Project description:To investigate the impact of a plant´s response to abiotic stress on plant defense against subsequent biotic stress, we determined the transcriptional response of Arabidopsis thaliana to low temperature stress (4°C) and subsequent mechanical wounding or larval feeding damage by the herbivores Mamestra brassicae (generalist) and Pieris brassicae (specialist). In total, 21%, 4% and 14% of all genes responsive to M. brassicae, P. brassicae or mechanical wounding were differentially regulated in previously cold-treated compared to untreated plants.
Project description:Plants within the Brassicaceae family have a unique defence mechanism known as the “glucosinolate-myrosinase” system. Upon tissue disruption by insect herbivores, glucosinolates are hydrolysed by the enzyme myrosinase (EC 3.2.1.147) into a variety of degradation products, which can deter insect herbivory. This process has been termed as “The Mustard Oil Bomb”. Seeds of Brassica napus have been genetically modified to remove myrosinase containing myrosin cells. The modified plants have been named MINELESS due to a lack of toxic mines in seeds. This study aimed to get insights into defence responses of B. napus wild-type and MINELESS seedlings, after being challenged by larvae of the generalist herbivore Mamestra brassicae. The microarray analysis showed 494 and 159 genes to be differentially regulated after M. brassicae feeding on wild-type and MINELESS seedlings, respectively. Many of the observed transcriptional responses i B. napus and the MINELESS mutant are related to those found in Arabidopsis thaliana plants when they are exposed to insects.
Project description:Infection of lepidopterans by baculoviruses has been traditionally studied using in vitro systems which enable efficient and highly synchronous infection. Many studies using varied virus-host combinations have yielded great insight into the molecular processes by which these large double-stranded DNA viruses achieve infection of host cells. However, a key difference in the virus strategy for infection between individual hosts, and within an individual host, lies with the production of two different forms of the virus; occlusion derived virus, which enables primary infection of insect gut tissues and budded virus, which efficiently infects a variety of different insect tissues throughout the host. To examine the primary infection of midgut cells specifically, we used MacoNPV infection of Mamestra configurata fourth instar larvae as our model and measured the expression of viral genes over a time course of infection. Both digital PCR and RNA sequencing methods showed the profile of transcription to be different from those typically seen with in vitro methods, having unique collections of genes expressed early, as well as much greater expression of p6.9 and much reduced expression of polh and p10 late, in comparison with in vitro studies. These differences likely reflect unique characteristics of midgut cell infection, and provide clues as to the processes these viruses use to regulate expression of different viral forms used to access different host tissues. Baculoviruses are versatile DNA viruses with great potential both as gene therapy vehicles and as biological control tools. Extensive study of their transcriptome in vitro has yielded valuable tools for use in protein expression systems, however it is critical that we obtain a fuller understanding of their in vivo activities before their full medical and agricultural potential can be realized. In these studies we have assessed the gene expression program from a group II alphabaculovirus in the midgut of its complementary larval host and confirmed that the in vivo activities of baculoviruses are unique from what is known of their in vitro transcriptome. These studies provide a first foray with next-generation molecular tools into the characterization of baculovirus biology in vivo.
