Abstract
Polyamines (PAs) are natural compounds involved in many growth and developmental processes in plants, and, specifically in fruits, play a vital role regulating its development, ripening and senescence processes. Putrescine (PUT), spermine (SPE), and spermidine (SPD) are prominent PAs applied exogenously to extend shelf life of fruits. They also originate endogenously during developmental phases of horticultural crops and simultaneously affect the quality attributes and shelf life. Their anti-ethylene nature is being exploited to enhance the shelf life when exogenously applied on fruits. In growth and development of fruits, PA levels generally fall, which marks the beginning of senescence at postharvest phase. PUT, SPE and SPD treatments are being applied during postharvest phase to prolong the shelf life. They enhance the shelf life of fruits by reducing respiration rate, ethylene release and enhance firmness and quality attributes in fruits. PAs have a mitigating impact on biotic and abiotic stresses including chilling injury (CI) in tropical and sub-tropical fruits. PAs are environment friendly in nature and are biodegradable without showing any negative effect on environment. Biotechnological interventions by using chimeric gene constructs of PA encoding genes has boosted the research to develop transgenic fruits and vegetables which would possess inherent or in situ mechanism of enhanced biosynthesis of PAs at different stages of development and thereby will enhance the shelf life and quality in fruits. Internal and external quality attributes of fruits are improved by modulation of antioxidant system and by strengthening biophysical morphology of fruits by electrostatic interaction between PAs and phospholipids in the cell wall.
Highlights
Polyamines (PAs) are the aliphatic, cationic organic compounds participating in the growth and development of living organisms
S-adenosyl methionine (SAM) whose precursor is methionine acts as a balancing intermediate to facilitate the synthesis of ethylene and at the same time facilitates the biosynthesis of natural PAs, SPE and SPD
(Human-SAMDC) gene driven by a fruit specific promoter (2A11) led to an overexpression of this gene followed by reduction in ethylene production by 50%, and the fruit ripening on-vine was delayed by 11 days as compared to wild type fruits
Summary
Polyamines (PAs) are the aliphatic, cationic organic compounds participating in the growth and development of living organisms. When PAs are applied exogenously, they play a vital role in enhancing the shelf life of fruits. The present paper reviewed the effect of exogenously applied PAs on physiology and shelf life of fruits (Table 1). We reviewed the application of biotechnological tools by way of developing in situ mechanism for over-expression of genes encoding PAs and their impact on the quality of tomato fruit. This article analysed the diverse role of exogenous application of PAs and over expression of genes encoding PAs and is enlightening the scientific research to be followed in this direction in order to enhance the shelf life. The in situ over-expression of such genes encoding PAs will provide us the inherent mechanism to develop fruits having prolonged shelf life and low CI under normal and cold storage conditions, respectively
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