title: Badh2, encoding betaine aldehyde dehydrogenase, inhibits the biosynthesis of 2-acetyl-1-pyrroline, a major component in rice fragrance.
abstract: In rice (Oryza sativa), the presence of a dominant Badh2 allele encoding betaine aldehyde dehydrogenase (BADH2) inhibits the synthesis of 2-acetyl-1-pyrroline (2AP), a potent flavor component in rice fragrance. By contrast, its two recessive alleles, badh2-E2 and badh2-E7, induce 2AP formation. Badh2 was found to be transcribed in all tissues tested except for roots, and the transcript was detected at higher abundance in young, healthy leaves than in other tissues. Multiple Badh2 transcript lengths were detected, and the complete, full-length Badh2 transcript was much less abundant than partial Badh2 transcripts. 2AP levels were significantly reduced in cauliflower mosaic virus 35S-driven transgenic lines expressing the complete, but not the partial, Badh2 coding sequences. In accordance, the intact, full-length BADH2 protein (503 residues) appeared exclusively in nonfragrant transgenic lines and rice varieties. These results indicate that the full-length BADH2 protein encoded by Badh2 renders rice nonfragrant by inhibiting 2AP biosynthesis. The BADH2 enzyme was predicted to contain three domains: NAD binding, substrate binding, and oligomerization domains. BADH2 was distributed throughout the cytoplasm, where it is predicted to catalyze the oxidization of betaine aldehyde, 4-aminobutyraldehyde (AB-ald), and 3-aminopropionaldehyde. The presence of null badh2 alleles resulted in AB-ald accumulation and enhanced 2AP biosynthesis. In summary, these data support the hypothesis that BADH2 inhibits 2AP biosynthesis by exhausting AB-ald, a presumed 2AP precursor.
authors.affiliation: National Maize Improvement Center of China, China Agricultural University, Beijing 100193, People's Republic of China.
authors.forename: Saihua
authors.initials: S
authors.lastname: Chen
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Weiwei
authors.initials: W
authors.lastname: Shi
authors.forename: Qing
authors.initials: Q
authors.lastname: Ji
authors.forename: Fei
authors.initials: F
authors.lastname: He
authors.forename: Ziding
authors.initials: Z
authors.lastname: Zhang
authors.forename: Zhukuan
authors.initials: Z
authors.lastname: Cheng
authors.forename: Xiangnong
authors.initials: X
authors.lastname: Liu
authors.forename: Mingliang
authors.initials: M
authors.lastname: Xu
mesh_terms: D050728:Betaine-Aldehyde Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D020869:Gene Expression Profiling; D005816:Genetic Complementation Test; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009812:Odorants; D012275:Oryza / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D011758:Pyrroles / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
chemical_list: D010940:Plant Proteins; D011758:Pyrroles; D050728:Betaine-Aldehyde Dehydrogenase; C426303:2-acetyl-1-pyrroline