Abstract
In mango (Mangifera indica L.), fruitlet abscission limits productivity. The INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) peptide acts as a key component controlling abscission events in Arabidopsis. IDA-like peptides may assume similar roles in fruit trees. In this study, we isolated two mango IDA-like encoding-genes, MiIDA1 and MiIDA2. We used mango fruitlet-bearing explants and fruitlet-bearing trees, in which fruitlets abscission was induced using ethephon. We monitored the expression profiles of the two MiIDA-like genes in control and treated fruitlet abscission zones (AZs). In both systems, qRT-PCR showed that, within 24 h, both MiIDA-like genes were induced by ethephon, and that changes in their expression profiles were associated with upregulation of different ethylene signaling-related and cell-wall modifying genes. Furthermore, ectopic expression of both genes in Arabidopsis promoted floral-organ abscission, and was accompanied by an early increase in the cytosolic pH of floral AZ cells—a phenomenon known to be linked with abscission, and by activation of cell separation in vestigial AZs. Finally, overexpression of both genes in an Atida mutant restored its abscission ability. Our results suggest roles for MiIDA1 and MiIDA2 in affecting mango fruitlet abscission. Based on our results, we propose new possible modes of action for IDA-like proteins in regulating organ abscission.
Highlights
Abscission is a unique developmental process, which facilitates the detachment of excess, damaged, or no longer needed plant organs [1,2,3]
A closer examination of the MiIDA PIP domains revealed that MiIDA1 shares the highest similarity with the PIP motif of AtIDA/IDL1 proteins, yet unexpectedly it contains a threonine at position 10, instead of the conserved arginine [19,20], representing an atypical PIPT-type version of IDA/IDL1 proteins
Our data provide different lines of evidence, supporting the conserved functions of both MiIDA1 and MiIDA2 in regulating mango fruitlet abscission, and suggest that the putative mango IDA-HAE/HSL2-like module operates in an ethylene-dependent manner
Summary
Abscission is a unique developmental process, which facilitates the detachment of excess, damaged, or no longer needed plant organs [1,2,3]. Abscission of plant organs, including leaves, flowers, and fruits, is achieved by the degradation of the middle lamella localized between differentiated cells in specialized abscission zones (AZ) found at the base of the shedding organs [1,2,3]. The sequence of events occurring at the AZ is proposed to be divided into four main stages, including: (i) Differentiation of cells in the AZ. Different factors trigger and/or affect abscission events. The two main hormones affecting organ abscission are ethylene, acting as an inducer, and auxin (mainly IAA), acting as a suppressor. Since it was demonstrated that IAA is required as a prerequisite for organ shedding [8], it is possible that IAA plays distinct roles during the early and later stages of abscission
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