Development fo type VI glandular trichomes
Glandular trichomes are multicellular structures, originating from epidermal cells that produce various food-, medicine- and agriculture-relevant chemicals. The glandular trichomes of tomato (Solanum lycopersicum) are capable of making a diverse array of (specialized) metabolites. The type VI glandular trichomes of cultivated tomato make, amongst other metabolites, a bouquet of volatile mono- and sesquiterpenes, which are involved in the direct or indirect defense against herbivores. The biosynthesis of some of these terpenes is induced by the hormone jasmonic acid (JA), upon herbivory. How multicellular glandular trichomes develop is unknown and the regulation of volatile terpene biosynthesis remains enigmatic.
To identify genes involved in controlling the development of type VI glandular trichomes in tomato.
To identify genes involved in regulating terpene biosynthesis in glandular trichomes.
The knowledge from this project may be applicable to improve glandular trichome density and mono- sesquiterpenes production in crops, in order to boost direct defenses against pests or to obtain fewer glandular trichomes to achieve better biological control. Characterization of candidate target genes from this research will not only allow functional identification but can be helpful to select alleles that can potentially alter insect resistance in crops.
The main objectives of this project are: a) to verify the hypothesis that other molecular players act upstream, downstream or in a network with transcription factor 1 (TF1) in its regulating role. b) to reveal how TF1 regulates in glandular trichomes the biosynthesis of volatile terpenes and if it controls the production of other specialized metabolites.
In the first year, the TF1 promoter will be cloned and characterized in silico using bioinformatics tools and in vivo by fusing the TF1 promoter to the GUS-GFP reporter. TF1 will be cloned under control of a beta-estradiol inducible promoter or fused with GFP reporter gene under control of a constitutive promoter construct, for further experiments. Transgenic plants overexpressing TF1 will be characterized. Bioinformatic studies will be done to find putative orthologs of TF1.
In the second year, the constructs will be transformed using Agrobacterium tumefaciens into cultivated tomato plants. The resulting transgenic plants will be characterized and grown to obtain seeds. The promoter of TF1 will be used for Yeast-one-hybrid (Y1H) assays to find proteins that could regulate TF1 expression. RNAseq transcriptome analyses will be performed on transgenic lines overexpressing TF1 and lines in which TF1 is knocked down or knocked out.
In the third year RNAseq analyses will be performed of lines expressing TF1 under beta-estradiol inducible promoter treated with estradiol. Collectively, all RNAseq and Y1H experiments will lead to a list of genes putatively involved in the TF1 regulatory network. Transgenic lines for some of these candidates will be created in the third year to characterize their function. The fourth year will focus on analyzing these transgenic plants.