Another hormone, salicylic acid, may also be involved in plant responses to eggs since SA deficient mutants of A. thaliana showed different responses to pierid eggs than wild type plants. Further studies are necessary Perifosine to understand the role of JA in concert with other phytohormones in signaling in order to regu late egg induced defenses. Gene transcripts for terpenoid biosynthesis were detected at only low levels There is strong evidence that damage dependent JA levels activate distinct sets of defense genes leading to terpenoid formation. To elucidate the molecular basis underlying volatile biosynthesis associated with the indirect defenses of elm in response to egg laying, we compared the different treatments with reference to transcripts involved in terpenoid metabolism.

Although it has been established previously that a volatile blend with an enhanced fraction of terpenoids that is attractive to egg parasitoids is produced by these elms 2 3 d after egg laying, we detected only a few transcripts involved in terpenoid metabolism in the elm leaves fol lowing egg treatment. The respective genes may be dif ferentially expressed, but below the detection threshold of our analysis or else possibly the expression is not con trolled at the transcript level. In general it is supposed that herbivore induced de novo production of terpenoids takes place several hours following the activation of ter pene synthase genes. Enhanced abundance of transcripts for terpene synthases were also found in samples taken from the needles of Pinus sylvestris, that were laden with eggs of the herbivorous sawfly Diprion pini, these egg laden pine needles emit a volatile terpen oid blend that attracts egg parasitoids.

However, tran script levels for a sesquiterpene synthase from P. sylvestris which produces B farnesene, the compound re sponsible for the attraction of an egg parasitoid of sawfly eggs, were not enhanced by Entinostat D. pini egg laying. The time window in which egg induced elm leaf ma terial was harvested for sequencing and the large size of our database should have enabled the detection of even relatively rare transcripts associated with the early and late direct and indirect defense responses against the leaf beetle. In A. thaliana the number of up or down regulated genes increased as time elapsed from 1 3 d after pierid eggs have been laid on plants. Because transcripts for terpenoid metabolism are under represented in our database, we can only speculate about the molecular basis of egg induced volatile production for indirect defense in elm.