Characterizing ethylene pathway genes during the development, ripening, and postharvest response in Citrus reticulata Blanco fruit pulp

Authors: Karishma Kashyap, SOFIA BANU

Abstract: Ethylene is involved in the regulation of the natural process of fruit pulp development and postharvest storage. The present study was carried out to determine the expression of eight genes encoding ethylene biosynthesis and signaling during development in Khasi mandarin (Citrus reticulata Blanco) fruit pulp as well as during postharvest storage in the fruit pulp (at 4 °C and 20 °C). Gibberellic acid (GA3) is known to improve internal fruit quality and to mediate various stress responses during postharvest fruit storage in species like citrus. The effect of GA3 during postharvest storage was also investigated to understand the regulation of the ethylene genes on its own biosynthesis and signaling. The results suggest that 1-aminocyclopropane-1-carboxylate synthase-2 (ACS2), ethylene response sensor-1 (ERS1), constitutive triple response-1 (CTR1), and ethylene insensitive 3-like-1(EIL1) have a physiological role in the ripening of Khasi mandarin fruit pulp. 1-Aminocyclopropane-1-carboxylate synthase-1 (ACS1), ethylene response-1 (ETR1), and ethylene insensitive-2 (EIN2) were found to be developmentally regulated in immature fruit pulp, suggesting their role in rapid growth of the fruit pulp. Postharvest storage at 4 °C and 20 °C influenced the expression of different ethylene-related genes during ripening in Khasi mandarin fruit pulp. Cold storage (4 °C) markedly triggered the transcription of ethylene biosynthetic genes, especially ACS1 and ACS2 in the fruit pulp. Exogenous application of GA3 enhanced cold tolerance especially at the transcript level of ACS1, ACS2, ETR1, and ERS1 genes in the pulp of Khasi mandarin fruit during cold storage when harvested at the full maturity stage.

Keywords: Nonclimacteric, biosynthesis, signaling, maturation, postharvest

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