Assessing the impact of impaired phytol degradation or storage over tocopherol content in tomato

• Grant number: 25/07880-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: July 01, 2025
• End date: June 30, 2026
• Field of knowledge: Biological Sciences - Botany - Pant Physiology
• Principal Investigator: Maria Magdalena Rossi
• Grantee: Eduardo Kenzo Nakamura
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 23/03330-3 - Light and stress signal transduction pathways: how to optimize multiple responses for improving crop yield and quality, AP.TEM

Abstract

Tocopherols, also known as Vitamin E, are powerful antioxidants that protect cell membranes against oxidative damage. They are essential for plant photosynthesis and for reducing the progression of certain animal diseases. Tocopherols are synthesized exclusively by photosynthetic organisms, with one of the components being a phytyl-derived side chain originated from phytyl diphosphate (PDP). The PDP is produced either through the methylerythritol phosphate or by a two-step phosphorylation process, catalyzed by PHYTOL KINASE (VTE5) and PHYTYL-PHOSPHATE KINASE (VTE6), using the phytol released during chlorophyll (Chl) degradation as substrate. In the past decade, Chl-derived phytol recycling has been identified as the primary source of PDP for tocopherol metabolism. Although phytol availability is a determinant for tocopherol synthesis, it can be also be diverted into storage as fatty acid phytyl esters (FAPES) through acylation catalyzed by PHYTYL ESTER SYNTHASES (PESs), or it can be degraded into phytenal. Phytenal is further broken down by the action of PHYTANOYL-COA HYDROXYLASE (PAHX) and 2-HYDROXY-PHYTANOYL-COA LYASE (HPCL). Interestingly, in a context of intense Chl degradation, leaves of Arabidopsis thaliana plants deficient in either AtHPCL or AtPAHX accumulate tocopherols. However, it remains unclear whether impairing FAPEs synthesis can similarly increase tocopherol levels. In this context, we hypothesize that phytol degradation and storage as FAPEs are key determinants of phytol availability for tocopherol biosynthesis in tomato. To test this, we propose to generate plants with constitutive impairment of phytol degradation, as well as plants either with impaired phytol degradation or FAPEs synthesis exclusively along fruit ripening, for assessing tocopherol accumulation dynamics.