植物科学

Aphids are a serious pest of crops across the world. Aphids feed by inserting their flexible hypodermal needlelike mouthparts, or stylets, into their host plant tissues. They navigate their way to the phloem where they feed on its sap causing little mechanical damage to the plant. Additionally, while feeding, aphids secrete proteinaceous effectors in their saliva to alter plant metabolism and disrupt plant defenses to gain an advantage over the plant. Even with these arsenals to overcome plant responses, plants have evolved ways to detect and counter with defense responses to curtail aphid infestation. One of such response of cowpea to cowpea aphid infestation, is accumulation of the metabolite methylglyoxal. Methylglyoxal is an α,β-dicarbonyl ketoaldehyde that is toxic at high concentrations. Methylglyoxal levels increase modestly after exposure to a number of different abiotic and biotic stresses and has been shown to act as an emerging defense signaling molecule at low levels. Here we describe a protocol to measure methylglyoxal in cowpea leaves after cowpea aphid infestation, by utilizing a perchloric acid extraction process. The extracted supernatant was neutralized with potassium carbonate, and methylglyoxal was quantified through its reaction with N-acetyl-L-cysteine to form N-α-acetyl-S-(1-hydroxy-2-oxo-prop-1-yl)cysteine, a product that is quantified spectrophotometrically.

Plant-insect interaction is an important field for studying plant immunity. The beet armyworm, Spodoptera exigua, is one of the best-known agricultural pest insects and is usually used to study plant interactions with chewing insects. Here, we describe a protocol for insect feeding assays with Spodoptera exigua lavae using model host plant Arabidopsis thaliana, which is simple and easy to conduct, and can be used to evaluate the effect of host genes on insect growth and thus to study plant resistance to chewing insects.

Plants need to respond appropriately to wounding and herbivorous insects. Peptide signals have been implicated in local and systemic induction of appropriate plant defense responses. To study these peptide signals and their perception in host plants, it is important to have reproducible bioassays. Several assays, such as treatment of peptide solution via pressure infiltration, have been developed. Here, we provide detailed protocols for peptide feeding and mechanical wounding for tomato seedlings. To directly introduce peptides into tomato seedlings, peptide solution is fed through the excised stem via the transpiration stream. To mimic the wounding caused by insect feeding, leaflets of tomato seedlings are mechanically damaged with a hemostat; and wounded and systemic unwounded leaves are harvested and analyzed separately. Samples from both assays may be further assessed by examining the transcript level of marker genes by quantitative real-time PCR (qRT-PCR).

Rice is one of the world’s most important crops, but its production suffers from insect pests. Rice brown planthopper (BPH; Nilaparvata lugens Stål) and striped stem borer (SSB, Chilo suppressalis Walker) are the two most serious pests in rice production. We reported that serotonin is an essential mediator in the interaction between rice and insect. Here, we established a method for extraction and determination of serotonin in rice and BPH.

Aphids constitute a large group of Hemipterans that use their slender stylets to tap into the sieve elements of plants from which they consume copious amounts of phloem sap, thus depriving the plant of photoassimilates. Some aphids also transmit viral diseases of plants. Myzus persicae Sülzer, commonly known as the green peach aphid (GPA), which is a polyphagous insect with a host range that covers 50 plant families, is considered amongst the top 3 insect pest of plants. The interaction between Arabidopsis thaliana and the GPA is utilized as a model pathosystem to study plant-aphid interaction. Here we describe the protocol used in our laboratories for rearing the GPA, and no-choice and fecundity bioassays to study GPA performance on Arabidopsis. In addition, we describe the procedure for the electrical penetration graph (EPG) technique to monitor feeding behavior of the GPA on Arabidopsis.