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.

Seed-Specific Expression of a Feedback-Insensitive Form of CYSTATHIONINE-γ-SYNTHASE in Arabidopsis Stimulates Metabolic and Transcriptomic Responses Associated with Desiccation Stress

“…Additionally, four lipid transfer proteins, LTP4 (At5g59310), LTP3 (At5g59320), LTP6 (At3g08770), and LTP1 (At2g38540), that showed increased expression, are known as cell wall-localized small proteins that participate in responses to water deprivation and salt stress (Arondel et al, 2000; Table I). The expression levels of FATTY ACID DESATURASE2 (At3g12120), whose function is essential for the proper maintenance of low cytosolic Na + concentrations for salt tolerance during seed germination (Zhang et al, 2012), also increased, as well as the vegetative storage protein VSP2 (At5g24770), whose degradation serves as nitrogen and carbon sources that are available immediately for seed development and whose transcript is induced by osmotic and nutritional stresses (Liu et al, 2005; Table I). Finally, two HOMEOBOX proteins, HB12 (At3g61890) and HB7 (At2g46680), were upregulated significantly (Table I).…”

Sulfite Reductase Defines a Newly Discovered Bottleneck for Assimilatory Sulfate Reduction and Is Essential for Growth and Development in Arabidopsis thaliana

“…VSPs are believed to serve as transient storage proteins to keep unused amino acids during plant development when excess photosynthates are produced but may have additional functions, such as plant defense. Their expression can be induced by wounding and phosphate starvation (Fujiwara et al, 2002;Liu et al, 2005). Remarkably, they carry no Met residues besides the starting Met and only two to three Cys residues.…”

The shoot meristem identity gene TFL1 is involved in flower development and trafficking to the protein storage vacuole

“…One known role for PSVs is storage of defense proteins, such as lectins (11), chitinase, and glucanase (4). Some Arabidopsis vegetative storage proteins are anti-insect acid phosphatases (12). PSVs are found in roots, tubers, bark parenchyma, and paraveinal parenchyma (13)(14)(15) and are probably in the perennial root systems of plants whose shoots die in winter (e.g., perennial grasses) (16)(17)(18)(19)(20).…”