Respiratory pathway enzymes are differentially altered in flood tolerant and sensitive rice types during O₂ deprivation stress and post-stress recovery phase

Abstract

O₂ deprivation stress leads to pronounced alterations in respiratory metabolism. The transcript level and specific activity of enzymes involved in glycolysis and ethanolic fermentation have previously been shown to be up-regulated in response to this stress. In this study, we compared transcript and protein levels of pyruvate decarboxylase (PDC) and transcript levels of alcohol dehydrogenase (ADH), glucose phosphate isomerase (GPI), phosphofructokinase (PFK), triose phosphate isomerase (TPI), glyceraldehyde phosphate dehydrogenase (GAPDH), enolase (ENO) and pyruvate kinase (PK) in flood-sensitive IR54 and flood-tolerant FR13A rice types. The samples were obtained during the stress period as well as in the post-stress recovery phase. The level of constitutive expression of various transcripts was comparable in IR54 and FR13A rice types. The levels of PDC2 subunit appeared higher in shoots of FR13A relative to IR54 during stress and recovery. The Western profile of PDC showed an additional band in FR13A that was not apparent in IR54. During the recovery phase, IR54 shoots maintained higher levels of gpi, pfk, tpi, gapdh, eno, pk and pdc1 gene transcripts as compared with FR13A. On the other hand, adh1 gene transcript levels were relatively higher in FR13A rice at the 6 h stress and 3 h recovery stages. It thus appears that both transcriptional and post-transcriptional controls play a part in the response of contrasting rice types to O₂ deprivation stress.