γ-Aminobutyric acid is involved in overlapping pathways against chilling injury by modulating glutamate decarboxylase and defense responses in papaya fruit

Ghulam Khaliq; Sajid Ali; Shaghef Ejaz; Gholamreza Abdi; Yahya Faqir; Jiahua Ma; Mohammed Wasim Siddiqui; Asgar Ali

doi:10.3389/fpls.2023.1233477

γ-Aminobutyric acid is involved in overlapping pathways against chilling injury by modulating glutamate decarboxylase and defense responses in papaya fruit

Front Plant Sci. 2023 Nov 16:14:1233477. doi: 10.3389/fpls.2023.1233477. eCollection 2023.

Authors

Ghulam Khaliq¹, Sajid Ali², Shaghef Ejaz², Gholamreza Abdi³, Yahya Faqir⁴, Jiahua Ma⁴, Mohammed Wasim Siddiqui⁵, Asgar Ali⁶

Affiliations

¹ Department of Horticulture, Faculty of Agriculture, Lasbela University of Agriculture, Water and Marine Sciences, Uthal, Pakistan.
² Department of Horticulture, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan.
³ Department of Biotechnology, Persian Gulf Research Institute, Persian Gulf University, Bushehr, Iran.
⁴ Engineering Research Center for Biomass Resource Utilization and Modification of Sichuan Province, Southwest University of Science and Technology, Mianyang, China.
⁵ Department of Food Science and Post-Harvest Technology, Bihar Agricultural University, Sabour, India.
⁶ Centre of Excellence for Postharvest Biotechnology (CEPB), School of Biosciences, University of Nottingham Malaysia, Semenyih, Malaysia.

Abstract

The effect of γ-aminobutyric acid (GABA) treatment at two concentrations (1 mM or 5 mM) on papaya fruit stored at 4°C and 80%-90% relative humidity for 5 weeks was investigated. The application of GABA at 5 mM apparently inhibited chilling injury, internal browning, electrolyte leakage, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), polyphenol oxidase (PPO), phospholipase D (PLD), and lipoxygenase (LOX) activities of papaya fruit. Fruit treated with 5 mM GABA enhanced the activities of ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), superoxide dismutase (SOD), glutamate decarboxylase (GAD), and phenylalanine ammonia-lyase (PAL). In addition, GABA treatment significantly displayed higher levels of proline, endogenous GABA accumulation, phenolic contents, and total antioxidant activity than the nontreated papaya. The results suggested that GABA treatment may be a useful approach to improving the chilling tolerance of papaya fruit by reducing oxidative stress and enhancing the defense system.

Keywords: GABA; GAD; abiotic stress; chilling injury; papaya; proline.