title: Arabidopsis vegetative storage protein is an anti-insect acid phosphatase.
abstract: Indirect evidence previously suggested that Arabidopsis (Arabidopsis thaliana) vegetative storage protein (VSP) could play a role in defense against herbivorous insects. To test this hypothesis, other AtVSP-like sequences in Arabidopsis were identified through a Basic Local Alignment Search Tool search, and their transcriptional profiles were investigated. In response to methyl jasmonate application or phosphate starvation, AtVSP and AtVSP-like genes exhibited differential expression patterns, suggesting distinct roles played by each member. Arabidopsis VSP2 (AtVSP2), a gene induced by wounding, methyl jasmonate, insect feeding, and phosphate deprivation, was selected for bacterial expression and functional characterization. The recombinant protein exhibited a divalent cation-dependent phosphatase activity in the acid pH range. When incorporated into the diets of three coleopteran and dipteran insects that have acidic gut lumen, recombinant AtVSP2 significantly delayed development of the insects and increased their mortality. To further determine the biochemical basis of the anti-insect activity of the protein, the nucleophilic aspartic acid-119 residue at the conserved DXDXT signature motif was substituted by glutamic acid via site-directed mutagenesis. This single-amino acid alteration did not compromise the protein's secondary or tertiary structure, but resulted in complete loss of its acid phosphatase activity as well as its anti-insect activity. Collectively, we conclude that AtVSP2 is an anti-insect protein and that its defense function is correlated with its acid phosphatase activity.
authors.affiliation: Department of Entomology, Texas A&M University, College Station, TX 77843, USA.
authors.forename: Yilin
authors.initials: Y
authors.lastname: Liu
authors.forename: Ji-Eun
authors.initials: JE
authors.lastname: Ahn
authors.forename: Sumana
authors.initials: S
authors.lastname: Datta
authors.forename: Ron A
authors.initials: RA
authors.lastname: Salzman
authors.forename: Jaewoong
authors.initials: J
authors.lastname: Moon
authors.forename: Beatrice
authors.initials: B
authors.lastname: Huyghues-Despointes
authors.forename: Barry
authors.initials: B
authors.lastname: Pittendrigh
authors.forename: Larry L
authors.initials: LL
authors.lastname: Murdock
authors.forename: Hisashi
authors.initials: H
authors.lastname: Koiwa
authors.forename: Keyan
authors.initials: K
authors.lastname: Zhu-Salzman
mesh_terms: D000085:Acetates / Q000494:pharmacology; D000135:Acid Phosphatase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D003517:Cyclopentanes / Q000494:pharmacology; D004330:Drosophila / Q000187:drug effects / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007300:Insect Control; D007313:Insecta / Q000187:drug effects / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D054883:Oxylipins; D010710:Phosphates / Q000172:deficiency; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D000085:Acetates; D029681:Arabidopsis Proteins; D003517:Cyclopentanes; D054883:Oxylipins; D010710:Phosphates; D012333:RNA, Messenger; C463539:VSP2 protein, Arabidopsis; C072239:methyl jasmonate; D000135:Acid Phosphatase