A simple and highly efficient protocol for somatic embryogenesis and plant regeneration from proembryonic mass suspension culture in 'Autumn Royal Seedless'

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Salivary Glucose Oxidase from Caterpillars Mediates the Induction of Rapid and Delayed-Induced Defenses in the Tomato Plant

Caterpillars produce oral secretions that may serve as cues to elicit plant defenses, but in other cases these secretions have been shown to suppress plant defenses. Ongoing work in our laboratory has focused on the salivary secretions of the tomato fruitworm, Helicoverpa zea. In previous studies we have shown that saliva and its principal component glucose oxidase acts as an effector by suppressing defenses in tobacco. In this current study, we report that saliva elicits a burst of jasmonic acid (JA) and the induction of late responding defense genes such as proteinase inhibitor 2 (Pin2). Transcripts encoding early response genes associated with the JA pathway were not affected by saliva. We also observed a delayed response to saliva with increased densities of Type VI glandular trichomes in newly emerged leaves. Proteomic analysis of saliva revealed glucose oxidase (GOX) was the most abundant protein identified and we confirmed that it plays a primary role in the induction of defenses in tomato. These results suggest that the recognition of GOX in tomato may represent a case for effector-triggered immunity. Examination of saliva from other caterpillar species indicates that saliva from the noctuids Spodoptera exigua and Heliothis virescens also induced Pin2 transcripts

Identification of NAD(P)H Quinone Oxidoreductase Activity in Azoreductases from P. aeruginosa: Azoreductases and NAD(P)H Quinone Oxidoreductases Belong to the Same FMN-Dependent Superfamily of Enzymes

Water soluble quinones are a group of cytotoxic anti-bacterial compounds that are secreted by many species of plants, invertebrates, fungi and bacteria. Studies in a number of species have shown the importance of quinones in response to pathogenic bacteria of the genus Pseudomonas. Two electron reduction is an important mechanism of quinone detoxification as it generates the less toxic quinol. In most organisms this reaction is carried out by a group of flavoenzymes known as NAD(P)H quinone oxidoreductases. Azoreductases have previously been separate from this group, however using azoreductases from Pseudomonas aeruginosa we show that they can rapidly reduce quinones. Azoreductases from the same organism are also shown to have distinct substrate specificity profiles allowing them to reduce a wide range of quinones. The azoreductase family is also shown to be more extensive than originally thought, due to the large sequence divergence amongst its members. As both NAD(P)H quinone oxidoreductases and azoreductases have related reaction mechanisms it is proposed that they form an enzyme superfamily. The ubiquitous and diverse nature of azoreductases alongside their broad substrate specificity, indicates they play a wide role in cellular survival under adverse conditions

Polyphenol oxidase-mediated resistance to common cutworm

โครงการหนึ่งอาจารย์หนึ่งผลงาน ประจำปี 255

Increasing resistance of tomato to lepidopteran insects by overexpression of polyphenol oxidase

Polyphenol oxidases (PPOs), which catalyze the oxidation of phenolics to quinones, have been reported to confer resistance to Pseudomonas syringae and are assumed to be involved in insect resistance. To assess the impact of PPO expression on resistance to 2 major lepidopteran insects, the common cutworm (Spodoptera litura (F.)) and the cotton bollworm (Heliothis armigera (Hübner)), we used transgenic tomato plants constitutively expressing sense- and antisense-oriented potato PPO genes. The transgenic plants expressing a sense PPO construct (overexpressing PPO [OP] plants) exhibited 2- to 5.3-fold higher PPO activity levels whereas the antisense PPO transgenic plants (suppressed PPO [SP] plants) exhibited 2.6- to 9-fold lower PPO activity levels than nontransformed controls. The growth rates of both common cutworm and cotton bollworm larvae were significantly correlated with PPO activity levels. The PPO-overexpressing transgenic plants clearly showed an increase in resistance; growth rates of common cutworm were up to 1.7 times lower than on controls and larvae consumed less foliage. In addition, increased PPO activity led to higher larval mortality. These results suggest a critical role for PPO-mediated phenolic oxidation in insect resistance. Manipulation of PPO activity could provide resistance simultaneously to both disease and insect pests, and therefore might be used as a component of effective integrated pest management for tomato production