Understanding the glandular trichomes development pathway in tomato (Solanum lycopersicum) using mutants and natural genetic variations

Author(s)

Eloisa Vendemiatti

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2015-09-04

Examining board members

Lazaro Eustaquio Pereira Peres; Leonardo Silva Boiteux; Fabio Tebaldi Silveira Nogueira

• Advisor: Lazaro Eustaquio Pereira Peres

Abstract

Trichomes are epidermal structures that can be classified into two types: glandular or non-glandular, and they are mainly related to plant defense strategies. Little is known about the glandular trichome development pathway, since most of the studies are in Arabidopsis thaliana, a model in which this kind of trichome is absent. The Solanum genus has a wide variety of trichomes, especially glandular ones (Types I, IV, VI and VII). The study of these structures are gaining more prominence, since they are sources of several secondary metabolites of economic and ecological importance. Wild species are considered genetic resources for tomato (S. lycopersicum), such as S. galapagense which has natural genetic variations that gives resistance to herbivores attack. Among these variations is the presence of type IV glandular trichomes, a source of the acyl sugar allelochemical. The absence of type IV glandular trichomes is considered to be one of the causes of tomato susceptibility to insects. In this study, it was determined that tomato actually has type IV trichomes, but these structures are present only in the cotyledons and the first pair of leaves. Thus, the presence of type IV trichomes in wild species would be considered a neotenic feature, i.e. the maintenance of juvenile structures in adulthood. In addition, it was determined that tomato mutants affecting youthfulness (e.g. Mouse ears and fasciated) have type IV trichomes in adulthood. Moreover, the presence of these structures was correlated with the expression of miR156, besides the increased formation of type IV trichomes in a transgenic line overexpressing this micro RNA related to youthfulness. On the genetic basis of type IV trichomes presence in wild species, in this work it was created a near isogenic line (NIL) containing the natural genetic variation here named Galapagos enhanced trichomes (Get). This variation is derived from S. galapagense and harbors type IV trichomes in adult leaves, when introgressed in cultivated tomato (cv. Micro-Tom). The preliminary genetic map of Get in the tomato chromosome 2 was conducted through the analysis of \"single nucleotide polymorphism\" (SNPs) between MT and MT-Get. The eventual cloning of GET will contribute not only to unravel the genetic basis of glandular trichomes formation, but will also contribute to create varieties resistant to insects, reducing the pesticides use. (AU)

• FAPESP's process: 13/16784-0 - Natural variations study affecting defense against herbivory in tomato and its relationship with plant hormones.
• Grantee: Eloisa Vendemiatti
• Support Opportunities: Scholarships in Brazil - Master