Abstract
In plants, the Gretchen GH3 (GH3) protein is involved in free auxin (IAA) and amino acid conjugation, thus controlling auxin homeostasis. To date, many GH3 gene families have been identified from different plant species. However, the GH3 gene family in kiwifruit (Actinidia chinensis) has not been reported. In this study, 12 AcGH3 genes were identified, phylogenetic analysis of AtGH3 (Arabidopsis), SlGH3 (Solanum lycopersicum), and AcGH3 provided insights into various orthologous relationships among these proteins, which were categorized into three groups. Expression analysis of AcGH3 genes at different postharvest stages suggested limited or no role for most of the AcGH3 genes at the initiation of fruit ripening. AcGH3.1 was the only gene exhibiting ripening-associated expression. Further study showed that the expression of AcGH3.1 gene was induced by NAA (1-naphthylacetic acid, auxin analogue) and inhibited by 1-MCP (1-methylcyclopropene, ethylene receptor inhibitor), respectively. AcGH3.1 gene silencing inhibited gene expression and delayed fruit softening in kiwifruit. The results indicate that AcGH3.1 may play an important role in the softening process of fruits. Analysis of the AcGH3.1 promoter revealed the presence of many cis-elements related to hormones, light, and drought. The determination of GUS (β-Galactosidase) enzyme activity revealed that promoter activity increased strikingly upon abscisic acid (ABA), ethylene, or NAA treatment, and significantly decreased with salicylic acid (SA) treatment. The present study could help in the identification of GH3 genes and revelation of AcGH3.1 gene function during postharvest stages, which pave the way for further functional verification of the AcGH3.1 gene.
Highlights
Kiwifruits have long been called the ‘king of fruits’ due to its unique flavor and exceptional nutritional value
The first Gretchen Hagen 3 (GH3) gene was isolated from soybean by differential screening after auxin treatment, and its transcription level was induced within 10 min after auxin treatment [8]
A. chinensis; these genes were named as AcGH3.1-AcGH3.12
Summary
Kiwifruits have long been called the ‘king of fruits’ due to its unique flavor and exceptional nutritional value. The fruit quality of kiwifruits declines rapidly after ripening, and is not resistant to storage and transportation. The speed of softening after harvesting directly determines the shelf life, flavor and edible value of the fruit. Many studies have found that auxin (IAA). Plays an important role in fruit ripening and aging. Exogenous IAA treatment of immature tomato fruit can delay fruit ripening and lead to parthenocarpy [1]. It is believed that IAA can delay the ripening of the climacteric fruit, and the fruit starts to fully mature due to the loss of hormone function of IAA [2]
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