Understanding The Carotenoid Biosynthesis Pathway in Orange Actinidia Species
type: CreativeWork
description: Carotenoids belong to the tetraterpene family and are involved in diverse biological processes in plants. Along with a primary role in photosynthesis, they also provide distinct colours (red, yellow, and orange) to fruit, vegetables, and flowers to attract pollinators and facilitate pollination and seed dispersal. Carotenoids provide novelty to fruits and vegetables and are beneficial to human health primarily as provitamin A, therefore, they are essential for dietary intake. The aim of this thesis is to understand and characterize carotenogenesis in kiwifruit (Actinidia species) and its regulation in the orange Actinidia species. Metabolic analysis of orange Actinidia valvata (OF), yellow A. polygama (YF), and green A. arguta (GF) revealed high accumulation of β-carotene (provitamin A) in orange and yellow fruits, whereas green fruit accumulated xanthophylls (primarily lutein). Transcriptomic analysis between OF and GF revealed upregulation of carotenoid pathway genes (DXS, PSY2, GGPPS, PDS, Z-ISO, and ZDS) in OF fruit during ripening (a contrast from GF). Increased expression of chlorophyll degradation genes (SGR, RCCR, and NYC1) in OF species explains increased chlorophyll turnover in the early ripening stages. Transient overexpression of Actinidia PSY2 (a rate-limiting step in most plant species) and SGRs in Nicotiana tabacum leaves resulted in a significant increase in carotenoids and de-greening, respectively. The rapid de-greening accompanied by β-carotene accumulation can also depend on the transcriptional regulation of the pathway and plastid diversity (for carotenoid sequestration). Key genes that encode pathway enzymes were differentially regulated, therefore, candidate transcription factors based on differential expression analysis were selected and functionally characterized in heterologous plant systems. New candidates that regulate carotenogenesis (MYB1R, DIVARICATA, bHLH154, and bHLH137) and de-greening (bZIP53, bZIP44, and WRKY53) were identified. S…
abstract: Carotenoids belong to the tetraterpene family and are involved in diverse biological processes in plants. Along with a primary role in photosynthesis, they also provide distinct colours (red, yellow, and orange) to fruit, vegetables, and flowers to attract pollinators and facilitate pollination and seed dispersal. Carotenoids provide novelty to fruits and vegetables and are beneficial to human health primarily as provitamin A, therefore, they are essential for dietary intake. The aim of this thesis is to understand and characterize carotenogenesis in kiwifruit (Actinidia species) and its regulation in the orange Actinidia species. Metabolic analysis of orange Actinidia valvata (OF), yellow A. polygama (YF), and green A. arguta (GF) revealed high accumulation of β-carotene (provitamin A) in orange and yellow fruits, whereas green fruit accumulated xanthophylls (primarily lutein). Transcriptomic analysis between OF and GF revealed upregulation of carotenoid pathway genes (DXS, PSY2, GGPPS, PDS, Z-ISO, and ZDS) in OF fruit during ripening (a contrast from GF). Increased expression of chlorophyll degradation genes (SGR, RCCR, and NYC1) in OF species explains increased chlorophyll turnover in the early ripening stages. Transient overexpression of Actinidia PSY2 (a rate-limiting step in most plant species) and SGRs in Nicotiana tabacum leaves resulted in a significant increase in carotenoids and de-greening, respectively. The rapid de-greening accompanied by β-carotene accumulation can also depend on the transcriptional regulation of the pathway and plastid diversity (for carotenoid sequestration). Key genes that encode pathway enzymes were differentially regulated, therefore, candidate transcription factors based on differential expression analysis were selected and functionally characterized in heterologous plant systems. New candidates that regulate carotenogenesis (MYB1R, DIVARICATA, bHLH154, and bHLH137) and de-greening (bZIP53, bZIP44, and WRKY53) were identified. S…
author: Bhargava, Nitisha
license: https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm
date published: 2025-08-27
date modified: 2026-07-24T01:02:59Z
provider: University of Auckland
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: ResearchSpace@Auckland

PropertyValue
property ID: Handle
value: https://hdl.handle.net/2292/73593