ABSTRACT
Aphid saliva is predicted to contain proteins that modulate plant defenses and facilitate feeding. Armet is a well-characterized bifunctional protein in mammalian systems. Here we report a new role of Armet, namely as an effector protein in the pea aphid, Acyrthosiphon pisum. Pea aphid Armet's physical and chemical properties and its intracellular role are comparable to those reported for mammalian Armets. Uniquely, we detected Armet in aphid watery saliva and in the phloem sap of fava beans fed on by aphids. Armet's transcript level is several times higher in the salivary gland when aphids feed on bean plants than when they feed on an artificial diet. Knockdown of the Armet transcript by RNA interference disturbs aphid feeding behavior on fava beans measured by the electrical penetration graph technique and leads to a shortened life span. Inoculation of pea aphid Armet protein into tobacco leaves induced a transcriptional response that included pathogen-responsive genes. The data suggest that Armet is an effector protein mediating aphid-plant interactions.
Subject(s)
Aphids/physiology , Host-Pathogen Interactions/physiology , Insect Proteins/metabolism , Saliva/metabolism , Salivary Proteins and Peptides/metabolism , Vicia faba/parasitology , Amino Acid Sequence , Animals , Base Sequence , Blotting, Western , Circular Dichroism , Cloning, Molecular , Eating/physiology , Endoplasmic Reticulum Stress , Evolution, Molecular , Immunoenzyme Techniques , Immunoglobulin G/immunology , Insect Proteins/genetics , Insect Proteins/immunology , Molecular Sequence Data , RNA, Messenger/genetics , Rabbits , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Saliva/chemistry , Salivary Proteins and Peptides/genetics , Salivary Proteins and Peptides/immunology , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Vicia faba/metabolismABSTRACT
DNA methylation is a general epigenetic mechanism for plants, animals, and fungi to adapt to environmental variation. Two biotypes of the Russian wheat aphid (Diuraphis noxia), Biotype 1 and Biotype 2, have different virulence to host plants. In this study, in addition to a high polymorphism, DNA methylation at cytosines were observed in genomic fragments of four genes in Biotype 1 and Biotype 2, after the genomic DNA was treated with sodium bisulfite. These genes presumably encode proteins and enzymes in salivary glands of aphids. The two Biotype 1 showed different methylation levels, that is, Biotype 1 showed a higher methylation on the four genes. Two thirds of methyl cytosines were in a sequence context of CHH (H = A, C, or T). Some polymorphism and methylation sites were located at important positions in terms of enzyme function, such as close to catalytic residues or inhibitor binding residues. These findings may provide clues to explore the evolutionary mode between Russian wheat aphid virulence and resistance genes of host plants.
Subject(s)
Aphids/genetics , Aphids/metabolism , Hydrolases/genetics , Polymorphism, Genetic , Amino Acid Sequence , Animals , Aphids/chemistry , Base Sequence , Cloning, Molecular , Cytosine/metabolism , DNA Methylation , Hydrolases/metabolism , Molecular Sequence Data , Salivary Glands/metabolismABSTRACT
OBJECTIVE: To investigate the effect of plant growth substances on induction and culture of callus from Rhodiola quadrifida and also to analyze salidroside contents in the callus. METHOD: The optimum combination of plant growth substances in MS solid medium for induction and culture of callus was established using orthogonal design. The contents of salidroside was analyzed by HPLC. RESULT: MS medium containing 2,4-D 1 mg x L(-1), NAA 2 mg x L(-1), 6-BA 0.5 mg x L(-1) and KT 0.1 mg x L(-1) could induce the callus from R. quadrifida most effectively;the induction rate was 83.3%. The optimized combination of plant growth substances for callus subculture was 2,4-D 1 mg x L(-1), 6-BA 0.1 mg x L(-1) and KT 0.5 mg x L(-1). The dry weight could reach 11.77 g x L(-1) when the callus was cultured in the optimum medium for 30 d and salidroside content was 0.28%. CONCLUSION: The quantities of plant growth substances required for induction and culture of callus are different in R. quadrifida. The callus could produce salidroside.
