solani- resistant and susceptible rice lines. It appeared that R. solani infection was associated with the activation of the glycolytic pathway, OPPP, secondary metabolism and TCA cycle and low starch synthesis.