Deficiency in the amino aldehyde dehydrogenase encoded by GmAMADH2, the homologue of rice Os2AP, enhances 2‐acetyl‐1‐pyrroline biosynthesis in soybeans (Glycine max L.)

Abstract

Summary2-Acetyl-1-pyrroline (2AP), the volatile compound that provides the 'popcorn-like' aroma in a large variety of cereal and food products, is widely found in nature. Deficiency in amino aldehyde dehydrogenase (AMADH) was previously shown to be the likely cause of 2AP biosynthesis in rice (Oryza sativa L.). In this study, the validity of this mechanism was investigated in soybeans (Glycine max L.). An assay of AMADH activity in soybeans revealed that the aromatic soybean, which contains 2AP, also lacked AMADH enzyme activity. Two genes, GmAMADH1 and GmAMADH2, which are homologous to the rice Os2AP gene that encodes AMADH, were characterized.The transcription level of GmAMADH2 was lower in aromatic varieties than in nonaromatic varieties, whereas the expression of GmAMADH1 did not differ. A double nucleotide (TT) deletion was found in exon 10 of GmAMADH2 in all aromatic varieties. This variation caused a frame-shift mutation and a premature stop codon. Suppression of GmAMADH2 by introduction of a GmAMADH2-RNAi construct into the calli of the two nonaromatic wild-type varieties inhibited the synthesis of AMADH and induced the biosynthesis of 2AP. These results suggest that deficiency in the GmAMADH2 product, AMADH, plays a similar role in soybean as in rice, which is to promote 2AP biosynthesis. This phenomenon might be a conserved mechanism among plant species.

Identification of aroma volatiles and understanding 2-acetyl-1-pyrroline biosynthetic mechanism in aromatic mung bean (Vigna radiata (L.) Wilczek)

“…Fitzgerald et al (2008) reported that the BADH2 expression was higher in nonfragrant rice varieties than fragrant genotypes. Arikit et al (2011b) demonstrated that the expression levels of GmAMADH2 in soybean were much lower in aromatic varieties than non-aromatic ones. These reports clearly establish recessive nature of BADH2 fragrant allele in all 2AP synthesized species and can also be applicable to SMB.…”

Studies on Aroma Gene and its Application in Rice Genetics and Breeding

“…For example, a 2 bp deletion in exon 10 of the GmBADH2 gene was located on chromosome 6 will cause the gene to prematurely terminate the translation process in Glycine max, thereby producing a fragrance (Juwattanasomran et al, 2011(Juwattanasomran et al, , 2012. 2-AP could be synthesized in large quantities if the GmBADH2 gene was silenced in soybean, and fragrant soybeans could be produced immediately (Arikit et al, 2011). At the same time, studies in sorghum found that the SbBADH2 gene is a recessive gene that controlled the fragrant in Sorghum (Yundaeng et al, 2013).The history of domestication of sorghum, rice, and soybeans is not the same, but the fragrant of the three crops is dominated by a single recessive gene (Murty et al, 1982;, in which the aroma gene is mutated and the production of these crop aromas is closely related, and the recessive gene controlling the fragrant have a certain degree of homology (Arikit et al, 2011).…”

“…2-AP could be synthesized in large quantities if the GmBADH2 gene was silenced in soybean, and fragrant soybeans could be produced immediately (Arikit et al, 2011). At the same time, studies in sorghum found that the SbBADH2 gene is a recessive gene that controlled the fragrant in Sorghum (Yundaeng et al, 2013).The history of domestication of sorghum, rice, and soybeans is not the same, but the fragrant of the three crops is dominated by a single recessive gene (Murty et al, 1982;, in which the aroma gene is mutated and the production of these crop aromas is closely related, and the recessive gene controlling the fragrant have a certain degree of homology (Arikit et al, 2011). Although the loss of aroma gene in rice, sorghum and soybeans does not affect their survival, it will play an active role in drought conditions.…”

Single base substitution causing the fragrant phenotype and development of a type-specific marker in aromatic coconut (Cocos nucifera)

“…Transformation of aromatic rice with the wild-type Badh2 significantly reduced the amount of 2AP (Bradbury et al, 2008;. Mutation of Badh2 was also reported to generate mutants with aromatic flavor in soybean (Arikit et al, 2011;Juwattanasomran et al, 2011), sorghum (Yundaeng et al, 2013), and cucumber (Yundaeng et al, 2015).…”