Light-mediated isomerization of carotenoids control nuclear gene expression and regulate metabolic feedback in Arabidopsis and tomato

Abstract

Light promotes the biosynthesis of carotenoids and regulates nuclear gene expression during different stages of photomorphogenesis. Previous studies have shown that perturbation in the light quantity causes accumulation of cis-carotenes in etiolated seedlings of Arabidopsis (Columbia background) and tomato (MicroTom background) CRTISO mutants and show perturbed chloroplast biogenesis. In this thesis, I focused on studying the effects of light quality on carotenoid accumulation and nuclear gene expression using different types of light with variations in their light spectrum. I have extensively reviewed (chapter 1) how certain chemical reactions occurring in the carotenoid pathway may act as a photoswitch that can detect the changes in the light quality and manage the production of apocarotenoid signals, which in turn regulate nuclear gene expression in response to environmental and developmental cues to ensure plant survival. To further investigate the response of one such proposed, yet to be proven unidirectional photoswitch, I have carried out chemical and genetic experiments to understand how light quality can rate-limit the unidirectional prolycopene photoswitch which can affect carotenoid isomerization and regulate the communication between chloroplast and nucleus during the different stages of photomorphogenesis. In chapter 2, I have hypothesised that a light spectrum with shorter wavelengths within the blue region would rate-limit prolycopene photoisomerization thereby delaying the abundance of the cis-apocarotenoid signal (cis-ACS) and reduce the substrates required for the biosynthesis of ACS and phytohormones that mediate feedback control over carotenoid gene expression during photomorphogenesis. In research chapter 3, we have specifically looked into individual light spectrums and used monochromatic lights to investigate how such lights can turn on/off some light sensitive genes that are involved during early stages of photomorphogenesis.We exposed microtom WT and tangerine tomato cotyledons to dark and monochromatic blue and red light for 5 and 30 minutes. In chapter 4, we have further focused on studying the overall impact of CRTISO activity on plant development.

Date of Thesis submission	2023
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Chris Cazzonelli (Supervisor), Jonathan Plett (Supervisor) & Priti Krishna (Supervisor)