Table_3_Diverse Functions of IAA-Leucine Resistant PpILR1 Provide a Genic Basis for Auxin-Ethylene Crosstalk During Peach Fruit Ripening.DOCX

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.

生长素和乙烯在桃（Prunus persica）果实的成熟过程中扮演着至关重要的角色；然而，这两种植物激素之间的相互作用复杂且尚未完全明了。在本研究中，我们分离了一种桃中ILR基因，即PpILR1，该基因编码一种色氨酸-3-乙酸（IAA）-氨基水解酶。功能分析表明，PpILR1充当1-氨基环丙烷-1-羧酸合酶（PpACS1）的转录激活剂，并水解生长素底物以释放游离生长素。当将Cys137突变为Ser137时，PpILR1未能表现出水解酶活性，但在烟草和桃的瞬时表达实验中仍继续作为PpACS1的转录激活剂发挥作用。此外，过表达PpILR1的转基因番茄植株表现出乙烯和异戊二烯内酯相关的表型，包括早期花梗脱落、叶片和叶柄的卷曲，以及果实的提前成熟，这些现象与乙烯生物合成和果实成熟相关基因的表达增加以及分枝和节间生长的抑制（与异戊二烯内酯生物合成相关）一致。综上所述，这些研究结果为植物中IAA-氨基酸水解酶的作用提供了新的见解，并将PpILR1蛋白定位在桃果实成熟过程中生长素和乙烯途径的交汇点上。这些结果对未来桃果的栽培和储存具有重大的影响。