I thought you did an excellent job, nice and clear explainations, good transitions and summary.

1. perhaps you could explain why you use  arabidopsis instead of cabbage. My assumption is that much work, including sequencing of the genome, had been done on the arabidopsis so you were able to add-remove genetic components you wanted to test for.

2. how long is a generation of the cabbage butterfly?

3. Choice experiment. Why did you not use multiple larvae released into cage with the two types of arabidopsis? Some what confusing because there were two different growth stages and two different stimuli tested for in the same testing

4. Excellent job of editing and presenting. It fit nicely on the video

Jay

Dear Jay,

Thank you for your comments. Let me answer your questions and give you some additional information on the life cycle of Pieris rapae.

1. Larvae of the small white butterfly will feed from almost all cruciferous plants. We use Arabidopsis thaliana because of its short generation time, small size and above all its sequenced genome and vast number of available mutants. These mutants allow us to unravel the defense responses during the host-insect interaction. As demonstrated in the video, we show that jasmonic acid plays a major role in the plant's defensive capacities towards Pieris rapae. Interestingly, we also show that glucosinolates, whose breakdown products are toxic to many generalist caterpillars, are used as by Pieris rapae female butterflies (specialist on cruciferous plants) as oviposition cues. We have recently published a paper in Plant Physiology (March 2008) on this topic.

2. Pieris rapae life cycle. The development of Pieris rapae strongly depends on the temperature and ranges from 5-7 weeks. We rear our insects at 23C. Eggs hatch in 3-7 days; Larvae have 5 larval stages (L1-L5; ~ 10-14 day); Pupae (7-14 days); Adults (~14-20 days). Under our rearing conditions eggs hatch in 5 days, complete larval development until pupation takes 12 days, pupa take ~7 days to eclosion, adult life is ~2 weeks.

3. Using the video we wanted to show different experimental set-ups for testing plant-insect interaction. A choice test (preference) will give you additional insights that are not necessarily displayed in a no-choice test (edibility). There are other possibilities for choice tests, including the one you mentioned. The results obtained with this approach, e.g. leaf area eaten, are hard to quantify and rather subjective. Therefore, we mostly use the no-choice set-up to determine the effect on caterpillar performance.

Martin