# FveDAD2 negatively regulates branch crowns by affecting abscisic acid metabolism through FveHB7 in woodland strawberry

## TL;DR

This study shows how strigolactone signaling regulates strawberry branching by affecting abscisic acid metabolism.

## Contribution

The novel interaction between FveDAD2, FveSMXL7, and FveHB7 in regulating branch crowns through ABA metabolism is revealed.

## Key findings

- FveDAD2 is identified as the SL receptor regulating branching in strawberry.
- FveSMXL7 represses FveHB7 transcription, which in turn affects ABA catabolism.
- ABA levels in shoot tips correlate with branching phenotypes in transgenic lines.

## Abstract

The branch crown is an important trait of the strawberry that influences plant architecture and yield. Strigolactones (SLs) are significant hormones involved in the plant growth response and are crucial for regulating branching. Previous studies have shown that SL signaling regulates branching by affecting abscisic acid (ABA) biosynthesis. In this study, we observed that the SL signaling pathway can affect branching by regulating ABA catabolism in strawberry. FveDAD2 in woodland strawberry was identified as the receptor for SL. Three FveDAD2-RNAi transgenic lines exhibited the phenotype of multibranched crowns and smaller fruits. Like the alpha/beta hydrolase DWARF14 (D14), the interaction of FveDAD2 with FveSMXL7 depended on SL. The FveSMXL7-RNAi transgenic plants exhibited a less branched phenotype compared to the control plant. In addition, FveSMXL7 binds to the promoter of FveHB7 and represses its transcription. FveHB7, a homeobox transcription factor, negatively regulates the transcription of the ABA 8′-hydroxylase gene (FveABA8'OH1). The expression of FveHB7 was up-regulated, while the expression of the FveABA8'OH1 was down-regulated in FveSMXL7-RNAi. ABA levels were reduced in the shoot tips of the FveDAD2-RNAi lines and increased in the FveSMXL7-RNAi lines. Treating wild-type plants with 20 μM ABA significantly suppressed the number of branch crowns, while 40 μM ABA rescued the phenotype of FveDAD2-RNAi. In conclusion, our research indicates that SL signaling may regulate branching by affecting ABA catabolism. These findings provide a theoretical basis for elucidating the mechanism of the development of branch crowns in the strawberry.