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Contact Us

The Department of Entomology
The Robert H. Smith Faculty of Agriculture, Food and Environment
The Hebrew University of Jerusalem
Herzl 229, Rehovot 7610001, ISRAEL

Tel: 08-9489223 
Fax: 08-9366768
Email: orlytal@savion.huji.ac.il

Research

Research Interests and Activity

Evolution of polyphagy in the whitefly Bemisia tabaci
Developing insect proof plants
Climate change effects and herbivorous insect population outbreaks

 

 
evolution-of-polyphagy-in-the-whitefly-bemisia-tabaci.jpg
ראה גם: Shai Morin
 

Evolution of polyphagy in the whitefly Bemisia tabaci

A small proportion of insect herbivores, including some of the world's most important agricultural are polyphagous, meaning that they are capable of feeding on a wide range of plant families. How polyphagous species cope with the diverse and unpredicted toxic defensive chemistry of their plant hosts remains largely unknown at the molecular level, but it is largely believed that polyphagous (generalist) herbivores typically possess enzyme systems capable of detoxifying a broad range of plant defensive chemicals, including novel chemistry they have never encountered, albeit not as efficiently as specialist herbivores Insect detoxification systems typically include six main enzyme families: cytochrome P450 monooxygenases (P450s or CYPs for genes), glutathione S-transferases (GSTs), carboxylesterases (COEs), UDP-glucosyltransferases (UGTs), sulfotransferases and ATP-binding cassette (ABC) transporters.

Our experimental system includes 10 species representing nine high-level genetic groups of the B. tabaci complex. In several parallel projects in the lab, these 10 species are subjected to three complimentary feeding systems: plant hosts known to accumulate high levels of defensive compounds (bell pepper, poinsettia, cassava, tobacco and Arabidopsis thaliana), artificial feeding assays in which specific plant toxic chemicals are supplemented and two plant species, in which we have genetically modified (up-regulated) a specific chemical defensive pathway (tobacco plants over-expressing phenylpropanoids and Arabidopsis thaliana plants over-expressing glucosinolates). Using a custom designed Agilent microarray chip containing ~700 Bemisia tabaci detoxification genes, a detailed matrix of planned gene expression comparisons (between different species on a similar host or within a species on different hosts) and complementing performance assays (egg laying rate, egg to adult development rate and survival), we are identifying differentially expressed genes likely to be involved in the ability of one or more Bemisia tabaci species to successfully neutralize plant defensive chemistry.

 

developing-insect-proof-plants.jpg
ראה גם: Shai Morin

Developing insect proof plants

The main goal of this project is to develop an RNA interference (RNAi) technology that will allow the production of pest-resistant crops capable of protecting themselves from B. tabaci by silencing insect detoxification genes without which successful host utilization can not occur. B. tabaci is a polyphagous pest species and requires an induced detoxification system capable of degrading a broad range of plant toxins present in their hosts. Insect detoxification enzymes typically include four main super-families: cytochrome P450 monooxygenases (P450s), glutathione S-transferases (GSTs), carboxylesterases (COEs), and UDP-glycosyltransferases (UGTs).

The most novel aspect of this proposal comes from its ecological assumptions. Silencing of specific detoxification genes will significantly interfere with B. tabaci performance on plant hosts. However, it will not cause pest extinction, but more likely result in low population densities that will be successfully controlled by natural enemies. We hypothesize that this approach is more natural, preferable and sustainable to silencing the activity of pest essential house-keeping genes (that can lead to species eradication) for two reasons: (1) Essential genes are conserved in evolution and there is a high risk that non-target species will be affected. (2) Pest population eradication will have a strong impact on the biodiversity of the agroecological system and can lead to the disappearance of natural enemies and to the rise of secondary pests.

 

climate-change-effects-and-herbivorous-insect-population-outbreaks.jpg
ראה גם: Shai Morin

Climate change effects and herbivorous insect population outbreaks

Climate change will affect the future distribution and population dynamics of herbivorous insect pests involved in the transmission of plant infectious diseases. Here, we focus on whiteflies, one of the most important groups of vectors of plant virus diseases. Our whitefly model species, B. tabaci, is the most important whitefly virus vector and can transmit over 200 species of plant viruses. One of the leading hypotheses in this project predicts that populations of our model species, B. tabaci, will thrive under global warming effects of climate change due to their short developmental times, parthenogenetic reproduction, great reproductive capacity, and ability to establish multiple generations per year.

We use deterministic and stochastic modeling approaches to predict expected changes in B. tabaci population dynamics under anticipated climate change for the next decades. Generating a prediction for insect population response to climate change is done by coupling a weather generator that produces realizations of temperature and precipitation series under a given climate conditions with a model representing the insect population dynamics. Environmental system modeling of pest insects population dynamics, will allow the necessary incorporation of pest risk assessment and simulation models into comprehensive management planning systems of both natural and agricultural ecosystems in response to climate change.