Analysis of chlorophyll and degradation products in tomato plants deficient for chlorophyllase and phytol kinase

• Grant number: 13/25001-0
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: March 10, 2014
• End date: May 09, 2014
• Field of knowledge: Biological Sciences - Botany - Pant Physiology
• Principal Investigator: Maria Magdalena Rossi
• Grantee: Juliana Almeida Barros da Silva
• Supervisor: Stefan Hörtensteiner
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: University of Zurich (UZH), Switzerland

Abstract

Besides its economical and nutritional importance, tomato (Solanum lycopersicum) is a model system for plant physiology studies. The fresh fruit as well as the derivatives are sources of several antioxidants including vitamin E (VTE). The understanding of the mechanisms involved in the biosynthesis, transport and accumulation of VTE in plants is highly desirable due its significant role in human health and plant physiology. In a previous work, by performing a metabolic analysis of tocopherol forms (±, b, g and d) in ripe fruits of introgression lines (IL) of Solanum pennellii, we mapped several quantitative trait loci (QTL) for VTE content. Integrated analysis at the metabolic, genetic and genomic levels allowed us to propose 16 candidate loci putatively affecting tocopherol content in tomato fruit. Two chlorophyllase (CLH) genes, which catalyze dephytylation of chlorophyll, co-localize with QTL on chromosome 6 and 9. It has been shown that the free phytol derived from chlorophyll degradation can be channeled into tocopherol synthesis when is phosphorylated to phytyl-diphosphate by the sequential activity of two enzymes, including the phytol kinase (VTE5). Interestingly, a VTE5 gene was identified linked to chromosome 9 QTL as well. To understand the regulation of phytol metabolism in fleshy fruits, our group works on functional characterization of tomato CLH and VTE5, focusing on the interplay between chlorophyll dephytylation and tocopherol biosynthesis. In this sense, the present project proposes to characterize chlorophylls and their breakdown intermediates in leaves and fruits of CLH and VTE5-deficient plants generated either by stable transformation using RNAi or by screening of an ethyl-methanesulfonate (EMS)-mutagenised plant collection. (AU)