Inactivation of an aminoaldehyde dehydrogenase is responsible for fragrance in rice

Louis M T Bradbury, Susan A. Gillies, Donald J. Brushett, Daniel L E Waters, Robert J. Henry

Research output: Contribution to journalArticle

138 Citations (Scopus)

Abstract

Rice (Oryza sativa) has two betaine aldehyde dehydrogenase homologs, BAD1 and BAD2, encoded on chromosome four and chromosome eight respectively. BAD2 is responsible for the characteristic aroma of fragrant rice. Complementary DNA clones of both BAD1 and BAD2 were isolated and expressed in E. coli. BAD2 had optimum activity at pH 10, little to no affinity towards N-acetyl-γ- aminobutyraldehyde (NAGABald) with a Km of approximately 10 mM and moderate affinity towards γ-guanidinobutyraldehyde (GGBald) and betaine aldehyde (bet-ald) with Km values of approximately 260 μM and 63 μM respectively. A lower Km of approximately 9 μM was observed with γ-aminobutyraldehyde (GABald), suggesting BAD2 has a higher affinity towards this substate in vivo. The enzyme encoded on chromosome four, BAD1, had optimum activity at pH 9.5, showed little to no affinity towards bet-ald with a Km of 3 mM and had moderate affinity towards GGBald, NAGABald and GABald with Km values of approximately 545, 420 and 497 μM respectively. BAD1 had a half life roughly double that of BAD2. We discuss the implications of these findings on the pathway of fragrance generation in Basmati and Jasmine rice and the potential of rice to accumulate the osmoprotectant glycine betaine.

Original languageEnglish
Pages (from-to)439-449
Number of pages11
JournalPlant Molecular Biology
Volume68
Issue number4-5
DOIs
Publication statusPublished - Nov 2008

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