Differential regulation of genes co-involved in aroma production and stress amelioration during salt acclimation in indica rice cultivars

Abstract

The present study investigated the effects of salt acclimation on the expression of genes, viz., proline dehydrogenase (PDH), Δ1-pyrroline-5-carboxylate-synthetase (P5CS), P5C dehydrogenase (P5CDH), ornithine aminotransferase (OAT), betaine aldehyde dehydrogenase 1 (BADH1), BADH2, triose phosphate isomerase (TPI), ornithine decarboxylase (ODC), arginine decarboxylase (ADC), S-adenosyl-methionine decarboxylase (SAMDC), spermidine synthase (SPDS), spermine synthase (SPMS), diamine oxidase (DAO) and polyamine oxidase (PAO) in four indigenous aromatic varieties, viz., Tulaipanji (TP), Radhunipagal (RP), Kalonunia (KN) and Gobindobhog (GB) along with a non-aromatic cultivar, IR-64. The PDH, P5CS, P5CDH and OAT expression showed the regulation of the P5C pathway of aroma synthesis, with OAT appearing to regulate the crosstalk between the P5C and the polyamine (PA) pathway for the production of aroma. The role of PA pathway was further validated by monitoring the expression of ODC, ADC, SAMDC, SPDS, SPMS, DAO and PAO. The BADH2 expression reflected the fact that the enzyme encoded by the gene was directly and negatively associated with aroma content in rice. The TPI expression established that the enzyme encoded by this gene leading to the synthesis of methylglyoxal (MG) is also a key regulator for aroma synthesis. The current study established the varietal differences in the expression of the aforementioned genes in the selected rice cultivars. The salt-stressed aromatic varieties followed the P5C pathway to synthesize aroma. TP and RP exhibited the capability to generate aroma via PA-dependent pathway. Salt-stressed KN, on the contrary, accumulated higher BADH2 and lower TPI transcripts, which correlated with our previous report of KN accumulating low aroma during salinization due to efficient metabolite channelization towards stress amelioration.