Related Experiment Video
Updated: May 11, 2026

Quantification of Endogenous Auxin and Cytokinin During Internode Culture of Ipecac
Published on: March 15, 2018
Endogenous cytokinin in developing kiwifruit is implicated in maintaining fruit flesh chlorophyll levels
Sarah M Pilkington1, Mirco Montefiori, Amy L Galer
1The New Zealand Institute for Plant & Food Research Limited, Private Bag 92169, Auckland, New Zealand.
Background And Aims:
Green kiwifruit (Actinidia deliciosa) retain high concentrations of chlorophyll in the fruit flesh, whereas in gold-fleshed kiwifruit (A. chinensis) chlorophyll is degraded to colourless catabolites during fruit development, leaving yellow carotenoids visible. The plant hormone group the cytokinins has been implicated in the delay of senescence, and so the aim of this work was to investigate the link between cytokinin levels in ripening fruit and chlorophyll de-greening.
Methods:
The expression of genes related to cytokinin metabolism and signal transduction and the concentration of cytokinin metabolites were measured. The regulation of gene expression was assayed using transient activation of the promoter of STAY-GREEN2 (SGR2) by cytokinin response regulators.
Key Results:
While the total amount of cytokinin increased in fruit of both species during maturation and ripening, a high level of expression of two cytokinin biosynthetic gene family members, adenylate isopentenyltransferases, was only detected in green kiwifruit fruit during ripening. Additionally, high levels of O-glucosylated cytokinins were detected only in green kiwifruit, as was the expression of the gene for zeatin O-glucosyltransferase, the enzyme responsible for glucosylating cytokinin into a storage form. Season to season variation in gene expression was seen, and some de-greening of the green kiwifruit fruit occurred in the second season, suggesting environmental effects on the chlorophyll degradation pathway. Two cytokinin-related response regulators, RRA17 and RRB120, showed activity against the promoter of kiwifruit SGR2.
Conclusions:
The results show that in kiwifruit, levels of cytokinin increase markedly during fruit ripening, and that cytokinin metabolism is differentially regulated in the fruit of the green and gold species. However, the causal factor(s) associated with the maintenance or loss of chlorophyll in kiwifruit during ripening remains obscure.
More Related Videos
07:58Non-invasive Assay for Chlorophyll Biosynthesis Kinetics Determination during Early Stages of Arabidopsis De-etiolation
Published on: January 12, 2024
06:28Preparation of Intact Tissue for Microscopic Analysis of the Endosperm Cell Layer in Developing and Mature Arabidopsis Seeds
Published on: May 16, 2025
Related Concept Videos
Plant Hormones
Cell Signaling in Plants
Fruit Development, Structure, and Function
Protein Transport to the Inner Chloroplast Membrane
Positive Regulator Molecules
Positive Regulator Molecules