Photoactivated TiO2 Nanocomposite Delays the Postharvest Ripening Phenomenon through Ethylene Metabolism and Related Physiological Changes in Capsicum Fruit.

Arijit Ghosh,Subhas Chandra Debnath,Malay Kumar Adak,Masayuki Fujita,Indraneel Saha,Mirza Hasanuzzaman,Alok Kumar Hazra

doi:10.3390/plants11040513

Abstract

Capsicum is one of the most perishable fruit which undergo rapid loss of commercial value during postharvest storage. In this experiment our aim is to evaluate the effect of photoactivated TiO2 nano-particle complexed with chitosan or TiO2-nanocomposite (TiO2-NC) on extension self-life of Capsicum fruit and its effect on related morphological, physiological and molecular attributes at room temperature (25 °C). Initially, TiO2-NC coated fruits recorded superior maintenance of total soluble solids accumulation along with retention of firmness, cellular integrity, hydration, color etc. On the extended period of storage, fruit recorded a lower bioaccumulation of TiO2 in comparison to metallic silver over the control. On the level of gene expression for ethylene biosynthetic and signaling the TiO2-NC had more regulation, however, discretely to moderate the ripening. Thus, ACC synthase and oxidase recorded a significantly better downregulation as studied from fruit pulp under TiO2-NC than silver. On the signaling path, the transcripts for CaETR1 and CaETR2 were less abundant in fruit under both the treatment when studied against control for 7 d. The reactive oxygen species (ROS) was also correlated to retard the oxidative lysis of polyamine oxidation by diamine and polyamine oxidase activity. The gene expression for hydrolytic activity as non-specific esterase had corroborated the development of essential oil constituents with few of those recorded in significant abundance. Therefore, TiO2-NC would be reliable to induce those metabolites modulating ripening behavior in favor of delayed ripening. From gas chromatography-mass spectrometry (GC-MS) analysis profile of all tested essential oil constituents suggesting positive impact of TiO2-NC on shelf-life extension of Capsicum fruit. Our results indicated the potentiality of TiO2-NC in postharvest storage those may connect ethylene signaling and ROS metabolism in suppression of specific ripening attributes.

Highlights

Fruit ripening is a unique process in plant biology where differential gene expression leads to a set of cellular and biochemical events, mostly catabolic in nature
We focused on effects of TiO2 -NC coating on quality indices, physiochemical properties and molecular characteristics of Capsicum fruit during postharvest storage at 25 ◦ C for 7 d
The surface morphology as critically analyzed by Scanning Electron Microscopy (SEM) studies for fruit coat which recorded a distinct variation through the treatments (Figure 1)

Summary

Introduction

Fruit ripening is a unique process in plant biology where differential gene expression leads to a set of cellular and biochemical events, mostly catabolic in nature. Those are regulated throughout the ripening period with some metabolic fluxes under coverage of growth regulators such as auxin, ethylene (ET), gibberellin, abscisic acid and kinetins [1]. Regardless of climacteric and non-climacteric types ET evokes several signaling cascades for fruit senescence through gene expression. Those govern catabolic processes of biomolecules which may expedite ripening within postharvest storage [3,4]

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