title: The Arabidopsis BE1 gene, encoding a putative glycoside hydrolase localized in plastids, plays crucial roles during embryogenesis and carbohydrate metabolism.
abstract: Carbohydrate metabolism is central to plant growth and development. However, little is known about its role in embryogenesis. Here, we report the characterization of multiple alleles of the BRANCHING ENZYME1 (BE1) gene (also known as EMB2729). The weak allele of be1-3, characterized by positional cloning, carries a single-nucleotide substitution in an exon-intron junction and shows various developmental defects during post-germination growth. This mutation causes a reduced level of BE1 mRNA that, likely generated from cryptically spliced pre-mRNA, contains a Glu-to-Lys substitution at codon 366. In four null alleles, BE1 is disrupted by T-DNA insertions, causing embryo developmental arrests at the heart stage. Light microscopy reveals reduced cell divisions and abnormal cell differentiation, thereby leading to defects in setting up the shoot apical meristem, embryonic vascular tissues and cotyledons. Overexpression of BE1 results in a pleiotropic phenotype, indicating that the fine-tuned BE1 level is crucial for plant growth and development. BE1 encodes a putative glycoside hydrolase that is highly conserved in higher plants. A BE1-GFP fusion protein, which is fully functional in complementing be1 mutants, is localized in plastids. The be1-3 phenotype can be partially rescued by glucose, fructose or sucrose, implying the involvement of BE1 in carbohydrate metabolism in plastids.
authors.affiliation: College of Life Sciences, Shanxi Agricultural University, Taigu 030801, China.
authors.forename: Xingchun
authors.initials: X
authors.lastname: Wang
authors.forename: Li
authors.initials: L
authors.lastname: Xue
authors.forename: Jiaqiang
authors.initials: J
authors.lastname: Sun
authors.forename: Jianru
authors.initials: J
authors.lastname: Zuo
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000166:cytology / Q000196:embryology* / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D050260:Carbohydrate Metabolism / Q000187:drug effects / Q000235:genetics*; D003001:Cloning, Molecular; D047108:Embryonic Development / Q000187:drug effects / Q000235:genetics*; D005632:Fructose / Q000494:pharmacology; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D005947:Glucose / Q000494:pharmacology; D006026:Glycoside Hydrolases / Q000235:genetics* / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D054046:Plant Stomata / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018087:Plastids / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012639:Seeds / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D013395:Sucrose / Q000494:pharmacology; D000516:alpha-Amylases / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D005632:Fructose; D013395:Sucrose; C552305:BE1 protein, Arabidopsis; D006026:Glycoside Hydrolases; D000516:alpha-Amylases; D005947:Glucose