Diverse Functions of IAA-Leucine Resistant PpILR1 Provide a Genic Basis for Auxin-Ethylene Crosstalk During Peach Fruit Ripening

Abstract

Auxin and ethylene play critical roles in the ripening of peach (Prunus persica) fruit; however, the interaction between these two phytohormones is complex and not fully understood. Here, we isolated a peach ILR gene, PpILR1, which encodes an indole-3-acetic acid (IAA)-amino hydrolase. Functional analyses revealed that PpILR1 acts as a transcriptional activator of 1-amino cyclopropane-1-carboxylic acid synthase (PpACS1), and hydrolyzes auxin substrates to release free auxin. When Cys137 was changed to Ser137, PpILR1 failed to show hydrolase activity but continued to function as a transcriptional activator of PpACS1 in tobacco and peach transient expression assays. Furthermore, transgenic tomato plants overexpressing PpILR1 exhibited ethylene- and strigolactone-related phenotypes, including premature pedicel abscission, leaf and petiole epinasty, and advanced fruit ripening, which are consistent with increased expression of genes involved in ethylene biosynthesis and fruit ripening, as well as suppression of branching and growth of internodes (related to strigolactone biosynthesis). Collectively, these results provide novel insights into the role of IAA-amino acid hydrolases in plants, and position the PpILR1 protein at the junction of auxin and ethylene pathways during peach fruit ripening. These results could have substantial implications on peach fruit cultivation and storage in the future.

Thidiazuron Promotes Leaf Abscission by Regulating the Crosstalk Complexities between Ethylene, Auxin, and Cytokinin in Cotton

“…Here, we showed that TDZ reduced IAA content and transport, while induced ethylene content and signal genes in all the detected tissues ( Figure 7 , Figure 8 and Figure 10 ). Furthermore, several ILRs gene encoding the IAA-amino acid conjugate hydrolase were found to be up-regulated after TDZ treatment, which may increase the AZ sensitivity to ethylene and promote abscission [ 40 ]. Meanwhile, the increase of endogenous ethylene and the degradation of endogenous CTK can lead to the degradation of the cell wall and the separation of cells [ 15 ].…”

Ethylene and Auxin: Hormonal Regulation of Volatile Compound Production During Tomato (Solanum lycopersicum L.) Fruit Ripening

“…Regarding ethylene-auxin crosstalk, recent reports have elucidated antagonistic effects of the two plant hormones, including auxin acting as a ripening repressor and thereby opposing the known role of ethylene in inducing ripening in tomato fruit (Su et al, 2015;Li et al, 2016). However, since the auxin-ethylene relationship is extremely intricate, some of the phenotypic effects have yet to be assigned to either phytohormone (Wang et al, 2021).…”

The microRNA ppe-miR393 mediates auxin-induced peach fruit softening by promoting ethylene production

“…Treating SH peach with exogenous NAA results in increased expression of PpACS1 and a major increase in ethylene production and fruit softening ( Tatsuki et al 2018 ). Recent studies have shown that several genes coordinate auxin and ethylene signals during peach fruit ripening ( Wang et al 2021a , b , 2019a ). However, whether miRNAs are involved in the molecular mechanism of peach softening has until now remained unclear.…”

“…The MF fruits soften rapidly due to high levels of ethylene ( Haji et al 2003 ). The inability of SH fruits to produce ethylene is due to the low IAA concentrations which inhibit the expression of 1-aminocyclopropane-1-carboxylic acid synthase 1 ( PpACS1 ), and the fruits maintain a degree of hardness after harvesting ( Tatsuki et al 2013 ; Pan et al 2015 ; Wang et al 2021a ). This failure of SH peaches to soften is caused by mutations of the auxin biosynthesis gene YUCCA flavin mono-oxygenase 11 ( PpYUC11 ) ( Cirilli et al 2018 ; Tatsuki et al 2018 ).…”