Trichome Development in Tomato (Solanum lycopersicum)

Downie, Matthew (2024) Trichome Development in Tomato (Solanum lycopersicum). Doctoral thesis, University of East Anglia.

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Abstract

The ariel surfaces of most plant species are covered in trichomes; hair like structure which reduce water loss and protect against insect pests. It is increasingly clear that Mixta transcription factors promote the development of these micro-organs in most plant species by a distinct mechanism to the activator inhibitor model proposed for Arabidopsis thaliana trichome regulation. However, many plant genomes encode multiple Mixta genes but neither the redundancy nor the totality of Mixta function have been investigated and therefore the role of these transcription factors in trichome density and type determination are not fully understood. This study showed the genome of tomato (Solanum lycopersicum) contains four Mixta genes, which exclusively and redundantly regulate a discrete category of trichome: type I-V. A multiplex genome editing approach was used to generate single and multiple Mixta mutants which showed the unique functions of single Mixta genes and the combined effects of mutant combinations. The sister clade to Mixta, MYB17, is further hypothesised to promote trichome development. Double MYB17-A/-B mutants showed reduced trichome density as well as novel changes in cuticle development. Mutants of the previously characterised HD-ZIP IV transcription factor Woolly were analysed and shown to overlap in its promotion of type I-V trichomes but also have a broader range of phenotypes including trichome type determination. RNA sequencing of quadruple Mixta and woolly mutant lines showed these transcription factors regulate the same downstream targets but have limited regulation of each other. Furthermore, the changes in histone gene expression suggested MX1 may play novel roles in regulation of chromatin structure. These discoveries further our understanding of genetic regulation of trichome development by unravelling the dissimilar activities of otherwise structurally similar transcription factors. Furthermore, this work poses new questions about the evolution of trichomes in land plants.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Kitty Laine
Date Deposited:	03 Jun 2025 12:18
Last Modified:	03 Jun 2025 12:18
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99387
DOI:

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