Abstract
Auxin plays essential roles in plant development. Gretchen Hagen 3 (GH3) genes belong to a major auxin response gene family and GH3 proteins conjugate a range of acylsubstrates to alter the levels of hormones. Currently, the role of GH3 genes in postharvest physiological regulation of ripening and softening processes in papaya fruit is unclear. In this study, we identified seven CpGH3 genes in a papaya genome database. The CpGH3.1a, CpGH3.1b, CpGH3.5, CpGH3.6, and CpGH3.9 proteins were identified as indole-3-acetic acid (IAA)-specific amido synthetases. We analyzed the changes in IAA-amido synthetase activity using aspartate as a substrate for conjugation and found a large increase (over 5-fold) during the postharvest stages. Ascorbic acid (AsA) application can extend the shelf life of papaya fruit. Our data showed that AsA treatment regulates postharvest fruit maturation processes by promoting endogenous IAA levels. Our findings demonstrate the important role of GH3 genes in the regulation of auxin-associated postharvest physiology in papaya.
Highlights
The ripening of fruit is a genetically controlled process that involves complex multi-hormonal crosstalk
Seven Gretchen Hagen 3 (GH3) genes were identified in C. papaya; these genes were all named according to the phylogenetic relationship between C. papaya and the model plant A. thaliana
The results indicated that the GH3 gene family could be grouped into three major subfamilies, I, II, and III
Summary
The ripening of fruit is a genetically controlled process that involves complex multi-hormonal crosstalk. Auxin (indole-3-acetic acid, IAA) is a ubiquitous signaling molecule that has a vital role in plant development and growth including cell elongation and division, organ differentiation, embryogenesis, lateral root elongation, shoot architecture, and fruit development (Quint and Gray, 2006; Teale et al, 2008). Along with the hormone ethylene, auxin plays vital roles in many aspects of fleshy fruit development including fruit set and fruit ripening (Jones et al, 2002; Ruan et al, 2012). High concentrations of IAA are required for the biosynthesis of ethylene, which plays a significant role in fruit softening in “melting flesh” peaches at the late ripening stage (Pan et al, 2015). Auxin coordinates plant development by regulating the expression of auxin response gene families such as Aux/IAA (auxin/indole acetic acid), GH3 (Gretchen Hagen 3), SAUR
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