title: An unusual posttranscriptional processing in two betaine aldehyde dehydrogenase loci of cereal crops directed by short, direct repeats in response to stress conditions.
abstract: Various abilities to synthesize and accumulate glycine betaine (GB) are crucial for angiosperms to develop salt and drought tolerances. In higher plants, GB is synthesized by a two-step oxidation of choline via an intermediate form of betaine aldehyde, and catalyzed by choline monooxygenase and betaine aldehyde dehydrogenase (BADH). In this study, numerous truncated and/or recombinant transcripts of two BADH homologs resulting from an unusual posttranscriptional processing were detected in rice (Oryza sativa) and other cereal crops, including maize (Zea mays), wheat (Triticum aestivum), and barley (Hordeum vulgare). The observed events took place at the 5' exonic region, and led to the insertion of exogenous gene sequences and a variety of deletions that resulted in the removal of translation initiation codon, loss of functional domain, and frame-shifts with premature termination by introducing stop codon. By contrast, the BADH transcripts from dicotyledonous species, such as spinach (Spinacia oleracea), Arabidopsis (Arabidopsis thaliana), and tomato (Solanum lycopersicum), had correctly processed mRNA. This suggests the differentiation of posttranscriptional processing in BADH genes potentially contributes to the variation of GB-synthesizing capacities among various plant species. In addition, comprehensive sequence analyses demonstrated that extensive sequence similarities (named as short, direct repeats) are of paired presence surrounding the junctions of both the deletion and/or insertion sites in the unusual BADH transcripts. The site selection for the deletion/insertion was altered in response to the stress conditions. This indicates that the sequence elements of short, direct repeats are probably required for the recognition of the deletion/insertion sites.
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science , Sichuan University, Chengdu 610064, China.
authors.forename: Xiangli
authors.initials: X
authors.lastname: Niu
authors.forename: Wenjing
authors.initials: W
authors.lastname: Zheng
authors.forename: Bao-Rong
authors.initials: BR
authors.lastname: Lu
authors.forename: Guangjun
authors.initials: G
authors.lastname: Ren
authors.forename: Weizao
authors.initials: W
authors.lastname: Huang
authors.forename: Songhu
authors.initials: S
authors.lastname: Wang
authors.forename: Junli
authors.initials: J
authors.lastname: Liu
authors.forename: Zizhi
authors.initials: Z
authors.lastname: Tang
authors.forename: Di
authors.initials: D
authors.lastname: Luo
authors.forename: Yuguo
authors.initials: Y
authors.lastname: Wang
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Liu
mesh_terms: D001483:Base Sequence; D050728:Betaine-Aldehyde Dehydrogenase / Q000235:genetics*; D018556:Crops, Agricultural; D017931:DNA Primers; D002523:Edible Grain / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D012333:RNA, Messenger; D050728:Betaine-Aldehyde Dehydrogenase